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Sample records for standard covers precipitation-hardening

  1. Simultaneous surface engineering and bulk hardening of precipitation hardening stainless steel

    DEFF Research Database (Denmark)

    Frandsen, Rasmus Berg; Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    This article addresses simultaneous bulk precipitation hardening and low temperature surface engineering of two commercial precipitation hardening stainless steels: Sandvik Nanoflex® and Uddeholm Corrax®. Surface engineering comprised gaseous nitriding or gaseous carburising. Microstructural....... The duration and temperature of the nitriding/carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening stainless steel....... characterisation of the cases developed included X-ray diffraction analysis, reflected light microscopy and micro-hardness testing. It was found that the incorporation of nitrogen or carbon resulted in a hardened case consisting of a combination of (tetragonal) martensite and expanded (cubic) austenite...

  2. Precipitation and Hardening in Magnesium Alloys

    Science.gov (United States)

    Nie, Jian-Feng

    2012-11-01

    Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

  3. Precipitation hardening of a Cu-free Au-Ag-Pd-In dental alloy

    Energy Technology Data Exchange (ETDEWEB)

    Seol, Hyo-Joung [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Son, Kuk-Hyeon [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Yu, Chin-Ho [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kwon, Yong Hoon [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kim, Hyung-Il [Department of Dental Materials, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of)]. E-mail: hilkim@pusan.ac.kr

    2005-10-27

    The hardening mechanism and related microstructural changes of the Cu-free dental casting alloy composed of Au-Ag-Pd-In was examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The Au-Ag-Pd-In alloy showed apparent age-hardenability. In the SEM photograph, three phases were observed in the solution-treated specimen, that is, the Au-Ag based phase with small amounts of In and Pd as matrix, the InPd phase as particle-like structures, and the Pd-rich phase as lamellar precipitates. By aging the specimen, the very fine Pd-rich inter-granular precipitates grew toward the grain interior as lamellar structure, and finally the coarsened Pd-rich precipitates covered a large part of the Au-Ag based matrix. The hardness increase in the early stage of the age-hardening process was assumed to be caused by the diffusion and aggregation of Pd atoms from the Au-Ag based matrix. The hardness decrease in the later stage of age-hardening process was caused by coarsening of the lamellar precipitates composed of the Pd-rich phase.

  4. Precipitation hardening of a Cu-free Au-Ag-Pd-In dental alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Son, Kuk-Hyeon; Yu, Chin-Ho; Kwon, Yong Hoon; Kim, Hyung-Il

    2005-01-01

    The hardening mechanism and related microstructural changes of the Cu-free dental casting alloy composed of Au-Ag-Pd-In was examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The Au-Ag-Pd-In alloy showed apparent age-hardenability. In the SEM photograph, three phases were observed in the solution-treated specimen, that is, the Au-Ag based phase with small amounts of In and Pd as matrix, the InPd phase as particle-like structures, and the Pd-rich phase as lamellar precipitates. By aging the specimen, the very fine Pd-rich inter-granular precipitates grew toward the grain interior as lamellar structure, and finally the coarsened Pd-rich precipitates covered a large part of the Au-Ag based matrix. The hardness increase in the early stage of the age-hardening process was assumed to be caused by the diffusion and aggregation of Pd atoms from the Au-Ag based matrix. The hardness decrease in the later stage of age-hardening process was caused by coarsening of the lamellar precipitates composed of the Pd-rich phase

  5. Precipitation-hardening stainless steel bars, shapes, and forgings (ASME SA-564 with additional requirements)

    International Nuclear Information System (INIS)

    1975-05-01

    A standard prescribing requirements for precipitation-hardening stainless steel bars, shapes, and forgings (ASME SA-564 with additional requirements) for nuclear and associated applications is presented. This standard supersedes RDT M 7-6T, dated January 1974. (U.S.)

  6. Anomalous precipitation hardening in Al-(1 wt%)Cu thin films

    NARCIS (Netherlands)

    Bergers, L. J. C.; De Hosson, J. Th. M.; Geers, M. G. D.; Hoefnagels, J. P. M.

    2018-01-01

    This paper concentrates on the precipitation hardening of Al-(1 wt%)Cu thin films. It is shown that in contrast to bulk, the well-known approach of precipitation hardening in confined systems like thin layers and thin films does not operate in the conventional way. This work analyses and discusses

  7. Influence of Microstructure and Process Conditions on Simultaneous Low-Temperature Surface Hardening and Bulk Precipitation Hardening of Nanoflex®

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.

    2015-01-01

    Precipitation hardening martensitic stainless steel Nanoflex was low-temperature nitrided or nitrocarburized. In these treatments, simultaneous hardening of the bulk, by precipitation hardening, and the surface by dissolving nitrogen/carbon can be obtained because the treatment temperatures...... and times for these essentially different hardening mechanisms are compatible. The effect of the processing history of the steel on the nitrided/nitrocarburized case was investigated by varying the amounts of austenite and martensite through variation of the degree of plastic deformation by tensile strain...... consisting of martensite results in the deepest nitrided case, while a shallow case develops on a microstructure consisting of austenite. For an initial microstructure consisting of both martensite and austenite a non-uniform case depth is achieved. Simultaneous bulk and surface hardening is only possible...

  8. Precipitation hardening in dilute Al–Zr alloys

    Directory of Open Access Journals (Sweden)

    Pedro Henrique Lamarão Souza

    2018-01-01

    Full Text Available The aim of this study was to investigate the effect of solute content (hipoperitectic Al–0.22 wt.%Zr and hiperperitectic Al–0.32 wt.%Zr on the precipitation hardening and microstructural evolution of dilute Al–Zr alloys isothermally aged. The materials were conventionally cast in a muffle furnace, solidified in a water-cooled Cu mold and subsequently heat-treated at the temperature of 650 K (377 °C for 4, 12, 24, 100 and 400 h. Mechanical characterization was performed at room temperature, using a microhardness tester and microstructural characterization was carried out on a Transmission Electron Microscope – TEM. The observed microhardness values increased during isothermal aging, due to the precipitation of nanometer-scale Al3Zr L12 particles. Peak strength was achieved within 100 h of aging. After aging for 400 h, microhardness values presented a slight decrease for both alloys, thus indicating overaging due to the coalescence of precipitates. Microhardness values increased with solute content, due to the precipitation of a higher number density of finer precipitates. After 400 h of heat-treating, coalescence was higher for the alloy with lower solute content and, also, the presence of antiphase boundaries – APBs, planar faults associated with the L12 to D023 structural transition, were observed. Comparing theoretical calculations of the increment in strength due to precipitation strengthening with experimental results, it was observed that their values are in reasonable agreement. The Orowan dislocation looping mechanism takes place during precipitation hardening for both alloys in the peak hardness condition.

  9. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    Science.gov (United States)

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  10. Changes in hardness of magnesium alloys due to precipitation hardening

    Directory of Open Access Journals (Sweden)

    Tatiana Oršulová

    2018-04-01

    Full Text Available This paper deals with the evaluation of changes in hardness of magnesium alloys during precipitation hardening that are nowadays widely used in different fields of industry. It focuses exactly on AZ31, AZ61 and AZ91 alloys. Observing material hardness changes serves as an effective tool for determining precipitation hardening parameters, such as temperature and time. Brinell hardness measurement was chosen based on experimental needs. There was also necessary to make chemical composition analysis and to observe the microstructures of tested materials. The obtained results are presented and discussed in this paper.

  11. Improving precipitation hardening behavior of Mg−Zn based alloys with Ce−Ca microalloying additions

    Energy Technology Data Exchange (ETDEWEB)

    Langelier, B., E-mail: langelb@mcmaster.ca [Mechanical & Mechatronics Engineering, The University of Waterloo, N2L 3G1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, L8S 4L8 (Canada); Korinek, A. [Canadian Centre for Electron Microscopy, McMaster University, L8S 4L8 (Canada); Donnadieu, P. [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Esmaeili, S. [Mechanical & Mechatronics Engineering, The University of Waterloo, N2L 3G1 (Canada)

    2016-10-15

    The precipitation hardening behavior of newly developed Mg−Zn−Ca−Ce alloys, with modified texture and improved ductility, is studied to delineate the microstructural characteristics that lead to effective hardening upon ageing treatments. Advanced electron microscopy and atom probe techniques are used to analyze the structural characteristics in relevance to the hardening potential. It has been found that the formation of a new basal precipitate phase, which evolves from a single atomic layer GP zone, and is finely distributed in both under-aged and peak-aged microstructures, has a significant impact in the improvement of the hardening response compared with the base Mg−Zn alloys. It has also been found that the β′{sub 1} rod precipitates, commonly formed during ageing treatments of Mg−Zn alloys, have their size and distribution significantly refined in the Ca−Ce containing alloys. The role of alloy chemistry in the formation of the fine basal plate GP zones and the refinement in β′{sub 1} precipitation and their relationships to the hardening behavior are discussed. It is proposed that Ca microalloying governs the formation of the GP zones and the enhancement of hardening, particularly in the under-aged conditions, but that this is aided by a beneficial effect from Ce. - Highlights: • Ce−Ca microalloying additions improve hardening in Mg−Zn, over Ce or Ca alone. • Improved hardening is due to refined β′{sub 1} rods, and fine basal plate precipitates. • Atom probe tomography identifies Ca in both β′{sub 1} and the fine basal plates. • The fine basal plates originate as ordered monolayer GP zones with 1:1 Zn:Ca (at.%). • With ageing GP zones become more Zn-rich and transform to the fine basal plates.

  12. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  13. Precipitation hardening of a FeMnC TWIP steel by vanadium carbides

    International Nuclear Information System (INIS)

    Chateau, J P; Dumay, A; Jacques, A; Allain, S

    2010-01-01

    A fine precipitation of spherical vanadium carbides is obtained in a Fe22Mn0.6C base steel during the final recrystallisation heat treatment. Precipitates formed in recrystallised grains have a cube-cube orientation relation with the matrix, confirmed by Moire patterns observed in TEM. The theoretical size for loss of coherency is below the nm, much lower than the precipitates' size. Deformation contrasts were observed around the precipitates and their residual coherency was measured. It was shown to decrease when the carbides' size increases, to vanish above 30 nm. The net increase of the yield stress was estimated to be 140 MPa. Precipitation hardening by vanadium carbides do not alter the strain hardening rate by TWIP effect, as they do not seem to act as obstacles for the propagation of microtwins.

  14. Ultrafine-Grained Precipitation Hardened Copper Alloys by Swaging or Accumulative Roll Bonding

    Directory of Open Access Journals (Sweden)

    Igor Altenberger

    2015-05-01

    Full Text Available There is an increasing demand in the industry for conductive high strength copper alloys. Traditionally, alloy systems capable of precipitation hardening have been the first choice for electromechanical connector materials. Recently, ultrafine-grained materials have gained enormous attention in the materials science community as well as in first industrial applications (see, for instance, proceedings of NANO SPD conferences. In this study the potential of precipitation hardened ultra-fine grained copper alloys is outlined and discussed. For this purpose, swaging or accumulative roll-bonding is applied to typical precipitation hardened high-strength copper alloys such as Corson alloys. A detailed description of the microstructure is given by means of EBSD, Electron Channeling Imaging (ECCI methods and consequences for mechanical properties (tensile strength as well as fatigue and electrical conductivity are discussed. Finally the role of precipitates for thermal stability is investigated and promising concepts (e.g. tailoring of stacking fault energy for grain size reduction and alloy systems for the future are proposed and discussed. The relation between electrical conductivity and strength is reported.

  15. Microstructural evolution and the variation of tensile behavior after aging heat treatment of precipitation hardened martensitic steel

    International Nuclear Information System (INIS)

    Shin, Jong-Ho; Jeong, JaeSuk; Lee, Jong-Wook

    2015-01-01

    The effects of aging temperature on the microstructural evolution and the tensile behavior of precipitation hardened martensitic steel were investigated. Microscopic analysis using transmission electron microscope (TEM) was combined with the microstructural analysis using the synchrotron X-ray diffraction (XRD) to characterize the microstructural evolution with aging temperature. Peak hardness was obtained by precipitation of the Ni 3 Al ordered phase. After aging at temperature range from 420 to 590 °C, spherical Ni 3 Al precipitates and ellipsoidal M 23 C 6 carbides were observed within laths and at lath boundaries, respectively. Strain hardening behavior was analyzed with Ludwik equation. It is observed that the plastic strain regimes can be divided into two different stages by a rapid increase in strain hardening followed by a comparatively lower increase. At the first strain hardening stage, the aged specimen exhibited higher strain hardening exponent than the as-quenched specimen, and the exponent in the aged specimen was not changed considerably with increasing aging temperature. It is revealed that the strain hardening exponents at the first and the second stages were associated with the Ni 3 Al precipitates and the domain size representing the coherent scattering area, respectively. - Highlights: • All of aged specimen exhibited higher strain hardening exponent than the as-quenched specimen at the first stage. • The value of strain hardening exponent in the aged specimen was nearly constant with aging temperature. • Ni 3 Al precipitation dominantly influenced to the increase of strain hardening exponent at the first strain hardening stage. • Domain size was associated with strain hardening exponent at the second strain hardening stage

  16. Microstructural evolution and the variation of tensile behavior after aging heat treatment of precipitation hardened martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Jong-Ho, E-mail: jongho.shin@doosan.com [Casting and Forging Technology Development Team, Doosan Heavy Industries and Construction, 22 Doosanvolvo-ro, Changwon 642-792 (Korea, Republic of); Jeong, JaeSuk [Materials and Manufacturing Development Team, Doosan Heavy Industries and Construction, 22 Doosanvolvo-ro, Changwon 642-792 (Korea, Republic of); Lee, Jong-Wook [Casting and Forging Technology Development Team, Doosan Heavy Industries and Construction, 22 Doosanvolvo-ro, Changwon 642-792 (Korea, Republic of)

    2015-01-15

    The effects of aging temperature on the microstructural evolution and the tensile behavior of precipitation hardened martensitic steel were investigated. Microscopic analysis using transmission electron microscope (TEM) was combined with the microstructural analysis using the synchrotron X-ray diffraction (XRD) to characterize the microstructural evolution with aging temperature. Peak hardness was obtained by precipitation of the Ni{sub 3}Al ordered phase. After aging at temperature range from 420 to 590 °C, spherical Ni{sub 3}Al precipitates and ellipsoidal M{sub 23}C{sub 6} carbides were observed within laths and at lath boundaries, respectively. Strain hardening behavior was analyzed with Ludwik equation. It is observed that the plastic strain regimes can be divided into two different stages by a rapid increase in strain hardening followed by a comparatively lower increase. At the first strain hardening stage, the aged specimen exhibited higher strain hardening exponent than the as-quenched specimen, and the exponent in the aged specimen was not changed considerably with increasing aging temperature. It is revealed that the strain hardening exponents at the first and the second stages were associated with the Ni{sub 3}Al precipitates and the domain size representing the coherent scattering area, respectively. - Highlights: • All of aged specimen exhibited higher strain hardening exponent than the as-quenched specimen at the first stage. • The value of strain hardening exponent in the aged specimen was nearly constant with aging temperature. • Ni{sub 3}Al precipitation dominantly influenced to the increase of strain hardening exponent at the first strain hardening stage. • Domain size was associated with strain hardening exponent at the second strain hardening stage.

  17. Formation and evolution of the hardening precipitates in a Mg-Y-Nd alloy

    International Nuclear Information System (INIS)

    Barucca, G.; Ferragut, R.; Fiori, F.; Lussana, D.; Mengucci, P.; Moia, F.; Riontino, G.

    2011-01-01

    The formation and evolution of hardening precipitates in a Mg-Y-Nd (WE43) alloy during artificial ageing at 150 and 210 deg. C is followed by small angle X-ray scattering (SAXS) measurements, Vickers microhardness tests and transmission electron microscopy (TEM) observations. A quantitative description of the alloy studied during the early and advanced stages of the precipitation sequence is presented. In situ SAXS evolution at 210 deg. C of the size, volume fraction and number density of the subnanometer and nanometer particles that evolve in the β'' phase was obtained. TEM and microhardness results indicate that the hardening mechanism is based on β'' transformation of pre-precipitates and their growth at 150 deg. C, while at 210 deg. C hardening is mainly associated with β'' → β' transformation.

  18. work hardening, recovery and recrystallization of alloys containing dispersed precipitates

    International Nuclear Information System (INIS)

    Padilha, A.F.

    1989-01-01

    This paper reviews the work hardening, recovery and recrystallization mechanisms in alloys containing dispersed precipitates. In the section on work hardening, the influence od spacing, particle size and shape on the density and distribution of dislocations have been discussed. They represent a large part of the energy stored in the material following drformation, which in turn is driving force for recrystallization. Next, the role of precipitates on recovery, on the formation and the growth of recrystallized regions has been discussed in detail. The competition between recovery and recrystallization and recrystallization of supersaturated solid solutions have also been mentioned. Finally, the technological relevance of the aspects treated in this paper has been discussed. (author) [pt

  19. Linear Friction Welding Process Model for Carpenter Custom 465 Precipitation-Hardened Martensitic Stainless Steel

    Science.gov (United States)

    2014-04-11

    Carpenter Custom 465 precipitation-hardened martensitic stainless steel to develop a linear friction welding (LFW) process model for this material...Model for Carpenter Custom 465 Precipitation-Hardened Martensitic Stainless Steel The views, opinions and/or findings contained in this report are... Martensitic Stainless Steel Report Title An Arbitrary Lagrangian-Eulerian finite-element analysis is combined with thermo-mechanical material

  20. Developing precipitation hardenable high entropy alloys

    Science.gov (United States)

    Gwalani, Bharat

    High entropy alloys (HEAs) is a concept wherein alloys are constructed with five or more elements mixed in equal proportions; these are also known as multi-principle elements (MPEs) or complex concentrated alloys (CCAs). This PhD thesis dissertation presents research conducted to develop precipitation-hardenable high entropy alloys using a much-studied fcc-based equi-atomic quaternary alloy (CoCrFeNi). Minor additions of aluminium make the alloy amenable for precipitating ordered intermetallic phases in an fcc matrix. Aluminum also affects grain growth kinetics and Hall-Petch hardenability. The use of a combinatorial approach for assessing composition-microstructure-property relationships in high entropy alloys, or more broadly in complex concentrated alloys; using laser deposited compositionally graded AlxCrCuFeNi 2 (0 mechanically processed via conventional techniques. The phase stability and mechanical properties of these alloys have been investigated and will be presented. Additionally, the activation energy for grain growth as a function of Al content in these complex alloys has also been investigated. Change in fcc grain growth kinetic was studied as a function of aluminum; the apparent activation energy for grain growth increases by about three times going from Al0.1CoCrFeNi (3% Al (at%)) to Al0.3CoCrFeNi. (7% Al (at%)). Furthermore, Al addition leads to the precipitation of highly refined ordered L12 (gamma') and B2 precipitates in Al0.3CoCrFeNi. A detailed investigation of precipitation of the ordered phases in Al0.3CoCrFeNi and their thermal stability is done using atom probe tomography (APT), transmission electron microscopy (TEM) and Synchrotron X-ray in situ and ex situ analyses. The alloy strengthened via grain boundary strengthening following the Hall-Petch relationship offers a large increment of strength with small variation in grain size. Tensile strength of the Al0.3CoFeNi is increased by 50% on precipitation fine-scale gamma' precipitates

  1. Formation and evolution of the hardening precipitates in a Mg-Y-Nd alloy

    Energy Technology Data Exchange (ETDEWEB)

    Barucca, G. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Ferragut, R. [Dipartimento di Fisica, LNESS and CNISM, Politecnico di Milano, Via Anzani 42, I-22100 Como (Italy); Fiori, F. [Dipartimento SAIFET, Sezione di Scienze Fisiche, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Lussana, D. [Dipartimento di Chimica IFM and NIS Centre, Universita di Torino, Via P. Giuria 9, I-10125 Torino (Italy); Mengucci, P., E-mail: p.mengucci@univpm.it [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Moia, F. [Dipartimento di Fisica, LNESS and CNISM, Politecnico di Milano, Via Anzani 42, I-22100 Como (Italy); Riontino, G. [Dipartimento di Chimica IFM and NIS Centre, Universita di Torino, Via P. Giuria 9, I-10125 Torino (Italy)

    2011-06-15

    The formation and evolution of hardening precipitates in a Mg-Y-Nd (WE43) alloy during artificial ageing at 150 and 210 deg. C is followed by small angle X-ray scattering (SAXS) measurements, Vickers microhardness tests and transmission electron microscopy (TEM) observations. A quantitative description of the alloy studied during the early and advanced stages of the precipitation sequence is presented. In situ SAXS evolution at 210 deg. C of the size, volume fraction and number density of the subnanometer and nanometer particles that evolve in the {beta}'' phase was obtained. TEM and microhardness results indicate that the hardening mechanism is based on {beta}'' transformation of pre-precipitates and their growth at 150 deg. C, while at 210 deg. C hardening is mainly associated with {beta}'' {yields} {beta}' transformation.

  2. Precipitation hardening in a 12%Cr-9%Ni-4%Mo-2%Cu stainless steel

    International Nuclear Information System (INIS)

    Haettestrand, Mats; Nilsson, Jan-Olof; Stiller, Krystyna; Liu Ping; Andersson, Marcus

    2004-01-01

    A combination of complementary techniques including one-dimensional and three-dimensional atom probe, energy-filtered transmission electron microscopy and conventional transmission electron microscopy has been used to assess the precipitation reactions at 475 deg. C in a 12%Cr-9%Ni-4%Mo-2%Cu precipitation hardening stainless steel. The continuous hardening up to at least 1000 h of ageing was attributed to a sequence of precipitation reactions involving nickel-rich precipitates nucleating at copper clusters followed by molybdenum-rich quasicrystalline precipitates and nickel-rich precipitates of type L1 0 . An estimate of the relative contributions to the strength increment during tempering based on measurements of particle densities was performed. Nickel-rich precipitates were found to play the most important role up to about 40 h of ageing after which the effect of quasicrystalline particles became increasingly important

  3. Effect of solution treatment on precipitation behaviors and age hardening response of Al–Cu alloys with Sc addition

    International Nuclear Information System (INIS)

    Chen, B.A.; Pan, L.; Wang, R.H.; Liu, G.; Cheng, P.M.; Xiao, L.; Sun, J.

    2011-01-01

    Highlights: ► Effects of Sc addition on the precipitation and age hardening of Al–Cu alloy were investigated. ► The critical influence of solution treatment on the Sc effect was revealed. ► A significant enhancement in age hardening response was experimentally found and quantitatively assessed. - Abstract: Influences of solution treatment on precipitation behaviors and age hardening response of Al–2.5 wt% Cu–0.3 wt% Sc alloys were investigated, in comparison with Sc-free one. The Al 3 Sc dispersoids, formed during homogenization, were either survived or dissolved to become Sc solute atoms in solution treatment, depending on the solution temperature. When the temperature for solution treatment is 873 K, most of the Al 3 Sc dispersoids were dissolved and a significant enhancement in the uniform precipitation of finer θ′-Al 2 Cu particles was achieved in following aging treatment, causing a noticeable increase in peak-aging hardness by about 90% compared to Sc-free alloys. The enhanced age hardening effect was quantitatively related to the remarkable reduction in effective inter-particle spacing of the plate-shaped θ′-Al 2 Cu precipitates. When the temperature for solution treatment is 793 K, however, most of the Al 3 Sc dispersoids were survived after solution treatment and facilitated the heterogeneous precipitation of θ′-Al 2 Cu plates directly on the {1 0 0} facets of dispersoids in following aging treatment. Concomitantly, the uniform precipitation of θ′-Al 2 Cu plates was greatly suppressed, resulting in a reduced age hardening response. The age hardening responses were quantitatively assessed by using a modified strengthening model that is applicable to the plate-shaped precipitates. The calculations were in good agreement with experimental results. The present results show the importance of controlling solution treatments to achieve significant promotion effect of Sc addition on the precipitation hardening in heat-treatable aluminum

  4. Solution and precipitation hardening of two-phase gamma titanium alloy; Mischkristall- und Ausscheidungshaertung zweiphasiger Gamma-Titanaluminidlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Christoph, U. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung

    1997-12-31

    The present study on solution and precipitation hardening of two-phase gamma titanium aluminides was directed towards improved creep resistance. Alloys were systematically doped with carbon up to 0.37 atomic percent. Solid solutions and precipitates of carbon were formed by different thermal treatments. The hardening obtained as a result of the different precipitate conditions was measured by deformation experiments between 293 and 973 K. An increase of yield stress of up to 300 MPa was observed for finely distributed perovskite precipitates. This increase of yield stress was maintained up to 973 K and was shown to be dominantly athermal in character from activation parameter measurements. Electron microscopic investigations confirmed the athermal nature of the perovskite precipitates to dislocation motion. The precipitates thus act as barriers to dislocation glide over a wide temperature range and can therefore increase the creep resistance at the anticipated operation temperature of 973 K. In addition to studying the mechanism of precipitation hardening, the pinning of dislocations by the formation of impurity atmospheres has also been investigated. This phenomenon is effective at intermediate temperatures of around 550 K and is thought to be caused by very mobile elements such as iron and boron. These elements are present in all alloys of technical relevance. (orig.) 158 refs.

  5. Modeling copper precipitation hardening and embrittlement in a dilute Fe-0.3at.%Cu alloy under neutron irradiation

    Science.gov (United States)

    Bai, Xian-Ming; Ke, Huibin; Zhang, Yongfeng; Spencer, Benjamin W.

    2017-11-01

    Neutron irradiation in light water reactors can induce precipitation of nanometer sized Cu clusters in reactor pressure vessel steels. The Cu precipitates impede dislocation gliding, leading to an increase in yield strength (hardening) and an upward shift of ductile-to-brittle transition temperature (embrittlement). In this work, cluster dynamics modeling is used to model the entire Cu precipitation process (nucleation, growth, and coarsening) in a Fe-0.3at.%Cu alloy under neutron irradiation at 300°C based on the homogenous nucleation mechanism. The evolution of the Cu cluster number density and mean radius predicted by the modeling agrees well with experimental data reported in literature for the same alloy under the same irradiation conditions. The predicted precipitation kinetics is used as input for a dispersed barrier hardening model to correlate the microstructural evolution with the radiation hardening and embrittlement in this alloy. The predicted radiation hardening agrees well with the mechanical test results in the literature. Limitations of the model and areas for future improvement are also discussed in this work.

  6. Temperature Effects on the Tensile Properties of Precipitation-Hardened Al-Mg-Cu-Si Alloys

    Directory of Open Access Journals (Sweden)

    J.B. Ferguson

    2016-02-01

    Full Text Available Because the mechanical performance of precipitation-hardened alloys can be significantly altered with temperature changes, understanding and predicting the effects of temperatures on various mechanical properties for these alloys are important. In the present work, an analytical model has been developed to predict the elastic modulus, the yield stress, the failure stress, and the failure strain taking into consideration the effect of temperatures for precipitation-hardenable Al-Mg-Cu-Si Alloys (Al-A319 alloys. In addition, other important mechanical properties of Al-A319 alloys including the strain hardening exponent, the strength coefficient, and the ductility parameter can be estimated using the current model. It is demonstrated that the prediction results based on the proposed model are in good agreement with those obtained experimentally in Al-A319 alloys in the as-cast condition and after W and T7 heat treatments.

  7. Combinative hardening effects of precipitation in a commercial aged Al–Cu–Li–X alloy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhongwei, E-mail: chzw@nwpu.edu.cn; Zhao, Kai; Fan, Li

    2013-12-20

    The combinative effects of precipitates on microstructure and hardness of an Al–Cu–Li–X alloy (X=Mg, Zn, Mn, Zr) in artificial ageing of 165 °C were investigated by a transmission electron microscopy and hardness test. Results show that the hardness appears at regression in early ageing stage and increases rapidly during subsequent ageing of 16 h. Hardening effects of as-quenched sample are mainly attributed to β′ (Al{sub 3}Zr) dispersoids, quenched-in vacancies and dislocations. Though most of the fine and uniform precipitates θ′ (Al{sub 2}Cu), δ′ (Al{sub 3}Li), σ (Al{sub 5}Cu{sub 6}Mg{sub 2}) and GP zone came into being in ageing of 0.5 h, annihilation of quenched-in vacancies and reduction of dislocation were ascribed to the hardening regression at early stages of ageing. As further ageing is in progress, all precipitates including T{sub 1} (Al{sub 2}CuLi), σ, δ′ and θ′ have appeared during the ageing of 16 h that follows, and their combinative hardening effects are responsible for the rapid hardness increase at peak-ageing.

  8. A Combined Precipitation, Yield Stress, and Work Hardening Model for Al-Mg-Si Alloys Incorporating the Effects of Strain Rate and Temperature

    Science.gov (United States)

    Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore

    2018-05-01

    In this study, a combined precipitation, yield strength, and work hardening model for Al-Mg-Si alloys known as NaMo has been further developed to include the effects of strain rate and temperature on the resulting stress-strain behavior. The extension of the model is based on a comprehensive experimental database, where thermomechanical data for three different Al-Mg-Si alloys are available. In the tests, the temperature was varied between 20 °C and 350 °C with strain rates ranging from 10-6 to 750 s-1 using ordinary tension tests for low strain rates and a split-Hopkinson tension bar system for high strain rates, respectively. This large span in temperatures and strain rates covers a broad range of industrial relevant problems from creep to impact loading. Based on the experimental data, a procedure for calibrating the different physical parameters of the model has been developed, starting with the simplest case of a stable precipitate structure and small plastic strains, from which basic kinetic data for obstacle limited dislocation glide were extracted. For larger strains, when work hardening becomes significant, the dynamic recovery was linked to the Zener-Hollomon parameter, again using a stable precipitate structure as a basis for calibration. Finally, the complex situation of concurrent work hardening and dynamic evolution of the precipitate structure was analyzed using a stepwise numerical solution algorithm where parameters representing the instantaneous state of the structure were used to calculate the corresponding instantaneous yield strength and work hardening rate. The model was demonstrated to exhibit a high degree of predictive power as documented by a good agreement between predictions and measurements, and it is deemed well suited for simulations of thermomechanical processing of Al-Mg-Si alloys where plastic deformation is carried out at various strain rates and temperatures.

  9. Study of the precipitation hardening process in recycled Al-Si-Cu cast alloys

    Directory of Open Access Journals (Sweden)

    Kuchariková L.

    2017-03-01

    Full Text Available The formation of extremely small uniformly dispersed particles of a second phase within the original phase matrix during heat treatment changed material properties. Therefore the characterization of precipitation had been investigated using high resolution transmission electron microscopy (TEM and electron diffraction of thin foils for an AlSi9Cu3 cast alloy. For investigation the hardening effect onto mechanical properties of aluminium cast was used heat treatment, which consisted from solution treatment at 515°C / 4 hours (h, followed by quenching into water with temperature 50°C and artificial aging using different temperatures 170°C and 190°C with different holding time 2, 4, 8, 16, and 32 hours. The observations of microstructure and substructure reveals that precipitation hardening has caused great changes in size, morphology and distributions of structural components, the formation of precipitates of Cu phases, and the change of mechanical properties as well.

  10. Effects of La on the age hardening behavior and precipitation kinetics in the cast Al–Cu alloy

    International Nuclear Information System (INIS)

    Yao Dongming; Bai Zhihao; Qiu Feng; Li Yanjun; Jiang Qichuan

    2012-01-01

    Highlights: ► La addition enhances the hardness of the Al–Cu alloy. ► La addition facilitates the formation of the θ′ precipitates. ► La addition decreases the nucleation activation energy of the θ′ precipitates. - Abstract: The hardness and thermal stability are the important problems of the cast Al–Cu alloy related to the microstructural changes. In order to increase the possibilities of high temperature applications of the cast Al–Cu alloy, it is necessary to gain a more detail understanding of the correlation between the age hardening and the microstructure in the cast Al–Cu alloy, and the thermal stability of the θ′ precipitates at elevated temperatures. The aim of this work is to investigate the effects of La addition on the age hardening behavior and precipitation kinetics in the Al–Cu alloy in the temperature range from 435 to 523 K. The results indicated that La addition considerably increases the number of the θ′ precipitates and decreases their sizes, which results in the enhanced age hardening effect. The precipitation kinetics analysis showed that the activation energy (13 kJ/mol) of the θ′ precipitate nucleation of the modified alloy is smaller than that (19 kJ/mol) of the unmodified alloy. The decrease in the activation energy of the θ′ precipitate nucleation can be explained with both the enhanced nucleation process due to La/Cu/vacancy aggregating and the increased interaction between Al and Cu atoms.

  11. Specific features of precipitation hardening of austenitic steels with various base. 2. Kinetics and mechanism of carbide precipitation

    International Nuclear Information System (INIS)

    Kositsyna, I.I.; Sagaradze, V.V.; Khakimova, O.N.

    1997-01-01

    Electron microscopic studies were carried out to determine the kinetics and mechanisms of precipitation hardening in Fe-Mn, Fe-Mn-Cr, Fe-Cr-Mn-N, Fe-Cr-Ni and Fe-Ni base stainless steels (45G20M2F2, 50Kh16G15N6M2F2, 45Kh18N10G10M2F2, 40Kh18Ni18M2F2, 45N26M2F2). The steels were heat treated under various conditions. It is revealed that in manganese steels the particles of vanadium carbide nucleate according to homogeneous mechanism at all aging temperatures (600-750 deg C). The presence of chromium in the matrix promotes the transition to heterogeneous mechanism of carbide nucleation and growth. With nickel content increasing the plasticity of precipitation hardened steels gets better due to more intense diffusion of atoms and vacancies to grain boundaries and, hence, the widening of near-boundary zones free of carbide particles

  12. a Calorimetric Study of the Precipitation Hardening Mechanisms in AN Al-Cu-Mg-Si Alloy

    Science.gov (United States)

    Hayoune, Abdelali

    2013-08-01

    The precipitation phenomena and the related hardening in an Al-Cu-Mg-Si alloy were studied by calorimetry, X-ray diffraction analysis and microhardness measurements. The main calorimetric peaks were identified to be due to β‧‧, θ‧ and Q‧ phases precipitation. The hardening during aging at room temperature and 160°C, was respectively, explained by atomic clusters and GP zones formation and by GP zones and β‧‧/θ‧ phases coprecipitation. Although the mechanical properties variation during aging at 200°C is simple, the corresponding microstructural evolution is complex: on the basis of the DSC results, the increasing of microhardness values, is mainly due to the coprecipitation of GP zones and β‧‧/θ‧ phases, however, the maximum hardening is explained by the coexistence of β‧‧/θ‧ and θ‧‧ phases. Another important conclusion is that during aging at 160°C and 200°C, the θ‧ phase is essentially developed from GP zones.

  13. Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

    Science.gov (United States)

    Schade, Christopher

    To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as

  14. The natural aging and precipitation hardening behaviour of Al-Mg-Si-Cu alloys with different Mg/Si ratios and Cu additions

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Lipeng [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 China (China); Jia, Zhihong, E-mail: zhihongjia@cqu.edu.cn [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 China (China); Zhang, Zhiqing; Sanders, Robert E.; Liu, Qing [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 China (China); Yang, Guang [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Centre for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049 (China)

    2015-03-11

    The natural aging and artificial aging behaviours of Al-Mg-Si-Cu alloys with different Mg/Si ratios and Cu additions were investigated using Vickers microhardness measurements, differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM) characterisation. Excess Si and Cu additions enhanced the alloy hardening ability during natural (NA) and artificial aging (AA). Alloys with low Cu and high Si contents exhibited higher precipitation hardening than alloys rich in Mg during artificial aging. In contrast, the alloys with high amounts of Cu were less dependent on the Mg/Si ratio during precipitation hardening due to their similar aging kinetics. The main precipitate phases that contributed to the peak-aging hardness were the L, Q′ and β″ phases. In the over-aging conditions, the alloys rich in Mg and Cu had finer and more numerous precipitates than their Si-rich equivalents due to the preferential precipitation of the L phase. The combination of excess Mg and high Cu resulted in an alloy with a relatively low hardness in T4 temper and a relatively higher hardness after the paint baking cycle. Thus, this alloy has good potential for use in auto body panel applications.

  15. Aqueous electrochemistry of precipitation-hardened nickel base alloys

    International Nuclear Information System (INIS)

    Hosoya, K.; Ballinger, R.; Prybylowski, J.; Hwang, I.S.

    1990-11-01

    An investigation has been conducted to explore the importance of local crack tip electrochemical processes in precipitation-hardened Ni-Cr-Fe alloys driven by galvanic couples between grain boundary precipitates and the local matrix. The electrochemical behavior of γ' [Ni 3 (Al,Ti)] has been determined as a function of titanium concentration, temperature, and solution pH. The electrochemical behavior of Ni-Cr-Fe solid solution alloys has been investigated as a function of chromium content for a series of 10 Fe-variable Cr (6--18%)-balance Ni alloys, temperature, and pH. The investigation was conducted in neutral and pH3 solutions over the temperature range 25--300 degree C. The results of the investigation show that the electrochemical behavior of these systems is a strong function of temperature and composition. This is especially true for the γ' [Ni 3 (Al,Ti)] system where a transition from active/passive behavior to purely active behavior and back again occurs over a narrow temperature range near 100 degree C. Behavior of this system was also found to be a strong function of titanium concentration. In all cases, the Ni 3 (Al,Ti) phase was active with respect to the matrix. The peak in activity near 100 degree C correlates well with accelerated crack growth in this temperature range, observed in nickel-base alloy X-750 heat treated to precipitate γ' on the grain boundaries. 20 refs., 23 figs., 3 tabs

  16. Nano Precipitation and Hardening of Die-Quenched 6061 Aluminum Alloy.

    Science.gov (United States)

    Utsunomiya, Hiroshi; Tada, Koki; Matsumoto, Ryo; Watanabe, Katsumi; Matsuda, Kenji

    2018-03-01

    Die quenching is applied to an age-hardenable aluminium alloys to obtain super-saturated solid solution. The application is advantageous because it can reduce number of manufacturing processes, and may increase strength by strain aging. If die quenching is realized in forging as well as sheet forming, it may widen industrial applicability further. In this study, Al-Mg-Si alloy AA6061 8 mm-thick billets were reduced 50% in height without cracks by die-quench forging. Supersaturated solid solution was successfully obtained. The die-quenched specimen shows higher hardness with nano precipitates at shorter aging time than the conventional water-quenched specimen.

  17. PRECIPITATION HARDENING IN B2-ORDERED NiAl BY Ni2AlTiCOMPOUND

    Institute of Scientific and Technical Information of China (English)

    W.H. Tian; K. Ohishi; M. Nemoto

    2001-01-01

    Microstructural variations and correlated hardness changes in B2-ordered NiAl containing fine precipitation of Ni2AlTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L21-type Ni2AlTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2AlTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2-ordered NiAl was investigated by compression tests over the temperature range of 873-1273K. The fine precipitation of Ni2AlTi was found to enhance greatly the yield strength and the high-temperature strength is comparison with that of superalloy Mar-M200.``

  18. TEM Studies of Boron-Modified 17Cr-7Ni Precipitation-Hardenable Stainless Steel via Rapid Solidification Route

    Science.gov (United States)

    Gupta, Ankur; Bhargava, A. K.; Tewari, R.; Tiwari, A. N.

    2013-09-01

    Commercial grade 17Cr-7Ni precipitation-hardenable stainless steel has been modified by adding boron in the range 0.45 to 1.8 wt pct and using the chill block melt-spinning technique of rapid solidification (RS). Application of RS has been found to increase the solid solubility of boron and hardness of 17Cr-7Ni precipitation-hardenable stainless steel. The hardness of the boron-modified rapidly solidified alloys has been found to increase up to ~280 pct after isochronal aging to peak hardness. A TEM study has been carried out to understand the aging behavior. The presence of M23(B,C)6 and M2(B,C) borocarbides and epsilon-carbide in the matrix of austenite and ferrite with a change in heat treatment temperature has been observed. A new equation for Creq is also developed which includes the boron factor on ferrite phase stability. The study also emphasizes that aluminum only takes part in ferrite phase stabilization and remains in the solution.

  19. Tribological effects of yttrium and nitrogen ion implantation on a precipitation hardening stainless steel

    International Nuclear Information System (INIS)

    Alonso, F.; Arizaga, A.; Garcia, A.; Onate, J.I.

    1994-01-01

    Yttrium, nitrogen and combined yttrium and nitrogen implantations have been carried out on an ASTM A286 precipitation hardening iron base alloy to evaluate the benefits in their tribological behaviour. Microindentation tests have shown a significant 20%-60% increment in hardness on the nitrogen implanted material, with a limited improvement in elastic recovery of the indentation. An abrasive test on the same material has also produced a 50% reduction in scratch depth. Y + and Y + +N + implantations also hardened the material but to a lesser extent. Reciprocating ball on disk friction and wear testing at 400 C resulted in very severe damage in all cases. X-ray photoelectron spectroscopy analyses combined with Ar sputtering have disclosed that nitrogen is mainly in a nitrided form, yttrium remains oxidized at the surface, below which there is an apparent increase in the metallic bond. ((orig.))

  20. The sub-zero Celsius treatment of precipitation hardenable semi-austenitic stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Somers, Marcel A. J.

    2015-01-01

    A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite-to-martensite...... treatment. Magnetometry showed that the additional thermal step in boiling nitrogen yields a minor increment of the fraction of martensite, but has a noteworthy accelerating effect on the transformation kinetics, which more pronounced when the isothermal holding is performed at a higher temperature. Data...... is interpreted in terms of instantaneous nucleation of martensite during cooling followed by time dependent growth during isothermal holding....

  1. Precipitation hardening of Zn0.1 at.%Ti single crystals deformed on the (0 0 0 1) system

    International Nuclear Information System (INIS)

    Boczkal, G.; Mikulowski, B.

    2004-01-01

    The mechanical properties (the critical resolved shear stress - CRSS, the work-hardening coefficient - θ A ) and a thermodynamic parameter (the activation volume--V*) have been studied in single crystals of Zn0.1 at.%Ti. The sample orientation allowed slip on the (0 0 0 1) system over a large range of strain. The investigations were conducted on samples which were both heat treated and not. The investigations were made using compression and stress relaxation tests in the range of easy glide at temperatures from 77 to 493 K. The single crystals appear to be hardened by precipitates while Ti solubility in Zn is negligible. Two types of the precipitates have been identified by TEM and microanalysis; very small precipitates were located uniformly in the matrix, and large needle-shaped obstacles with size of the order of 0.1 mm on the (0 0 0 1) orientation. The CRSS and the θ A showed a strong dependence on the temperature. The determined values of the CRSS were in the range of 4 MPa for 493 K to 12 MPa for 77 K. The obtained values of the activation volume V* were in the range of (10-110) x 10 -16 cm 3 and it was strongly dependent on the temperature and the stress at the beginning of relaxation. This value is attributed to small precipitates which are barriers for dislocation movement

  2. Precipitation hardening of cast Zr-containing A356 aluminium alloy

    International Nuclear Information System (INIS)

    Baradarani, B.; Raiszadeh, R.

    2011-01-01

    The effect of small additions of zirconium on the hardness, grain size, precipitate type and size of cast A356 aluminium alloy was investigated. The cast alloys were solution treated and then artificially aged for different periods of time. Hardness tests and scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) studies were carried out on the as-cast, as-solutionised and age-hardened specimens. Incoherent, coarse Al 3 Zr particles formed in the microstructure during the solidification of the alloy and caused grain refinement in the as-cast structure. These particles dissolved and reprecipitated as smaller-size particles during the solution treatment, causing the hardness of the alloy to remain constant at high temperatures for long periods of time due to the slow diffusion of Zr in the α-Al.

  3. Precipitation of β′ phase and hardening in dental-casting Ag–20Pd–12Au–14.5Cu alloys subjected to aging treatments

    International Nuclear Information System (INIS)

    Kim, Yonghwan; Niinomi, Mitsuo; Hieda, Junko; Nakai, Masaaki; Cho, Ken; Fukui, Hisao

    2014-01-01

    The age-hardening behavior of the dental-casting Ag–20Pd–12Au–14.5Cu alloy subjected to aging treatment at around 673 K is well known, and this hardening has been widely employed in various applications. To date, the age-hardening of this alloy has been explained to attribute to the precipitation of a β phase, which is a B2-type ordered CuPd phase or PdCu x Zn 1−x phase. In this study, results obtained from microstructural observations using a transmission electron microscopy and a scanning transmission electron microscopy revealed that a fine L1 0 -type ordered β′ phase precipitated in the matrix and a coarse-structure region (consisting of Ag- and Cu-rich regions) appeared after aging treatment at 673 K and contributed to increase in hardness. The microstructure of the coarse β phase, which existed before aging treatment, did not change by aging treatment. Thus, it is concluded that the fine β′ phase precipitated by aging treatment contributed more to increase in hardness than the coarse-structure region and coarse β phase. - Highlights: • Hardness of Ag–20Pd–12Au–14.5Cu alloy increased significantly by aging treatment. • A fine β′ phase and a coarse structure region appeared after aging treatment. • The microstructure of a coarse β phase did not change by aging treatment. • It is considered that the fine β′ phase contributed most to age-hardening

  4. High-temperature plastic flow of a precipitation-hardened FeCoNiCr high entropy alloy

    Energy Technology Data Exchange (ETDEWEB)

    He, J.Y.; Wang, H.; Wu, Y.; Liu, X.J. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Nieh, T.G. [Department of Materials Science and Engineering, the University of Tennessee, Knoxville, TN 37996 (United States); Lu, Z.P., E-mail: luzhaoping@163.com [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-02-16

    In this work, we systematically investigated flow behavior of a high entropy alloy (HEA) strengthened by coherent γ′ precipitates in the temperature range of 1023–1173 K. In contrast to the single-phase FeCoNiCrMn HEA, this precipitate-hardened alloy, i.e., (FeCoNiCr){sub 94}Ti{sub 2}Al{sub 4}, exhibited large reduction of the steady-state strain rate (by ~2 orders of magnitude) or drastic enhancement in flow stress, indicating significant improvement in high-temperature properties. Our results showed that the deformation could be divided into two regimes. At temperatures below 1123 K, coherent γ′ precipitates effectively blocked the dislocation motion, thus resulted in a threshold stress effect. Above 1123 K, however, γ′ particles dissolved and the deformation was controlled by the ordinary dislocation climb mechanism. In addition, we conducted transmission electron microscopy to characterize dislocation-precipitate interaction to provide microstructural evidences to support our conclusion of the specific deformation mechanisms in the two temperature regimes.

  5. Microstructural evolution in 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened stainless steel

    International Nuclear Information System (INIS)

    Ping, D.H.; Ohnuma, M.; Hirakawa, Y.; Kadoya, Y.; Hono, K.

    2005-01-01

    The microstructure of 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened (PH) stainless steel has been investigated using transmission electron microscopy, three-dimensional atom probe and small-angle X-ray scattering. A high number density (∼10 23-25 m -3 ) of ultra-fine (1-6 nm) β-NiAl precipitates are formed during aging at 450-620 deg. C, which are spherical in shape and dispersed uniformly with perfect coherency with the matrix. As the annealing temperature increases, the size and concentration of the precipitates increase concurrently while the number density decreases. The Mo and Cr segregation to the precipitate-matrix interface has been detected and is suggested to suppress precipitate coarsening. In the sample aged for 500 h at 450 deg. C, the matrix decomposes into Cr-rich (α') and Cr-poor (α) regions. The decrease in the strength at higher temperature (above 550 deg. C) is attributed to the formation of larger carbides and reverted austenite

  6. The secondary hardening phenomenon in strain-hardened MP35N alloy

    International Nuclear Information System (INIS)

    Asgari, S.; El-Danaf, E.; Shaji, E.; Kalidindi, S.R.; Doherty, R.D.

    1998-01-01

    Mechanical testing and microscopy techniques were used to investigate the influence of aging on the structure and strengthening of MP35N alloy. It was confirmed that aging the deformed material at 600 C for 4 h provided additional strengthening, here referred to as secondary hardening, in addition to the primary strain hardening. The secondary hardening phenomenon was shown to be distinctly different from typical age hardening processes in that it only occurred in material deformed beyond a certain cold work level. At moderate strains, aging caused a shift in the entire stress-strain curve of the annealed material to higher stresses while at high strains, it produced shear localization and limited work softening. The secondary hardening increment was also found to be grain size dependent. The magnitude of the secondary hardening appeared to be controlled by the flow stress in the strain hardened material. A model is proposed to explain the observations and is supported by direct experimental evidence. The model is based on formation of h.c.p. nuclei through the Suzuki mechanism, that is segregation of solute atoms to stacking faults, on aging the strain hardened material. The h.c.p. precipitates appear to thicken only in the presence of high dislocation density produced by prior cold work

  7. Mechanical Characteristic of Remanufacturing of FV520B Precipitation Hardening Stainless Steel Using MAG Surfacing Deposition

    Directory of Open Access Journals (Sweden)

    LIU Jian

    2017-10-01

    Full Text Available Surfacing deposition forming method was adopted to carry out remanufacturing experiment of FV520B precipitation hardening stainless steel. Then the mechanical property characteristic of the remanufacturing layer was tested and studied, contrasted with the corresponding property of substrate. The results show that the remanufacturing layer, formed with MAG surfacing of FV520B precipitation hardening stainless steel has mechanical characteristic with high strength and hardness, the tensile strength reaches 1195MPa, exceeds 1092MPa of substrate, yield strength is 776MPa and average hardness is 336HV, is close to the corresponding property of substrate which is 859MPa and 353HV respectively; however, the elongation and impact toughness of the remanufacturing layer is merely 8.92% and 61J/cm2 respectively, it has a large gap with the corresponding property 19.72% and 144J/cm2 respectively of substrate. Fracture and microstructure analysis on specimens shows that the microstructure of remanufacturing layer is fast cooling non-equilibrium crystallized lath martensite, and carbide precipitated strengthening phase such as NbC, MoC, M23C6,etc, which is the reason that remanufacturing layer has high strength and high hardness. But as lack of aging treatment and Cu strengthening phase, and the weak interface between contaminating brittle phase or large size spherical particles and substrate will deteriorate the deformability and induce stress concentration and cracking when the material is load-carrying, and is the main reason of the remanufacturing layer having lower static tensile elongation and impact toughness.

  8. Computer modelling of age hardening for cast aluminium alloys

    International Nuclear Information System (INIS)

    Wu, Linda; Ferguson, W George

    2009-01-01

    Age hardening, or precipitation hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. Although various age hardening models have been developed for aluminium alloys, from the large volume of literature reviewed, it appears that the bulk of the research has been concentrated on wrought aluminium alloys, only a few of the established precipitation models have been applied to the casting aluminium alloys. In the present work, there are two modelling methods that have been developed and applied to the casting aluminium alloys A356 and A357. One is based on the Shercliff-Ashby methodology to produce a process model, by which we mean a mathematical relationship between process variables (alloy composition, ageing temperature and time) and material properties (yield strength or hardness) through microstructure evolution (precipitate radius, volume fraction). The other method is based on the Kampmann and Wagner Numerical (KWN) model which deals with concomitant nucleation, growth and coarsening and is thus capable of predicting the full evolution of the particle size distribution and then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening.

  9. Thermal Management in Friction-Stir Welding of Precipitation-Hardening Aluminum Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Piyush; Reynolds, Anthony

    2015-05-25

    Process design and implementation in FSW is mostly dependent on empirical information gathered through experience. Basic science of friction stir welding and processing can only be complete when fundamental interrelationships between process control parameters and response variables and resulting weld microstructure and properties are established to a reasonable extent. It is known that primary process control parameters like tool rotation and translation rate and forge axis force have complicated and interactive relationships to the process response variables such as peak temperature, time at temperature etc. Of primary influence to the other process response parameters are temperature and its gradient at the deformation and heat affected zones. Through review of pertinent works in the literature and some experimental results from boundary condition work performed in precipitation hardening aluminum alloys this paper will partially elucidate the nature and effects of temperature transients caused by variation of thermal boundaries in Friction Stir Welding.

  10. Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1980-01-01

    The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.

  11. Precipitation hardened nickel-base alloys for sour gas environments

    International Nuclear Information System (INIS)

    Igarashi, M.; Mukai, S.; Kudo, T.; Okada, Y.; Ikeda, A.

    1987-01-01

    SCC (Stress Corrosion Cracking) in sour gas environments of γ'(gamma prime: Ni/sub 3/(Ti and/or Al)) and γ''(gamma double prime: Ni/sub 3/Nb) precipitation hardened nickel-base alloys has been studied using the SSRT (Slow Strain Rate Tensile) test, anodic polarization measurement and transmission electron microscopy (TEM). The γ'-type alloy containing Ti was more susceptible to SCC in the SSRT tests up to 350 0 F(450 K) than the γ''-type alloy containing Nb. The susceptibility to SCC was related to their deformation structures in terms of stress localization and sensitivity to pitting corrosion in H/sub 2/S solutions. TEM observation showed the γ'-type alloy deformed by the superlattice dislocations in coplanar structures. This mode of deformation induced the stress localization to some boundaries such as grain boundary and as a result the susceptibility to SCC of the γ'-type alloy was increased. On the other hand, the γ''-type alloy deformed by the massive dislocation not in coplanar structures so that it was less susceptible to SCC in terms of the stress localization. The anodic polarization measurement suggested the γ'-type alloy was more susceptible to pitting corrosion compared with the γ''-type alloy

  12. Microstructural effects on the yield strength and its temperature dependence in a bainitic precipitation hardened Cr-Mo-V steel

    International Nuclear Information System (INIS)

    Toerroenen, K.; Kotilainen, H.; Nenonen, P.

    1980-03-01

    The plastic deformation behaviour of a precipitation hardened bainitic Cr-Mo-V steel is analyzed at ambient and low temperatures. The temperature dependent component of the yield strength is composed of the Peierls-Nabarro force and also partly of the strengthening contribution of the lath- and cell boundaries or the solid solution hardening. The temperature dependence below 230 K is in accordance with the models presented by Yanoshevich and Ryvkina as well as Dorn and Rajnak. The temperature independent component can be calculated merely from the dislocation density, which is stabilized by the vanadium-rich carbides. The linear additivity cannot be used for the superposition of the strengthening effects of various strengthening parameters, By using the phenomenological approach starting from the dislocation movement mechanisms upon yielding the laws for the superposition are discussed. (author)

  13. Accelerated age hardening by plastic deformation in Al-Cu with minor additions of Si and Ge

    International Nuclear Information System (INIS)

    Victoria Castro Riglos, M.; Taquire de la Cruz, M.; Tolley, Alfredo

    2011-01-01

    An extremely fast hardening response with no reduction in peak hardness was obtained in Al-Cu with minor additions of Si and Ge by 8% plastic deformation before artificial aging. The mechanism for the accelerated hardening was determined by detailed characterization with transmission electron microscopy. Plastic deformation was found to enhance the nucleation rate of Si-Ge precipitates, resulting in a higher volume density. Such precipitates catalyzed the formation of θ' precipitates that are responsible for hardening.

  14. EVALUATION OF PRECIPITATION HARDENING HEAT TREATMENT OF PH 17-7 STAINLESS STEEL SPRING

    Directory of Open Access Journals (Sweden)

    A. A. Babakoohi Ashrafi

    2016-06-01

    Full Text Available In this paper, the influence of heat treatment on PH17-7 stainless steel spring was evaluated. Precipitation hardening phenomenon of  PH 17-7 steel was evaluated in three stages. First, the spring constant changes with time and temperature was evaluated. Second, the spring constant changes with respect to its original length at constant temperature and time with blocking (spring length after compression, 18 and 21 mm were investigated.  And finally, the spring heat treatment at 480 °C for 80 min and then holding at 230 °C in oil bath for 60 min without blocking were investigated. The results showed that the use of 18 mm block have large spring constant than 21 mm block. The optimal conditions (480°C for 80 min for this spring to reaching maximum spring constant were determined.

  15. Radiation-hardened bulk CMOS technology

    International Nuclear Information System (INIS)

    Dawes, W.R. Jr.; Habing, D.H.

    1979-01-01

    The evolutionary development of a radiation-hardened bulk CMOS technology is reviewed. The metal gate hardened CMOS status is summarized, including both radiation and reliability data. The development of a radiation-hardened bulk silicon gate process which was successfully implemented to a commercial microprocessor family and applied to a new, radiation-hardened, LSI standard cell family is also discussed. The cell family is reviewed and preliminary characterization data is presented. Finally, a brief comparison of the various radiation-hardened technologies with regard to performance, reliability, and availability is made

  16. Hardening Azure applications

    CERN Document Server

    Gaurav, Suraj

    2015-01-01

    Learn what it takes to build large scale, mission critical applications -hardened applications- on the Azure cloud platform. This 208 page book covers the techniques and engineering principles that every architect and developer needs to know to harden their Azure/.NET applications to ensure maximum reliability and high availability when deployed at scale. While the techniques are implemented in .NET and optimized for Azure, the principles here will also be valuable for users of other cloud-based development platforms. Applications come in a variety of forms, from simple apps that can be bui

  17. On the grain boundary hardening in a B-bearing 304 austenitic stainless steel

    International Nuclear Information System (INIS)

    Yao, X.X.

    1999-01-01

    The precipitates, (Cr,Fe) 23 (C,B) 6 carbides and (Cr,Fe) 2 B borides, formed along the grain boundaries in a 304 austenitic stainless steel containing boron of 33 ppm after solution treatment at 1100 C for 1 h followed by isothermal ageing for 0.5 h at temperatures ranging from 750 to 1050 C have been identified. The influence of these precipitates on the grain boundary hardening has been investigated by means of micro-Vickers hardness measurements. It is found that the degree of grain boundary hardening below 900 C decreases, while it increases above 900 C with increasing ageing temperature. The dissolution of (Cr,Fe) 23 (C,B) 6 carbides and the precipitation of (Cr,Fe) 2 B borides are associated with the changes of grain boundary hardening in this B-bearing 304 austenitic stainless steel between 750 and 1100 C. The non-equilibrium boron segregation enhances the grain boundary hardening when the ageing temperature is above 900 C. (orig.)

  18. The effect of Ca and RE elements on the precipitation kinetics of Mg17Al12 phase during artificial aging of magnesium alloy AZ91

    International Nuclear Information System (INIS)

    Amir Esgandari, B.; Mehrjoo, H.; Nami, B.; Miresmaeili, S.M.

    2011-01-01

    Highlights: → Ca and RE elements decrease the precipitation rate during aging of AZ91 alloy. → Precipitation kinetics and mechanism during aging of the alloys were studied. → Effect of Ca and RE on creep properties of age hardened AZ91 alloy was studied. - Abstract: The effect of simultaneous alloying with Ca and rare earth (RE) elements on the age hardening kinetics of AZ91 was studied through the fitting of the Johnson-Mehl-Avrami (JMA) equation. The results showed that the addition of both Ca and RE elements not only suppress discontinuous precipitation of the Mg 17 Al 12 phase during the age hardening process, but also decrease the alloy hardness. Fitting the JMA equation to the experimental data indicated that the phase transformation during age hardening of an alloy variant containing both Ca and RE (at 170 deg. C and 190 deg. C) and standard AZ91 (at 170 deg. C) takes place by the nucleation of precipitates on dislocations. In contrast, the precipitation during age hardening of AZ91 at 190 deg. C occurs via nucleation at grain boundaries. Although it was observed that the creep strength of age hardened specimens are lower than that of the as cast specimens, but age hardening treatment has lower deleterious influence on the creep resistance of the alloy containing Ca and RE in comparison with conventional AZ91. This may be ascribed to the decreased precipitation rate resulting from the addition of both Ca and RE elements.

  19. SEU testing of a novel hardened register implemented using standard CMOS technology

    International Nuclear Information System (INIS)

    Monnier, T.; Roche, F.M.; Cosculluela, J.; Velazco, R.

    1999-01-01

    A novel memory structure, designed to tolerate SEU perturbations, has been implemented in registers and tested. The design was completed using a standard submicron nonradiation hardened CMOS technology. This paper presents the results of heavy ions tests which evidence the noticeable improvement of the SEU-robustness with an increased LET threshold and reduced cross-section, without significant impact to die real estate, write time, or power consumption

  20. Study of radiation hardening in reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Nogiwa, Kimihiro; Nishimura, Akihiko

    2008-01-01

    In order to investigate the dependence of hardening on copper precipitate diameter and density, in-situ transmission electron microscopy (TEM) observations during tensile tests of dislocation gliding through copper rich-precipitates in thermally aged and neutron irradiated Fe-Cu alloys were performed. The obstacle strength has been estimated from the critical bow-out angle, φ, of dislocations. The obstacle distance on the dislocation line measured from in-situ TEM observations were compared with number density and diameter measured by 3D-AP (three dimensional atom probe) and TEM observation. A comparison is made between hardening estimation based on the critical bowing angles and those obtained from conventional tensile tests. (author)

  1. Formulating the strength factor α for improved predictability of radiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Tan, L., E-mail: tanl@ornl.gov; Busby, J.T.

    2015-10-15

    Analytical equations were developed to calculate the strength factors of precipitates, Frank loops, and cavities in austenitic alloys, which strongly depend on barrier type, size, geometry and density, as well as temperature. Calculated strength factors were successfully used to estimate radiation hardening using the broadly employed dispersed barrier-hardening model, leading to good agreement with experimentally measured hardening in neutron-irradiated type 304 and 316 stainless steel variants. The formulated strength factor provides a route for more reliable hardening predictions and can be easily incorporated into component simulations and design.

  2. Precipitation washout (a bibliography with abstracts). Period covered: 1964--June 1975

    International Nuclear Information System (INIS)

    Lehmann, E.J.

    1975-06-01

    The reports cited in this bibliography cover the removal of pollutants, radioactive isotopes, and dust by rain and snow. The theory, modeling, sampling, and effects of precipitation washout are presented. (auth)

  3. Effect of Y addition on the aging hardening behavior and precipitation evolution of extruded Mg-Al-Zn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ren, L.B. [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Chengdu, Sichuan 610031 (China); School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Quan, G.F., E-mail: quangf@home.swjtu.edu.cn [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Chengdu, Sichuan 610031 (China); School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhou, M.Y.; Guo, Y.Y.; Jiang, Z.Z.; Tang, Q. [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Chengdu, Sichuan 610031 (China); School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

    2017-04-06

    Abstract:: The 443 K aging hardening behavior and microstructure evolution of extruded Mg-Al-Zn-Y alloys was investigated in aspects of yttrium (Y) content (0.2–0.8 wt%), holding time (0.5–156 h) and the initial states (as-extruded, solution treated). The grain size, precipitation evolution, phases and chemical composition were characterized by the optical microscope, scanning electron microscope, X-ray diffraction, and energy dispersive spectrometer, respectively. The corresponding mechanical response, including the hardness, uniaxial tensile strength were measured with the Vickers hardness tester and universal testing machine, respectively. The results show that, firstly, there is reversal hardness anisotropy between extrusion direction and normal direction in as-extruded Mg-Al-Zn-Y sheets compared with T5 treated ones. Secondly, the short-term aging softening exist at the beginning of T5 treatment which results in a lower hardness even be close to that of solution treated ones, but not for T6 conditions. Thirdly, the suppression of discontinuous precipitation during the aging treatment become more remarkable with increasing Y addition which because of the reduction of diffusional coherency strain near grain boundary, increasing activation energy for the discontinuous precipitates (β-Mg{sub 17}Al{sub 12} phase, DPs) formation and the dilution region of Al near the Al{sub 2}Y. Serrated GBs can also provide more nucleation sites for DPs and lead to relatively more precipitates during T5 treatment. Moreover, the proportional precipitation strengthening in yield strength and hardness was verified in Mg-Al-Zn-Y alloy during the aging process.

  4. A Prognostic Methodology for Precipitation Phase Detection using GPM Microwave Observations —With Focus on Snow Cover

    Science.gov (United States)

    Takbiri, Z.; Ebtehaj, A.; Foufoula-Georgiou, E.; Kirstetter, P.

    2017-12-01

    Improving satellite retrieval of precipitation requires increased understanding of its passive microwave signature over different land surfaces. Passive microwave signals over snow-covered surfaces are notoriously difficult to interpret because they record both emission from the land below and absorption/scattering from the liquid/ice crystals. Using data from the Global Precipitation Measurement (GPM) core satellite, we demonstrate that the microwave brightness temperatures of rain and snowfall shifts from a scattering to an emission regime from summer to winter, due to expansion of the less emissive snow cover underneath. We present evidence that the combination of low- (10-19 GHz) and high-frequency (89-166 GHz) channels provides the maximum amount of information for snowfall detection. The study also examines a prognostic nearest neighbor matching method for the detection of precipitation and its phase from passive microwave observations using GPM data. The nearest neighbor uses the weighted Euclidean distance metric to search through an a priori database that is populated with coincident GPM radiometer and radar data as well as ancillary snow cover fraction. The results demonstrate prognostic capabilities of the proposed method in detection of terrestrial snowfall. At the global scale, the average probability of hit and false alarm reaches to 0.80 and remains below 0.10, respectively. Surprisingly, the results show that the snow cover may help to better detect precipitation as the detection rate of terrestrial precipitation is increased from 0.75 (no snow cover) to 0.84 (snow-covered surfaces). For solid precipitation, this increased rate of detection is larger than its liquid counterpart by almost 8%. The main reasons are found to be related to the multi-frequency capabilities of the nearest neighbor matching that can properly isolate the atmospheric signal from the background emission and the fact that the precipitation can exhibit an emission-like (warmer

  5. Performance of Evapotranspirative Covers Under Enhanced Precipitation: Preliminary Data

    International Nuclear Information System (INIS)

    David C. Anderson; Lloyd T. Desotell; David B. Hudson; Gregory J. Shott; Vefa Yucel

    2007-01-01

    Since January 2001, drainage lysimeter studies have been conducted at Yucca Flat, on the Nevada Test Site, in support of an evapotranspirative cover design. Yucca Flat has an arid climate with average precipitation of 16.5 cm annually. The facility consists of six drainage lysimeters 3 m in diameter, 2.4 m deep, and backfilled with a single layer of native soil. The bottom of each lysimeter is sealed and equipped with a small drain that enables direct measurement of saturated drainage. Each lysimeter has eight time-domain reflectometer probes to measure moisture content-depth profiles paired with eight heat-dissipation probes to measure soil-water potential depth profiles. Sensors are connected to dataloggers which are remotely accessed via a phone line. The six lysimeters have three different surface treatments: two are bare-soil; two were revegetated with native species (primarily shadscale, winterfat, ephedra, and Indian rice grass); and two were allowed to revegetate naturally with such species as Russian thistle, halogeton, tumblemustard and cheatgrass. Beginning in October 2003, one half of the paired cover treatments (one bare soil, one invader species, and one native species) were irrigated with an amount of water equal to two times the natural precipitation to achieve a three times natural precipitation treatment. From October 2003 through December 2005, all lysimeters received 52.8 cm precipitation, and the four irrigated lysimeters received an extra 105.6 cm of irrigation. No drainage has occurred from any of the nonirrigated lysimeters, but moisture has accumulated at the bottom of the bare-soil lysimeter and the native-plant lysimeter. All irrigated lysimeters had some drainage. The irrigated baresoil lysimeter had 48.3 cm of drainage or 26.4 percent of the combined precipitation and applied irrigation for the entire monitoring record. The irrigated invader species lysimeter had 5.8 cm of drainage, about 3.2 percent of the combined precipitation and

  6. Application of the Standardized Precipitation Index (SPI in Greece

    Directory of Open Access Journals (Sweden)

    Christos A. Karavitis

    2011-08-01

    Full Text Available The main premise of the current effort is that the use of a drought index, such as Standardized Precipitation Index (SPI, may lead to a more appropriate understanding of drought duration, magnitude and spatial extent in semi-arid areas like Greece. The importance of the Index may be marked in its simplicity and its ability to identify the beginning and end of a drought event. Thus, it may point towards drought contingency planning and through it to drought alert mechanisms. In this context, Greece, as it very often faces the hazardous impacts of droughts, presents an almost ideal case for the SPI application. The present approach examines the SPI drought index application for all of Greece and it is evaluated accordingly by historical precipitation data. Different time series of data from 46 precipitation stations, covering the period 1947–2004, and for time scales of 1, 3, 6, 12 and 24 months, were used. The computation of the index was achieved by the appropriate usage of a pertinent software tool. Then, spatial representation of the SPI values was carried out with geo-statistical methods using the SURFER 9 software package. The results underline the potential that the SPI usage exhibits in a drought alert and forecasting effort as part of a drought contingency planning posture.

  7. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Makoto, E-mail: makoto.fukuda@qse.tohoku.ac.jp [Tohoku University, Sendai, 980-8579 (Japan); Kiran Kumar, N.A.P.; Koyanagi, Takaaki; Garrison, Lauren M. [Oak Ridge National Laboratory, Oak Ridge, TN, 37831 (United States); Snead, Lance L. [Massachusetts Institute of Technology, Cambridge, MA, 02139 (United States); Katoh, Yutai [Oak Ridge National Laboratory, Oak Ridge, TN, 37831 (United States); Hasegawa, Akira [Tohoku University, Sendai, 980-8579 (Japan)

    2016-10-15

    Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten. - Highlights: • The microstructure and irradiation hardening of single crystal pure W irradiated in HFIR was investigated. • The neutron energy spectrum influence was evaluated by comparing the HFIR results with previous work in Joyo and JMTR. • In the dose range up to ∼1 dpa, the neutron energy spectrum influence of irradiation hardening was not clear. • In the dose range above 1 dpa, the neutron energy influence on irradiation hardening and microstructural development was clearly observed. • The irradiation induced precipitates caused significant irradiation hardening of pure W irradiated in HFIR.

  8. Hardening and stress relaxation during repeated heating of 15Kh2MFA and 15Kh2NMFA steels welded joints

    International Nuclear Information System (INIS)

    Zubchenko, A.S.; Suslova, E.A.

    1986-01-01

    Results of investigation of temperature-time conditions of hardening of welded joints of 15Kh2MFA and 15Kh2NMFA steels and their relaxation resistance, effect of metal structure of imitated heat affected zone (HAZ) on intensity of precipitation hardening at repeated heating are presented as well as the results of the process of relaxation of residual stresses at welded joints samples heating carried out by automatic welding under the flux with the use of adding materials and technology of manufacturing of vessels of WWER-440 and WWER-1000 reactors. Peculiarities of the hardening at repeated heating of the HAZ metal imitated at these steels. Precipitation hardening of overheated 15Kh2MFA steel is connected with precipitations at repeated heating of carbides of the M 7 C 3 , M 3 C and VC type. Stress relaxation in welded joints runs more intensively at the initial stage of repeated heating, i.e. during the same period of the process of dispersed carbide precipitations

  9. Microstructure and age-hardening effects of aluminium alloys with additions of scandium and zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Galun, R.; Mordike, B.L. [Inst. fuer Werkstoffkunde und Werkstofftechnik, Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany); Maiwald, T.; Smola, B. [Zentrum fuer Funktionswerkstoffe GmbH, Clausthal-Zellerfeld (Germany); Mergen, R.; Manner, M.; Uitz, W. [Miba Gleitlager GmbH, Laakirchen (Australia)

    2004-12-01

    The aim of the work presented in this report was to produce age-hardenable aluminium alloys containing scandium and zirconium by a casting process with similar cooling conditions like an industrial casting process. Microstructure, precipitation structure and age-hardening response of different alloys with up to 0.4 wt.% Sc and Zr were investigated. Age-hardening experiments from the as-cast condition without solution annealing showed a significant increase of hardness of about 100% for Sc-rich alloys and of 50% for Zr-rich alloys compared to the as-cast condition. TEM investigations revealed the formation of precipitates of ternary Al{sub 3}(Sc{sub x}Zr{sub 1-x}) phases with a cubic cP4 crystal structure. In addition to the strengthening effect, a high thermal stability especially of the precipitates in Zr-rich alloys up to 400 C let these alloys look very promising for high-temperature applications. (orig.)

  10. Concrete, hardened: Self desiccation

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

    1999-01-01

    The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

  11. X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

    Science.gov (United States)

    Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

    2018-05-01

    In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration ( Q a) and the activation energy of microstrain relaxation ( Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

  12. X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

    Science.gov (United States)

    Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

    2018-04-01

    In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration (Q a) and the activation energy of microstrain relaxation (Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

  13. On the correlation between irradiation-induced microstructural features and the hardening of reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Lambrecht, M.; Meslin, E.; Malerba, L.; Hernandez-Mayoral, M.; Bergner, F.; Pareige, P.; Radiguet, B.; Almazouzi, A.

    2010-01-01

    A correlation is attempted between microstructural observations by various complementary techniques, which have been implemented within the PERFECT project and the hardening measured by tensile tests of reactor pressure vessel steel and model alloys after irradiation to a dose of ∼7 x 10 19 n cm -2 . This is done, using the simple hardening model embodied by the Orowan equation and applying the most suitable superposition law, as suggested by a parametric study using the DUPAIR line tension code. It is found that loops are very strong obstacles to dislocation motion, but due to their low concentration, they only play a minor role in the hardening itself. For the precipitates, the contrary is found, although they are quite soft (due to their very small sizes and their coherent nature), they still play the dominant role in the hardening. Vacancy clusters are important for the formation of both loops and precipitates, but they will play almost no role in the hardening by themselves.

  14. Effects of Mo Content on Microstructure and Mechanical Property of PH13-8Mo Martensitic Precipitation-Hardened Stainless Steel

    Science.gov (United States)

    Yubing, Pei; Tianjian, Wang; Zhenhuan, Gao; Hua, Fan; Gongxian, Yang

    This paper introduces the effects of Mo content on microstructure and mechanical property of PH13-8Mo martensitic precipitation-hardened stainless steel which is used for LP last stage blade in steam turbine. Thermodynamic software Thermo-Calc has been used to calculate precipitation temperature and the mass fraction of precipitated phases in PH13-8Mo steel with different Mo content. The result shows that when the mass of Mo is below 0.6wt.%, chi-phase mu-phase and sigma-phase could disappear. The microstructure and mechanical property of high Mo PH13-8Mo (Mo=0.57wt.%) and low Mo PH13-8Mo (Mo=2.15wt.%)have been investigated in different heat treatments. The investigations reveal that austenitizing temperature decrease with the reduce of Mo content, so the optimum solution temperature for low Mo PH13-8Mo is lower than that for high Mo PH13-8Mo.The influence of solution temperature on grain size is weakened with the increase of Mo content, Mo rich carbides could retard coarsening of grain. An enormous amount of nano-size uniformly distributed β-NiAl particles are found in both kinds of steels using transmission electron microscopy, they are the most important strengthening phase in PH13-8Mo.

  15. Embrittlement of irradiated ferritic/martensitic steels in the absence of irradiation hardening

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States); Shiba, K. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States)

    2007-07-01

    Full text of publication follows: Neutron irradiation of 9-12% Cr ferritic/martensitic steels below 425-450 deg. C produces microstructural defects that cause an increase in yield stress and ultimate tensile strength. This irradiation hardening causes embrittlement, which is observed in Charpy impact and toughness tests as an increase in ductile-brittle transition temperature (DBTT). Based on observations that show little change in strength in these steels irradiated above 425-450 deg. C, the general conclusion has been that no embrittlement occurs above this irradiation-hardening temperature regime. In a recent study of F82H steel irradiated at 300, 380, and 500 deg. C, irradiation hardening-an increase in yield stress-was observed in tensile specimens irradiated at the two lower temperatures, but no change was observed for the specimens irradiated at 500 deg. C. As expected, an increase in DBTT occurred for the Charpy specimens irradiated at 300 and 380 deg. C. However, there was an unexpected increase in the DBTT of the specimens irradiated at 500 deg. C. The observed embrittlement was attributed to the irradiation-accelerated precipitation of Laves phase. This conclusion was based on results from a detailed thermal aging study of F82H, in which tensile and Charpy specimens were aged at 500, 550, 600, and 650 deg. C to 30,000 h. These studies indicated that there was a decrease in yield stress at the two highest temperatures and essentially no change at the two lowest temperatures. Despite the strength decrease or no change, the DBTT increased for Charpy specimens irradiated at all four temperatures. Precipitates were extracted from thermally aged specimens, and the amount of precipitate was correlated with the increase in transition temperature. Laves phase was identified in the extracted precipitates by X-ray diffraction. Earlier studies on conventional elevated-temperature steels also showed embrittlement effects above the irradiation-hardening temperature

  16. Hardened Solar Array High Temperature Adhesive.

    Science.gov (United States)

    1981-04-01

    SHERWOOO. D SASIU.IS F3361S-0-C-201S UNCLASSI ED 1AC-SCG-IOOIIR AFVAL-TR-OL-201? NLm,,hinii EhhhEE11I1 AFWAL-TR-81- 2017 i : HARDENED SOLAR ARRAY D HIGH...Tg and as a consequence forms a film on the container and also precipitates as tacky waxlike particles, rather than the desired flocullated

  17. Effect of land cover, stream discharge, and precipitation on water quality in Puerto Rico

    Science.gov (United States)

    Hall, J. S.; Uriarte, M.

    2017-12-01

    In 2015, Puerto Rico experienced one of the worst droughts in its history, causing widespread water rationing and sparking concerns for future resources. The drought represents precipitation extremes that provide valuable insight into the effects of land cover (LC), on modulating discharge and water quality indices at varying spatial scales. We used data collected from 38 water quality and 55 precipitation monitoring stations in Puerto Rico from 2005 to 2016, paired with a 2010 land cover map to (1) determine whether temporal variability in discharge, precipitation, or antecedent precipitation was a better predictor of water quality, (2) find the spatial scale where LC has the greatest impact on water quality, and (3) quantify impacts of LC on water quality indices, including dissolved oxygen (mg/L), total nitrogen (mg/L), phosphorous (mg/L), turbidity (NTRU), fecal coliforms (colony units/100mL) and instantaneous discharge (ft3/s). The resulting linear mixed effects models account for between 36-68% of the variance in water quality. Preliminary results indicate that phosphorous and nitrogen were best predicted from instantaneous stream discharge, the log of discharge was the better predictor for turbidity and fecal coliforms, and summed 2 and 14-day antecedent precipitation indices were better predictors for dissolved oxygen and discharge, respectively. Increased urban and pasture area reliably decreased water quality in relation to forest cover, while agriculture and wetlands had little or mixed effects. Turbidity and nitrogen responded to a watershed level LC, while phosphorous, fecal coliforms, and discharge responded to LC in 60 m riparian buffers at the watershed scale. Our results indicate that LC modulates changing precipitation regimes and the ensuing impacts on water quality at a range of spatial scales.

  18. Hardening mechanism of an Ag-Pd-Cu-Au dental casting alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Kim, Gi-Chul; Son, Kuk-Hyeon; Kwon, Yong Hoon; Kim, Hyung-Il

    2005-01-01

    Age-hardening behaviour and the related microstructural changes were studied to elucidate the hardening mechanism of an Ag-Pd-Cu-Au dental casting alloy by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). By considering hardness test and XRD results together, it was revealed that the hardness increased during the early stage of phase transformation of α into α 1 . In the SEM photographs, two phases of matrix and particle-like structures were observed, and the precipitation of element from the matrix progressed during isothermal aging. By SEM observations and EPMA analysis, it could be supposed that the increase in hardness was caused by the diffusion and aggregation of Cu atoms from the Ag-rich α matrix containing Au and Cu in the early stage of age-hardening process, and that the decrease in hardness was caused by the progress of coarsening of Cu-rich lamellar precipitates in the later stage of the age-hardening process. The changes in the Ag-rich matrix caused both the increase and decrease in hardness, and the CuPd phase containing small amounts of Zn and Sn did not contribute to the hardness changes

  19. The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset

    Science.gov (United States)

    Huffman, George J.; Adler, Robert F.; Arkin, Philip; Chang, Alfred; Ferraro, Ralph; Gruber, Arnold; Janowiak, John; McNab, Alan; Rudolf, Bruno; Schneider, Udo

    1997-01-01

    The Global Precipitation Climatology Project (GPCP) has released the GPCP Version 1 Combined Precipitation Data Set, a global, monthly precipitation dataset covering the period July 1987 through December 1995. The primary product in the dataset is a merged analysis incorporating precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit -satellite infrared data, and rain gauge observations. The dataset also contains the individual input fields, a combination of the microwave and infrared satellite estimates, and error estimates for each field. The data are provided on 2.5 deg x 2.5 deg latitude-longitude global grids. Preliminary analyses show general agreement with prior studies of global precipitation and extends prior studies of El Nino-Southern Oscillation precipitation patterns. At the regional scale there are systematic differences with standard climatologies.

  20. Model Fitting for Predicted Precipitation in Darwin: Some Issues with Model Choice

    Science.gov (United States)

    Farmer, Jim

    2010-01-01

    In Volume 23(2) of the "Australian Senior Mathematics Journal," Boncek and Harden present an exercise in fitting a Markov chain model to rainfall data for Darwin Airport (Boncek & Harden, 2009). Days are subdivided into those with precipitation and precipitation-free days. The author abbreviates these labels to wet days and dry days.…

  1. Effect of aging hardening on in situ synthesis magnesium matrix composites

    International Nuclear Information System (INIS)

    Zhang Xiuqing; Liao Lihua; Ma Naiheng; Wang Haowei

    2006-01-01

    Magnesium matrix composites reinforced with TiC particulates was synthesized using in situ synthesis technique. The result of XRD revealed the presence of TiC in precursor blocks and TiC/AZ91 composites. Effect of aging hardening on the composites was described using Brinell hardness measurements and scanning electron microscopy (SEM). The results revealed that the aging hardening peak of TiC/AZ91 composite appeared earlier comparatively with that of AZ91 magnesium alloy. And the appearance of aging hardening peak was earlier under the higher aging temperature such as 200 deg. C. The precipitating behavior of Mg 17 Al 12 phase in AZ91 alloy and TiC/AZ91 composites was described. Little discontinuous was discovered in the composites, and the amount of continuous precipitate in the composite matrix is smaller comparatively to that of AZ91 alloy. These results were analyzed with the fine grain size, much more interface between TiC and magnesium and high-density dislocation in magnesium matrix, which was contributed to the addition of TiC particulates

  2. Age hardening of a sintered Al-Cu-Mg-Si-(Sn) alloy

    International Nuclear Information System (INIS)

    Kent, D.; Schaffer, G.B.; Drennan, J.

    2005-01-01

    The age hardening response of a sintered Al-3.8 wt% Cu-1.0 wt% Mg-0.70 wt% Si alloy with and without 0.1 wt% Sn was investigated. The sequence of precipitation was characterised using transmission electron microscopy. The ageing response of the sintered Al-Cu-Mg-Si-(Sn) alloy is similar to that of cognate wrought 2xxx series alloys. Peak hardness was associated with a fine, uniform dispersion of lath shaped precipitates, believed to be either the β'or Q' phase, oriented along α directions and θ' plates lying on {0 0 1} α planes. Natural ageing also resulted in comparable behaviour to that observed in wrought alloys. Porosity in the powder metallurgy alloys did not significantly affect the kinetics of precipitation during artificial ageing. Trace levels of tin, used to aid sintering, slightly reduced the hardening response of the alloy. However, this was compensated for by significant improvements in density and hardness

  3. Comparative Study of Hardening Mechanisms During Aging of a 304 Stainless Steel Containing α'-Martensite

    Science.gov (United States)

    Jeong, S. W.; Kang, U. G.; Choi, J. Y.; Nam, W. J.

    2012-09-01

    Strain aging and hardening behaviors of a 304 stainless steel containing deformation-induced martensite were investigated by examining mechanical properties and microstructural evolution for different aging temperature and time. Introduced age hardening mechanisms of a cold rolled 304 stainless steel were the additional formation of α'-martensite, hardening of α'-martensite, and hardening of deformed austenite. The increased amount of α'-martensite at an aging temperature of 450 °C confirmed the additional formation of α'-martensite as a hardening mechanism in a cold rolled 304 stainless steel. Additionally, the increased hardness in both α'-martensite and austenite phases with aging temperature proved that hardening of both α'-martensite and austenite phases would be effective as hardening mechanisms in cold rolled and aged 304 stainless steels. The results suggested that among hardening mechanisms, hardening of an α'-martensite phase, including the diffusion of interstitial solute carbon atoms to dislocations and the precipitation of fine carbide particles would become a major hardening mechanism during aging of cold rolled 304 stainless steels.

  4. Precipitation under cyclic strain in solution-treated Al4wt%Cu I: mechanical behavior

    Energy Technology Data Exchange (ETDEWEB)

    Farrow, Adam M [Los Alamos National Laboratory; Laird, Campbell [UNIV OF PENNSYLVANIA

    2008-01-01

    Solution-treated AL-4wt%Cu was strain-cycled at ambient temperature and above, and the precipitation and deformation behaviors investigated by TEM. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy super-saturation generated by cyclic strain and the presence of a continually refreshed dislocation density to provide heterogeneous nucleation sites. Texture effects as characterized by Orientation Imaging Microscopy appear to be responsible for latent hardening in specimens tested at room temperature, with increasing temperatures leading to a gradual hardening throughout life due to precipitation. Specimens exhibiting rapid precipitation hardening appear to show a greater effect of texture due to the increased stress required to cut precipitates in specimens machined from rolled plate at an angle corresponding to a lower average Schmid factor. The accelerated formation of grain boundary precipitates appears to be partially responsible for rapid inter-granular fatigue failure at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

  5. Isotope composition of winter precipitation and snow cover in the foothills of the Altai

    Directory of Open Access Journals (Sweden)

    N. S. Malygina

    2017-01-01

    Full Text Available Over the past three decades, several general circulation models of the atmosphere and ocean (atmospheric and oceanic general circulation models  – GCMs have been improved by modeling the hydrological cycle with the use of isotopologues (isotopes of water HDO and H2 18O. Input parameters for the GCM models taking into account changes in the isotope composition of atmospheric precipitation were, above all, the results obtained by the network GNIP – Global Network of Isotopes in Precipitation. At different times, on the vast territory of Russia there were only about 40 simultaneously functioning stations where the sampling of atmospheric precipitation was performed. In this study we present the results of the isotope composition of samples taken on the foothills of the Altai during two winter seasons of 2014/15 and 2015/16. Values of the isotope composition of precipitation changed in a wide range and their maximum fluctuations were 25, 202 and 18‰ for δ18О, dexc and δD, respectively. The weighted-mean values of δ18О and δD of the precipitation analyzed for the above two seasons were close to each other (−21.1 and −158.1‰ for the first season and −21.1 and −161.9‰ for the second one, while dexc values differed significantly. The comparison of the results of isotope analysis of the snow cover integral samples with the corresponding in the time interval the weighted-mean values of precipitation showed high consistency. However, despite the similarity of values of δ18О and δD, calculated for precipitation and snow cover, and the results, interpolated in IsoMAP (from data of the GNIP stations for 1960–2010, the dexc values were close to mean annual values of IsoMAP for only the second winter season. According to the trajectory analysis (the HYSPLIT model, the revealed differences between both, the seasons, and the long-term average values of IsoMAP, were associated with a change of main regions where the air masses

  6. Development of Bake Hardening Effect by Plastic Deformation and Annealing Conditions

    Directory of Open Access Journals (Sweden)

    Kvačkaj, T.

    2006-01-01

    Full Text Available The paper deals with the classification of steel sheets for automotives industry on the basis of strength and structural characteristics. Experimental works were aimed to obtain the best possible strengthening parameters as well as work hardening and solid solution ferrite hardening, which are the result of thermal activation of interstitial carbon atoms during paint-baking of auto body. Hardening process coming from interstitial atoms is realized as two-step process. The first step is BH (bake hardening effect achieved by interaction of interstitial atoms with dislocations. The Cottrels atmosphere is obtained. The second step of BH effect is to produced the hardening from precipitation of the carbon atoms in e-carbides, or formation of Fe32C4 carbides. WH (work hardening effect is obtained as dislocation hardening from plastic deformations during sheet deep drawing. Experimental works were aimed at as to achieve such plastic material properties after cold rolling, annealing and skin-pass rolling, which would be able to classify the material ZStE220BH into the drawing categories at the level of DQ – DDQ. As resulting from the experimental results, the optimal treatment conditions for the maximal sum (WH+BH = 86 MPa are as follows: total cold rolling deformation ecold = 65 %, annealing temperature Tanneal. = 700 °C.

  7. Plasma nitriding of a precipitation hardening stainless steel to improve erosion and corrosion resistance

    International Nuclear Information System (INIS)

    Cabo, Amado; Bruhl, Sonia P.; Vaca, Laura S.; Charadia, Raul Charadia

    2010-01-01

    Precipitation hardening stainless steels are used as structural materials in the aircraft and the chemical industry because of their good combination of mechanical and corrosion properties. The aim of this work is to analyze the structural changes produced by plasma nitriding in the near surface of Thyroplast PH X Supra®, a PH stainless steel from ThyssenKrupp, and to study the effect of nitriding parameters in wear and corrosion resistance. Samples were first aged and then nitriding was carried out in an industrial facility at two temperatures, with two different nitrogen partial pressures in the gas mixture. After nitriding, samples were cut, polished, mounted in resin and etched with Vilella reagent to reveal the nitrided case. Nitrided structure was also analyzed with XRD. Erosion/Corrosion was tested against sea water and sand flux, and corrosion in a salt spray fog (ASTM B117). All nitrided samples presented high hardness. Samples nitrided at 390 deg C with different nitrogen partial pressure showed similar erosion resistance against water and sand flux. The erosion resistance of the nitrided samples at 500 deg C was the highest and XRD revealed nitrides. Corrosion resistance, on the contrary, was diminished; the samples suffered of general corrosion during the salt spray fog test. (author)

  8. MICROSTRUCTURAL FEATURES EVALUATION OF AGE-HARDENED A 226 CAST ALLOY BY IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Lenka Kuchariková

    2018-01-01

    Full Text Available Age-hardening provides one of the most widely used mechanisms for the strengthening of aluminum alloys. The age-hardening involves three steps: solution treatment, quenching and aging. The temperature of solution treatment and aging is very important in order to reach desired properties of castings. The optimum temperature of solution treatment and aging led to formation microstructural features in form which does not lead to decreasing properties, but increasing ones. The major microstructural features in A 226 cast alloys which are responsible for increasing properties are: eutectic Si particles, Cu-rich phases, Fe-rich phases and porosity. The increase of properties depends on morphology, size and volume of microstructural features. In order to assess age-hardening influence on microstructural features in A226 cast alloys were used as possibilities of evaluation by means of image analysis. Quantitative analysis decelerate changes in microstructure includes the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu further increase in the hardness and tensile strength in the alloy. Changes of mechanical properties were measured in line with STN EN ISO.

  9. Estimation of radiation hardening in ferritic steels using the cluster dynamics models

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Jun Hyun; Kim, Whung Whoe; Hong, Jun Hwa [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2005-07-01

    Evolution of microstructure under irradiation brings about the mechanical property changes of materials, of which the major concern is radiation hardening in this work. Radiation hardening is generally expressed in terms of an increase in yield strength as a function of radiation dose and temperature. Cluster dynamics model for radiation hardening has been developed to describe the evolution of point defects clusters (PDCs) and copperrich precipitates (CRPs). While the mathematical models developed by Stoller focus on the evolution of PDCs in ferritic steels under neutron irradiation, we slightly modify the model by including the CRP growth and estimate the magnitude of hardening induced by PDC and CRP. The model is then used to calculate the changes in yield strength of RPV steels. The calculation results are compared to measured yield strength values, obtained from surveillance testing of PWR vessel steels in France.

  10. Characterization and Strain-Hardening Behavior of Friction Stir-Welded Ferritic Stainless Steel

    Science.gov (United States)

    Sharma, Gaurav; Dwivedi, Dheerendra Kumar; Jain, Pramod Kumar

    2017-12-01

    In this study, friction stir-welded joint of 3-mm-thick plates of 409 ferritic stainless steel (FSS) was characterized in light of microstructure, x-ray diffraction analysis, hardness, tensile strength, ductility, corrosion and work hardening properties. The FSW joint made of ferritic stainless steel comprises of three distinct regions including the base metal. In stir zone highly refined ferrite grains with martensite and some carbide precipitates at the grain boundaries were observed. X-ray diffraction analysis also revealed precipitation of Cr23C6 and martensite formation in heat-affected zone and stir zone. In tensile testing of the transverse weld samples, the failure eventuated within the gauge length of the specimen from the base metal region having tensile properties overmatched to the as-received base metal. The tensile strength and elongation of the longitudinal (all weld) sample were found to be 1014 MPa and 9.47%, respectively. However, in potentiodynamic polarization test, the corrosion current density of the stir zone was highest among all the three zones. The strain-hardening exponent for base metal, transverse and longitudinal (all weld) weld samples was calculated using various equations. Both the transverse and longitudinal weld samples exhibited higher strain-hardening exponents as compared to the as-received base metal. In Kocks-Mecking plots for the base metal and weld samples at least two stages of strain hardening were observed.

  11. Initiation and propagation of cleared channels in neutron-irradiated pure copper and a precipitation hardened CuCrZr alloy

    DEFF Research Database (Denmark)

    Singh, B.N; Edwards, D.J.; Bilde-Sørensen, Jørgen

    2004-01-01

    The phenomenon of plastic flow localization in the form of "cleared" channels has been frequently observed in neutron irradiated metals and alloys for more than 40 years. So far, however, no experimental evidence as to how and where these channels areinitiated during post-irradiation deformation...... has emerged. Recently we have studied the problem of initiation and propagation of cleared channels during post-irradiation tensile tests of pure copper and a copper alloy irradiated with fission neutrons.Tensile specimens of pure copper and a precipitation hardened copper alloy (CuCrZr) were neutron...... irradiated at 323 and 373K to displacement doses in the range of 0.01 to 0.3 dpa (displacement per atom) and tensile tested at the irradiation temperature.The stress-strain curves clearly indicated the occurrence of a yield drop. The post-deformation microstructural examinations revealed that the channels...

  12. Alternative cover design

    International Nuclear Information System (INIS)

    1988-11-01

    The special study on Alternative Cover Designs is one of several studies initiated by the US Department of Energy (DOE) in response to the proposed US Environmental Protection Agency (EPA) groundwater standards. The objective of this study is to investigate the possibility of minimizing the infiltration of precipitation through stabilized tailings piles by altering the standard design of covers currently used on the Uranium Mill Tailings Remedial Action (UMTRA) Project. Prior. to the issuance of the proposed standards, UMTRA Project piles had common design elements to meet the required criteria, the most important of which were for radon diffusion, long-term stability, erosion protection, and groundwater protection. The standard pile covers consisted of three distinct layers. From top to bottom they were: rock for erosion protection; a sand bedding layer; and the radon barrier, usually consisting of a clayey sand material, which also functioned to limit infiltration into the tailings. The piles generally had topslopes from 2 to 4 percent and sideslopes of 20 percent

  13. Alloy hardening of a smectic A liquid crystal doped with gold nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Oswald, P.; Milette, J.; Relaix, S.; Reven, L.; Dequidt, A.; Lejček, Lubor

    2013-01-01

    Roč. 103, AUG (2013), "46004-p1"-"46004-p6" ISSN 0295-5075 Institutional support: RVO:68378271 Keywords : smectic A liquid crystals * gold nanoparticles * edge dislocation * precipitation hardening Subject RIV: BK - Fluid Dynamics Impact factor: 2.269, year: 2013

  14. Mechanism of Secondary Hardening in Rapid Tempering of Dual-Phase Steel

    Science.gov (United States)

    Saha, Dulal Chandra; Nayak, Sashank S.; Biro, Elliot; Gerlich, Adrian P.; Zhou, Y.

    2014-12-01

    Dual-phase steel with ferrite-martensite-bainite microstructure exhibited secondary hardening in the subcritical heat affected zone during fiber laser welding. Rapid isothermal tempering conducted in a Gleeble simulator also indicated occurrence of secondary hardening at 773 K (500 °C), as confirmed by plotting the tempered hardness against the Holloman-Jaffe parameter. Isothermally tempered specimens were characterized by analytic transmission electron microscopy and high-angle annular dark-field imaging. The cementite (Fe3C) and TiC located in the bainite phase of DP steel decomposed upon rapid tempering to form needle-shaped Mo2C (aspect ratio ranging from 10 to 25) and plate-shaped M4C3 carbides giving rise to secondary hardening. Precipitation of these thermodynamically stable and coherent carbides promoted the hardening phenomenon. However, complex carbides were only seen in the tempered bainite and were not detected in the tempered martensite. The martensite phase decomposed into ferrite and spherical Fe3C, and interlath-retained austenite decomposed into ferrite and elongated carbide.

  15. Acidic precipitation: considerations for an air-quality standard

    Energy Technology Data Exchange (ETDEWEB)

    Evans, L.S.; Hendrey, G.R.; Stensland, G.J.; Johnson, D.W.; Francis, A.J.

    1980-01-01

    Acidic precipitation, wet or frozen deposition with a hydrogen ion concentration greatern than 2.5 ..mu..eq l/sup -1/ is a significant air pollution problem in the United States. The chief anions accounting for the hydrogen ions in rainfall are nitrate and sulfate. Agricultural systems are more likely to derive net nutritional benefits from increasing inputs of acidic rain than are forest systems when soils alone are considered. Agricultural soils may benefit because of the high N and S requirements of agricultural plants. Detrimental effects to forest soils may result if atmospheric H/sup +/ inputs significantly add to or exceed H/sup +/ production by soils. Acidification of fresh waters of southern Scandinavia, southwestern Scotland, southeastern Canada, and northeastern United States is caused by acid deposition. Areas of these regions in which this acidification occurs have in common, highly acidic precipitation with volume weighted mean annual H/sup +/ concentrations of 25 ..mu..eq l/sup -1/ or higher and slow weathering granitic or precambrian bedrock with thin soils deficient in minerals which would provide buffer capacity. Biological effects of acidification of fresh waters are detectable below pH 6.0. As lake and stream pH levels decrease below pH. 6.0, many species of plants, invertebrates, and vertebrates are progressively eliminated. Generally, fisheries are impacted below pH 5.0 and are completely destroyed below pH 4.8. There are few studies that document effects of acidic precipitation on terrestrial vegetation to establish an air quality standard. It must be demonstrated that current levels of precipitation acidity alone significantly injure terrestrial vegetation. In terms of documented damanges, current research indicates that establishing a standard for precipitation for the volume weighted annual H/sup +/ concentration at 25 ..mu..eq l/sup -1/ may protect the most sensitive areas from permanent lake acidification.

  16. Spatial Variation of Temperature and Precipitation in Bhutan and Links to Vegetation and Land Cover

    Directory of Open Access Journals (Sweden)

    Ugyen Dorji

    2016-02-01

    Full Text Available Bhutan, located in the Himalayas in the South Asian monsoon region, has extremely high variation in elevation, climatic conditions, and land cover despite its small geographical area, as well as great biodiversity. This paper provides the first comprehensive description of climatic conditions in Bhutan. It assesses the spatial variation of temperature and precipitation across the country and evaluates the causes for this variation based on daily data from 70 meteorological stations that have been recording data for time spans ranging from 3 to 21 years. Temperature and precipitation show contrasting spatial variation, with temperature primarily affected by elevation and precipitation by latitude. Models were developed using mixed linear regression models to predict seasonal and annual mean temperature and precipitation based on geographical location. Using linear regression we found that temperatures changed by about 0.5°C for every 100 m of change in elevation, with lapse rates being highest in February, March, and November and lowest from June to August. The lapse rate was highest for minimum temperatures and lowest for maximum temperatures, with the greatest difference during winter. The spatial distribution of precipitation was mainly controlled by latitude, having a quadratic relationship, with the highest rates in the southern foothills of the Himalayan range and the lowest at midlatitudes. The land cover is affected by topography and local climate, with variations in temperature being a main deciding factor for vegetation types; most human settlements and associated land uses are concentrated at lower elevations.

  17. Significance of rate of work hardening in tempered martensite embrittlement

    International Nuclear Information System (INIS)

    Pietikainen, J.

    1995-01-01

    The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of work hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe 3 C appear in quite different tempering temperature ranges. The M S temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of work hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of work hardening are considered. (orig.)

  18. Plastic limit analysis with non linear kinematic strain hardening for metalworking processes applications

    International Nuclear Information System (INIS)

    Chaaba, Ali; Aboussaleh, Mohamed; Bousshine, Lahbib; Boudaia, El Hassan

    2011-01-01

    Limit analysis approaches are widely used to deal with metalworking processes analysis; however, they are applied only for perfectly plastic materials and recently for isotropic hardening ones excluding any kind of kinematic hardening. In the present work, using Implicit Standard Materials concept, sequential limit analysis approach and the finite element method, our objective consists in extending the limit analysis application for including linear and non linear kinematic strain hardenings. Because this plastic flow rule is non associative, the Implicit Standard Materials concept is adopted as a framework of non standard plasticity modeling. The sequential limit analysis procedure which considers the plastic behavior with non linear kinematic strain hardening as a succession of perfectly plastic behavior with yielding surfaces updated after each sequence of limit analysis and geometry updating is applied. Standard kinematic finite element method together with a regularization approach is used for performing two large compression cases (cold forging) in plane strain and axisymmetric conditions

  19. A project of X-ray hardening correction in large ICT

    International Nuclear Information System (INIS)

    Fang Min; Liu Yinong; Ni Jianping

    2005-01-01

    This paper presents a means of polychromatic X-ray beam hardening correction using a standard function to transform the polychromatic projection to monochromatic projection in large Industrial Computed Tomography (ICT). Some parameters were defined to verify the validity of hardening correction in large ICT and optimized. Simulated experiments were used to prove that without prior knowledge of the composition of the scanned object, the correction method using monochromatic reconstruction arithmetic could remove beam hardening artifact greatly. (authors)

  20. Modeling of Precipitation Sequence and Ageing Kinetics in Al-Mg-Si Alloys

    NARCIS (Netherlands)

    Bahrami, A.

    2010-01-01

    Al-Mg-Si alloys are heat treatable alloys in which strength is obtained by precipitation hardening. Precipitates, formed from a supersaturated solid solution during ageing heat treatment, are GP-zones, B", B´ and B-Mg2Si. Precipitation kinetics and strength vary with alloy composition and process

  1. Comparison of early stages of precipitation in molybdenum-rich and molybdenum-poor maraging stainless steels

    International Nuclear Information System (INIS)

    Andersson, M.; Stiller, K.; Haettestrand, M.

    2004-01-01

    Full text: The precipitation hardening process in the molybdenum-rich Sandvik alloy 1RK91, with composition 12.8Cr-8.6Ni-2.3Mo-1.7Cu-1.2Ti-0.7Al (at. %), has previously been investigated with APFIM, energy-filtering transmission electron microscopy, and conventional transmission electron microscopy. The initial ageing response corresponds to Ni 3 (Al, Ti)-type precipitates, nucleating on copper clusters after only five minutes of ageing at 475 o C. After several hours of ageing, the precipitation hardening also includes contribution from molybdenum-rich quasicrystalline precipitates of icosahedral symmetry (R'), and another nickel-rich phase of type L1 0 . This complex precipitation behaviour, in combination with a resistance to coarsening of R', results in a continuous increase in material hardness for up to several hundred of hours of ageing. A significant difference in ageing response has been observed between the Sandvik alloy 1RK91 and molybdenum-poor alloy Carpenter 455 with composition 12.3Cr-7.9Ni-0.3Mo-1.8Cu-1.3Ti-0.1Al (at. %). During ageing at 475 o C, the hardness of Carpenter 455 saturates with a subsequent softening after just a few hours. The reason for the discrepancy in the ageing behaviour of the two steels is not well understood, since the precipitation reactions in Carpenter 455 have not been thoroughly surveyed. Therefore, the precipitation hardening process of Carpenter 455 has been studied, by using three-dimensional atom probe and energy-filtering transmission electron microscopy. The results have been compared with the precipitation hardening process of 1RK91 in order to explain the difference in ageing response of the two steels. Special interest has been devoted to understand the influence of molybdenum in the precipitation process of 1RK91. Refs 3 (author)

  2. Precipitation in partially stabilized zirconia

    International Nuclear Information System (INIS)

    Bansal, G.K.

    1975-01-01

    Transmission electron microscopy was used to study the substructure of partially stabilized ZrO 2 (PSZ) samples, i.e., 2-phase systems containing both cubic and monoclinic modifications of zirconia, after various heat treatments. Monoclinic ZrO 2 exists as (1) isolated grains within the polycrystalline aggregate (a grain- boundary phase) and (2) small plate-like particles within cubic grains. These intragranular precipitates are believed to contribute to the useful properties of PSZ via a form of precipitation hardening. These precipitates initially form as tetragonal ZrO 2 , with a habit plane parallel to the brace 100 brace matrix planes. The orientation relations between the tetragonal precipitates and the cubic matrix are brace 100 brace/sub matrix/ 2 parallel brace 100 brace /sub precipitate/ or (001)/sub precipitate/ and broken bracket 100 broken bracket/sub matrix/ 2 parallel broken bracket 100 broken bracket/sub precipitate/ or [001]/sub precipitate/. (U.S.)

  3. Nickel Alloy, Corrosion and Heat-Resistant, Sheet, Strip, and Plate 72Ni - 15.5Cr - 0.95 (Cb (Nb) + Ta) - 2.5Ti - 0.70Al - 7.0Fe Consumable Electrode, Remelted or Vacuum Induction Melted, Solution Heat Treated, Precipitation-Hardenable

    CERN Document Server

    SAE Aerospace Standards. London

    2012-01-01

    Nickel Alloy, Corrosion and Heat-Resistant, Sheet, Strip, and Plate 72Ni - 15.5Cr - 0.95 (Cb (Nb) + Ta) - 2.5Ti - 0.70Al - 7.0Fe Consumable Electrode, Remelted or Vacuum Induction Melted, Solution Heat Treated, Precipitation-Hardenable

  4. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

  5. Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

    Science.gov (United States)

    Wen, Peng; Cai, Zhipeng; Feng, Zhenhua; Wang, Gang

    2015-12-01

    Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

  6. Hardening mechanisms of spray formed Al-Zn-Mg-Cu alloys with scandium and other elemental additions

    International Nuclear Information System (INIS)

    Sharma, M.M.; Amateau, M.F.; Eden, T.J.

    2006-01-01

    The hardening mechanisms in spray formed Al-Zn-Mg-Cu alloys with additions of chromium, zinc and scandium were studied. The microstructure of the spray formed alloys was analyzed by transmission electron microscopy. A range of tensile strengths were achieved, and varied based on elemental additions, and second phase particle strengthening. To explain the significantly higher strength in one alloy with scandium, theoretical results due to the yield stress of Al-Zn-Mg-Cu alloys as a function of volume fraction and precipitate particle size, were compared to experimental data. Both the possibilities of coherency and order strengthening are examined. The significant additional hardening achieved in the alloy with scandium is attributed to small ordered particles of Al 3 Sc, which precipitated during aging

  7. Precipitation kinetics in warm forming of AW-7020 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, M., E-mail: Manoj.kumar@ait.ac.at [Leichtmetall-Kompetenzzentrum Ranshofen GmbH, Austrian Institute of Technology, Postfach 26, A-5282 Ranshofen (Austria); Institute of Material Science and Technology, TU Vienna (Austria); Poletti, C. [Present address: Institute of Material Science and Welding, TU Graz (Austria); Institute of Material Science and Technology, TU Vienna (Austria); Degischer, H.P. [Institute of Material Science and Technology, TU Vienna (Austria)

    2013-01-20

    The warm formability of the precipitation hardening AW-7020 (AlZn 4.5Mg1) alloy is investigated by testing extruded tubes. The precipitation kinetics of different conditions before and after warm deformation is studied by differential scanning calorimetry and transmission electron microcopy. The precipitation conditions are correlated with the results of hardness tests at room temperature and of tensile tests at temperatures between 200 and 350 Degree-Sign C at different strain rates. The yield strength decreases with increasing test temperature approaching that of samples in the annealed condition, while the strain at fracture increases. The overall influence of the strain rate on ductility is dominated by the corresponding time required for deformation. The formability of the starting condition T1 as well as the corresponding strain hardening exponent is particularly promising for high strain rates at 250 Degree-Sign C, where the metastable precipitates of the T1 condition are dissolved. The short exposure of about 30 s at 250 Degree-Sign C re-establishes the potential for precipitation strengthening by natural ageing after the warm deformation and a following paint baking heat treatment maintains the hardness level.

  8. Precipitation Effect on Mechanical Properties and Phase Stability of High Manganese Steel

    Science.gov (United States)

    Bae, Cheoljun; Kim, Rosa; Lee, Un-Hae; Kim, Jongryoul

    2017-09-01

    High manganese (Mn) steels are attractive for automotive applications due to their excellent tensile strength and superior elongation. However, the relatively low yield strength of Mn steels compared to other advanced high-strength steels is a critical problem limiting their use in structural parts. In order to increase the yield strength, the precipitation hardening effect of Mn steels was investigated by the addition of carbide-forming elements. Changes in the austenite phase stability were also evaluated in terms of stacking fault energy (SFE). As a result, fine V(C,N) precipitates were found to increase the yield strength effectively but to lower the SFE by the consumption of matrix carbons. For achieving precipitation hardening without sacrificing austenite stability, the soluble carbon content was discussed.

  9. Age-hardening and related phase transformation in an experimental Ag-Cu-Pd-Au alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Lee, Doung-Hun; Lee, Hee-Kyung; Takada, Yukyo; Okuno, Osamu; Kwon, Yong Hoon; Kim, Hyung-Il

    2006-01-01

    The age-hardening behaviour, phase transformation and related microstructural changes of an experimental Ag-Cu-Pd-Au alloy were examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The specimen alloy showed apparent age-hardenability at the aging temperatures of 350 deg. C and 400 deg. C. By aging the solution-treated specimen at 400 deg. C, two phases of the Ag-rich α 1 phase and the Pd-containing Cu-rich α 2 phase were transformed into four phases of the Ag-rich α 1 ' phase, the Cu-rich α 2 ' phase, the CsCl-type CuPd phase and the AuCu(I) ordered phase. Microstructure of the solution-treated specimen consisted of the Ag-rich α 1 matrix, Cu-rich α 2 particle-like structures of various sizes and the lamellar structure of the α 1 and α 2 phases. When the peak hardness was obtained, the very fine lamellar structure consisting of the Ag-rich α 1 ' and Cu-rich α 2 ' phases was newly formed in the matrix. By further aging, the very fine lamellar structure grew and coarsened apparently, and the matrix was covered with the coarsened lamellar structure. The hardness increase was considered to be caused mainly by the diffusion and precipitation of Cu from the Ag-rich α 1 matrix, and the hardness decrease in the latter stage of age-hardening process was caused by the coarsening of the very fine lamellar structure. The CsCl-type CuPd phase and the AuCu(I) ordered phase did not contribute to the hardness increase

  10. Precipitation evolution and kinetics in a magnesium-neodymium-zinc alloy

    International Nuclear Information System (INIS)

    Sanaty-Zadeh, A.; Xia, X.; Luo, A.A.; Stone, D.S.

    2014-01-01

    Highlights: • Precipitation sequence and kinetics in Mg–3Nd–0.2Zn wt.% alloy were studied. • Lower amount of zinc than 0.5 wt.% does not change the sequence of precipitation. • A new orientation with respect to the matrix was detected for β″ precipitates. • β″ Precipitates contribute to the age hardening of the alloy. • Quenched-in vacancies play an important role in early stage of precipitation. -- Abstract: In this research, the precipitation sequence investigation and phase identification in Mg–3Nd–0.2Zn–0.46Zr (wt.%) system were performed using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques. The results showed the precipitation sequence to be: Super saturated solid solution (SSSS) → Clustering of atoms/short range ordering → β″ → β′ → β which shows that low zinc content (less than 0.5 %wt) does not influence the precipitation sequence. TEM studies revealed that in addition to prismatic planes, β′′ precipitates lie on pyramidal planes in Mg matrix, which has not been reported previously in this system. Further investigation using TEM and aging experiments showed that these precipitates are responsible for the age hardening of the alloy. Furthermore, the kinetic studies showed that quenched-in vacancies play an important role in the early stage of precipitation and formation of β′′ while formation of β′ is dominantly diffusion controlled process and quenched-in vacancies are no longer effective

  11. Novel circuits for radiation hardened memories

    International Nuclear Information System (INIS)

    Haraszti, T.P.; Mento, R.P.; Moyer, N.E.; Grant, W.M.

    1992-01-01

    This paper reports on implementation of large storage semiconductor memories which combine radiation hardness with high packing density, operational speed, and low power dissipation and require both hardened circuit and hardened process technologies. Novel circuits, including orthogonal shuffle type of write-read arrays, error correction by weighted bidirectional codes and associative iterative repair circuits, are proposed for significant improvements of SRAMs' immunity against the effects of total dose and cosmic particle impacts. The implementation of the proposed circuit resulted in fault-tolerant 40-Mbit and 10-Mbit monolithic memories featuring a data rate of 120 MHz and power dissipation of 880 mW. These experimental serial-parallel memories were fabricated with a nonhardened standard CMOS processing technology, yet provided a total dose hardness of 1 Mrad and a projected SEU rate of 1 x 10 - 12 error/bit/day. Using radiation hardened processing improvements by factors of 10 to 100 are predicted in both total dose hardness and SEU rate

  12. Probing the nanostructural evolution of age-hardenable Al alloys with atom-probe tomography

    International Nuclear Information System (INIS)

    Biswas, Aniruddha

    2010-01-01

    Atom Probe Tomographic (APT) Microscope is a lens-less point-projection 3-D analytical microscope that has the unique capability of (i) three-dimensional imaging at the atomic scale and (ii) compositional analysis with sub-nanometre spatial resolution and single-atom sensitivity. Modern 3-D APT microscope offers the highest the spatial resolution among all the available analytical techniques. It can simultaneously achieve a spatial resolution better than 0.3 nm in all three directions of a three-dimensional analysis-volume. As a result, 3-D APT microscopy, especially as practiced by the high speed, large field of view instruments is the most appropriate tool for studying nano-scale precipitates and their heterophase interfaces. This talk will introduce the technique, discuss its brief historical background and use examples from age-hardenable Al-alloys. The results include a detailed APT study of the compositional evolution of the nano-scale precipitates: θ and Q present in commercial age hardenable aluminium alloy, W319

  13. Precipitation of T1 and θ′ Phase in Al-4Cu-1Li-0.25Mn During Age Hardening: Microstructural Investigation and Phase-Field Simulation

    Science.gov (United States)

    Häusler, Ines; Schwarze, Christian; Bilal, Muhammad Umer; Valencia Ramirez, Daniela; Hetaba, Walid; Darvishi Kamachali, Reza; Skrotzki, Birgit

    2017-01-01

    Experimental and phase field studies of age hardening response of a high purity Al-4Cu-1Li-0.25Mn-alloy (mass %) during isothermal aging are conducted. In the experiments, two hardening phases are identified: the tetragonal θ′ (Al2Cu) phase and the hexagonal T1 (Al2CuLi) phase. Both are plate shaped and of nm size. They are analyzed with respect to the development of their size, number density and volume fraction during aging by applying different analysis techniques in TEM in combination with quantitative microstructural analysis. 3D phase-field simulations of formation and growth of θ′ phase are performed in which the full interfacial, chemical and elastic energy contributions are taken into account. 2D simulations of T1 phase are also investigated using multi-component diffusion without elasticity. This is a first step toward a complex phase-field study of T1 phase in the ternary alloy. The comparison between experimental and simulated data shows similar trends. The still unsaturated volume fraction indicates that the precipitates are in the growth stage and that the coarsening/ripening stage has not yet been reached. PMID:28772481

  14. A hardenability test proposal

    Energy Technology Data Exchange (ETDEWEB)

    Murthy, N.V.S.N. [Ingersoll-Rand (I) Ltd., Bangalore (India)

    1996-12-31

    A new approach for hardenability evaluation and its application to heat treatable steels will be discussed. This will include an overview and deficiencies of the current methods and discussion on the necessity for a new approach. Hardenability terminology will be expanded to avoid ambiguity and over-simplification as encountered with the current system. A new hardenability definition is proposed. Hardenability specification methods are simplified and rationalized. The new hardenability evaluation system proposed here utilizes a test specimen with varying diameter as an alternative to the cylindrical Jominy hardenability test specimen and is readily applicable to the evaluation of a wide variety of steels with different cross-section sizes.

  15. Precipitation hardening and microstructure evolution of the Ti-7Nb-10Mo alloy during aging.

    Science.gov (United States)

    Yi, Ruowei; Liu, Huiqun; Yi, Danqing; Wan, Weifeng; Wang, Bin; Jiang, Yong; Yang, Qi; Wang, Dingchun; Gao, Qi; Xu, Yanfei; Tang, Qian

    2016-06-01

    A biomedical β titanium alloy (Ti-7Nb-10Mo) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and aging. Age-hardening behavior, microstructure evolution and its influence on mechanical properties of the alloy during aging were investigated, using X-ray diffraction, transmission electron microscopy, tensile and hardness measurements. The electrochemical behavior of the alloy was investigated in Ringer's solution. The microstructure of solution-treated (ST) alloy consists of the supersaturated solid solution β phase and the ωath formed during athermal process. The ST alloy exhibits Young's modulus of 80 GPa, tensile strength of 774 MPa and elongation of 20%. The precipitation sequences during isothermal aging at different temperatures were determined as β+ωath→β+ωiso (144 h) at Taging=350-400 °C, β+ωath→β+ωiso+α→β+α at Taging=500°C, and β+ωath→β+α at Taging=600-650 °C, where ωiso forms during isothermal process. The mechanical properties of the alloy can be tailored easily through controlling the phase transition during aging. Comparing with the conventional Ti-6Al-4V alloy, the Ti-7Nb-10Mo alloy is more resistant to corrosion in Ringer's solution. Results show that the Ti-7Nb-10Mo alloy is promising for biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Scintillation-Hardened GPS Receiver

    Science.gov (United States)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  17. Comparison of Thermal Creep Strain Calculation Results Using Time Hardening and Strain Hardening Rules

    International Nuclear Information System (INIS)

    Kim, Junehyung; Cheon, Jinsik; Lee, Byoungoon; Lee, Chanbock

    2014-01-01

    One of the design criteria for the fuel rod in PGSFR is the thermal creep strain of the cladding, because the cladding is exposed to a high temperature for a long time during reactor operation period. In general, there are two kind of calculation scheme for thermal creep strain: time hardening and strain hardening rules. In this work, thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules are compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule are compared with those by using MACSIS. Thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules were compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule were compared with those by using MACSIS. Tertiary creep started earlier in time hardening rule than in strain hardening rule. Also, calculation results by MACSIS with strain hardening and those obtained by using LIFE-METAL were almost identical to each other

  18. Changes in Structural Characteristics of Hypoeutectic Al-Si Cast Alloy after Age Hardening

    Directory of Open Access Journals (Sweden)

    Lenka HURTALOVÁ

    2012-09-01

    Full Text Available The contribution describes influence of the age-hardening consist of solution treatment at 515 °C with holding time 4 hours, water quenching at 40 °C and artificial aging at different temperature 150 °C, 170 °C and 190 °C with different holding time 2, 4, 8, 16 and 32 hours on mechanical properties (tensile strength and Brinell hardness and changes in morphology of eutectic Si, Fe-rich and Cu-rich intermetallic phases in secondary (recycled AlSi9Cu3 cast alloy. A combination of different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy (SEM upon deep etching and energy dispersive X-ray analysis (EDX were therefore been used for the identification of the various phases. Quantitative study of changes in morphology of eutectic Si, Cu-rich and Fe-rich phases was carried out using Image Analyzer software NIS-Elements. Mechanical properties were measured in line with EN ISO. Age-hardening led to changes in microstructure include the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe- rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu further increase in the hardness and tensile strength in the alloy.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2430

  19. Simulation of precipitation and strengthening in MG-RE alloys

    OpenAIRE

    Liu, Hong

    2017-01-01

    Magnesium - rare earth (Mg-RE) alloys have received considerable attention in the past decades for wider applications in the aerospace industry due to their relatively high strength and excellent creep resistance. Most rare-earth containing magnesium alloys, such as Mg-Y, Mg-Gd, and Mg-Y-Nd, are precipitation hardenable. A technical barrier to the wider applications of such alloys is the lack of a sufficiently large age hardening response. To further improve this response, an improved underst...

  20. Age-hardening susceptibility of high-Cr ODS ferritic steels and SUS430 ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dongsheng, E-mail: chen.dongsheng85@gmail.com [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko; Han, Wentuo; Je, Hwanil [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2015-10-15

    Highlights: • The role of oxide particles in α/α′ phase decomposition behavior; microstructure of phase decomposition observed by TEM. • The characteristics of ductility loss caused by age-hardening. • Correlation of phase decomposition and age-hardening explained by dispersion strengthened models. • Age-hardening susceptibility of ODS steels and SUS430 steel. - Abstract: The effect of aging on high-Cr ferritic steels was investigated with focusing on the role of oxide particles in α/α′ phase decomposition behavior. 12Cr-oxide dispersion strengthened (ODS) steel, 15Cr-ODS steel and commercial SUS430 steel were isothermally aged at 475 °C for up to 10,000 h. Thermal aging caused a larger hardening in SUS430 than 15Cr-ODS, while 12Cr-ODS showed almost no hardening. A characteristic of the ODS steels is that the hardening was not accompanied by the significant loss of ductility that was observed in SUS430 steel. After aging for 2000 h, SUS430 steel shows a larger ductile–brittle transition temperature (DBTT) shift than 15Cr-ODS steel, which suggests that the age-hardening susceptibility is lower in 15Cr-ODS steel than in conventional SUS430 steel. Thermal aging leaded to a large number of Cr-rich α′ precipitates, which were confirmed by transmission electron microscopy (TEM). Correlation of age-hardening and phase decomposition was interpreted by Orowan type strengthening model. Results indicate that oxide particles cannot only suppress ductility loss, but also may influence α/α′ phase decomposition kinetics.

  1. Technology of hardening fills for mined spaces

    International Nuclear Information System (INIS)

    Simek, P.; Holas, M.; Chyla, A.; Pech, P.

    1985-01-01

    The technology is described of hardening fills for mined spaces of uranium deposits in North Bohemian chalk. A special equipment was developed for the controlled preparation of a hardening mixture. The composition of the fill is determined by the strength of the filled rock, expecially by the standard strength, i.e., the minimal strength of the filling under uniaxial pressure. The said parameter determines the consumption of binding materials and thereby the total costs of the filling. A description is presented of the filling technology, including rabbit tube transport of the mixture and quality control. (Pu)

  2. Dose and dose rate effects on coherent-to-incoherent transition of precipitates upon irradiation

    Institute of Scientific and Technical Information of China (English)

    LI Zhengchao

    2006-01-01

    A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coherent precipitates is loss of coherency, and TEM cross-section observations show that the fraction of the incoherent precipitates is dependent on dose but not on dose rate during heavy ion irradiation.

  3. Effect of laser shot peening on precipitation hardened aluminum alloy 6061-T6 using low energy laser

    Science.gov (United States)

    Sathyajith, S.; Kalainathan, S.

    2012-03-01

    Mechanical properties of engineering material can be improved by introducing compressive residual stress on the material surface and refinement of their microstructure. Variety of mechanical process such as shot peening, water jet peening, ultrasonic peening, laser shot peening were developed in the last decades on this contrast. Among these, lasers shot peening emerged as a novel industrial treatment to improve the crack resistance of turbine blades and the stress corrosion cracking (SCC) of austenic stainless steel in power plants. In this study we successfully performed laser shot peening on precipitation hardened aluminum alloy 6061-T6 with low energy (300 mJ, 1064 nm) Nd:YAG laser using different pulse densities of 22 pulses/mm 2 and 32 pulses/mm 2. Residual stress evaluation based on X-ray diffraction sin 2 ψ method indicates a maximum of 190% percentage increase on surface compressive stress. Depth profile of micro-hardness shows the impact of laser generated shock wave up to 1.2 mm from the surface. Apart from that, the crystalline size and micro-strain on the laser shot peened surfaces have been investigated and compared with the unpeened surface using X-ray diffraction in conjunction with line broadening analysis through the Williamson-Hall plot.

  4. Radiation-hardenable diluents for radiation-hardenable compositions

    International Nuclear Information System (INIS)

    Schuster, K.E.; Rosenkranz, H.J.; Furh, K.; Ruedolph, H.

    1979-01-01

    Radiation-crosslinkable diluents for radiation-hardenable compositions (binders) consisting of a mixture of triacrylates of a reaction product of trimethylol propane and ethylene oxide with an average degree of ethoxylation of from 2.5 to 4 are described. The ethoxylated trimethylol propane is substantially free from trimethylol propane and has the following distribution: 4 to 5% by weight of monoethoxylation product, 14 to 16% by weight of diethoxylation product, 20 to 30% by weight of triethoxylation product, 20 to 30% by weight of tetraethoxylation product, 16 to 18% by weight of pentaethoxylation product, and 6 to 8% by weight of hexaethoxylation product. The diluents effectively reduce the viscosity of radiation-hardenable compositions and do not have any adverse effect upon their reactivity or upon the properties of the resulting hardened products

  5. Phase-field modeling of Mn-Ni-Si precipitate behavior on the bcc-Fe matrix

    International Nuclear Information System (INIS)

    Chang, Kun Ok; Kwon, Jun Hyun

    2016-01-01

    The formation of Mn-Ni-Si precipitate (hereafter MNS precipitate) is widely accepted by one of the main reasons of late stage hardening and embrittlement of Reactor Pressure Vessel (RPV) during nuclear power plant (NPP) operation. Since MNS precipitate is not considered in current regulatory model, this late stage hardening can be a limiting factor for life extension of nuclear power plants up to 80 or more years. The stability of the MNS precipitate was investigated from the thermodynamic view point and they concluded that MNS precipitate is a stable phase even with very little Cu contents, and they assessed UW1 thermodynamic database which can predict the thermodynamic stability of MNS precipitate at operating temperature of NPP ( ∼ 290 .deg. C). Based on the non-classical nucleation theory, we performed the phase-field modeling of nucleation and growth of MNS precipitate. The microstructure evolution of Mn-Ni-Cu precipitate has been simulated using the phase-field method and their approaches are focused on a role of the Cu contents. Also, a role of the interstitial loop on the nucleation and growth kinetics of MNS precipitate was analyzed.

  6. Influence of Cooling Condition on the Performance of Grinding Hardened Layer in Grind-hardening

    Science.gov (United States)

    Wang, G. C.; Chen, J.; Xu, G. Y.; Li, X.

    2018-02-01

    45# steel was grinded and hardened on a surface grinding machine to study the effect of three different cooling media, including emulsion, dry air and liquid nitrogen, on the microstructure and properties of the hardened layer. The results show that the microstructure of material surface hardened with emulsion is pearlite and no hardened layer. The surface roughness is small and the residual stress is compressive stress. With cooling condition of liquid nitrogen and dry air, the specimen surface are hardened, the organization is martensite, the surface roughness is also not changed, but high hardness of hardened layer and surface compressive stress were obtained when grinding using liquid nitrogen. The deeper hardened layer grinded with dry air was obtained and surface residual stress is tensile stress. This study provides an experimental basis for choosing the appropriate cooling mode to effectively control the performance of grinding hardened layer.

  7. Aspect-oriented security hardening of UML design models

    CERN Document Server

    Mouheb, Djedjiga; Pourzandi, Makan; Wang, Lingyu; Nouh, Mariam; Ziarati, Raha; Alhadidi, Dima; Talhi, Chamseddine; Lima, Vitor

    2015-01-01

    This book comprehensively presents a novel approach to the systematic security hardening of software design models expressed in the standard UML language. It combines model-driven engineering and the aspect-oriented paradigm to integrate security practices into the early phases of the software development process. To this end, a UML profile has been developed for the specification of security hardening aspects on UML diagrams. In addition, a weaving framework, with the underlying theoretical foundations, has been designed for the systematic injection of security aspects into UML models. The

  8. Concurrent strengthening of ultrafine-grained age-hardenable Al-Mg alloy by means of high-pressure torsion and spinodal decomposition

    International Nuclear Information System (INIS)

    Tang, Yongpeng; Goto, Wataru; Hirosawa, Shoichi; Horita, Zenji; Lee, Seungwon; Matsuda, Kenji; Terada, Daisuke

    2017-01-01

    In this study, the age-hardening behavior and precipitate microstructures of severely-deformed and then artificially-aged Al-13.4 wt%Mg alloy has been investigated by Vickers hardness test, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and atom probe tomography (APT). The combined processing of high-pressure torsion (HPT) and aging treatment at a temperature below spinodal lines results in a higher attained hardness of ∼HV296 with an age-hardenability (i.e ΔHV31 ± 2) comparable to that of the undeformed specimen without HPT (i.e. ΔHV33 ± 2). The corresponding TEM microstructures consist of modulated structures associated with spinodal decomposition, and quantitative estimation of the amplitude, as well as the wavelength, of Mg fluctuations was successfully conducted by APT for the first time for this alloy system. The linear relationship between the increment of Vickers hardness and the estimated amplitude of the undeformed specimen supposed that Kato's spinodal-hardening mechanism works even in the HPTed specimen with a high number density of grain boundaries. Therefore, our proposed strategy; i.e. taking advantage of spinodal decomposition, is regarded as a convincing approach to achieving concurrent strengthening by ultrafine-grained and precipitation hardenings for the alloys that decompose via spinodal decomposition.

  9. Age-hardening and related phase transformation in an experimental Ag-Cu-Pd-Au alloy

    Energy Technology Data Exchange (ETDEWEB)

    Seol, Hyo-Joung [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Lee, Doung-Hun [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Lee, Hee-Kyung [Department of Dental Technology, Daegu Health College, San 7 Taejeon-dong, Buk-gu, Daegu 702-722 (Korea, Republic of); Takada, Yukyo [Division of Dental Biomaterials, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan); Okuno, Osamu [Division of Dental Biomaterials, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan); Kwon, Yong Hoon [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kim, Hyung-Il [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of)]. E-mail: hilkim@pusan.ac.kr

    2006-01-05

    The age-hardening behaviour, phase transformation and related microstructural changes of an experimental Ag-Cu-Pd-Au alloy were examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The specimen alloy showed apparent age-hardenability at the aging temperatures of 350 deg. C and 400 deg. C. By aging the solution-treated specimen at 400 deg. C, two phases of the Ag-rich {alpha}{sub 1} phase and the Pd-containing Cu-rich {alpha}{sub 2} phase were transformed into four phases of the Ag-rich {alpha}{sub 1}{sup '} phase, the Cu-rich {alpha}{sub 2}{sup '} phase, the CsCl-type CuPd phase and the AuCu(I) ordered phase. Microstructure of the solution-treated specimen consisted of the Ag-rich {alpha}{sub 1} matrix, Cu-rich {alpha}{sub 2} particle-like structures of various sizes and the lamellar structure of the {alpha}{sub 1} and {alpha}{sub 2} phases. When the peak hardness was obtained, the very fine lamellar structure consisting of the Ag-rich {alpha}{sub 1}{sup '} and Cu-rich {alpha}{sub 2}{sup '} phases was newly formed in the matrix. By further aging, the very fine lamellar structure grew and coarsened apparently, and the matrix was covered with the coarsened lamellar structure. The hardness increase was considered to be caused mainly by the diffusion and precipitation of Cu from the Ag-rich {alpha}{sub 1} matrix, and the hardness decrease in the latter stage of age-hardening process was caused by the coarsening of the very fine lamellar structure. The CsCl-type CuPd phase and the AuCu(I) ordered phase did not contribute to the hardness increase.

  10. Structure and Young modulus of age hardening elinvar 45NKhT

    International Nuclear Information System (INIS)

    Baraz, V.R.; Strizhak, V.A.; Tsykin, D.N.

    1996-01-01

    The influence of quenching and ageing on structural features and Young modulus of precipitation hardening elinvar alloy 45 NKhT is under study. It is shown that the quenched alloy possesses a decreased elastic modulus which value drops with a quenching temperature increase. The ally ageing results in restoration of elastic modulus. The temperature range of Young modulus stability is shown to be independent of heat treatment conditions. The anomalies of elastic modulus in quenched alloy are conditioned by structural and magnetoelastic factors. The mechanisms of continuous and discontinuous precipitation mechanism has no effect on efficiency of Young modulus restoration. 13 refs., 6 figs

  11. Analysis of precipitation in a Cu-Cr-Zr alloy

    Institute of Scientific and Technical Information of China (English)

    Zhao Mei; Lin Guobiao; Wang Zidong; Zhang Maokui

    2008-01-01

    Precipites in Cu-0.42%Cr-0.21%Zr alloy were analyzed by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM). After the solid solution was performed at 980℃ for 2 h, water-quenched and aged at 450℃ for 20 h, the precipite had a bimodal distribution of precipitate size. The coarse precipitates are pure Cr and Cu5Zr, the dispersed fine precipitate is CrCu2(Zr, Mg) and pure Cr ranging from 1 to 50 nm. The coarse phases formed during solidification and were left undissolved during solid solution. The fine precipitates are the hardening precipitates that form due to decomposition of the supersaturated solid solution during aging.

  12. Method of case hardening depth testing by using multifunctional ultrasonic testing instrument

    International Nuclear Information System (INIS)

    Salchak, Y A; Sednev, D A; Ardashkin, I B; Kroening, M

    2015-01-01

    The paper describes usability of ultrasonic case hardening depth control applying standard instrument of ultrasonic inspections. The ultrasonic method of measuring the depth of the hardened layer is proposed. Experimental series within the specified and multifunctional ultrasonic equipment are performed. The obtained results are compared with the results of a referent method of analysis. (paper)

  13. Irradiation-induced precipitates in a neutron irradiated 304 stainless steel studied by three-dimensional atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, T., E-mail: ttoyama@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Nozawa, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Van Renterghem, W. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Matsukawa, Y.; Hatakeyama, M.; Nagai, Y. [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, Narita-cho 2145-2, Oarai, Ibaraki 311-1313 (Japan); Al Mazouzi, A. [EDF R and D, Avenue des Renardieres Ecuelles, 77818 Moret sur Loing Cedex (France); Van Dyck, S. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium)

    2011-11-15

    Highlights: > Irradiation-induced precipitates in a 304 stainless steel were investigated by three-dimensional atom probe. > The precipitates were found to be {gamma}' precipitates (Ni{sub 3}Si). > Post-irradiation annealing was performed to discuss the contribution of the precipitates to irradiation-hardening. - Abstract: Irradiation-induced precipitates in a 304 stainless steel, neutron-irradiated to a dose of 24 dpa at 300 deg. C in the fuel wrapper plates of a commercial pressurized water reactor, were investigated by laser-assisted three-dimensional atom probe. A high number density of 4 x 10{sup 23} m{sup -3} of Ni-Si rich precipitates was observed, which is one order of magnitude higher than that of Frank loops. The average diameter was {approx}10 nm and the average chemical composition was 40% Ni, 14% Si, 11% Cr and 32% Fe in atomic percent. Over a range of Si concentrations, the ratio of Ni to Si was {approx}3, close to that of {gamma}' precipitate (Ni{sub 3}Si). In some precipitates, Mn enrichment inside the precipitate and P segregation at the interface were observed. Post-irradiation annealing was performed to discuss the contribution of the precipitates to irradiation-hardening.

  14. Strengthening of stainless steel weldment by high temperature precipitation

    Directory of Open Access Journals (Sweden)

    Sergio Neves Monteiro

    2017-10-01

    Full Text Available The mechanical behavior and the strengthening mechanism of stainless steel welded joints at 600 °C have been investigated. The welds were composed of AISI 304 stainless steel, as base metal, and niobium containing AISI 347 stainless steel, as weld metal. The investigation was conducted by means of creep tests. The welded specimens were subjected to both high temperature (600 °C and long periods (up to 2000 h under constant load, and both mechanical properties and microstructural changes in the material were monitored. It was found that the exposure of the material at 600 °C under load contributes to a strengthening effect on the weld. The phenomenon might be correlated with an accelerated process of second phase precipitation hardening. Keywords: Stainless steel, Weld, AISI 304, Precipitation hardening

  15. Strain hardening by dynamic slip band refinement in a high-Mn lightweight steel

    International Nuclear Information System (INIS)

    Welsch, E.; Ponge, D.; Hafez Haghighat, S.M.; Sandlöbes, S.; Choi, P.; Herbig, M.; Zaefferer, S.; Raabe, D.

    2016-01-01

    The strain hardening mechanism of a high-Mn lightweight steel (Fe-30.4Mn-8Al-1.2C (wt%)) is investigated by electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM). The alloy is characterized by a constant high strain hardening rate accompanied by high strength and high ductility (ultimate tensile strength: 900 MPa, elongation to fracture: 68%). Deformation microstructures at different strain levels are studied in order to reveal and quantify the governing structural parameters at micro- and nanometer scales. As the material deforms mainly by planar dislocation slip causing the formation of slip bands, we quantitatively study the evolution of the slip band spacing during straining. The flow stress is calculated from the slip band spacing on the basis of the passing stress. The good agreement between the calculated values and the tensile test data shows dynamic slip band refinement as the main strain hardening mechanism, enabling the excellent mechanical properties. This novel strain hardening mechanism is based on the passing stress acting between co-planar slip bands in contrast to earlier attempts to explain the strain hardening in high-Mn lightweight steels that are based on grain subdivision by microbands. We discuss in detail the formation of the finely distributed slip bands and the gradual reduction of the spacing between them, leading to constantly high strain hardening. TEM investigations of the precipitation state in the as-quenched state show finely dispersed atomically ordered clusters (size < 2 nm). The influence of these zones on planar slip is discussed.

  16. Controls on plant functional surface cover types along a precipitation gradient in the Negev Desert of Israel

    NARCIS (Netherlands)

    Buis, E.; Veldkamp, A.; Boeken, B.; Breemen, van N.

    2009-01-01

    We studied the controls on functional surface cover types in four catchments along a semi-arid to arid precipitation gradient in the northern Negev Desert of Israel. First, we selected four functional types, based on their unique water use and redistribution functionality: shrubs, Asphodelus

  17. Dependence of precipitation of trace elements on pH in standard water

    Science.gov (United States)

    Verma, Shivcharan; Mohanty, Biraja P.; Singh, K. P.; Behera, B. R.; Kumar, Ashok

    2018-04-01

    The present work aimed to study the dependence of precipitation of trace elements on the pH of solution. A standard solution was prepared by using ultrapure deionized water (18.2 MΩ/cm) as the solvent and 11 water-soluble salts having different elements as solutes. Five samples of different pH values (2 acidic, 2 basic, and 1 neutral) were prepared from this standard solution. Sodium-diethyldithiocarbamate was used as the chelating agent to precipitate the metal ions present in these samples of different pH values. The targets were prepared by collecting these precipitates on mixed cellulose esters filter of 0.4 μm pore size by vacuum filtration. Elemental analysis of these targets was performed by particle-induced X-ray emission (PIXE) using 2.7 MeV protons from the single Dee variable energy cyclotron at Panjab University, Chandigarh, India. PIXE data were analyzed using GUPIXWIN software. For most of the elements, except Hg with oxidation state +2, such as Co, Ni, Zn, Ba, and Cd, a general trend of enhancement in precipitation was observed with the increase in pH. However, for other elements such as V, As, Mo, Ag, and Bi, which have oxidation state other than +2, no definite pattern was observed. Precipitation of Ba and As using this method was negligible at all five pH values. From these results, it can be concluded that the precipitation and recovery of elements depend strongly on the pH of the water sample.

  18. Investigation of precipitation and hardening response of maraging stainless steels 17-4 and 13-8+Mo during multi-pass welding

    Science.gov (United States)

    Hamlin, Robert J.

    Martensitic precipitation strengthened stainless steels 17-4 and 13-8+Mo are candidate alloys for high strength military applications. These applications will require joining by fusion welding processes thus, it is necessary to develop an understanding of microstructural and mechanical property changes that occur during welding. Previous investigations on these materials have demonstrated that significant softening occurs in the heat affected zone (HAZ) during welding, due to dissolution of the strengthen precipitates. It was also observed that post weld heat treatments (PWHT's) were required to restore the properties. However, PWHT's are expensive and cannot be applied when welding on a large scale or making a repair in the field. Thus, the purpose of the current work is to gain a fundamental understanding of the precipitation kinetics in these systems so that optimized welding procedures can be developed that do not require a PWHT. Multi-pass welding provides an opportunity to restore the strengthening precipitates that dissolve during primary weld passes using the heat from secondary weld passes. Thus, a preliminary investigation was performed to determine whether the times and temperatures associated with welding thermal cycles were sufficient to restore the strength in these systems. A Gleeble thermo-mechanical simulator was used to perform multi-pass welding simulations on samples of each material using a 1000 J/mm and 2000 J/mm heat input. Additionally, base metal and weld metal samples were used as starting conditions to evaluate the difference in precipitation response between each. Hardness measurements were used to estimate the extent of precipitate dissolution and growth. Microstructures were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). It was determined that precipitate dissolution occurred during primary welding thermal cycles and that significant hardening could be

  19. Effects of Static Recrystallization and Precipitation on Mechanical Properties of 00Cr12 Ferritic Stainless Steel

    Science.gov (United States)

    Shao, Yi; Liu, Chenxi; Yue, Tengxiao; Liu, Yongchang; Yan, Zesheng; Li, Huijun

    2018-05-01

    The 00Cr12 ferritic stainless steel samples were isothermally held at different temperatures in the range of 700 °C to 1000 °C to investigate the effect of static recrystallization and precipitation on mechanical properties, such as microhardness, tensile strength, and yield strength. The results show that the formation of the fine recrystallized grain, as well as precipitation, coarsening, and dissolution of the second-phase particles, influences the mechanical properties remarkably. The fine recrystallized grain can provide a positive grain boundary-strengthening effect in the sample under a relatively high holding temperature. Coarsening and dissolution of M23C6 result in partial depletion of precipitate hardening. In contrast, the size and number density of MX particles are almost constant, regardless of the holding temperature; therefore, it can provide a better precipitation-hardening effect.

  20. Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)

    Science.gov (United States)

    Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)

    2017-01-01

    Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.

  1. Age hardening in die-cast Mg–Al–RE alloys due to minor Mn additions

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, S.M., E-mail: suming.zhu@rmit.edu.au [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Abbott, T.B. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Magontec Limited, Sydney, New South Wales 2000 (Australia); Gibson, M.A. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); CSIRO Manufacturing Flagship, Clayton, Victoria 3168 (Australia); Nie, J.F. [Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Easton, M.A. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia)

    2016-02-22

    Die-cast Mg–Al–rare earth (RE) alloys are normally used in the as-cast condition without the application of heat treatment because it is a common perception that heat treatment will not provide benefit to these alloys. This paper reports, for the first time, that enhanced age hardenability can be achieved in die-cast Mg–Al–RE alloys with minor Mn additions. For example, the yield strength of Mg–4 wt%Al–3 wt%La alloy with 0.32 wt% Mn is increased by ∼34 MPa (∼26%) after ageing at 200 °C for 32 h (T5). The enhanced age hardenability is associated with the precipitation of nanoscale Al–Mn particles during ageing.

  2. Effect of precipitates on mechanical properties of AA2195

    International Nuclear Information System (INIS)

    Kim, Jae-Hee; Jeun, Jeong-Hoon; Chun, Hyun-Jin; Lee, Ye Rim; Yoo, Joon-Tae; Yoon, Jong-Hoon; Lee, Ho-Sung

    2016-01-01

    Addition of 1–4 wt.% lithium into a conventional Al–Cu–Mg alloy allows lower density and higher mechanical properties, which are attractive for aerospace applications. In this study, fundamental investigations including phase and microstructure evolution, resulting in strengthening, of the AA2195 are conducted to observe a possibility of production with commercial level. Precipitation sequence and kinetics during post-annealing were evaluated with variations of temperature and holding time. Microstructures revealed formation and evolution in representative precipitates including θ (Al_2Cu), ß′ (Al_3Zr), and T (Al_xLi_yCu) series. Aluminum alloys have low hardness, modulus, and strength before aging, but precipitates such as θ′ (Al_2Cu), ß′ (Al_3Zr), and T_1 (Al_2LiCu) show enhanced mechanical properties of AA2195 tempered because of their interaction with dislocation. However, longer holding time and higher annealing temperature result in significant decreases in mechanical properties due to the presence of incoherent precipitates (θ phase) and coarsening of the precipitates via grain-boundary diffusion. In the current study, the tensile strength of 560 MPa was obtained with post-heat treatment without work hardening. This value has never been achieved in other studies. The maximum strength was reported as 500 MPa without a work hardening process. - Highlights: • A relationship between microstructure and mechanical properties to post annealing AA2195. • A formation and dissolution of the precipitates were observed for various treatment. • An optimum post-annealing condition was obtained.

  3. Effect of precipitates on mechanical properties of AA2195

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Hee [Launcher Structure and Materials Team, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Jeun, Jeong-Hoon [Department of Materials Science and Engineering, Seoul National University, Seoul (Korea, Republic of); Chun, Hyun-Jin [Southeast University, Nanjing (China); Lee, Ye Rim [Department of Aerospace System Engineering, University of Science & Technology, Daejeon (Korea, Republic of); Yoo, Joon-Tae [Launcher Structure and Materials Team, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Yoon, Jong-Hoon [Launcher Structure and Materials Team, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Department of Aerospace System Engineering, University of Science & Technology, Daejeon (Korea, Republic of); Lee, Ho-Sung, E-mail: hslee@kari.re.kr [Launcher Structure and Materials Team, Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Department of Aerospace System Engineering, University of Science & Technology, Daejeon (Korea, Republic of)

    2016-06-05

    Addition of 1–4 wt.% lithium into a conventional Al–Cu–Mg alloy allows lower density and higher mechanical properties, which are attractive for aerospace applications. In this study, fundamental investigations including phase and microstructure evolution, resulting in strengthening, of the AA2195 are conducted to observe a possibility of production with commercial level. Precipitation sequence and kinetics during post-annealing were evaluated with variations of temperature and holding time. Microstructures revealed formation and evolution in representative precipitates including θ (Al{sub 2}Cu), ß′ (Al{sub 3}Zr), and T (Al{sub x}Li{sub y}Cu) series. Aluminum alloys have low hardness, modulus, and strength before aging, but precipitates such as θ′ (Al{sub 2}Cu), ß′ (Al{sub 3}Zr), and T{sub 1} (Al{sub 2}LiCu) show enhanced mechanical properties of AA2195 tempered because of their interaction with dislocation. However, longer holding time and higher annealing temperature result in significant decreases in mechanical properties due to the presence of incoherent precipitates (θ phase) and coarsening of the precipitates via grain-boundary diffusion. In the current study, the tensile strength of 560 MPa was obtained with post-heat treatment without work hardening. This value has never been achieved in other studies. The maximum strength was reported as 500 MPa without a work hardening process. - Highlights: • A relationship between microstructure and mechanical properties to post annealing AA2195. • A formation and dissolution of the precipitates were observed for various treatment. • An optimum post-annealing condition was obtained.

  4. Age hardening of cold-worked Zr-2.5 wt% Nb pressure tube alloy

    International Nuclear Information System (INIS)

    Kishore, R.; Singh, R.N.; Dey, G.K.; Sinha, T.K.

    1992-01-01

    Specimens for hardness and tensile tests, machined from a cold-worked zirconium-2.5% niobium pressure tube, with their axes parallel to longitudinal and transverse directions, were aged for 1 hr. at 300-500 C. The age hardening behaviour was monitored by mechanical tests, electron-microscopy and x-ray diffraction. In addition a few studies were carried on longitudinal tension specimens subjected to prolonged ageing (100-1000 hrs) at 300 C. It was observed that the short-term (1 hour) thermal ageing of this material at 300-400 C caused an increase in both strength and hardness without affecting ductility. It appears that the observed age-hardening is due to precipitation hardening by a niobium-rich phase and softening by recovery of cold-work and that the phenomenon is influenced by crystallographic texture. Further it was noted that a prolonged ageing at 300 C upto 1000 hrs, did not cause any appreciable changes in strength and ductility of the material compared to those obtained by 1 hour ageing at the same temperature. (author). 11 refs., 3 figs., 2 tabs

  5. Thermokinetic Simulation of Precipitation in NiTi Shape Memory Alloys

    Science.gov (United States)

    Cirstea, C. D.; Karadeniz-Povoden, E.; Kozeschnik, E.; Lungu, M.; Lang, P.; Balagurov, A.; Cirstea, V.

    2017-06-01

    Considering classical nucleation theory and evolution equations for the growth and composition change of precipitates, we simulate the evolution of the precipitates structure in the classical stages of nucleation, growth and coarsening using the solid-state transformation Matcalc software. The formation of Ni3Ti, Ni4Ti3 or Ni3Ti2 precipitate is the key to hardening phenomenon of the alloys, which depends on the nickel solubility in the bulk alloys. The microstructural evolution of metastable Ni4Ti3 and Ni3Ti2 precipitates in Ni-rich TiNi alloys is simulated by computational thermokinetics, based on thermodynamic and diffusion databases. The simulated precipitate phase fractions are compared with experimental data.

  6. Why semiconductors must be hardened when used in space

    International Nuclear Information System (INIS)

    Winokur, P.S.

    2000-01-01

    The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest

  7. Microstructural Evolution and Mechanical Properties of Simulated Heat-Affected Zones in Cast Precipitation-Hardened Stainless Steels 17-4 and 13-8+Mo

    Science.gov (United States)

    Hamlin, Robert J.; DuPont, John N.

    2017-01-01

    Cast precipitation-hardened (PH) stainless steels 17-4 and 13-8+Mo are used in applications that require a combination of high strength and moderate corrosion resistance. Many such applications require fabrication and/or casting repair by fusion welding. The purpose of this work is to develop an understanding of microstructural evolution and resultant mechanical properties of these materials when subjected to weld thermal cycles. Samples of each material were subjected to heat-affected zone (HAZ) thermal cycles in the solution-treated and aged condition (S-A-W condition) and solution-treated condition with a postweld thermal cycle age (S-W-A condition). Dilatometry was used to establish the onset of various phase transformation temperatures. Light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were used to characterize the microstructures, and comparisons were made to gas metal arc welds that were heat treated in the same conditions. Tensile testing was also performed. MatCalc thermodynamic and kinetic modeling software was used to predict the evolution of copper (Cu)-rich body center cubic precipitates in 17-4 and β-NiAl precipitates in 13-8+Mo. The yield strength was lower in the simulated HAZ samples of both materials prepared in the S-A-W condition when compared to their respective base metals. Samples prepared in the S-W-A condition had higher and more uniform yield strengths for both materials. Significant changes were observed in the matrix microstructure of various HAZ regions depending on the peak temperature, and these microstructural changes were interpreted with the aid of dilatometry results, LOM, SEM, and EDS. Despite these significant changes to the matrix microstructure, the changes in mechanical properties appear to be governed primarily by the precipitation behavior. The decrease in strength in the HAZ samples prepared in the S-A-W condition was attributed to the dissolution of precipitates

  8. A non-linear kinematic hardening function

    International Nuclear Information System (INIS)

    Ottosen, N.S.

    1977-05-01

    Based on the classical theory of plasticity, and accepting the von Mises criterion as the initial yield criterion, a non-linear kinematic hardening function applicable both to Melan-Prager's and to Ziegler's hardening rule is proposed. This non-linear hardening function is determined by means of the uniaxial stress-strain curve, and any such curve is applicable. The proposed hardening function considers the problem of general reversed loading, and a smooth change in the behaviour from one plastic state to another nearlying plastic state is obtained. A review of both the kinematic hardening theory and the corresponding non-linear hardening assumptions is given, and it is shown that material behaviour is identical whether Melan-Prager's or Ziegler's hardening rule is applied, provided that the von Mises yield criterion is adopted. (author)

  9. Laser transformation hardening effect on hardening zone features and surface hardness of tool steel AISI D2

    Directory of Open Access Journals (Sweden)

    D. Lesyk

    2017-06-01

    Full Text Available The relationship of technological input regimes of the laser transformation hardening on change the hardening depth, hardening width, and hardening angle, as well as surface hardness of the tool steel AISI D2 using multifactor experiment with elements of the analysis of variance and regression equations was determined. The laser transformation hardening process implemented by controlling the heating temperature using Nd:YAG fiber laser with scanner, pyrometer and proportional-integral-differential controller. The linear and quadratic regression models are developed, as well as response surface to determine the effect of the heating temperature and feed rate of the treated surface on the energy density of the laser beam, hardening depths, hardening width, hardening angle, and surface hardness are designed. The main effect on the energy density of the laser beam has a velocity laser treatment, on the other hand, the main effect on the geometrical parameters of the laser hardened zone and surface hardness has temperature heating are shown. The optimum magnitudes of the heating temperature (1270 °C and feed rate of the treated surface (90 mm/min for laser transformation hardening of the tool steel AISI D2 using fiber laser with scanner were defined.

  10. The effect of austenitizing conditions in the ductile iron hardening process on longitudinal ultrasonic wave velocity

    Directory of Open Access Journals (Sweden)

    A. W. Orłowicz

    2014-04-01

    Full Text Available The paper presents results of a research on the effect of austenitizing temperature and time adopted in the hardening operation on the ultrasonic wave velocity in ductile iron. It has been found that with increasing austenitizing temperature and with the passage of the austenitizing time, a monotonic decrease of the ultrasonic longitudinal wave velocity value occurred. Implementation of ultrasonic testing of results obtained in the course of the cast iron hardening process both in production and as-cast conditions, requires development of a test methodology that must take into account the influence of base material structure (degree of nodularization, graphite precipitation count on the ultrasound wave velocity.

  11. Superheat effect on bainite steel hardenability

    International Nuclear Information System (INIS)

    Kubachek, V.V.; Sklyuev, P.V.

    1978-01-01

    The bainite hardenability of 34KhN1M and 35 KhN1M2Ph steels has been investigated by the end-face hardening technique. It is established that, as the temperature of austenitization rises from 900 to 1280 deg C, the temperature of bainite transformation increases and bainite hardenability of the steels falls off. A repeated slow heating to 900 deg C of previously overheated 34KhN1M steel breaks up grain, lowers the temperature of the bainite transformation and raises the hardenability to values obtained with ordinary hardening from 900 deg C. A similar heating of previously overheated 35KhN1M2Ph steel is accompanied by restoration of initial coarse grains and maintenance of both the elevated bainite transformation temperature and to lower hardenability corresponding to hardening from the temperature of previous overheating

  12. Effect of high-temperature pre-precipitation on microstructure and properties of 7055 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    陈康华; 黄兰萍

    2003-01-01

    The near-solvus pre-precipitation following higher temperature solution treatment was performed on 7055 aluminum alloy. The effect of the pre-precipitation on the microstructure, age hardening and stress corrosion cracking of 7055 alloy was investigated. The optical and transmission electron microscopy results show that the near-solvus pre-precipitation can be limited to grain boundary and enhance the discontinuity of grain boundary precipitates in the sequent age. The stress corrosion cracking resistance of aged 7055 alloys could be improved with non-deteriorated strength and plasticity via the pre-precipitation.

  13. Tuning Low Cycle Fatigue Properties of Cu-Be-Co-Ni Alloy by Precipitation Design

    Directory of Open Access Journals (Sweden)

    Yanchuan Tang

    2018-06-01

    Full Text Available As material for key parts applied in the aerospace field, the Cu-Be-Co-Ni alloy sustains cyclic plastic deformation in service, resulting in the low cycle fatigue (LCF failure. The LCF behaviors are closely related to the precipitation states of the alloy, but the specific relevance is still unknown. To provide reasonable regulation of the LCF properties for various service conditions, the effect of precipitation states on the LCF behaviors of the alloy was investigated. It is found that the alloy composed fully of non-shearable γ′ precipitates has higher fatigue crack initiation resistance, resulting in a longer fatigue life under LCF process with low total strain amplitude. The alloy with fine shearable γ′I precipitates presents higher fatigue crack propagation resistance, leading to a longer fatigue life under LCF process with high total strain amplitude. The cyclic stress response behavior of the alloy depends on the competition between the kinematic hardening and isotropic softening. The fine shearable γ′I precipitates retard the decrease of effective stress during cyclic loading, causing cyclic hardening of the alloy. The present work would help to design reasonable precipitation states of the alloy for various cyclic loading conditions to guarantee its safety in service.

  14. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    International Nuclear Information System (INIS)

    Huang, Zhi Yong; Chaboche, Jean-Louis; Wang, Qing Yuan; Wagner, Danièle; Bathias, Claude

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C

  15. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean-Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320 Chatillon (France); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C.

  16. Standardized precipitation index zones for Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Giddings, L.; Soto, M. [Instituto de Ecologia, A.C., Xalapa, Veracruz (Mexico); Rutherford, B.M.; Maarouf, A. [Faculty of Environmental Studies, York University, Toronto, Ontario (Canada)

    2005-01-01

    Precipitation zone systems exists for Mexico based on seasonality, quantity of precipitation, climates and geographical divisions, but none are convenient for the study of the relation of precipitation with phenomena such as El nino. An empirical set of seven exclusively Mexican and six shared zones was derived from three series of Standardized Precipitation Index (SPI) images, from 1940 through 1989: a whole year series (SPI-12) of 582 monthly images, a six month series (SPI-6) of 50 images for winter months (November through April), and a six month series (SPI-6) of 50 images for summer months (May through October). By examination of principal component and unsupervised classification images, it was found that all three series had similar zones. A set of basic training fields chosen from the principal component images was used to classify all three series. The resulting thirteen zones, presented in this article, were found to be approximately similar, varying principally at zones edges. A set of simple zones defined by just a few vertices can be used for practical operations. In general the SPI zones are homogeneous, with almost no mixture of zones and few outliers of one zone in the area of others. They are compared with a previously published map of climatic regions. Potential applications for SPI zones are discussed. [Spanish] Existen varios sistemas de zonificacion de Mexico basados en la estacionalidad, cantidad de precipitacion, climas y divisiones geograficas, pero ninguno es conveniente para el estudio de la relacion de la precipitacion con fenomenos tales como El Nino. En este trabajo se presenta un conjunto de siete zonas empiricas exclusivamente mexicanas y seis compartidas, derivadas de tres series de imagenes de SPI (Indice Estandarizado de la Precipitacion), desde 1940 a 1989: una serie de 582 imagenes mensuales (SPI-12), una series de 50 imagenes (SPI-6) de meses de invierno (noviembre a abril), y otra de 50 imagenes (SPI-6) de meses de verano

  17. Standard Enucleation with Aluminium Oxide Implant (Bioceramic Covered with Patient's Sclera

    Directory of Open Access Journals (Sweden)

    Gian Luigi Zigiotti

    2012-01-01

    Full Text Available Purpose. We describe in our study a modified standard enucleation, using sclera harvested from the enucleated eye to cover the prosthesis in order to insert a large porous implant and to reduce postoperative complication rates in a phthisis globe. Methods. We perform initially a standard enucleation. The porous implant (Bioceramic is then covered only partially by the patient's sclera. The implant is inserted in the posterior Tenon's space with the scleral covering looking at front. All patients were followed at least for twelve months (average followup 16 months. Results. We performed nineteen primary procedures (19 patients, 19 eyes, M; F and secondary, to fill the orbital cavity in patients already operated by standard evisceration (7 patients, 7 eyes. There were no cases of implant extrusion. The orbital volume was well reintegrated. Conclusion. Our procedure was safe and effective. All patients had a good cosmetic result after final prosthetic fitting and we also achieved good prothesis mobility.

  18. Segmentation-free empirical beam hardening correction for CT

    Energy Technology Data Exchange (ETDEWEB)

    Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  19. Segmentation-free empirical beam hardening correction for CT.

    Science.gov (United States)

    Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

    2015-02-01

    The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed

  20. Precipitation behavior of aluminum alloy 2139 fabricated using additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Brice, Craig, E-mail: craig.a.brice@lmco.com [NASA Langley Research Center, Hampton, VA 23681 (United States); Shenoy, Ravi [Northrop Grumman Corporation Technical Services, Hampton, VA 23681 (United States); Kral, Milo; Buchannan, Karl [University of Canterbury, Christchurch (New Zealand)

    2015-11-11

    Additive manufacturing (AM) is an emerging technology capable of producing near net shape structures in a variety of materials directly from a computer model. Standard metallic alloys that were developed for cast or wrought processing have largely been adopted for AM feedstock. In many applications, these legacy alloys are quite acceptable. In the aluminum alloy family, however, there is a significant performance gap between the casting alloys currently being used in AM processes and the high strength/toughness capability available in certain wrought alloys. The precipitation hardenable alloys, most often used in high performance structures, present challenges for processing by AM. The near net shape nature of AM processes does not allow for mechanical work prior to the heat treatment that is often necessary to develop a uniform distribution of precipitates and give peak mechanical performance. This paper examines the aluminum (Al) alloy 2139, a composition that is strengthened by homogeneous precipitation of Ω (Al{sub 2}Cu) plates and thus ideally suited for near net shape processes like AM. Transmission electron microscopy, microhardness, and tensile testing determined that, with proper processing conditions, Al 2139 can be additively manufactured and subsequently heat treated to strength levels comparable to those of peak aged wrought Al 2139.

  1. Precipitation behavior of aluminum alloy 2139 fabricated using additive manufacturing

    International Nuclear Information System (INIS)

    Brice, Craig; Shenoy, Ravi; Kral, Milo; Buchannan, Karl

    2015-01-01

    Additive manufacturing (AM) is an emerging technology capable of producing near net shape structures in a variety of materials directly from a computer model. Standard metallic alloys that were developed for cast or wrought processing have largely been adopted for AM feedstock. In many applications, these legacy alloys are quite acceptable. In the aluminum alloy family, however, there is a significant performance gap between the casting alloys currently being used in AM processes and the high strength/toughness capability available in certain wrought alloys. The precipitation hardenable alloys, most often used in high performance structures, present challenges for processing by AM. The near net shape nature of AM processes does not allow for mechanical work prior to the heat treatment that is often necessary to develop a uniform distribution of precipitates and give peak mechanical performance. This paper examines the aluminum (Al) alloy 2139, a composition that is strengthened by homogeneous precipitation of Ω (Al_2Cu) plates and thus ideally suited for near net shape processes like AM. Transmission electron microscopy, microhardness, and tensile testing determined that, with proper processing conditions, Al 2139 can be additively manufactured and subsequently heat treated to strength levels comparable to those of peak aged wrought Al 2139.

  2. Evolution of mechanical behavior of 6XXX aluminium alloy due to the precipitation state during a thermo-mechanical process

    International Nuclear Information System (INIS)

    Bardel, Didier; Perez, Michel; Nelias, Daniel; Chaise, Thibaut; Garnier, Jerome; Bourlier, Florent

    2014-01-01

    The aim of this research is to link the microstructural state and the mechanical properties of an age hardening alloy during a fast heat treatment such as encountered during welding. A coupled model between precipitation state and mechanical properties is used to predict the yield strength and hardening behavior that can be observed experimentally. The method permits the identification of the kinematic and isotropic contributions in the hardening model. The methodology is applied to a 6061-T6 aluminium alloy which is used in the Jules Horowitz reactor vessel. The general idea of this methodology is to couple an efficient microstructural model to a mechanical one based on the dislocation theory and ad'hoc experiments. The theoretical background is based on the work of Kampmann and Wagner, known as the KWN model, to account for nucleation, growth/dissolution and coarsening of precipitates. This analysis requires transient thermo-mechanical experimental data. The efficiency of these models and their coupling are shown for a series 6XXX aluminium alloy which contains β'' and β' precipitates. Ultimately these models are coupled to a FEA model and allows to predict the distribution of precipitates within each element of the mesh, and subsequently its mechanical behavior. (authors)

  3. Update on radiation-hardened microcomputers for robotics and teleoperated systems

    International Nuclear Information System (INIS)

    Sias, F.R. Jr.; Tulenko, J.S.

    1993-01-01

    Since many programs sponsored by the Department of Defense are being canceled, it is important to select carefully radiation-hardened microprocessors for projects that will mature (or will require continued support) several years in the future. At the present time there are seven candidate 32-bit processors that should be considered for long-range planning for high-performance radiation-hardened computer systems. For Department of Energy applications it is also important to consider efforts at standardization that require the use of the VxWorks operating system and hardware based on the VMEbus. Of the seven processors, one has been delivered and is operating and other systems are scheduled to be delivered late in 1993 or early in 1994. At the present time the Honeywell-developed RH32, the Harris RH-3000 and the Harris RHC-3000 are leading contenders for meeting DOE requirements for a radiation-hardened advanced 32-bit microprocessor. These are all either compatible with or are derivatives of the MIPS R3000 Reduced Instruction Set Computer. It is anticipated that as few as two of the seven radiation-hardened processors will be supported by the space program in the long run

  4. A Study of Tensile Flow and Work-Hardening Behavior of Alloy 617

    Science.gov (United States)

    Singh, Aditya Narayan; Moitra, A.; Bhaskar, Pragna; Dasgupta, Arup; Sasikala, G.; Bhaduri, A. K.

    2018-04-01

    The simple power relationship σ = Κɛ p n satisfactorily expresses the tensile flow behavior of many metals and alloys in their uniform plastic strain regime. However, many FCC materials with low stacking fault energy have opposed such power law relationship. Alloy 617, an age-hardenable Ni-based superalloy is also observed not to obey the simple power law relationship neither in its solution-treated nor in its aged conditions. Various flow relationships were used to obtain the best fit for the tensile data, and different relationships were identified for the different aged conditions. The work-hardening rate (θ) demonstrates three distinct regions for all aged conditions, and there is an obvious change in the trend of θ versus σ. In the initial portion, θ decreases rapidly followed by a gradual increase in the second stage and again a decrease in its third stage is perceived in the Alloy 617. These three-stage characteristics are attributed to a commonly known precipitate, γ': Ni3(Ti, Al) which evolves during aging treatment and well recognized under transmission electron microscopy (TEM) observation. TEM results also reveal a slight degree of coarsening in γ' over aging. The tensile flow and the work-hardening behavior are well correlated with other microstructural evolution during the aging treatments.

  5. Study of the mechanisms involved in the laser superficial hardening process of metallic alloys

    International Nuclear Information System (INIS)

    Silva, Edmara Marques Rodrigues da

    2001-01-01

    The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO 2 laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the level of

  6. Mesoscale modeling of solute precipitation and radiation damage

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schwen, Daniel [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ke, Huibin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Univ. of Wisconsin, Madison, WI (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hales, Jason [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    This report summarizes the low length scale effort during FY 2014 in developing mesoscale capabilities for microstructure evolution in reactor pressure vessels. During operation, reactor pressure vessels are subject to hardening and embrittlement caused by irradiation-induced defect accumulation and irradiation-enhanced solute precipitation. Both defect production and solute precipitation start from the atomic scale, and manifest their eventual effects as degradation in engineering-scale properties. To predict the property degradation, multiscale modeling and simulation are needed to deal with the microstructure evolution, and to link the microstructure feature to material properties. In this report, the development of mesoscale capabilities for defect accumulation and solute precipitation are summarized. Atomic-scale efforts that supply information for the mesoscale capabilities are also included.

  7. Radiation-hardened nonvolatile MNOS RAM

    International Nuclear Information System (INIS)

    Wrobel, T.F.; Dodson, W.H.; Hash, G.L.; Jones, R.V.; Nasby, R.D.; Olson, R.J.

    1983-01-01

    A radiation hardened nonvolatile MNOS RAM is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s

  8. Optimization of resistively hardened latches

    International Nuclear Information System (INIS)

    Gagne, G.; Savaria, Y.

    1990-01-01

    The design of digital circuits tolerant to single-event upsets is considered. The results of a study are presented on which an analytical model was used to predict the behavior of a standard resistively hardened latch. It is shown that a worst case analysis for all possible single-event upset situations (on the latch or in the logic) can be derived from studying the effects of a transient disturbed write cycle. The existence of an intrinsic minimum write period to tolerate a transient of a given duration is also demonstrated

  9. Boundary and sub-boundary hardening in high-Cr ferritic steels during long-term creep at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Abe, F. [National Institute for Materials Science (NIMS) (Japan)

    2008-07-01

    The sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the sub-boundary hardening. This improves long-term creep strength. The enhancement of boundary and subboundary hardening by fine distribution of precipitates along boundaries is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steels P92 and P122. In NIMS 9% Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. (orig.)

  10. Snow Precipitation and Snow Cover Climatic Variability for the Period 1971–2009 in the Southwestern Italian Alps: The 2008–2009 Snow Season Case Study

    Directory of Open Access Journals (Sweden)

    Simona Fratianni

    2010-10-01

    Full Text Available Snow cover greatly influences the climate in the Alpine region and is one of the most relevant parameters for the climate change analysis. Nevertheless, snow precipitation variability is a relatively underexplored field of research because of the lack of long-term, continuous and homogeneous time series. After a historical research aiming to recover continuous records, three high quality time series of snow precipitation and snow depth recorded in the southwestern Italian Alps were analyzed. The comparison between the climatological indices over the 30 years reference period 1971–2000 and the decade 2000–2009 outlined a general decrease in the amount of snow precipitation, and a shift in the seasonal distribution of the snow precipitation in the most recent period. In the analysis of the last decade snow seasons characteristics, the attention was focused on the heavy snowfalls that occurred in Piedmont during the 2008–2009 snow season: MODerate resolution Imager Spectroradiometer (MODIS snow cover products were used to evaluate snow cover extension at different times during the snow season, and the results were set in relation to the temperatures.

  11. On the hardenability of Nb-modified metastable beta Ti-5553 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Campo, K.N.; Andrade, D.R.; Opini, V.C.; Mello, M.G.; Lopes, E.S.N.; Caram, R., E-mail: caram@fem.unicamp.br

    2016-05-15

    Among the commercially available titanium alloys, the metastable β Ti-5553 alloy (Ti–5Al–5V–5Mo–3Cr–0.5Fe wt.%) is an object of great interest because it is employed in aerospace structural applications, primarily in the replacement of steel components. One of the primary advantages of this alloy is its high hardenability, which allows it to retain the β phase at room temperature, even at low cooling rates, thereby allowing the thermoprocessing of thick parts. The aim of this investigation was to evaluate the effect of the replacement of V with Nb on the hardenability of Ti-5553. Based on the molybdenum equivalent criterion, the Nb-modified Ti-5553 alloy was designed to present 12 wt.% of Nb instead of 5 wt.% of V. Samples of both alloys were prepared by melting them in an arc furnace under an inert atmosphere, heat-treated at high temperatures for 12 h and plastic deformed using swage forging. Finally, these samples were solution heat-treated at temperatures above the β-transus followed by cooling at different rates using water quenching, furnace cooling and a modified Jominy end quench test. Characterization was performed by measuring Vickers hardness, X-ray diffraction, and light optical, scanning electron and transmission electron microscopy. The results obtained indicate that metastable β phase can be retained when the cooling rate is higher than 21 °C/s for both alloys. At lower cooling rates, α phase precipitation was observed, but it appeared to be less evident in the Nb-modified Ti-5553, suggesting that the replacement of V with Nb increased the hardenability of the alloy. - Highlights: • Hardenability of Ti alloys are assessed using a modified Jominy end quench test. • Ti-5553 and Nb-modified Ti-5553 are subjected to continuous cooling experiments. • β phase decomposition kinetics is reduced by replacing V with Nb in Ti-5553. • Nb-modified Ti-5553 features improved hardenability. • Replacement of V with Nb causes the

  12. Effect of Second Aging Treatment on the Microstructure and Mechanical Properties of SUH660 Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Do-Hoon; Kim, Jeoung Han [Hanbat National University, Daejeon (Korea, Republic of); Lee, You-Hwan [Taeyang Metal Industrial Co., Ltd., Ansan (Korea, Republic of)

    2016-10-15

    SUH660 is a precipitation hardening stainless steel which has high strength at moderately high temperature. In this study, the effect of a secondary aging-treatment after the standard 720 °C heat-treatment was investigated. The Rockwell C hardness test with detailed TEM observerations was performed to study the steel's hardening mechanism. The additional secondary aging treatment noticeably increased hardness and tensile strength. In particular, a secondary aging treatment at 630 °C for 24 hrs resulted in the maximum hardness of 35.5 HRC, which is higher than the hardness of a standard heat-treated sample by around 4 HRC. A transmission electron microscopy study revealed the size distribution of γ′ and h precipitates after standard aging treatment. In contrast, the η precipitate was not oberserved after the 630 °C secondary aging-treatment. Contrary to expectation, the γ′′ precipitate was not observed regardless of aging-treatment. The mechanism of the hardening process is discussed.

  13. Self-organizing map network-based precipitation regionalization for the Tibetan Plateau and regional precipitation variability

    Science.gov (United States)

    Wang, Nini; Yin, Jianchuan

    2017-12-01

    A precipitation-based regionalization for the Tibetan Plateau (TP) was investigated for regional precipitation trend analysis and frequency analysis using data from 1113 grid points covering the period 1900-2014. The results utilizing self-organizing map (SOM) network suggest that four clusters of precipitation coherent zones can be identified, including the southwestern edge, the southern edge, the southeastern region, and the north central region. Regionalization results of the SOM network satisfactorily represent the influences of the atmospheric circulation systems such as the East Asian summer monsoon, the south Asian summer monsoon, and the mid-latitude westerlies. Regionalization results also well display the direct impacts of physical geographical features of the TP such as orography, topography, and land-sea distribution. Regional-scale annual precipitation trend as well as regional differences of annual and seasonal total precipitation were investigated by precipitation index such as precipitation concentration index (PCI) and Standardized Anomaly Index (SAI). Results demonstrate significant negative long-term linear trends in southeastern TP and the north central part of the TP, indicating arid and semi-arid regions in the TP are getting drier. The empirical mode decomposition (EMD) method shows an evolution of the main cycle with 4 and 12 months for all the representative grids of four sub-regions. The cross-wavelet analysis suggests that predominant and effective period of Indian Ocean Dipole (IOD) on monthly precipitation is around ˜12 months, except for the representative grid of the northwestern region.

  14. Influence of Hardening Model on Weld Residual Stress Distribution

    Energy Technology Data Exchange (ETDEWEB)

    Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))

    2009-06-15

    This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

  15. Influence of Hardening Model on Weld Residual Stress Distribution

    International Nuclear Information System (INIS)

    Mullins, Jonathan; Gunnars, Jens

    2009-06-01

    This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

  16. Enhanced bake-hardening response of an Al–Mg–Si–Cu alloy with Zn addition

    Energy Technology Data Exchange (ETDEWEB)

    Guo, M.X., E-mail: mingxingguo@skl.ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Sha, G., E-mail: gang.sha@njust.edu.cn [School of Materials Science and Engineering, Nanjing University of Science and Technology, Jiangsu 210094 (China); Cao, L.Y. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Liu, W.Q. [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Zhang, J.S.; Zhuang, L.Z. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-07-15

    This study reports that Zn addition greatly enhances the bake-hardening response of an Al–Mg–Si–Cu alloy. The pre-aged alloy exhibits a high strength increment of 135 MPa after paint baking. Differential scanning calorimetry, atom probe tomography and high-resolution transmission electron microscopy reveal that Zn addition and pre-aging have significant effects on the solute nanostructure formation. Zn atoms partition into solute clusters/GP zones, and reduce the activation energy of β” precipitation in the alloy. - Highlights: • Zn addition can improve the bake-hardening response of an Al–Mg–Si–Cu alloy. • Zn addition can stabilize the solute clusters/GP zones from dissolution. • Zn addition can reduce the size of clusters formed in the pre-aging treatment. • Zn partitioned into solute clusters/GP zones and β” in the Zn-containing Al alloy.

  17. Age hardening in mechanically alloyed Al-Mg-Li-C-O

    Energy Technology Data Exchange (ETDEWEB)

    Papazian, J.M. (Corporate Research Center, Grumman Corporation, Bethpage, NY (USA)); Gilman, P. (Allied-Signal Inc., Morristown, NJ (USA))

    1990-05-01

    The age-hardening behavior of a series of mechanically alloyed Al-Mg-Li-C-O alloys containing 3.0-4.0 wt.% Mg and 1.3-1.75 wt.% Li was studied using hardness tests, differential scanning calorimetry (DSC) and transmission electron microscopy. The hardness tests showed an increased hardness after 100degC aging in all the alloys containing at least 1.5 at.% Li. Likewise, the calorimetry results showed the presence of pronounced precipitate dissolution peaks in these same alloys after 100degC aging. The volume fraction of precipitates formed (as measured by the dissolution enthalpies of the DSC peaks) increased systematically with increasing solute content. Transmission electron microscopy after 100 and 190degC aging showed images and diffraction spots similar to those of {delta}' (Al{sub 3}Li). Comparison of the DSC results with results from binary Al-Li and Al-Mg alloys indicated that the precipitates formed in the Al-Mg-Li-C-O alloys were similar to those formed in binary Al-Li alloys, and that the primary role of the magnesium was to lower the solid solubility of lithium. (orig.).

  18. Radiation hardening of integrated circuits technologies

    International Nuclear Information System (INIS)

    Auberton-Herve, A.J.; Leray, J.L.

    1991-01-01

    The radiation hardening studies started in the mid decade -1960-1970. To survive the different military or space radiative environment, a new engineering science borned, to understand the degradation of electronics components. The different solutions to improve the electronic behavior in such environment, have been named radiation hardening of the technologies. Improvement of existing technologies, and qualification method have been widely studied. However, at the other hand, specific technologies was developped : The Silicon On Insulator technologies for CMOS or Bipolar. The HSOI3HD technology (supported by DGA-CEA DAM and LETI with THOMSON TMS) offers today the highest hardening level for the integration density of hundreds of thousand transistors on the same silicon. Full complex systems would be realized on a single die with a technological radiation hardening and no more system hardening

  19. Precipitation sequence and its effect on age hardening of alumina-forming austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Joonoh, E-mail: mjo99@kims.re.kr [Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, Changwon, Gyeongnam 642-831 (Korea, Republic of); Lee, Tae-Ho [Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, Changwon, Gyeongnam 642-831 (Korea, Republic of); Heo, Yoon-Uk [Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, 77 Cheongam-ro, Nam-gu, Gyeongbuk 790-784 (Korea, Republic of); Han, Young-Soo [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kang, Jun-Yun; Ha, Heon-Young [Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, Changwon, Gyeongnam 642-831 (Korea, Republic of); Suh, Dong-Woo [Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, 77 Cheongam-ro, Nam-gu, Gyeongbuk 790-784 (Korea, Republic of)

    2015-10-01

    The precipitation sequence during ageing of Fe–14Cr–20Ni–0.9Nb–2.5Al based alumina-forming austenitic (AFA) steel was explored through a transmission electron microscopy analysis and a small angle neutron scattering experiment. The samples were aged at 700 °C for up to 504 h. Particles of NbC, M{sub 23}C{sub 6} and Ni{sub 3}Al-type L1{sub 2} were observed in the early stage of ageing. Metastable L1{sub 2} particles were formed both in grain interior and along grain boundary. M{sub 23}C{sub 6} carbides precipitated along grain boundary accompanied with precipitation of L1{sub 2} particles. After ageing for longer than 48 h, particles of B2-NiAl and Laves-Fe{sub 2}Nb were newly formed. We suggest the possibility of phase transition from L1{sub 2} to B2 with increase in ageing time. Finally, this study examined the change of mechanical properties during ageing through a Gleeble hot tension test and a Vickers hardness test, and then the relationship between precipitation behavior and mechanical properties was carefully investigated and discussed in terms of precipitation behavior.

  20. Working hardening modelization in zirconium alloys

    International Nuclear Information System (INIS)

    Sanchez, P.; Pochettino, Alberto A.

    1999-01-01

    Working hardening effects on mechanical properties and crystallographic textures formation in Zr-based alloys are studied. The hardening mechanisms for different grain deformations and topological conditions of simple crystal yield are considered. Results obtained show that the differences in the cold rolling textures (L and T textures) can be related with hardening microstructural parameters. (author)

  1. Reduction of metal artifacts: beam hardening and photon starvation effects

    Science.gov (United States)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  2. Practical aspects of systems hardening

    International Nuclear Information System (INIS)

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system

  3. Solution hardening and strain hardening at elevated temperatures

    International Nuclear Information System (INIS)

    Kocks, U.F.

    1982-10-01

    Solutes can significantly increase the rate of strain hardening; as a consequence, the saturation stress, at which strain hardening tends to cease for a given temperature and strain rate, is increased more than the yield stress: this is the major effect of solutes on strength at elevated temperatures, especially in the regime where dynamic strain-aging occurs. It is shown that local solute mobility can affect both the rate of dynamic recovery and the dislocation/dislocation interaction strength. The latter effect leads to multiplicative solution strengthening. It is explained by a new model based on repeated dislocation unlocking, in a high-temperature limit, which also rationalizes the stress dependence of static and dynamic strain-aging, and may help explain the plateau of the yield stress at elevated temperatures. 15 figures

  4. Transformation and precipitation in vanadium treated steels

    Science.gov (United States)

    Vassiliou, Andreas D.

    tempering and at higher tempering temperature introduced secondary hardening. The intensity of secondary hardening increased with increasing vanadium, whereas austenitising temperature had little or no effect. The softening after the secondary hardening was faster after austenitising at the higher temperature and when recrystallisation occurred at the highest tempering temperatures, the hardness was lower due to coarse recrystallised ferrite.Isothermal transformation studies showed that vanadium additions raised the Ar3 temperature and accelerated ferrite nucleation, whilst the growth of ferrite was delayed due to the formation of V(CN) interphase and general precipitation pinning, of the transformation front. Increasing nitrogen content in the V-steel increased the incubation period for ferrite nucleation and increasingly reduced the ferrite growth by increasing V(CN) precipitation pinning of the transformation front.Transformation during continuous cooling was examined in relation to the effect of vanadium, carbon and nitrogen together with the effect of austenitising temperature. Increasing austenitising temperature increased the austenite grain size, and it then became apparent that increasing vanadium, carbon and nitrogen increased the hardenability and raised the hardness level of the jominy curve for the non-martensitic products. (Abstract shortened by ProQuest.).

  5. High-throughput computational search for strengthening precipitates in alloys

    International Nuclear Information System (INIS)

    Kirklin, S.; Saal, James E.; Hegde, Vinay I.; Wolverton, C.

    2016-01-01

    The search for high-strength alloys and precipitation hardened systems has largely been accomplished through Edisonian trial and error experimentation. Here, we present a novel strategy using high-throughput computational approaches to search for promising precipitate/alloy systems. We perform density functional theory (DFT) calculations of an extremely large space of ∼200,000 potential compounds in search of effective strengthening precipitates for a variety of different alloy matrices, e.g., Fe, Al, Mg, Ni, Co, and Ti. Our search strategy involves screening phases that are likely to produce coherent precipitates (based on small lattice mismatch) and are composed of relatively common alloying elements. When combined with the Open Quantum Materials Database (OQMD), we can computationally screen for precipitates that either have a stable two-phase equilibrium with the host matrix, or are likely to precipitate as metastable phases. Our search produces (for the structure types considered) nearly all currently known high-strength precipitates in a variety of fcc, bcc, and hcp matrices, thus giving us confidence in the strategy. In addition, we predict a number of new, currently-unknown precipitate systems that should be explored experimentally as promising high-strength alloy chemistries.

  6. Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

    International Nuclear Information System (INIS)

    Wallace, S.A.

    1984-01-01

    The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness

  7. Investigation of modulus hardening of various co-clusters in aged Al-Cu-Mg-Ag alloy by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Ying, Puyou; Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2016-06-21

    The modulus hardening capability of various co-clusters in a low Cu/Mg ratio Al-Cu-Mg-Ag alloy aged at 165 °C is investigated by quantitative atom probe tomography analysis. Prolonged aging from 5 min to 2 h leads to the simultaneous increase in the critical shear stress of both Mg-Ag and Cu-Mg co-clusters. Regardless of the higher shear modulus of Cu-Mg co-clusters, calculation results show that Mg-Ag co-clusters possess a greater modulus hardening capability than Cu-Mg co-clusters, suggesting its primary contribution to the rapid hardening at the early aging stage. As aging extends from 30 min to 2 h, the increment in the critical shear stress of Mg-Ag co-clusters is lower than that of Cu-Mg co-clusters due to the precipitation of high density Ω phase. In addition, the shear modulus of Mg-Ag co-clusters is generally independent on its size at each investigated condition.

  8. Investigation of modulus hardening of various co-clusters in aged Al-Cu-Mg-Ag alloy by atom probe tomography

    International Nuclear Information System (INIS)

    Bai, Song; Liu, Zhiyi; Ying, Puyou; Wang, Jian; Li, Junlin

    2016-01-01

    The modulus hardening capability of various co-clusters in a low Cu/Mg ratio Al-Cu-Mg-Ag alloy aged at 165 °C is investigated by quantitative atom probe tomography analysis. Prolonged aging from 5 min to 2 h leads to the simultaneous increase in the critical shear stress of both Mg-Ag and Cu-Mg co-clusters. Regardless of the higher shear modulus of Cu-Mg co-clusters, calculation results show that Mg-Ag co-clusters possess a greater modulus hardening capability than Cu-Mg co-clusters, suggesting its primary contribution to the rapid hardening at the early aging stage. As aging extends from 30 min to 2 h, the increment in the critical shear stress of Mg-Ag co-clusters is lower than that of Cu-Mg co-clusters due to the precipitation of high density Ω phase. In addition, the shear modulus of Mg-Ag co-clusters is generally independent on its size at each investigated condition.

  9. The Natural Aging Effect on Hardenability in Al-Mg-Si: A Complex Interaction between Composition and Heat Treatment Parameters

    Directory of Open Access Journals (Sweden)

    Alex Poznak

    2018-05-01

    Full Text Available The technological relevance of Al-Mg-Si alloys has been rapidly growing over the last decade. Of particular interest to current and future applications is the problematic negative effect of prior natural aging on subsequent artificial age hardening. The influence of natural aging is dependent on both processing and compositional variables and has origins that are far from well-understood. This work examines the hardenability of 6000 series alloys under a wide range of conditions, paying particular attention to the natural aging effect. Experimental variables include alloy composition (Mg + Si, Mg/Si, cooling rate after solutionization, and duration of prior natural aging. Hardenability was evaluated with full hardness and conductivity aging curves for each condition, as well as select Transmission Electron Microscopy (TEM. Results are discussed based on the actions of naturally aged solute clusters during artificial aging. In particular, a complex interaction between vacancy concentration, cluster stability, and precipitation driving force is suggested.

  10. Precipitation kinetics and mechanical behavior in a solution treated and aged dual phase stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Badji, R., E-mail: riadbadji1@yahoo.fr [Welding and NDT Research Centre (CSC), B.P. 64, Cheraga (Algeria); Kherrouba, N.; Mehdi, B.; Cheniti, B. [Welding and NDT Research Centre (CSC), B.P. 64, Cheraga (Algeria); Bouabdallah, M. [LGSDS – ENP, 10, Avenue Hassan Badi, 16200 El Harrah, Alger (Algeria); Kahloun, C.; Bacroix, B. [LSPM – CNRS, Université Paris 13, 93430 Villetaneuse (France)

    2014-12-15

    The precipitation kinetics and the mechanical behavior in a solution treated and aged dual phase stainless steel (DSS) are investigated. X-ray diffraction, transmission and scanning electron microscopy techniques are used to characterize the microstructure and to identify its constituents. The precipitation kinetics analysis shows that the ferrite to σ phase transformation follows the modified Johnson Mehl Avrami (JMA) model containing an impingement parameter c that is adjusted to 0.3. Activation energies calculation leads to conclude that interface reaction is the main mechanism that controls the σ phase formation. Detailed analysis of the extent of the different tensile deformation domains reveals the significant contribution of both σ phase particles and dislocation accumulation to the strain hardening of the material. - Highlights: • The precipitation kinetics of the σ phase is affected by both soft and hard impingement phenomena. • Interface reaction is found to be the main mechanism that controls the ferrite to σ phase transformation. • Both σ phase particles and dislocation accumulation contribute to the strain hardening of the dual phase steel studied.

  11. Enhancing elevated temperature strength of copper containing aluminium alloys by forming L12 Al3Zr precipitates and nucleating θ″ precipitates on them.

    Science.gov (United States)

    Kumar Makineni, Surendra; Sugathan, Sandeep; Meher, Subhashish; Banerjee, Rajarshi; Bhattacharya, Saswata; Kumar, Subodh; Chattopadhyay, Kamanio

    2017-09-11

    Strengthening by precipitation of second phase is the guiding principle for the development of a host of high strength structural alloys, in particular, aluminium alloys for transportation sector. Higher efficiency and lower emission demands use of alloys at higher operating temperatures (200 °C-250 °C) and stresses, especially in applications for engine parts. Unfortunately, most of the precipitation hardened aluminium alloys that are currently available can withstand maximum temperatures ranging from 150-200 °C. This limit is set by the onset of the rapid coarsening of the precipitates and consequent loss of mechanical properties. In this communication, we present a new approach in designing an Al-based alloy through solid state precipitation route that provides a synergistic coupling of two different types of precipitates that has enabled us to develop coarsening resistant high-temperature alloys that are stable in the temperature range of 250-300 °C with strength in excess of 260 MPa at 250 °C.

  12. Welding thermal cycle-triggered precipitation processes in steel S700MC subjected to the thermo-mechanical control processing

    OpenAIRE

    Górka J.

    2017-01-01

    This study presents tests concerned with welding thermal process-induced precipitation processes taking place in 10 mm thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) with accelerated cooling. The thermomechanical processing of steel S700MC leads to its refinement, structural defects and solutioning with hardening constituents. Tests of thin foils performed using a transmission electron microscope revealed that the hardening of steel S700MC was primarily caused by...

  13. The development of radiation hardened robot for nuclear facility

    International Nuclear Information System (INIS)

    Kim, Seung Ho; Jung, Seung Ho; Kim, Byung Soo and others

    2000-04-01

    The work conducted in this stage covers development of core technology of tele-robot system including monitoring technique in high-level radioactive area, tele-sensing technology and radiation-hardened technology for the non-destructive tele-inspection system which monitors the primary coolant system during the normal operations of PHWR(Pressurized Heavy Water Reactor) NPPs and measures the decrease of bending part of feeder pipe during overall. Based on the developed core technology, the monitoring mobile robot system of the primary coolant system and the feeder pipe inspecting robot system are developed

  14. The development of radiation hardened robot for nuclear facility

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung Ho; Jung, Seung Ho; Kim, Byung Soo and others

    2000-04-01

    The work conducted in this stage covers development of core technology of tele-robot system including monitoring technique in high-level radioactive area, tele-sensing technology and radiation-hardened technology for the non-destructive tele-inspection system which monitors the primary coolant system during the normal operations of PHWR(Pressurized Heavy Water Reactor) NPPs and measures the decrease of bending part of feeder pipe during overall. Based on the developed core technology, the monitoring mobile robot system of the primary coolant system and the feeder pipe inspecting robot system are developed.

  15. The effect of Sc additions on the microstructure and age hardening behaviour of as cast Al–Sc alloys

    International Nuclear Information System (INIS)

    Costa, S.; Puga, H.; Barbosa, J.; Pinto, A.M.P.

    2012-01-01

    Highlights: ► The Sc effect on the microstructure and ageing behaviour of Al–Sc alloys is studied. ► Cast into copper mould allows the elimination of solution heat treatment. ► Directly aged as cast alloys exhibits higher hardness and precipitation kinetics. ► Sc addition and optimised ageing result in an increase in Al–Sc mechanical properties. -- Abstract: The grain refinement effect and the ageing behaviour of Al–0.5 wt.% Sc, Al–0.7 wt.% Sc, and Al–1 wt.% Sc alloys are studied on the basis of optic microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) observations and hardness measurements. In Al–Sc alloys the higher grain refinement is observed for Sc contents greater than 0.5 wt.% accompanied by a notorious morphology modification, from coarse columnar grains to a fine perfect equiaxed structure. The as cast structures are characterised by a rich supersaturated solid solution in Sc, that promotes a great age hardening response at 250 °C and 300 °C. The age hardening curves also demonstrate a low overageing kinetics for all the alloys. Although the higher Sc content in solid solution for the alloys with 0.7 and 1 wt.% Sc, the age hardening response of all the Al–Sc alloys remains similar. The direct age hardening response of the as cast Al–0.5 wt.% Sc is shown to be greater than the solutionised and age hardened alloy.

  16. Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel

    Directory of Open Access Journals (Sweden)

    Markus Bambach

    2016-08-01

    Full Text Available The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening initially and exhibits neither a plateau (stage IV hardening nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys.

  17. An experimental study on the influence of scatter and beam hardening in x-ray CT for dimensional metrology

    International Nuclear Information System (INIS)

    Lifton, J J; McBride, J W; Malcolm, A A

    2016-01-01

    Scattered radiation and beam hardening introduce artefacts that degrade the quality of data in x-ray computed tomography (CT). It is unclear how these artefacts influence dimensional measurements evaluated from CT data. Understanding and quantifying the influence of these artefacts on dimensional measurements is required to evaluate the uncertainty of CT-based dimensional measurements. In this work the influence of scatter and beam hardening on dimensional measurements is investigated using the beam stop array scatter correction method and spectrum pre-filtration for the measurement of an object with internal and external cylindrical dimensional features. Scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, a gradient-based surface determination method is found to be robust to the influence of artefacts and leads to more accurate dimensional measurements than those evaluated using the ISO50 method. In addition to these observations the GUM method for evaluating standard measurement uncertainties is applied and the standard measurement uncertainty due to scatter and beam hardening is estimated. (paper)

  18. Hydrogen embrittlement susceptibility of laser-hardened 4140 steel

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, L.W.; Lin, Z.W. [Nat. Taiwan Ocean Univ., Keelung (Taiwan). Inst. of Mater. Eng.; Shiue, R.K. [Institute of Materials Sciences and Engineering, National Dong Hwa University, Hualien, Taiwan (Taiwan); Chen, C. [Institute of Materials Sciences and Engineering, National Taiwan University, Taipei, Taiwan (Taiwan)

    2000-10-15

    Slow strain rate tensile (SSRT) tests were performed to investigate the susceptibility to hydrogen embrittlement of laser-hardened AISI 4140 specimens in air, gaseous hydrogen and saturated H{sub 2}S solution. Experimental results indicated that round bar specimens with two parallel hardened bands on opposite sides along the loading axis (i.e. the PH specimens), exhibited a huge reduction in tensile ductility for all test environments. While circular-hardened (CH) specimens with 1 mm hardened depth and 6 mm wide within the gauge length were resistant to gaseous hydrogen embrittlement. However, fully hardened CH specimens became susceptible to hydrogen embrittlement for testing in air at a lower strain rate. The strength of CH specimens increased with decreasing the depth of hardened zones in a saturated H{sub 2}S solution. The premature failure of hardened zones in a susceptible environment caused the formation of brittle intergranular fracture and the decrease in tensile ductility. (orig.)

  19. Manual for the GAW Precipitation Chemistry Programme: Guidelines, Data Quality Objectives and Standard Operating Procedures

    National Research Council Canada - National Science Library

    Allan, Mary A

    2004-01-01

    This is a manual for the Global Atmosphere Watch Precipitation Chemistry (GAW-PC) Programme. Where possible, it describes standard operating procedures and otherwise provides guidance on methods and procedures...

  20. Challenges in hardening technologies using shallow-trench isolation

    International Nuclear Information System (INIS)

    Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

    1998-02-01

    Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide

  1. Radiation hardened COTS-based 32-bit microprocessor

    International Nuclear Information System (INIS)

    Haddad, N.; Brown, R.; Cronauer, T.; Phan, H.

    1999-01-01

    A high performance radiation hardened 32-bit RISC microprocessor based upon a commercial single chip CPU has been developed. This paper presents the features of radiation hardened microprocessor, the methods used to radiation harden this device, the results of radiation testing, and shows that the RAD6000 is well-suited for the vast majority of space applications. (authors)

  2. Calculation of calcium diffusion coefficient of cement hardenings using minute pore data

    International Nuclear Information System (INIS)

    Hitomi, Takashi; Takeda, Nobufumi; Iriya, Keishiro

    2009-01-01

    This report describes the calculations of the diffusion coefficient of the Ca ion of cement hardenings using minute pore data. The observed hardenings were ordinary Portland cement (OPC), low-heat Portland cement with fly ash (LPC+FA) and highly fly ash containing silica fume cement (HFSC). The samples were cured in the standard and artificially leached by accelerated test. Minute pore datas of the cement hardenings were acquired with image processing of internal structural information obtained from high resolution X-ray computed tomography observations. Upon analysis, several voxels are combined into one bigger voxel, the diffusion coefficient of the voxels were determined in proportion to the number of voxels which were included in. The results reveal that the change in the calcium diffusion coefficient of OPC due to leaching was large, but the LPC+FA and HFSC cements exhibited even greater changes than OPC. It is suggested that the diffusion coefficients are proportional to the Ca/Si ratio of the samples. (author)

  3. On residual stresses and fatigue of laser hardened steels

    International Nuclear Information System (INIS)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

  4. On residual stresses and fatigue of laser hardened steels

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

  5. Comparative study of structure formation and mechanical behavior of age-hardened Ti–Nb–Zr and Ti–Nb–Ta shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Inaekyan, K. [Ecole de Technologie Superieure, 1100, Notre-Dame Str. West, Montreal Quebec H3C 1K3 (Canada); Brailovski, V., E-mail: vladimir.brailovski@etsmtl.ca [Ecole de Technologie Superieure, 1100, Notre-Dame Str. West, Montreal Quebec H3C 1K3 (Canada); Prokoshkin, S. [National University of Science and Technology “MISIS”, Leninskiy prosp. 4, Moscow 119049 (Russian Federation); Pushin, V. [Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, 18, S. Kovalevskoy Str., Ekaterinburg 620199 (Russian Federation); Dubinskiy, S.; Sheremetyev, V. [Ecole de Technologie Superieure, 1100, Notre-Dame Str. West, Montreal Quebec H3C 1K3 (Canada); National University of Science and Technology “MISIS”, Leninskiy prosp. 4, Moscow 119049 (Russian Federation)

    2015-05-15

    This work sets out to study the peculiar effects of aging treatment on the structure and mechanical behavior of cold-rolled and annealed biomedical Ti–21.8Nb–6.0Zr (TNZ) and Ti–19.7Nb–5.8Ta (TNT) (at.%) shape memory alloys by means of transmission electron microscopy, X-ray diffractometry, functional fatigue and thermomechanical testing techniques. Dissimilar effects of aging treatment on the mechanical behavior of Zr- and Ta-doped alloys are explained by the differences in the ω-phase formation rate, precipitate size, fraction and distribution, and by their effect on the alloys' critical stresses and transformation temperatures. Even short-time aging of the TNZ alloy leads to its drastic embrittlement caused by “overaging”. On the contrary, during aging of the TNT alloy, formation of finely dispersed ω-phase precipitates is gradual and controllable, which makes it possible to finely adjust the TNT alloy functional properties using precipitation hardening mechanisms. To create in this alloy nanosubgrained dislocation substructure containing highly-dispersed coherent nanosized ω-phase precipitates, the following optimum thermomechanical treatment is recommended: cold rolling (true strain 0.37), followed by post-deformation annealing (600 °C, 15–30 min) and age-hardening (300 °C, 30 min) thermal treatments. It is shown that in TNT alloy, pre-transition diffraction effects (diffuse reflections) can “mask” the β-phase substructure and morphology of secondary phases. - Highlights: • TNZ alloy is characterized by much higher ω-phase precipitation rate than TNT alloy. • Difference in precipitation rates is linked to the difference in Zr and Ta diffusion mobility. • Aging of nanosubgrained TNZ alloy worsens its properties irrespective of the aging time. • Aging time of nanosubgrained TNT alloy can be optimized to improve its properties.

  6. Multiple regression analysis of Jominy hardenability data for boron treated steels

    International Nuclear Information System (INIS)

    Komenda, J.; Sandstroem, R.; Tukiainen, M.

    1997-01-01

    The relations between chemical composition and their hardenability of boron treated steels have been investigated using a multiple regression analysis method. A linear model of regression was chosen. The free boron content that is effective for the hardenability was calculated using a model proposed by Jansson. The regression analysis for 1261 steel heats provided equations that were statistically significant at the 95% level. All heats met the specification according to the nordic countries producers classification. The variation in chemical composition explained typically 80 to 90% of the variation in the hardenability. In the regression analysis elements which did not significantly contribute to the calculated hardness according to the F test were eliminated. Carbon, silicon, manganese, phosphorus and chromium were of importance at all Jominy distances, nickel, vanadium, boron and nitrogen at distances above 6 mm. After the regression analysis it was demonstrated that very few outliers were present in the data set, i.e. data points outside four times the standard deviation. The model has successfully been used in industrial practice replacing some of the necessary Jominy tests. (orig.)

  7. Study of magnetic hardening in Sm(Co/sub 1-x/Cu/sub x/)/sub 5/ alloy

    International Nuclear Information System (INIS)

    Awan, M.S.; Bhatti, A.S.; Farooque, M.

    2008-01-01

    Magnetic hardening has been examined in the samarium (Sm), cobalt (Co) and copper (Cu) fused permanent magnets by correlating the magnetic properties with annealing temperature and microstructure of the samples. For the Sm(Co/sub 1-x/Cu/sub x/)/sub 5/ system, with various copper contents (x=0, 0.2, 0.3, 0.4 and 0.5) the shape of initial magnetization curve indicated that the magnetic hardening process involved in these types of magnets consists of domain wall pinning type. This is consistent with the microstructure studies which show the existence of nonmagnetic Cu-rich precipitates in the Co-rich matrix. Copper substituted samples were annealed in the temperature range (300 -1000) degree C for 3h under the protective atmosphere of argon (Ar) gas. Both cast and annealed samples prepared by tri-arc melting technique exhibit two-phase microstructure responsible for enhanced magnetic properties. Metallographic and surface studies were carried out using a digital optical microscope (OM). X-ray diffraction (XRD) studies confirmed that the alloys solidefied in the hexagonal crystal structure. The lattice parameters and unit cell volume increase with increasing Cu content. Scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) was used to examine the surface morphology, compositional variations, elemental segregations, formation and effect of annealing on the different phases. Later these parameters were related to the magnetic properties. Copper-rich phase precipitates in the Co- rich matrix may serves as the pinning centers for the domain wall motion. Introduction of these pinning centers improved the magnetic hardening of the alloy. Annealing the Cu-substituted alloy further improved the magnetic properties. During annealing, diffusion of copper played the key role for enhanced magnetic properties. It was found that both Cu substitution and subsequent annealing are the dominating factors determining the magnetic properties of these magnetic

  8. Laser Surface Hardening of Groove Edges

    Science.gov (United States)

    Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

    2013-06-01

    Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

  9. Impact of grain microstructure on the heterogeneity of precipitation strengthening in an Al–Li–Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dorin, Thomas, E-mail: thomas.dorin@deakin.edu.au [Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Institute for Frontier Materials, Deakin University, Geelong, Victoria 3217 (Australia); Constellium Technology Center, CS 10027, 38341 Voreppe Cedex (France); Deschamps, Alexis; De Geuser, Frédéric [Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Robaut, Florence [Consortium des Moyens Technologiques Communs, Grenoble-INP, F-38502 St. Martin d’Hères (France)

    2015-03-11

    The effect of grain microstructure on the age-hardening behavior is investigated on recrystallized and un-recrystallized Al–Cu–Li alloys by combining electron-backscatter-diffraction and micro-hardness mapping. The spatial heterogeneity of micro-hardness is found to be strongly dependent on the grain microstructure. Controlled experiments are carried out to change the pre-strain before artificial ageing. These experiments lead to an evaluation of the range of local strain induced by pre-stretching as a function of the grain microstructure and results in heterogeneous formation of the hardening T{sub 1} precipitates.

  10. Optimized radiation-hardened erbium doped fiber amplifiers for long space missions

    Science.gov (United States)

    Ladaci, A.; Girard, S.; Mescia, L.; Robin, T.; Laurent, A.; Cadier, B.; Boutillier, M.; Ouerdane, Y.; Boukenter, A.

    2017-04-01

    In this work, we developed and exploited simulation tools to optimize the performances of rare earth doped fiber amplifiers (REDFAs) for space missions. To describe these systems, a state-of-the-art model based on the rate equations and the particle swarm optimization technique is developed in which we also consider the main radiation effect on REDFA: the radiation induced attenuation (RIA). After the validation of this tool set by confrontation between theoretical and experimental results, we investigate how the deleterious radiation effects on the amplifier performance can be mitigated following adequate strategies to conceive the REDFA architecture. The tool set was validated by comparing the calculated Erbium-doped fiber amplifier (EDFA) gain degradation under X-rays at ˜300 krad(SiO2) with the corresponding experimental results. Two versions of the same fibers were used in this work, a standard optical fiber and a radiation hardened fiber, obtained by loading the previous fiber with hydrogen gas. Based on these fibers, standard and radiation hardened EDFAs were manufactured and tested in different operating configurations, and the obtained data were compared with simulation data done considering the same EDFA structure and fiber properties. This comparison reveals a good agreement between simulated gain and experimental data (vulnerability in terms of gain. The presented approach is a complementary and effective tool for hardening by device techniques and opens new perspectives for the applications of REDFAs and lasers in harsh environments.

  11. Precipitation and clustering in the early stages of ageing in Inconel 718

    International Nuclear Information System (INIS)

    Alam, Talukder; Chaturvedi, Mahesh; Ringer, Simon P.; Cairney, Julie M.

    2010-01-01

    Research highlights: → IN718 could be age hardened rapidly by secondary phase formation. → Co-located phases were observed in the earliest stage of detection. → Clustering of Ti/Al and Nb atoms was observed prior to precipitation. - Abstract: In this report we investigate the onset and evolution of precipitation in the early stages of ageing in the alloy WE 91, a variant of the Ni-Fe-Cr superalloy Inconel 718 (IN718). Transmission electron microscopy and atom probe tomography were used to study the size and volume fraction of γ' and γ'' precipitates and the extent of pre-precipitate clustering of Al/Ti and Nb. Co-located γ' and γ'' precipitates were observed from the shortest ageing times that precipitates could be visualised using atom probe. At shorter times, prior to the observation of precipitates, clustering of Al/Ti and Nb was shown to occur. The respective volume fraction of the γ' and γ'' precipitates and the clustering of Al/Ti and Nb suggest that γ'' nucleates prior to γ' during ageing at 706 deg. C for this alloy.

  12. Standard Deviation of Spatially-Averaged Surface Cross Section Data from the TRMM Precipitation Radar

    Science.gov (United States)

    Meneghini, Robert; Jones, Jeffrey A.

    2010-01-01

    We investigate the spatial variability of the normalized radar cross section of the surface (NRCS or Sigma(sup 0)) derived from measurements of the TRMM Precipitation Radar (PR) for the period from 1998 to 2009. The purpose of the study is to understand the way in which the sample standard deviation of the Sigma(sup 0) data changes as a function of spatial resolution, incidence angle, and surface type (land/ocean). The results have implications regarding the accuracy by which the path integrated attenuation from precipitation can be inferred by the use of surface scattering properties.

  13. Improvement of aging kinetics and precipitate size refinement in Mg–Sn alloys by hafnium additions

    Energy Technology Data Exchange (ETDEWEB)

    Behdad, S. [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Zhou, L. [Department of Materials Science and Engineering and Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816 (United States); Henderson, H.B.; Manuel, M.V. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Sohn, Y. [Department of Materials Science and Engineering and Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816 (United States); Agarwal, A. [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Boesl, B., E-mail: bboesl@fiu.edu [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States)

    2016-01-10

    Two Mg–Sn alloys were microalloyed by addition of Hafnium and their age-hardening response was studied at 200 °C. Time to reach peak hardness was significantly reduced and improved by Hf addition. TEM study showed Hf clusters in the close vicinity and at the surface of Mg{sub 2}Sn precipitates, which confirms that Hf clusters act as additional nucleation centers for Mg{sub 2}Sn precipitate formation. Our results support the validity of thermokinetic criterion proposed by Mendis for selection of microalloying elements in order to refine precipitate size, accelerate aging kinetics and enhance peak hardness.

  14. PRECIPITATION OF PROTACTINIUM

    Science.gov (United States)

    Moore, R.L.

    1958-07-15

    An lmprovement in the separation of protactinium from aqueous nitric acid solutions is described. 1t covers the use of lead dioxide and tin dioxide as carrier precipitates for the protactinium. In carrying out the process, divalent lead or divalent tin is addcd to the solution and oxidized, causing formation of a carrier precipitate of lead dioxide or stannic oxide, respectively.

  15. Hardening Embrittlement and Non-Hardening Embrittlement of Welding-Heat-Affected Zones in a Cr-Mo Low Alloy Steel

    Directory of Open Access Journals (Sweden)

    Yu Zhao

    2018-06-01

    Full Text Available The embrittlement of heat affected zones (HAZs resulting from the welding of a P-doped 2.25Cr-1Mo steel was studied by the analysis of the fracture appearance transition temperatures (FATTs of the HAZs simulated under a heat input of 45 kJ/cm with different peak temperatures. The FATTs of the HAZs both with and without tempering increased with the rise of the peak temperature. However, the FATTs were apparently lower for the tempered HAZs. For the as-welded (untempered HAZs, the FATTs were mainly affected by residual stress, martensite/austenite (M/A islands, and bainite morphology. The observed embrittlement is a hardening embrittlement. On the other hand, the FATTs of the tempered HAZs were mainly affected by phosphorus grain boundary segregation, thereby causing a non-hardening embrittlement. The results demonstrate that the hardening embrittlement of the as-welded HAZs was more severe than the non-hardening embrittlement of the tempered HAZs. Consequently, a post-weld heat treatment should be carried out if possible so as to eliminate the hardening embrittlement.

  16. Age-hardening of an Al-Li-Cu-Mg alloy (2091) processed by high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seungwon, E-mail: chominamlsw@gmail.com [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Horita, Zenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Hirosawa, Shoichi [Department of Mechanical Engineering and Materials Science, Yokohama National University, Yokohama 240-8501 (Japan); Matsuda, Kenji [Graduate School of Science and Engineering for Research, University of Toyama, Toyama 930-8555 (Japan)

    2012-06-01

    This research presents the successful strengthening of an Al-Li-Cu-Mg alloy (2091) through the simultaneous use of grain refinement and age hardening. Following solid-solution treatment, the alloy was processed by high-pressure torsion (HPT) at room temperature and the grain size was refined to {approx}140 nm. The Vickers microhardness increased with increasing strain, and saturated to a constant level of 225 Hv. A further increase in the hardness to {approx}275 Hv was achieved by aging the HPT-processed alloy at 100 Degree-Sign C and 150 Degree-Sign C. Bending tests for the samples treated using the peak aging conditions demonstrated that the stress was significantly increased while considerable ductility was retained. Transmission electron microscopy revealed that the small grains are well retained even after prolonged aging, and the precipitation of fine {delta} Prime particles occurred within the small grains, which confirms that simultaneous strengthening from grain refinement and age hardening is feasible in this alloy.

  17. Radiation-chemical hardening of phenol-formaldehyde oligomers

    International Nuclear Information System (INIS)

    Shlapatskaya, V.V.; Omel'chenko, S.I.

    1978-01-01

    Radiation-chemical hardening of phenol formaldehyde oligomers of the resol type has been studied in the presence of furfural and diallylphthalate diluents. The samples have been hardened on an electron accelerator at an electron energy of 1.0-1.1 MeV and a dose rate of 2-3 Mrad/s. The kinetics of hardening has been studied on the yield of gel fraction within the range of absorbed doses from 7 to 400 Mrad. Radiation-chemical hardening of the studied compositions is activated with sensitizers, namely, amines, metal chlorides, and heterocyclic derivatives of metals. Furfural and diallylphthalate compositions are suitable for forming glass-fibre plastic items by the wet method and coatings under the action of ionizing radiations

  18. Bake hardening of nanograin AA7075 aluminum alloy

    International Nuclear Information System (INIS)

    Dehghani, Kamran

    2011-01-01

    Highlights: ► The bake hardening behavior of AA7075 was studied and compared with its coarse-grain counterpart. ► Nanograin AA7075 exhibited 88–100% increase in bake hardenability. ► Nanograin AA7075 exhibited 36–38% increase in final yield strength after baking. ► Maximum bake hardenability and final yield stress were about 185 MPa and 719 MPa. - Abstract: In the present work, the bake hardening of nanostructured AA7075 aluminum alloy was compared with that of its coarse-grain counterpart. Surface severe plastic deformation (SSPD) was used to produce nanograin layers on both surfaces of workpieces. The nanostructured layers were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The thickness of nanostructured layer, having the grains of 50–110 nm, was about 75 μm on each side of workpiece. The bake hardenability of nanograin and coarse-grain AA7075 was then compared by pre-straining to 2, 4 and 6% followed by baking at 100 °C and 200 °C for 20 min. Comparing to coarse-grain case, there was about 88–100% increase in bake hardenability and about 36–38% increase in yield strength after the bake hardening of present nanograin AA7075. Such an increase in bake hardenability and strength was achieved when the thickness of two nanograin layers was about only one-tenth of the whole thickness.

  19. Precipitation-Induced Changes in Microstrain and Its Relation with Hardness and Tempering Parameter in 17-4 PH Stainless Steel

    Science.gov (United States)

    Mahadevan, S.; Manojkumar, R.; Jayakumar, T.; Das, C. R.; Rao, B. P. C.

    2016-06-01

    17-4 PH (precipitation hardening) stainless steel is a soft martensitic stainless steel strengthened by aging at appropriate temperature for sufficient duration. Precipitation of copper particles in the martensitic matrix during aging causes coherency strains which improves the mechanical properties, namely hardness and strength of the matrix. The contributions to X-ray diffraction (XRD) profile broadening due to coherency strains caused by precipitation and crystallite size changes due to aging are separated and quantified using the modified Williamson-Hall approach. The estimated normalized mean square strain and crystallite size are used to explain the observed changes in hardness. Microstructural changes observed in secondary electron images are in qualitative agreement with crystallite size changes estimated from XRD profile analysis. The precipitation kinetics in the age-hardening regime and overaged regime are studied from hardness changes and they follow the Avrami kinetics and Wilson's model, respectively. In overaged condition, the hardness changes are linearly correlated to the tempering parameter (also known as Larson-Miller parameter). Similar linear variation is observed between the normalized mean square strain (determined from XRD line profile analysis) and the tempering parameter, in the incoherent regime which is beyond peak microstrain conditions.

  20. In situ neutron diffraction and polycrystal plasticity modeling of a Mg–Y–Nd–Zr alloy: Effects of precipitation on individual deformation mechanisms

    International Nuclear Information System (INIS)

    Agnew, S.R.; Mulay, R.P.; Polesak, F.J.; Calhoun, C.A.; Bhattacharyya, J.J.; Clausen, B.

    2013-01-01

    In situ neutron diffraction compression tests were performed on Mg–Y–Nd–Zr alloy WE43, in the solution heat-treated, peak- and over-aged conditions. The flow curves and internal strain evolutions were modeled using polycrystal plasticity simulation, with the inclusion of an elastic phase to account for the presence of precipitates. The results reveal that prismatic plate-shaped precipitates strongly impede basal slip; the critical resolved shear strength (CRSS) of basal slip increases from 12 to 37 MPa, an increase of over 200%. However, hard deformation modes such as non-basal slip of 〈a〉 dislocations are required for macroscopic yielding. These hard modes are not as strongly affected by aging, with CRSS values which increase from 78 to 92 MPa, an increase of only 18%. The results of the study are consistent with recent modeling of the relative Orowan strengthening of individual deformation modes and the superposition of various strengthening effects (solid solution and precipitation). This finding helps to explain why the age-hardening response of Mg–Y–Nd–Zr alloys is not exceptional. It is concluded that future precipitation-strengthened alloy and process design strategies should focus on promoting high number densities of particles. The effect of aging upon twinning is surprising. The most age-hardened material exhibits more twinning than the solutionized material. To model this behavior using polycrystal plasticity, the critical stress to activate twinning (especially the strain hardening thereof) must be decreased

  1. Structural heredity influence upon principles of strain wave hardening

    Science.gov (United States)

    Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

    2017-02-01

    It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

  2. Surface Hardening of Ti-15V-3Al-3Cr-3Sn Alloy after Cyclic Hydrogenation and Subsequent Solution Treatment

    Directory of Open Access Journals (Sweden)

    Chia-Po Hung

    2014-01-01

    Full Text Available The as-received and preheated (1000°C-30 min. and 500°C-30 min. sheets of Ti-15V-3Al-3Cr-3Sn alloy (Ti-153 were treated according to the predetermined process including a cyclic electrolytic hydrogenation (at 50 mA/cm2 for 1 hr and at 5 mA/cm2 for 10 hrs combining a subsequent solution treatment to see the effects of various operating parameters on the evolution of microstructure and the variations of hardness. The hardening effect deriving from solid-solution strengthening of hydrogen eventually overrode that from precipitation hardening. The maximum hardness elevation was from 236.9 to 491.1 VHN.

  3. Design Features of Hardening Turners with Outstripping Plastic Deformation

    Directory of Open Access Journals (Sweden)

    V. M. Yaroslavtsev

    2014-01-01

    Full Text Available An efficiency of the cutting method with outstripping plastic deformation (OPD in lathe works is defined in many respects by design features of the add-on devices for mechanical hardening of a cut-off layer material in the course of cutting. Applied on lathes, deforming OPD devices can have differing dimensions, placement on the lathe, drive type (manual, electric, hydraulic, pneumatic, pneumohydraulic, electromagnetic, and autonomy degree towards the metalcutting equipment and industrial equipment.At the same time there are a number of inherent design features of work-hardening devices the modernized lathes with OPD use for machining. Now the OPD standard devices implement two principle construction options: loading device is placed on the machine or on the OPD slide support separate of the tool, or it is structurally aligned with the cutting tool. In the latter case the OPD device for turning is called a tool mandrel, which is mounted in a tool post of the machine or, at large dimensions, such a mandrel is mounted on the machine instead of the tool mandrel.When designing the OPD devices, is important to take into consideration production requirements and recommendations for the technological equipment, developed in the course of creation, working off and introduction of such installations for mechanical hardening of material. In compliance with it, OPD devices, their placement on the machine, and working displacements shouldn't limit technological capabilities of the applied metal-cutting equipment. OPD stresses have to be smoothly regulated, with maximum loads being limited to admissible values for the machine model to be modernized. It is necessary to ensure synchronized longitudinal and cross displacements of the cutting tool and OPD hardener with respect to the axis of billet rotation to enable regulation and readjustment of the hardener and tool placement. It ought to foresee the increased mobile components rigidity and manufacturing

  4. Thermomechanical properties of radiation hardened oligoesteracrylates

    International Nuclear Information System (INIS)

    Lomonosova, N.V.; Chikin, Yu.A.

    1984-01-01

    Thermomechanical properties of radiation hardened oligoesteracrylates are studied by the methods of isothermal heating and thermal mechanics. Films of dimethacrylate of ethylene glycol, triethylene glycol (TGM-3), tetraethylene glycol, tridecaethylene glycol and TGM-3 mixture with methyl methacrylate hardened by different doses (5-150 kGy) using Co 60 installation with a dose rate of 2x10 -3 kGy/s served as a subject of the research. During oligoesteracrylate hargening a space network is formed, chain sections between lattice points of which are in a stressed state. Maximum of deformation is observed at 210-220 deg C on thermomechanical curves of samples hardened by doses > 5 kGy, which form and intensity is dependent on an absorbed dose. Presence of a high-temperature maximum on diaqrams of isometric heating of spatially cross-linked oligoesteracrylates is discovered. High thermal stability of three-dimensional network of radiation hardened oligoesteracrylates provides satisfactory tensile properties (40% of initial strength) in sample testing an elevated temperatures (200-250 deg C)

  5. Nuclear EMP: key suppression device parameters for EMP hardening

    International Nuclear Information System (INIS)

    Durgin, D.L.; Brown, R.M.

    1975-03-01

    The electrical transients induced by EMP exhibit unique characteristics which differ considerably from transients associated with other phenomena such as lightning, switching, and circuit malfunctions. The suppression techniques developed to handle more common transients, though not necessarily the same devices, can be used for EMP damage protection. The suppression devices used for circuit level EMP protection are referred to as Terminal Protection Devices (TPD). Little detailed data describing the response of TPD's to EMP-related transients have been published. While most vendors publish specifications for TPD performance, there is little standardization of parameters and TPD response models are not available. This lack of parameter standardization has resulted in a proliferation of test data that is sometimes conflicting and often not directly comparable. This paper derives and/or defines a consistent set of parameters based on EMP circuit hardening requirements and on measurable component parameters and is concerned only with use of TPD's to prevent permanent damage. Three sets of parameters pertaining to pertinent TPD functional characteristics were defined as follows: standby parameters, protection parameters, and failure parameters. These parameters are used to evaluate a representative sample of TPD's and the results are presented in matrix form to facilitate the selection of devices for specific hardening problems

  6. STAMMEX high resolution gridded daily precipitation dataset over Germany: a new potential for regional precipitation climate research

    Science.gov (United States)

    Zolina, Olga; Simmer, Clemens; Kapala, Alice; Mächel, Hermann; Gulev, Sergey; Groisman, Pavel

    2014-05-01

    We present new high resolution precipitation daily grids developed at Meteorological Institute, University of Bonn and German Weather Service (DWD) under the STAMMEX project (Spatial and Temporal Scales and Mechanisms of Extreme Precipitation Events over Central Europe). Daily precipitation grids have been developed from the daily-observing precipitation network of DWD, which runs one of the World's densest rain gauge networks comprising more than 7500 stations. Several quality-controlled daily gridded products with homogenized sampling were developed covering the periods 1931-onwards (with 0.5 degree resolution), 1951-onwards (0.25 degree and 0.5 degree), and 1971-2000 (0.1 degree). Different methods were tested to select the best gridding methodology that minimizes errors of integral grid estimates over hilly terrain. Besides daily precipitation values with uncertainty estimates (which include standard estimates of the kriging uncertainty as well as error estimates derived by a bootstrapping algorithm), the STAMMEX data sets include a variety of statistics that characterize temporal and spatial dynamics of the precipitation distribution (quantiles, extremes, wet/dry spells, etc.). Comparisons with existing continental-scale daily precipitation grids (e.g., CRU, ECA E-OBS, GCOS) which include considerably less observations compared to those used in STAMMEX, demonstrate the added value of high-resolution grids for extreme rainfall analyses. These data exhibit spatial variability pattern and trends in precipitation extremes, which are missed or incorrectly reproduced over Central Europe from coarser resolution grids based on sparser networks. The STAMMEX dataset can be used for high-quality climate diagnostics of precipitation variability, as a reference for reanalyses and remotely-sensed precipitation products (including the upcoming Global Precipitation Mission products), and for input into regional climate and operational weather forecast models. We will present

  7. Precipitation hardenable iron-nickel-chromium alloy having good swelling resistance and low neutron absorbence

    International Nuclear Information System (INIS)

    Korenko, M.K.; Merrick, H.F.; Gibson, R.C.

    1982-01-01

    An iron-nickel-chromium age-hardenable alloy suitable for use in fast breeder reactor ducts and cladding utilizes the gamma-double prime strengthening phase and has a morphology of the gamma-double prime phase enveloping the gamma-prime phase and delta phase distributed at or near the grain boundaries. The alloy consists essentially of about 40-50 percent nickel, 7.5-14 percent chromium, 1.5-4 percent niobium, .25-.75 percent silicon, 1-3 percent titanium, .1-.5 percent aluminum, .02-1 percent carbon, .002-.015 percent boron, and the balance iron. Up to 2 percent manganese and up to .01 percent magnesium may be added to inhibit trace element effects; up to .1 percent zirconium may be added to increase radiation swelling resistance; and up to 3 percent molybdenum may be added to increase strength

  8. Precipitate statistics in an Al-Mg-Si-Cu alloy from scanning precession electron diffraction data

    Science.gov (United States)

    Sunde, J. K.; Paulsen, Ø.; Wenner, S.; Holmestad, R.

    2017-09-01

    The key microstructural feature providing strength to age-hardenable Al alloys is nanoscale precipitates. Alloy development requires a reliable statistical assessment of these precipitates, in order to link the microstructure with material properties. Here, it is demonstrated that scanning precession electron diffraction combined with computational analysis enable the semi-automated extraction of precipitate statistics in an Al-Mg-Si-Cu alloy. Among the main findings is the precipitate number density, which agrees well with a conventional method based on manual counting and measurements. By virtue of its data analysis objectivity, our methodology is therefore seen as an advantageous alternative to existing routines, offering reproducibility and efficiency in alloy statistics. Additional results include improved qualitative information on phase distributions. The developed procedure is generic and applicable to any material containing nanoscale precipitates.

  9. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

  10. Effect of scandium on structure and hardening of Al–Ca eutectic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Belov, N.A., E-mail: nikolay-belov@yandex.ru [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); Naumova, E.A. [Bauman Moscow State Technical University, 5, 2 ul. Baumanskaya, Moscow, 105005 (Russian Federation); Alabin, A.N. [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation); Matveeva, I.A. [UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation)

    2015-10-15

    The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al{sub 4}Ca and Al{sub 3}Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al{sub 4}Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °C on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °C, which was due to the precipitation of Al{sub 3}Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al{sub 4}Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting. - Highlights: • Al–Ca–Sc phase diagram in aluminum corner. • Formation of Al{sub 3}Sc nanoparticles in eutectic (Al) + Al{sub 4}Ca during heating at 300–450 °C. • Hardening and thermal stability of proposed (Al–Ca–Sc) and commercial (Al–Si–Mg, 356 type) eutectic alloys.

  11. Individual precipitates in Al alloys probed by the Bonn positron microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Balarisi, Osman; Eich, Patrick; Haaks, Matz; Klobes, Benedikt; Korff, Bjoern; Maier, Karl; Sottong, Reinhard [Helmholtz-Institut fuer Strahlen- und Kernphysik, Nussallee 14-16, 53115 Bonn (Germany); Huehne, Sven-Martin; Mader, Werner [Institut fuer Anorganische Chemie, Roemerstrasse 164, 53117 Bonn (Germany); Staab, Torsten [Fraunhofer ISC, Neunerplatz 2, 97082 Wuerzburg (Germany)

    2010-07-01

    Positron annihilation spectroscopy (PAS) is a unique tool for the characterization of open-volume defects such as vacancies. Therefore, age hardenable Al alloys, whose decomposition is mainly driven by the vacancy mechanism of diffusion, are often characterized by PAS techniques. Nevertheless, probing the defect state of individual precipitates grown in Al alloys requires a focused positron beam and has not been carried out up to now. In this respect we present the first investigations of the defect state of individual precipitates utilizing the Bonn Positron Microprobe (BPM). Furthermore, the analysis of the experimental data has to be facilitated by theoretical calculations of the observables of positron annihilation spectroscopy.

  12. The microstructural origin of work hardening stages

    DEFF Research Database (Denmark)

    Hughes, D. A.; Hansen, N.

    2018-01-01

    The strain evolution of the flow stress and work hardening rate in stages III and IV is explored by utilizing a fully described deformation microstructure. Extensive measurements by transmission electron microscopy reveal a hierarchical subdivision of grains by low angle incidental dislocation...... addition of the classical Taylor and Hall-Petch formulations. Model predictions agree closely with experimental values of flow stress and work hardening rate in stages III and IV. Strong connections between the evolutionary stages of the deformation microstructure and work hardening rates create a new...... (modern) basis for the classic problem of work hardening in metals and alloys. These connections lead the way for the future development of ultra high strength ductile metals produced via plastic deformation.(c) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved....

  13. Radiation hardenable coating mixture

    International Nuclear Information System (INIS)

    Howard, D.D.

    1977-01-01

    This invention relates to coatings that harden under radiation and to their compositions. Specifically, this invention concerns unsaturated urethane resins polymerisable by addition and to compositions, hardening under the effect of radiation, containing these resins. These resins feature the presence of at least one unsaturated ethylenic terminal group of structure CH 2 =C and containing the product of the reaction of an organic isocyanate compound with at least two isocyanate groups and one polyester polyol with at least two hydroxyl groups, and one unsaturated monomer compound polymerisable by addition having a single active hydrogen group reacting with the isocyanate [fr

  14. Influence of pretreatment on creep-rupture-strength and creep-behaviour of a matrix-hardening Ni-base-alloy

    International Nuclear Information System (INIS)

    Schirra, M.

    1982-01-01

    The creep and time-to-rupture behaviour of the matrix hardening Nickel base alloy Inconel 625 was investigated in the temperature range 650-800 0 C. Three different thermo-mechanical pretreatment were used: I = Hot rolled finish; II = 870 0 C annealed; III = Sol. treatment 1150 0 C 1 h. The temperature range of this study is for samples which have undergone treatment I and II well above the temperatures normally used. The results show an anomalous stress dependence of creep and time-to-rupture at around 750 0 C. The reason is to be found in the very complex precipitation processes occurring while the stress is applied. The results are explained according to findings about precipitation in this type of alloy. (orig.) [de

  15. Age hardening and creep resistance of cast Al–Cu alloy modified by praseodymium

    International Nuclear Information System (INIS)

    Bai, Zhihao; Qiu, Feng; Wu, Xiaoxue; Liu, Yingying; Jiang, Qichuan

    2013-01-01

    The effects of praseodymium on age hardening behavior and creep resistance of cast Al–Cu alloy were investigated. The results indicated that praseodymium facilitated the formation of the θ′ precipitates during the age process and improved the hardness of the Al–Cu alloy. Besides, praseodymium resulted in the formation of the Al 11 Pr 3 phase in the grain boundaries and among the dendrites of the modified alloy. Because of the good thermal stability of Al 11 Pr 3 phase, it inhibits grain boundary migration and dislocation movement during the creep process, which contributes to the improvement in the creep resistance of the modified alloy at elevated temperatures. - Highlights: • Pr addition enhances the hardness and creep resistance of the Al–Cu alloy. • Pr addition facilitates the formation of the θ′ precipitates. • Pr addition results in the formation of the Al11Pr3 phase in the Al–Cu alloy

  16. Precipitation and clustering in the early stages of ageing in Inconel 718

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Talukder, E-mail: talukder.alam@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006 (Australia); Chaturvedi, Mahesh [Department of Mechanical and Industrial Engineering, University of Manitoba, Winnipeg, MB R3T 5V6 (Canada); Ringer, Simon P.; Cairney, Julie M. [Australian Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006 (Australia)

    2010-11-15

    Research highlights: {yields} IN718 could be age hardened rapidly by secondary phase formation. {yields} Co-located phases were observed in the earliest stage of detection. {yields} Clustering of Ti/Al and Nb atoms was observed prior to precipitation. - Abstract: In this report we investigate the onset and evolution of precipitation in the early stages of ageing in the alloy WE 91, a variant of the Ni-Fe-Cr superalloy Inconel 718 (IN718). Transmission electron microscopy and atom probe tomography were used to study the size and volume fraction of {gamma}' and {gamma}'' precipitates and the extent of pre-precipitate clustering of Al/Ti and Nb. Co-located {gamma}' and {gamma}'' precipitates were observed from the shortest ageing times that precipitates could be visualised using atom probe. At shorter times, prior to the observation of precipitates, clustering of Al/Ti and Nb was shown to occur. The respective volume fraction of the {gamma}' and {gamma}'' precipitates and the clustering of Al/Ti and Nb suggest that {gamma}'' nucleates prior to {gamma}' during ageing at 706 deg. C for this alloy.

  17. Characterization and structure of precipitates in 6xxx Aluminium Alloys

    International Nuclear Information System (INIS)

    Holmestad, Randi; Bjørge, Ruben; Ehlers, Flemming J H; Torsæter, Malin; Marioara, Calin D; Andersen, Sigmund J

    2012-01-01

    Solute atom nanoscale precipitates are responsible for the favourable mechanical properties of heat treatable aluminium alloys such as Al-Mg-Si (6xxx). The shape, structure and strengthening properties of age-hardening precipitates depend on alloy composition and thermo-mechanical history. We seek an improved understanding of the physics related to nucleation and precipitation on the atomistic level in these alloys. Once these mechanisms are sufficiently well described and understood, the hope is that 'alloy design' simulations can assist tailoring of materials with desired properties. In pure Al-Mg-Si we have determined the structure of nearly all the known metastable precipitate phases, by combining advanced TEM techniques (such as high resolution TEM and nano-beam diffraction) with atom probe tomography and density functional theory. We are now studying effects of additions /substitutions of Cu, Ag and/or Ge that promote formation of more disordered precipitates, employing aberration corrected high angle annular dark field scanning TEM. We find that all metastable precipitates contain variations of a widely spaced 'Si/Ge network'. In spite of disorder or defects, this network is surprisingly well ordered, with hexagonal projected sub-cell dimensions a = b ≅ 0.4 nm and c (along the fully coherent precipitate main growth direction) equal to 0.405 nm or a multiple of it.

  18. Consequences of land use cover change and precipitation regimes on water quality in a tropical landscape: the case of São Paulo, Brazil

    Science.gov (United States)

    Ribeiro Piffer, P.; Reverberi Tambosi, L.; Uriarte, M.

    2017-12-01

    One of the most pressing challenges faced by modern societies is ensuring a sufficient supply of water considering the ever-growing conflict between environmental conservation and expansion of agricultural and urban frontiers worldwide. Land use cover change have marked effects on natural landscapes, putting key watershed ecosystem services in jeopardy. We investigated the consequences of land use cover change and precipitation regimes on water quality in the state of São Paulo, Brazil, a landscape that underwent major changes in past century. Water quality data collected bi-monthly between 2000 and 2014 from 229 water monitoring stations was analyzed together with 2011 land use cover maps. We focused on six water quality metrics (dissolved oxygen, total nitrogen, total phosphorus, turbidity, total dissolved solids and fecal coliforms) and used generalized linear mixed models to analyze the data. Models were built at two scales, the entire watershed and a 60 meters riparian buffer along the river network. Models accounted for 46-67% of the variance in water quality metrics and, apart from dissolved oxygen, which reflected land cover composition in riparian buffers, all metrics responded to land use at the watershed scale. Highly urbanized areas had low dissolved oxygen and high fecal coliforms, dissolved solids, phosphorus and nitrogen levels in streams. Pasture was associated with increases in turbidity, while sugarcane plantations significantly increased nitrogen concentrations. Watersheds with high forest cover had greater dissolved oxygen and lower turbidity. Silviculture plantations had little impact on water quality. Precipitation decreased dissolved oxygen and was associated with higher levels of turbidity, fecal coliforms and phosphorus. Results indicate that conversion of forest cover to other land uses had negative impacts on water quality in the study area, highlighting the need for landscape restoration to improve watersheds ecosystem services.

  19. Hardening and embrittlement mechanisms of reduced activation ferritic/martensitic steels irradiated at 573 K

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, H. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States); Hashimoto, N. [Hokkaido Univ., Materials Science and Engineering Div., Graduate School of Engineering, Sapporo (Japan); Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States)

    2007-07-01

    Full text of publication follows: It has been reported that reduced-activation ferritic/martensitic steels (RAFMs), such as F82H, ORNL9Cr-2WVTa, and JLF-1, showed a variety of changes in ductile-brittle transition temperature and yield stress after irradiation at 573 K up to 5 dpa, and those differences could not be interpreted solely by the difference of dislocation microstructure induced by irradiation. To investigate the impact of other microstructural feature, i.e. precipitates, the precipitation behavior of F82H, ORNL 9Cr-2WVTa, and JLF-1 was examined. It was revealed that irradiation-induced precipitation and amorphization of precipitates partly occurred and caused the different precipitation on block, packet and prior austenitic grain boundaries. In addition to these phenomena, irradiation-induced nano-size precipitates were also observed in the matrix. It was also revealed that the chemical compositions of precipitates approached the calculated thermal equilibrium state of M{sub 23}C{sub 6} at an irradiation temperature of 573 K. The calculation also suggests the presence of Laves phase at 573 K, which is usually not observed at this temperature, but the ion irradiation on aged F82H with Laves phase suggests that Laves phase becomes amorphous and could not be stable under irradiation at 573 K. This observation indicates the possibility that the irradiation-induced nano-size precipitation could be the consequence of the conflict between precipitation and amorphization of Laves phase. Over all, these observations suggests that the variety of embrittlement and hardening of RAFMs observed at 573 K irradiation up to 5 dpa might be the consequence of the transition phenomena that occur as the microstructure approaches thermal equilibrium during irradiation at 573 K. (authors)

  20. Fatigue hardening and softening studies on strain hardened 18-8 austenitic stainless steel

    International Nuclear Information System (INIS)

    Ramakrishna Prasad, C.; Vasudevan, R.

    1976-01-01

    Metals when subjected to fatigue harden or soften depending on their previous mechanical history. Annealed or mildly cold worked metals are known to harden while severely cold worked metals soften when subjected to fatigue loading. In the present work samples of austenitic 18-8 steel cold worked to 11% and 22% reduction in area were mounted in a vertical pulsator and fatigued in axial tension-compression. Clear cut effects were produced and it was noticed that these depended on the extent of cold work, the amplitude as well as the number of cycles of fatigue and mean stress if any. (orig.) [de

  1. Effect of strengthening mechanisms on cold workability and instantaneous strain hardening behavior during grain refinement of AA 6061-10 wt.% TiO2 composite prepared by mechanical alloying

    International Nuclear Information System (INIS)

    Sivasankaran, S.; Sivaprasad, K.; Narayanasamy, R.; Iyer, Vijay Kumar

    2010-01-01

    Research highlights: → Various strengthening mechanisms such as solid solution, grain size, precipitate, dislocation and dispersion strengthening promoted yield strength of the composites → The 5 h sintered composite yielded a large plastic strain (23%) at ambient temperature. → The domination of interparticle friction effects, grain size and dislocation strengthening diminished the deformation capacity of the composites greater than 5 h of milling. → Ultra-fine grained composite (40 h) yielded a high strength (>1000 MPa). → The proposed instantaneous new Poisson's ratio and the instantaneous strain hardening index used to study the extent of plastic zone and strain levels of the composite. - Abstract: The mechanical alloying (MA) of AA 6061 alloy reinforced with 10 wt.% fine anatase-titania composites powder milled with different timings (1, 5, 10, 20, 30, and 40 h) was cold consolidated and sintered. The main purpose of this study is to investigate the effect of microstructure and the various strengthening mechanisms such as solid solution, grain size, precipitate, dislocation and dispersion strengthening during grain refinement of AA 6061-10 wt.% TiO 2 composite via MA on cold working and strain hardening behavior. The sintered composite preforms were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. The strengthening mechanisms were estimated by using simplified models available in the literatures. The evaluation of cold deformation behavior under triaxial stress condition through room temperature cold-upsetting tests (incremental loads) was studied by correlating the strengthening mechanisms. Among the developed strengthening mechanisms the grain size and dislocation strengthening mechanisms diminished the deformation capacity of the composites. The strain hardening behavior was also examined by proposing instantaneous strain hardening index (n i ). The value of maximum instantaneous strain

  2. Phenomenological Analysis of the Kinematic Hardening of HSLA and IF Steels Using Reverse Simple Shear Tests

    International Nuclear Information System (INIS)

    Aouafi, A.; Bouvier, S.; Gasperini, M.; Lemoine, X.; Bouaziz, O.

    2007-01-01

    Reverse simple shear tests are used to analyse the Bauschinger effect and the evolution of the kinematic hardening for a wide range of equivalent von Mises strain [0.025 - 0.3]. This work is carried out on two high strength low-alloyed steels. In order to investigate the effect of the precipitates on the macroscopic behaviour, a ferritic mild steel is used as a reference. Different phenomenological descriptions of the back-stress tensor are examined in order to analyse their ability to describe the experimental behaviour

  3. Low-temperature gaseous surface hardening of stainless steel: the current status

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2009-01-01

    a hardened case at the surface, while maintaining the superior corrosion performance. This can be achieved by dissolving colossal amounts of nitrogen and/or carbon without forming nitrides and/or carbides, thus developing so-called expanded austenite. The present work gives an overview over results obtained...... on homogeneous expanded austenite and covers the crystallography for nitrogen- and carbon-stabilised expanded austenite, the solubility for nitrogen and carbon, the diffusion of these interstitials as well as the stability of expanded austenite with respect to nitride and carbide formation. Subsequently...

  4. Spatial and temporal variability of precipitation and drought in Portugal

    Directory of Open Access Journals (Sweden)

    D. S. Martins

    2012-05-01

    Full Text Available The spatial variability of precipitation and drought are investigated for Portugal using monthly precipitation from 74 stations and minimum and maximum temperature from 27 stations, covering the common period of 1941–2006. Seasonal precipitation and the corresponding percentages in the year, as well as the precipitation concentration index (PCI, was computed for all 74 stations and then used as an input matrix for an R-mode principal component analysis to identify the precipitation patterns. The standardized precipitation index at 3 and 12 month time scales were computed for all stations, whereas the Palmer Drought Severity Index (PDSI and the modified PDSI for Mediterranean conditions (MedPDSI were computed for the stations with temperature data. The spatial patterns of drought over Portugal were identified by applying the S-mode principal component analysis coupled with varimax rotation to the drought indices matrices. The result revealed two distinct sub-regions in the country relative to both precipitation regimes and drought variability. The analysis of time variability of the PC scores of all drought indices allowed verifying that there is no linear trend indicating drought aggravation or decrease. In addition, the analysis shows that results for SPI-3, SPI-12, PDSI and MedPDSI are coherent among them.

  5. Effect of copper precipitates on the toughness of low alloy steels for pressure boundary components

    International Nuclear Information System (INIS)

    Foehl, J.; Willer, D.; Katerbau, K.H.

    2004-01-01

    The ferritic bainitic steel 15NiCuMoNb5 (WB 36)is widely used for pressure boundary components. Due to the high copper content which leads to precipitation hardening high strength and toughness are characteristic for this type of steel. However, in the initial state, there is still a high amount of dissolved copper in an oversaturated state which makes the steel susceptible to thermal ageing. Ageing and annealing experiments were performed, and the change in microstructure was investigated by small angle neutron scattering (SANS), measurements of the residual electric resistance and hardness measurements. A correlation between micro structural changes and changes in mechanical properties could be established. It could clearly be shown that significant effects on strength and toughness have to be considered when the size of the copper rich precipitates vary in the range from 1.2 to 2.2 nm in radius. The changes in microstructure affect both, the Carpy impact transition temperature and the fracture toughness qualitatively and quantitatively in a similar way. The investigations have contributed to a better understanding of precipitation hardening by copper not only for this type of steel but also for copper containing steels and weld subjected to neutron irradiation. (orig.)

  6. A review of the stages of work hardening

    Energy Technology Data Exchange (ETDEWEB)

    Rollett, A.D.; Kocks, U.F.

    1993-07-01

    Stages of work hardening are reviewed with emphasis on links between each stage. Simple quantitative descriptions are given for each stage. Similarities between stage I, easy glide, and stage IV, large strain hardening, are pointed out both in terms of magnitude of the hardening rate and of the underlying mechanism of dislocation debris accumulation. Stage II is described as an athermal hardening stage that occurs when statistical variations in the dislocation ``forest`` lead to geometrical storage of dislocations. The steadily decreasing hardening rate observed in stage III is characterized by the increasing rate of loss of dislocation density due to dynamic recovery. Stage III appears to have an asymptote to a saturation stress which is determined by the characteristics of the dislocation tangles, or cell walls. The imperfect nature of the dynamic recovery process, however, leads to the accumulation of dislocation debris and this, by analogy with stage 1, causes the apparent saturation stress to rise, thus causing stage IV.

  7. Effect of bentonite addition on residual strength of microwave-hardened waterglass-containing moulding sands

    Directory of Open Access Journals (Sweden)

    M. Stachowicz

    2011-07-01

    Full Text Available The paper presents results of a preliminary research of the effect of bentonite addition on residual strength of microwave-hardened moulding sands, containing sodium waterglass. Strength was determined at ambient temperature, on cylindrical specimens baked in an oven. Moulding sands for examinations were based on high-silica sand with addition of 2.5 % of non-modified, domestic-made waterglass grade 145. The prepared standard cylindrical specimens were hardened using the innovative microwave heating process and next baked for 30 minutes at temperatures between 100 and 1200 °C. Strength parameters of the specimens were determined on the specimens cooled- down to ambient temperature. The obtained results were compared with literature data to evaluate the effect of the applied hardening method and of the special additive on residual strength as a function of baking temperature. A favourable effect was found of both the innovative heating process and the applied bentonite addition.

  8. Quantitative analysis of CT brain images: a statistical model incorporating partial volume and beam hardening effects

    International Nuclear Information System (INIS)

    McLoughlin, R.F.; Ryan, M.V.; Heuston, P.M.; McCoy, C.T.; Masterson, J.B.

    1992-01-01

    The purpose of this study was to construct and evaluate a statistical model for the quantitative analysis of computed tomographic brain images. Data were derived from standard sections in 34 normal studies. A model representing the intercranial pure tissue and partial volume areas, with allowance for beam hardening, was developed. The average percentage error in estimation of areas, derived from phantom tests using the model, was 28.47%. We conclude that our model is not sufficiently accurate to be of clinical use, even though allowance was made for partial volume and beam hardening effects. (author)

  9. Cover technology demonstration for low-level radioactive sites

    International Nuclear Information System (INIS)

    Barnes, F.J.; Warren, J.L.

    1988-01-01

    The performance of a shallow land burial site in isolating low-level radioactive and mixed waste is strongly influenced by the behavior of the precipitation falling on the site. Predicting the long-term integrity of a cover design requires a knowledge of the water balance dynamics, and the use of predictive models. The multiplicity of factors operating on a site in the years post-closure (precipitation intensity and duration, soil conditions, vegetation seasonality and variability) have made it extremely difficult to predict the effects of natural precipitation with accuracy. Preliminary results are presented on a three-year field demonstration at Los Alamos National Laboratory to evaluate the influence of different waste trench cap designs on water balance under natural precipitation. Erosion plots having two different vegetative covers (shrubs and grasses) and with either gravel-mulched or unmulched soil surface treatments have been established on three different soil profiles on an inactive waste site. Total runoff and soil loss from each plot are measured biweekly while plant canopy cover is measured seasonally. Preliminary results from the first year show that the application of a gravel mulch reduced runoff by 73 to 90%. Total soil loss was reduced by 83 to 93% by the mulch treatment. On unmulched plots, grass cover reduced both runoff and soil loss by about 50% compared to the shrub plots. Soil moisture reduction during the growing season was more pronounced on the shrub plots. This indicates that a more complex vegetative cover provides greater soil moisture storage capacity for winter precipitation than the usual grass cover

  10. Design considerations for a radiation hardened nonvolatile memory

    International Nuclear Information System (INIS)

    Murray, J.R.

    1993-01-01

    Sub-optimal design practices can reduce the radiation hardness of a circuit even though it is fabricated in a radiation hardened process. This is especially true for a nonvolatile memory, as compared to a standard digital circuit, where high voltages and unusual bias conditions are required. This paper will discuss the design technique's used in the development of a 64K EEPROM (Electrically Erasable Programmable Read Only Memory) to maximize radiation hardness. The circuit radiation test results will be reviewed in order to provide validation of the techniques

  11. Radiation-hardened bulk Si-gate CMOS microprocessor family

    International Nuclear Information System (INIS)

    Stricker, R.E.; Dingwall, A.G.F.; Cohen, S.; Adams, J.R.; Slemmer, W.C.

    1979-01-01

    RCA and Sandia Laboratories jointly developed a radiation-hardened bulk Si-gate CMOS technology which is used to fabricate the CDP-1800 series microprocessor family. Total dose hardness of 1 x 10 6 rads (Si) and transient upset hardness of 5 x 10 8 rads (Si)/sec with no latch up at any transient level was achieved. Radiation-hardened parts manufactured to date include the CDP-1802 microprocessor, the CDP-1834 ROM, the CDP-1852 8-bit I/O port, the CDP-1856 N-bit 1 of 8 decoder, and the TCC-244 256 x 4 Static RAM. The paper is divided into three parts. In the first section, the basic fundamentals of the non-hardened C 2 L technology used for the CDP-1800 series microprocessor parts is discussed along with the primary reasons for hardening this technology. The second section discusses the major changes in the fabrication sequence that are required to produce radiation-hardened devices. The final section details the electrical performance characteristics of the hardened devices as well as the effects of radiation on device performance. Also included in this section is a discussion of the TCC-244 256 x 4 Static RAM designed jointly by RCA and Sandia Laboratories for this application

  12. Space and Missile Systems Center Standard: Parts, Materials, and Processes Control Program for Launch Vehicles -SMC-S-011 (2012)

    Science.gov (United States)

    2012-07-03

    Precipitation Hardened Stainless Steel .......................................................... A-8  3.2.6  Titanium...shall require specific PMPCB approval. The drilling of holes, including beveling and spot facing, in martensitic steel hardened to 180 ksi UTS or...procedure shall be used to determine the presence of untempered martensite . 3.2.4 Corrosion-Resistant Steel Unstabilized austenitic steels may be used

  13. Influence of Glass Fiber on Fresh and Hardened Properties of Self Compacting Concrete

    Science.gov (United States)

    Bharathi Murugan, R.; Haridharan, M. K.; Natarajan, C.; Jayasankar, R.

    2017-07-01

    The practical need of self-compacting concrete (SCC) is increasing due to increase in the infrastructure competence all over the world. The effective way of increasing the strength of concrete and enhance the behaviour under extreme loading (fire) is the keen interest. Glass fibers were added for five different of volume fractions (0%, 0.1%, 0.3%, 0.5% and 0.6%) to determine the optimum percentage of glass fiber without compensating the fresh properties and enhanced hardened properties of SCC concrete. The fresh state of concrete is characterized by slump flow, T-50cm slump flow, and V-funnel and L- box tests. The results obtained in fresh state are compared with the acceptance criteria of EFNARC specification. Concrete specimens were casted to evaluate the hardened properties such as compressive strength, split tensile strength, flexural strength and modulus of elasticity. Incorporation the glass fiber into SCC reduces the workability but within the standard specification. The hardened properties of SCC glass fiber reinforced concrete were enhanced, due to bridging the pre-existing micro cracks in concrete by glass fiber addition.

  14. Precipitation kinetics of Al-1.12 Mg{sub 2}Si-0.35 Si and Al-1.07 Mg{sub 2}Si-0.33 Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gaber, A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Gaffar, M.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)]. E-mail: mgaafar@aucegypt.edu; Mostafa, M.S. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Zeid, E.F. Abo [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)

    2007-02-21

    The kinetics of hardening precipitates of Al-1.12 wt.% Mg{sub 2}Si-0.35 wt.% Si (excess Si) and Al-1.07 wt.% Mg{sub 2}Si-0.33 wt.% Cu (balanced + Cu) alloys have been investigated by means of differential scanning calorimetry and hardness measurements. The excess Si enhances the precipitation kinetics and improves the strength of the material. On the other hand, however addition of Cu assist formation of the Q' phase which positively changed the alloy strength. The high binding energy between vacancies and solute atoms (Si and Mg) enhances the combination of Si, Mg and vacancies to form Si-Mg-vacancy clusters. These clusters act as nucleation sites for GP-zones. The coexistence of the {beta}'- and Q'-precipitates in the balanced + Cu alloy results in a higher peak age hardening compared to the alloy with Si in excess.

  15. Tracking the path of dislocations across ordered Al3Zr nano-precipitates in three dimensions

    International Nuclear Information System (INIS)

    Lefebvre, W.; Masquelier, N.; Houard, J.; Patte, R.; Zapolsky, H.

    2014-01-01

    Graphical abstract: -- We report on the shear–bypassing transition of chemically ordered Al 3 Zr nanoprecipitates. Observation of complex combinations of lattice translations, revealed by scanning transmission electron microscopy, is used as the signature of precipitate shearing during cold deformation. A method is proposed to build a three-dimensional atomic model of sheared particles from a set of three atomic scale projections. An estimation of the antiphase boundary energy of the Al 3 Zr structure is achieved via the comparison of experimental findings to a model of precipitation hardening

  16. Microalloying in case hardening steels - a challenge for the lean production of gears

    Energy Technology Data Exchange (ETDEWEB)

    Trute, S.; Bleck, W. [RWTH Aachen (Germany). Dept. of Ferrous Metallurgy; Hippenstiel, F. [Edelstahlwerke Buderus AG, Wetzlar (Germany); Klinkenberg, C. [Niobium Products Company GmbH, Duesseldorf (Germany)

    2005-07-01

    Case hardening steels cover a dominant fraction of engineering steel production. Particularly with recent developments in automotive power train elements, where good hardenability, high tensile strength, high fatigue strength and high impact resistance are required. With a share of up to 40% the material and the heat treatment process take a main part of the overall manufacturing costs. Production costs can be reduced by shortening the overall process time from the melting to the finishing. New developments in carburising technology with an increased carburising temperature offer the possibility of time and cost reduction. Simultaneously a precise grain size control during austenitising is required. A homogenous former austenite grain size distribution results in a more uniform performance of the mechanical properties. This paper summarizes the results of recent research regarding the demands on steels for a high temperature carburising process. The possibility to prevent undesired grain growth by increasing the grain coarsening temperature using microalloying elements as well as the impact on the production process is discussed. (orig.)

  17. PRECIPITATION BEHAVIOR OF Co PHASES IN B2-ORDERED(Ni,Co)Al COMPOUND

    Institute of Scientific and Technical Information of China (English)

    W.H. Tian; A.L. Fan; M. Nemoto

    2002-01-01

    The precipitation behavior of Co phases in B2-ordered (Ni, Co)Al has been investigatedin terms of transmission electron microscopy. Fine precipitation off cc-Co occurs in(Ni, Co)Al by aging at temperature over 973K. The orientation relationship betweenthe fcc-Co precipitates and the B2-(Ni, Co)Al matrix follows the Kurdjumow-Sachs(K-S) orientation relation. But when the aging temperature is under 873K the Coprecipitates have a hcp crystal structure. The orientation relationship between thehcp-Co precipitates and the B2-(Ni, Co)Al matrix follows the Burgers orientation re-lation. (Ni, Co)Al is hardened appreciably by the fine precipitation of both the fcc-Coand hcp-Co phases. The temperature dependence of the yield strength of precipitate-containing B2-ordered (Ni, Co)Al was investigated by compression tests over the rangeof 298-1273K. The fine precipitation of Co phases enhances greatly the low and in-termediate temperature yield strength. When the deformation temperature was over873K, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni, Co)Al+Ni3Al alloy.

  18. Creep resistant, precipitation-dispersion-strengthened, martensitic stainless steel and method thereof

    Science.gov (United States)

    Buck, R.F.

    1994-05-10

    An iron-based, corrosion-resistant, precipitation strengthened, martensitic steel essentially free of delta ferrite for use at high temperatures has a nominal composition of 0.05--0.1 C, 8--12 Cr, 1--5 Co, 0.5--2.0 Ni, 0.41--1.0 Mo, 0.1--0.5 Ti, and the balance iron. This steel is different from other corrosion-resistant martensitic steels because its microstructure consists of a uniform dispersion of fine particles, which are very closely spaced, and which do not coarsen at high temperatures. Thus at high temperatures this steel combines the excellent creep strength of dispersion-strengthened steels, with the ease of fabricability afforded by precipitation hardenable steels. 2 figures.

  19. Creep resistant, precipitation-dispersion-strengthened, martensitic stainless steel and method thereof

    Science.gov (United States)

    Buck, Robert F.

    1994-01-01

    An iron-based, corrosion-resistant, precipitation strengthened, martensitic steel essentially free of delta ferrite for use at high temperatures has a nominal composition of 0.05-0.1 C, 8-12 Cr, 1-5 Co, 0.5-2.0 Ni, 0.41-1.0 Mo, 0.1-0.5 Ti, and the balance iron. This steel is different from other corrosion-resistant martensitic steels because its microstructure consists of a uniform dispersion of fine particles, which are very closely spaced, and which do not coarsen at high temperatures. Thus at high temperatures this steel combines the excellent creep strength of dispersion-strengthened steels, with the ease of fabricability afforded by precipitation hardenable steels.

  20. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  1. Damped summer warming accompanied with cloud cover increase over Eurasia from 1982 to 2009

    International Nuclear Information System (INIS)

    Tang Qiuhong; Leng Guoyong

    2012-01-01

    The relationship between summer temperature, total cloud cover and precipitation over Eurasia was investigated using observation-based products of temperature and precipitation, and satellite-derived cloud cover and radiation products. We used a partial least squares regression approach to separate the local influences of cloud cover and precipitation on temperature variations. Our results suggest that the variance of summer temperature is partly explained by changes in summer cloudiness. The summer temperature dependence on cloud cover is strong at the high latitudes and in the middle latitude semi-humid area, while the dependence on precipitation is strong in the Central Asia arid area and the southern Asia humid area. During the period 1982–2009, the damped warming in extended West Siberia was accompanied with increases in cloud cover, and the pronounced warming in Europe and Mongolia was associated with a decrease in cloud cover and precipitation. Our results suggest that cloud cover may be the important local factor influencing the summer temperature variation in Eurasia while precipitation plays an important role at the middle latitudes. (letter)

  2. Atomistic simulation of the pinning of edge dislocations in Ni by Ni3Al precipitates

    International Nuclear Information System (INIS)

    Kohler, Christopher; Kizler, Peter; Schmauder, Siegfried

    2005-01-01

    Classical molecular dynamics simulations of the interaction of edge dislocations in Ni with chains of spherical Ni 3 Al precipitates are performed using EAM potentials. The order hardening is investigated at temperature T=0 -bar K by determining the critical resolved shear stresses (CRSSs) for a superdislocation that is dissociated into four partial dislocations. The CRSS is computed as a function of the radius and the distance of the precipitates. It is found that for precipitates with a diameter smaller than the dissociation width of perfect edge dislocation in Ni, the CRSS of the trailing dislocation of the superdislocation is a fraction of about 0.4 of the CRSS of the leading dislocation

  3. Numerical and experimental comparison of plastic work-hardening rules

    International Nuclear Information System (INIS)

    Haisler, W.E.

    1977-01-01

    The purpose of this paper is to describe recent numerical and experimental correlation studies of several plastic work-hardening rules. The mechanical sublayer model and the combined kinematic-isotropic hardening rules are examined and the numerical results for several structural geometries are compared to experimental results. Both monotonic and cyclic loads are considered. The governing incremental plasticity relations are developed for both work-hardening models. The combined kinematic-isotropic hardening model is developed in terms of a ratio γ which controls the relative contribution of kinematic hardening (yield surface translation) and isotropic hardening (yield surface expansion). In addition to making use of a uniaxial stress-strain curve as input data, the model allows for the input of a yield surface size vs. uniaxial plastic strain curve obtained from a cyclic uniaxial reverse loading test. The mechanical sublayer model is developed in general form and a new method for determining the sublayer parameters (stress weighting factors and yield stresses) is presented. It is demonstrated that former procedures used to obtain the sublayer parameters are inconsistent for multiaxial loading. Numerical and experimental results are presented for a cylinder, circular plate with punch, and a steel pressure vessel. The numerical results are obtained with the computer program AGGIE I. The comparison study indicates that reasonable agreement is obtained with both hardening models; the choice depending upon whether the loading is monotonic or cyclic

  4. Application of Standardized Precipitation Index to assess meteorological drought in Bangladesh

    Directory of Open Access Journals (Sweden)

    Md. Anarul H. Mondol

    2016-09-01

    Full Text Available Bangladesh is one of the vulnerable countries of the world for natural disasters. Drought is one of the common and severe calamities in Bangladesh that causes immense suffering to people in various ways. The present research has been carried out to examine the frequency of meteorological droughts in Bangladesh using the long-term rainfall data of 30 meteorological observatories covering the period of 1948–2011. The study uses the highly effective Standardized Precipitation Index (SPI for drought assessment in Bangladesh. By assessing the meteorological droughts and the history of meteorological droughts of Bangladesh, the spatial distributions of meteorological drought indices were also analysed. The spatial and temporal changes in meteorological drought and changes in different years based on different SPI month intervals were analysed. The results indicate that droughts were a normal and recurrent feature and it occurred more or less all over the country in virtually all climatic regions of the country. As meteorological drought depends on only rainfall received in an area, anomaly of rainfall is the main cause of drought. Bangladesh experienced drought in the years 1950, 1951, 1953, 1954, 1957, 1958, 1960, 1961, 1962, 1963, 1965, 1966, 1967 and 1971 before independence and after independence Bangladesh has experienced droughts in the years 1972, 1973, 1975, 1979, 1980, 1983, 1985, 1992, 1994, 1995, 2002, 2004, 2006, 2009 and 2011 during the period 1948–2011. The study indicated that Rajshahi and its surroundings, in the northern regions and Jessore and its surroundings areas, the island Bhola and surrounding regions, in the south-west region, were vulnerable. In the Sylhet division, except Srimongal, the areas were not vulnerable but the eastern southern sides of the districts Chittagong, Rangamati, Khagrachhari, Bandarban and Teknaf were vulnerable. In the central regions, the districts of Mymensingh and Faridpur were more vulnerable

  5. The precipitation behavior of superalloy ATI Allvac 718Plus

    Energy Technology Data Exchange (ETDEWEB)

    Zickler, Gerald A.; Schnitzer, Ronald; Leitner, Harald [Department of Physical Metallurgy and Materials Testing, Christian Doppler Laboratory Early Stages of Precipitation, Montanuniversitaet Leoben (Austria); Radis, Rene [Christian Doppler Laboratory Early Stages of Precipitation, Institute of Materials Science and Technology, Vienna University of Technology (Austria); Institute for Materials Science and Welding, Graz University of Technology (Austria); Kozeschnik, Ernst [Christian Doppler Laboratory Early Stages of Precipitation, Institute of Materials Science and Technology, Vienna University of Technology (Austria); Stockinger, Martin [Boehler Schmiedetechnik GmbH and Co. KG., Kapfenberg (Austria)

    2010-03-15

    ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace gas turbines. The precipitation kinetics of the intermetallic {delta} (Ni{sub 3}Nb) and {gamma}' (Ni{sub 3}(Al,Ti)) phases in this alloy are of scientific as well as technological interest because of their significant influence on the mechanical properties. Important parameters like grain size are controlled by coarse {delta} precipitates located at grain boundaries, whereas small {gamma}' precipitates are responsible for strengthening by precipitation hardening. In the present study, the microstructure is investigated by three-dimensional atom probe tomography and simulated by computer modeling using the thermo-kinetic software MatCalc. The results of numerical simulations and experimental data are compared and critically discussed. It is shown that the chemical compositions of the phases change during isothermal aging, and the precipitation kinetics of {delta} and {gamma}' phases interact with each other as shown in a time temperature precipitation (TTP) plot. The TTP plot shows C-shaped curves with characteristic discontinuities in the temperature range, where simultaneous and concurrent precipitation of the {delta} and {gamma}' phases occurs. This leads to a competition in the diffusion of Nb and Al, which are partly present in both phases. Thus, the present study gives important information on heat treatments for ATI Allvac 718Plus in order to achieve the desired microstructure and mechanical properties. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  6. Satellite precipitation estimation over the Tibetan Plateau

    Science.gov (United States)

    Porcu, F.; Gjoka, U.

    2012-04-01

    Precipitation characteristics over the Tibetan Plateau are very little known, given the scarcity of reliable and widely distributed ground observation, thus the satellite approach is a valuable choice for large scale precipitation analysis and hydrological cycle studies. However,the satellite perspective undergoes various shortcomings at the different wavelengths used in atmospheric remote sensing. In the microwave spectrum often the high soil emissivity masks or hides the atmospheric signal upwelling from light-moderate precipitation layers, while low and relatively thin precipitating clouds are not well detected in the visible-infrared, because of their low contrast with cold and bright (if snow covered) background. In this work an IR-based, statistical rainfall estimation technique is trained and applied over the Tibetan Plateau hydrological basin to retrive precipitation intensity at different spatial and temporal scales. The technique is based on a simple artificial neural network scheme trained with two supervised training sets assembled for monsoon season and for the rest of the year. For the monsoon season (estimated from June to September), the ground radar precipitation data for few case studies are used to build the training set: four days in summer 2009 are considered. For the rest of the year, CloudSat-CPR derived snowfall rate has been used as reference precipitation data, following the Kulie and Bennartz (2009) algorithm. METEOSAT-7 infrared channels radiance (at 6.7 and 11 micometers) and derived local variability features (such as local standard deviation and local average) are used as input and the actual rainrate is obtained as output for each satellite slot, every 30 minutes on the satellite grid. The satellite rainrate maps for three years (2008-2010) are computed and compared with available global precipitation products (such as C-MORPH and TMPA products) and with other techniques applied to the Plateau area: similarities and differences are

  7. Structure and tensile properties of ferro-martensitic alloys hardened by chi phase precipitation

    International Nuclear Information System (INIS)

    Alamo, A.; Aubert, H.; Laniesse, J.; Lelong, C.; Pigoury, M.; Foucher, C.

    1985-08-01

    Transformation of ferrite into austenite and of austenite into martensite, precipitation of intermetallic phases and tensile properties of the steel Cr13-Mo1.5 are studied in function of Ti additions (from 0 to 3%) and Ni additions (from 2 to 8%) for its mechanical resistance at 400-650 0 C. 12 references are given [fr

  8. Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1995-01-01

    1.1 This practice provides a procedure for the exposure of cover materials for flat-plate solar collectors to the natural weather environment at temperatures that are elevated to approximate operating conditions. 1.2 This practice is suitable for exposure of both glass and plastic solar collector cover materials. Provisions are made for exposure of single and double cover assemblies to accommodate the need for exposure of both inner and outer solar collector cover materials. 1.3 This practice does not apply to cover materials for evacuated collectors or photovoltaics. 1.4 The values stated in SI units are to be regarded as the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  9. The effect of voids on the hardening of body-centered cubic Fe

    Energy Technology Data Exchange (ETDEWEB)

    Nakai, Ryosuke, E-mail: ryosuke.nakai@jupiter.qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Yabuuchi, Kiyohiro, E-mail: k-yabuuchi@iae.kyoto-u.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan)

    2016-04-01

    The mechanical properties of metals are affected by various types of defects. Hardening is usually described through the interaction between dislocations and obstacles, in the so-called line tension theory. The strength factor in the line tension theory represents the resistance of a defect against the dislocation motion. In order to understand hardening from the viewpoint of the microstructure, an accurate determination of the strength factor of different types of defects is essential. In the present study, the strength factor of voids in body-centered cubic (BCC) Fe was investigated by two different approaches: one based on the Orowan equation to link the measured hardness with the average size and density of voids, and the other involving direct observation of the interaction between dislocations and voids by transmission electron microscope (TEM). The strength factor of voids induced by ion irradiation estimated by the Orowan equation was 0.6, whereas the strength factor estimated by the direct TEM approach was 0.8. The difference in the strength factors measured by the two approaches is due to the positional relationship between dislocations and voids: the central region of a void is stronger than the tip. Moreover, the gliding plane and the direction of dislocation may also affect the strength factor of voids. This study determined the strength factor of voids in BCC Fe accurately, and suggested that the contribution of voids to the irradiation hardening is larger than that of dislocation loops and Cu-rich precipitates. - Highlights: • The strength factor of voids in BCC Fe was experimentally investigated. • The strength factor of voids estimated by the line tension theory was 0.6. • The strength factor of voids estimated by the bowing angle of dislocations was 0.8. • The different strength factors are due to the positional relationship.

  10. Special study on vegetative covers

    International Nuclear Information System (INIS)

    1988-11-01

    This report describes the findings of a special study on the use of vegetative covers to stabilize tailings piles for the Uranium Mill Tailings Remedial Action (UMTRA) Project. The principal rationale for using plants would be to establish a dynamic system for controlling water balance. Specifically, vegetation would be used to intercept and transpire precipitation to the atmosphere, rather than allowing water to drain into the tailings and mobilize contaminants. This would facilitate compliance with groundwater standards proposed for the UMTRA Project by the Environmental Protection Agency. The goals of the study were to evaluate the feasibility of using vegetative covers on UMTRA Project piles, define the advantages and disadvantages of vegetative covers, and develop general guidelines for their use when such use seems reasonable. The principal method for the study was to analyze and apply to the UMTRA Project the results of research programs on vegetative covers at other US Department of Energy (DOE) waste management facilities. The study also relied upon observations made of existing stabilized piles at UMTRA Project sites where natural vegetation is growing on the rock-covered surfaces. Water balance and erosion models were also used to quantify the long-term performance of vegetative covers planned for the topslopes of stabilized piles at Grand Junction and Durango, Colorado, two UMTRA Project sites where the decision was made during the course of this special study to use vegetative covers. Elements in the design and construction of the vegetative covers at these two sites are discussed in the report, with explanations of the differing features that reflect differing environmental conditions. 28 refs., 18 figs., 9 tabs

  11. Comparing the Palmer Drought Index and the Standardized Precipitation Index for Zagreb-Gric Observatory

    Science.gov (United States)

    Pandzic, Kreso

    2016-04-01

    Conventional Palmer Drought Index (PDSI) and recent Standardized Precipitation Index (SPI) are compared for Zagreb-Gric weather station. Historical time series of PDSI and SPI are compared. For that purpose monthly precipitation, air temperature and air humidity data for Zagreb-Gric Observatory and period 1862-2012 are used. The results indicate that SPI is simpler for interpretation than PDSI. On the other side, lack of temperature within SPI, make impossible use of it on climate change applications. A comparison of PDSI and SPI for the periods from 1 to 24 months indicate the best agreement between PDSI and SPI for the periods from 6 to 12 months. In addition, correlation coefficients of determination between annual corn crop per hectare and SPI 9- months time scale and PDSI from May to October are shown as significant.

  12. COMPLEX SURFACE HARDENING OF STEEL ARTICLES

    Directory of Open Access Journals (Sweden)

    A. V. Kovalchuk

    2014-01-01

    Full Text Available The method of complex surface hardening of steel detailswas designed. The method is a compound of two processes of hardening: chemical heat treatment and physical vapor deposition (PVD of the coating. The result, achieved in this study is much higher, than in other work on this topic and is cumulative. The method designed can be used in mechanical engineering, medicine, energetics and is perspective for military and space technologies.

  13. Radiation hardening of smart electronics

    International Nuclear Information System (INIS)

    Mayo, C.W.; Cain, V.R.; Marks, K.A.; Millward, D.G.

    1991-02-01

    Microprocessor based ''smart'' pressure, level, and flow transmitters were tested to determine the radiation hardness of this class of electronic instrumentation for use in reactor building applications. Commercial grade Complementary Metal Oxide Semiconductor (CMOS) integrated circuits used in these transmitters were found to fail at total gamma dose levels between 2500 and 10,000 rad. This results in an unacceptably short lifetime in many reactor building radiation environments. Radiation hardened integrated circuits can, in general, provide satisfactory service life for normal reactor operations when not restricted to the extremely low power budget imposed by standard 4--20 mA two-wire instrument loops. The design of these circuits will require attention to vendor radiation hardness specifications, dose rates, process control with respect to radiation hardness factors, and non-volatile programmable memory technology. 3 refs., 2 figs

  14. Radiation-hardened control system

    International Nuclear Information System (INIS)

    Vandermolen, R.I.; Smith, S.F.; Emery, M.S.

    1993-01-01

    A radiation-hardened bit-slice control system with associated input/output circuits was developed to prove that programmable circuits could be constructed to successfully implement intelligent functions in a highly radioactive environment. The goal for this effort was to design and test a programmable control system that could withstand a minimum total dose of 10 7 rads (gamma). The Radiation Hardened Control System (RHCS) was tested in operation at a dose rate that ranged up to 135 krad/h, with an average total dose of 10.75 Mrads. Further testing beyond the required 10 7 rads was also conducted. RHCS performed properly through the target dose of 10 7 rads, and sporadic intermittent failures in some programmable logic devices were noted after ∼ 13 Mrads

  15. Efficient simulation of press hardening process through integrated structural and CFD analyses

    International Nuclear Information System (INIS)

    Palaniswamy, Hariharasudhan; Mondalek, Pamela; Wronski, Maciek; Roy, Subir

    2013-01-01

    Press hardened steel parts are being increasingly used in automotive structures for their higher strength to meet safety standards while reducing vehicle weight to improve fuel consumption. However, manufacturing of sheet metal parts by press hardening process to achieve desired properties is extremely challenging as it involves complex interaction of plastic deformation, metallurgical change, thermal distribution, and fluid flow. Numerical simulation is critical for successful design of the process and to understand the interaction among the numerous process parameters to control the press hardening process in order to consistently achieve desired part properties. Until now there has been no integrated commercial software solution that can efficiently model the complete process from forming of the blank, heat transfer between the blank and tool, microstructure evolution in the blank, heat loss from tool to the fluid that flows through water channels in the tools. In this study, a numerical solution based on Altair HyperWorks® product suite involving RADIOSS®, a non-linear finite element based structural analysis solver and AcuSolve®, an incompressible fluid flow solver based on Galerkin Least Square Finite Element Method have been utilized to develop an efficient solution for complete press hardening process design and analysis. RADIOSS is used to handle the plastic deformation, heat transfer between the blank and tool, and microstructure evolution in the blank during cooling. While AcuSolve is used to efficiently model heat loss from tool to the fluid that flows through water channels in the tools. The approach is demonstrated through some case studies

  16. Stress corrosion cracking of age-hardenable nickel-base alloys in LWR-conditions

    International Nuclear Information System (INIS)

    Kekkonen, T.; Haenninen, H.

    1985-01-01

    At present it seems that the microstructure most resistant to stress corrosion cracking (SCC) in high temperature water is obtained by a solution annealing treatment at a relatively high temperature (appr. 1100 deg C) followed by water quenching and a single aging treatment (appr. 700 deg C/20 h). This should produce a microstructure with a high M 23 Cc 6 :MC ratio, semi-continous coherent M 23 C 6 precipitation, and an evenly distributed gamma prime in the matrix. However, since the actual mechanism of SCC in age-hardenable Ni-base alloys is unclear, the microstructural features resulting in the good resistance to SCC cannot be specified. Furthermore, the possible microstructural changes caused by prolonged use in LWR-conditions are unknown

  17. Forecasting summertime surface temperature and precipitation in the Mexico City metropolitan area: sensitivity of the WRF model to land cover changes

    Science.gov (United States)

    López-Bravo, Clemente; Caetano, Ernesto; Magaña, Víctor

    2018-02-01

    Changes in the frequency and intensity of severe hydrometeorological events in recent decades in the Mexico City Metropolitan Area have motivated the development of weather warning systems. The weather forecasting system for this region was evaluated in sensitivity studies using the Weather Research and Forecasting Model (WRF) for July 2014, a summer time month. It was found that changes in the extent of the urban area and associated changes in thermodynamic and dynamic variables have induced local circulations that affect the diurnal cycles of temperature, precipitation, and wind fields. A newly implemented configuration (land cover update and Four-Dimensional Data Assimilation (FDDA)) of the WRF model has improved the adjustment of the precipitation field to the orography. However, errors related to the depiction of convection due to parameterizations and microphysics remains a source of uncertainty in weather forecasting in this region.

  18. The influence of chemical composition on the properties and structure Al-Si-Cu(Mg) alloys

    OpenAIRE

    M. Kaczorowski; A. Krzyńska

    2007-01-01

    The mechanical properties of different chemical composition AlSiCuMg type cast alloys after precipitation hardening are presented. The aim of the study was to find out how much the changes in chemistry of aluminum cast alloys permissible by EN-PN standards may influence the mechanical properties of these alloys. Eight AlSi5Cu3(Mg) type cast alloys of different content alloying elements were selected for the study. The specimens cut form test castings were subjected to precipitation hardening ...

  19. Effect of distribution of striated laser hardening tracks on dry sliding wear resistance of biomimetic surface

    Science.gov (United States)

    Su, Wei; Zhou, Ti; Zhang, Peng; Zhou, Hong; Li, Hui

    2018-01-01

    Some biological surfaces were proved to have excellent anti-wear performance. Being inspired, Nd:YAG pulsed laser was used to create striated biomimetic laser hardening tracks on medium carbon steel samples. Dry sliding wear tests biomimetic samples were performed to investigate specific influence of distribution of laser hardening tracks on sliding wear resistance of biomimetic samples. After comparing wear weight loss of biomimetic samples, quenched sample and untreated sample, it can be suggested that the sample covered with dense laser tracks (3.5 mm spacing) has lower wear weight loss than the one covered with sparse laser tracks (4.5 mm spacing); samples distributed with only dense laser tracks or sparse laser tracks (even distribution) were proved to have better wear resistance than samples distributed with both dense and sparse tracks (uneven distribution). Wear mechanisms indicate that laser track and exposed substrate of biomimetic sample can be regarded as hard zone and soft zone respectively. Inconsecutive striated hard regions, on the one hand, can disperse load into small branches, on the other hand, will hinder sliding abrasives during wear. Soft regions with small range are beneficial in consuming mechanical energy and storing lubricative oxides, however, soft zone with large width (>0.5 mm) will be harmful to abrasion resistance of biomimetic sample because damages and material loss are more obvious on surface of soft phase. As for the reason why samples with even distributed bionic laser tracks have better wear resistance, it can be explained by the fact that even distributed laser hardening tracks can inhibit severe worn of local regions, thus sliding process can be more stable and wear extent can be alleviated as well.

  20. Hardening of niobium alloys at precrystallization annealing

    International Nuclear Information System (INIS)

    Vasil'eva, E.V.; Pustovalov, V.A.

    1989-01-01

    Niobium base alloys were investigated. It is shown that precrystallization annealing of niobium-molybdenum, niobium-vanadium and niobium-zirconium alloys elevates much more sufficiently their resistance to microplastic strains, than to macroplastic strains. Hardening effect differs sufficiently for different alloys. The maximal hardening is observed for niobium-vanadium alloys, the minimal one - for niobium-zirconium alloys

  1. Research of beam hardening correction method for CL system based on SART algorithm

    International Nuclear Information System (INIS)

    Cao Daquan; Wang Yaxiao; Que Jiemin; Sun Cuili; Wei Cunfeng; Wei Long

    2014-01-01

    Computed laminography (CL) is a non-destructive testing technique for large objects, especially for planar objects. Beam hardening artifacts were wildly observed in the CL system and significantly reduce the image quality. This study proposed a novel simultaneous algebraic reconstruction technique (SART) based beam hardening correction (BHC) method for the CL system, namely the SART-BHC algorithm in short. The SART-BHC algorithm took the polychromatic attenuation process in account to formulate the iterative reconstruction update. A novel projection matrix calculation method which was different from the conventional cone-beam or fan-beam geometry was also studied for the CL system. The proposed method was evaluated with simulation data and experimental data, which was generated using the Monte Carlo simulation toolkit Geant4 and a bench-top CL system, respectively. All projection data were reconstructed with SART-BHC algorithm and the standard filtered back projection (FBP) algorithm. The reconstructed images show that beam hardening artifacts are greatly reduced with the SART-BHC algorithm compared to the FBP algorithm. The SART-BHC algorithm doesn't need any prior know-ledge about the object or the X-ray spectrum and it can also mitigate the interlayer aliasing. (authors)

  2. A study on microstructure and strain-hardening rate of friction stir welded Al-Mg-Si alloys using a weak beam technique

    International Nuclear Information System (INIS)

    Sukedai, E; Yokoyama, T

    2012-01-01

    Mechanical properties of a friction stir welded Al-Mg-Si (6061-T6Al) alloy are evaluated by a tensile test. It is found that the strain-hardening rate is higher than that of a base material. In order to investigate the origin, TEM observations have been performed about 4 kinds of materials; base- and friction stir welded-materials, and both materials deformed to 5 % strain by tension. There are not so large differences about dislocation density, size and density of precipitates and crystal defects between the base material and the friction stir welded-materials, but a significant decrease of grain-size in the friction stir welded-materials is recognized. These results suggest a dynamic recovery occurs during FSW process, and it is speculated that the recovery leads to the differences of yield stress and strain-hardening rate between both materials.

  3. Kinetics of niobium carbide precipitation in ferrite; Cinetiques de precipitation du carbure de niobium dans la ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Gendt, D

    2001-07-01

    The aim of this study is to develop a NbC precipitation modelling in ferrite. This theoretical study is motivated by the fact it considers a ternary system and focus on the concurrence of two different diffusion mechanisms. An experimental study with TEP, SANS and Vickers micro-hardening measurements allows a description of the NbC precipitation kinetics. The mean radius of the precipitates is characterized by TEM observations. To focus on the nucleation stage, we use the Tomographic Atom Probe that analyses, at an atomistic scale, the position of the solute atoms in the matrix. A first model based on the classical nucleation theory and the diffusion-limited growth describes the precipitation of spherical precipitates. To solve the set of equations, we use a numerical algorithm that furnishes an evaluation of the precipitated fraction, the mean radius and the whole size distribution of the particles. The parameters that are the interface energy, the solubility product and the diffusion coefficients are fitted with the data available in the literature and our experimental results. It allows a satisfactory agreement as regards to the simplicity of the model. Monte Carlo simulations are used to describe the evolution of a ternary alloy Fe-Nb-C on a cubic centred rigid lattice with vacancy and interstitial mechanisms. This is realized with an atomistic description of the atoms jumps and their related frequencies. The model parameters are fitted with phase diagrams and diffusion coefficients. For the sake of simplicity, we consider that the precipitation of NbC is totally coherent and we neglect any elastic strain effect. We can observe different kinetic paths: for low supersaturations, we find an expected precipitation of NbC but for higher supersaturations, the very fast diffusivity of carbon atoms conducts to the nucleation of iron carbide particles. We establish that the occurrence of this second phenomenon depends on the vacancy arrival kinetics and can be related

  4. Allergic contact dermatitis from resin hardeners during the manufacture of thermosetting coating paints.

    Science.gov (United States)

    Foulds, I S; Koh, D

    1992-02-01

    5 production operators from 2 factories manufacturing thermosetting coating paint developed work-related skin disorders within 12 months of the introduction of a new powdered paint product. All 5 workers were found to have allergic contact dermatitis from 2 epoxy resin hardeners, both of which were commercial preparations of triglycidyl isocyanurate (TGIC). 2 of the workers had concomitant sensitization to epoxy resin in the standard series and several of the epoxy resin preparations at the workplace. TGIC has been reported as a contact sensitizer both in persons producing the chemical and among end-users of TGIC-containing products. These 5 reported cases document allergic contact dermatitis from commercial TGIC among exposed workers during an intermediate process of powdered paint manufacture. The possibility of substituting this epoxy resin hardener with less sensitizing alternatives should be explored.

  5. Landfill Top Covers

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter

    2011-01-01

    The purpose of the final cover of a landfill is to contain the waste and to provide for a physical separation between the waste and the environment for protection of public health. Most landfill covers are designed with the primary goal to reduce or prevent infiltration of precipitation...... into the landfill in order to minimize leachate generation. In addition the cover also has to control the release of gases produced in the landfill so the gas can be ventilated, collected and utilized, or oxidized in situ. The landfill cover should also minimize erosion and support vegetation. Finally the cover...... is landscaped in order to fit into the surrounding area/environment or meet specific plans for the final use of the landfill. To fulfill the above listed requirements landfill covers are often multicomponent systems which are placed directly on top of the waste. The top cover may be placed immediately after...

  6. Hardening device, by inserts, of electronic component against radiation

    International Nuclear Information System (INIS)

    Val, C.

    1987-01-01

    The hardening device includes at least two materials, one with high atomic number with respect to the other. One of these materials is set as inserts in a layer of the other material. The hardening device is then made by stacking of such layers, the insert density varying from one layer to the other, making thus vary the atomic number resulting from the hardening device along its thickness, following a predefined law [fr

  7. Investigation of srawberry hardening in low temperatures in vitro

    OpenAIRE

    Lukoševičiūtė, Vanda; Rugienius, Rytis; Kavaliauskaitė, Danguolė

    2007-01-01

    Cold resistance of different strawberry varieties in vitro and ability to retain hardening after defrosting and repeated hardening. Phytohormons – gibberellin and abscisic acid added in the growing medium were investigated in Horticulture plant genetic and biotechnology department of LIH. We tried to model common conditions in temperate zone when freeze-thaw cycles often occur during wintertime. For investigation in vitro strawberries for the first time hardened in light at the temperature of...

  8. Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation

    Science.gov (United States)

    CUI, Fengkui; LING, Yuanfei; XUE, Jinxue; LIU, Jia; LIU, Yuhui; LI, Yan

    2017-03-01

    The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s-1 base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established, Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained. Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel.

  9. HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT

    Directory of Open Access Journals (Sweden)

    S. S. Samotugin

    2017-01-01

    Full Text Available Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.

  10. A procedure for the hardening of materials

    International Nuclear Information System (INIS)

    Dearnaley, G.

    1984-01-01

    A method of hardening metals or ceramics which have fcc, bcc or hcp structures in which two species of differing atomic radii are introduced into the material to be hardened. One species is of a size such that it can diffuse through the lattice normally. The other is of a size such that it can diffuse readily only along dislocations. Ion bombardment is the preferred method of introducing the species with different atomic radii. The material to be hardened is subjected to heat and plastic deformation so as to cause a large number of dislocations with jogs. The species meet at the jogs where they interact and are trapped and set up strain fields which prevent further deformation of the material. (author)

  11. An Anisotropic Hardening Model for Springback Prediction

    Science.gov (United States)

    Zeng, Danielle; Xia, Z. Cedric

    2005-08-01

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

  12. An Anisotropic Hardening Model for Springback Prediction

    International Nuclear Information System (INIS)

    Zeng, Danielle; Xia, Z. Cedric

    2005-01-01

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test

  13. Initiation and propagation of cleared channels in neutron-irradiated pure copper and a precipitation hardened CuCrZr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Singh, B.N.; Edwards, D.J.; Bilde-Soerensen, J.B

    2004-10-01

    The phenomenon of plastic flow localization in the form of 'cleared' channels has been frequently observed in neutron irradiated metals and alloys for more than 40 years. So far, however, no experimental evidence as to how and where these channels are initiated during post-irradiation deformation has emerged. Recently we have studied the problem of initiation and propagation of cleared channels during post-irradiation tensile tests of pure copper and a copper alloy irradiated with fission neutrons. Tensile specimens of pure copper and a precipitation hardened copper alloy (CuCrZr) were neutron irradiated at 323 and 373K to displacement doses in the range of 0.01 to 0.3 dpa (displacement per atom) and tensile tested at the irradiation temperature. The stress-strain curves clearly indicated the occurrence of a yield drop. The post-deformation microstructural examinations revealed that the channels are formed already in the elastic regime and their density increases with increasing plastic strain. The channels appear to have been initiated at grain boundaries, twin boundaries, at relatively large inclusions and even at the previously formed cleared channels. Even though the channels are produced throughout the whole tensile test, no clear evidence has been found for the operation of Frank-Read sources in the volume between the channels. Channels have been observed to penetrate through annealing twins, in some cases stopping at the opposite twin boundary and in other cases penetrating even through the opposite twin boundary and continuing further into the grain. In some cases channels have been found to penetrate through grain boundaries too. It is suggested that the high stress levels reached during deformation of the irradiated specimens activate dislocation sources at the sites of stress concentration at the boundaries and inclusions. The propagation of these newly generated dislocations in the matrix causes the formation of cleared channels. Implications

  14. Initiation and propagation of cleared channels in neutron-irradiated pure copper and a precipitation hardened CuCrZr alloy

    International Nuclear Information System (INIS)

    Singh, B.N.; Edwards, D.J.; Bilde-Soerensen, J.B.

    2004-10-01

    The phenomenon of plastic flow localization in the form of 'cleared' channels has been frequently observed in neutron irradiated metals and alloys for more than 40 years. So far, however, no experimental evidence as to how and where these channels are initiated during post-irradiation deformation has emerged. Recently we have studied the problem of initiation and propagation of cleared channels during post-irradiation tensile tests of pure copper and a copper alloy irradiated with fission neutrons. Tensile specimens of pure copper and a precipitation hardened copper alloy (CuCrZr) were neutron irradiated at 323 and 373K to displacement doses in the range of 0.01 to 0.3 dpa (displacement per atom) and tensile tested at the irradiation temperature. The stress-strain curves clearly indicated the occurrence of a yield drop. The post-deformation microstructural examinations revealed that the channels are formed already in the elastic regime and their density increases with increasing plastic strain. The channels appear to have been initiated at grain boundaries, twin boundaries, at relatively large inclusions and even at the previously formed cleared channels. Even though the channels are produced throughout the whole tensile test, no clear evidence has been found for the operation of Frank-Read sources in the volume between the channels. Channels have been observed to penetrate through annealing twins, in some cases stopping at the opposite twin boundary and in other cases penetrating even through the opposite twin boundary and continuing further into the grain. In some cases channels have been found to penetrate through grain boundaries too. It is suggested that the high stress levels reached during deformation of the irradiated specimens activate dislocation sources at the sites of stress concentration at the boundaries and inclusions. The propagation of these newly generated dislocations in the matrix causes the formation of cleared channels. Implications of these

  15. Defect investigations of micron sized precipitates in Al alloys

    Science.gov (United States)

    Klobes, B.; Korff, B.; Balarisi, O.; Eich, P.; Haaks, M.; Kohlbach, I.; Maier, K.; Sottong, R.; Staab, T. E. M.

    2011-01-01

    A lot of light aluminium alloys achieve their favourable mechanical properties, especially their high strength, due to precipitation of alloying elements. This class of age hardenable Al alloys includes technologically important systems such as e.g. Al-Mg-Si or Al-Cu. During ageing different precipitates are formed according to a specific precipitation sequence, which is always directed onto the corresponding intermetallic equilibrium phase. Probing the defect state of individual precipitates requires high spatial resolution as well as high chemical sensitivity. Both can be achieved using the finely focused positron beam provided by the Bonn Positron Microprobe (BPM) [1] in combination with the High Momentum Analysis (HMA) [2]. Employing the BPM, structures in the micron range can be probed by means of the spectroscopy of the Doppler broadening of annihilation radiation (DBAR). On the basis of these prerequisites single precipitates of intermetallic phases in Al-Mg-Si and Al-Cu, i.e. Mg2Si and Al2Cu, were probed. A detailed interpretation of these measurements necessarily relies on theoretical calculations of the DBAR of possible annihilation sites. These were performed employing the DOPPLER program. However, previous to the DBAR calculation the structures, which partly contain vacancies, were relaxed using the ab-initio code SIESTA, i.e. the atomic positions in presence of a vacancy were recalculated.

  16. Defect investigations of micron sized precipitates in Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Klobes, B; Korff, B; Balarisi, O; Eich, P; Haaks, M; Kohlbach, I; Maier, K; Sottong, R [Helmholtz-Institut fuer Strahlen- und Kernphysik, Nussallee 14-16, D-53115 Bonn (Germany); Staab, T E M, E-mail: klobes@hiskp.uni-bonn.de [Fraunhofer ISC, Neunerplatz 2, D-97082 Wuerzburg (Germany)

    2011-01-01

    A lot of light aluminium alloys achieve their favourable mechanical properties, especially their high strength, due to precipitation of alloying elements. This class of age hardenable Al alloys includes technologically important systems such as e.g. Al-Mg-Si or Al-Cu. During ageing different precipitates are formed according to a specific precipitation sequence, which is always directed onto the corresponding intermetallic equilibrium phase. Probing the defect state of individual precipitates requires high spatial resolution as well as high chemical sensitivity. Both can be achieved using the finely focused positron beam provided by the Bonn Positron Microprobe (BPM) in combination with the High Momentum Analysis (HMA). Employing the BPM, structures in the micron range can be probed by means of the spectroscopy of the Doppler broadening of annihilation radiation (DBAR). On the basis of these prerequisites single precipitates of intermetallic phases in Al-Mg-Si and Al-Cu, i.e. Mg{sub 2}Si and Al{sub 2}Cu, were probed. A detailed interpretation of these measurements necessarily relies on theoretical calculations of the DBAR of possible annihilation sites. These were performed employing the DOPPLER program. However, previous to the DBAR calculation the structures, which partly contain vacancies, were relaxed using the ab-initio code SIESTA, i.e. the atomic positions in presence of a vacancy were recalculated.

  17. Effect of carbide precipitates on high temperature creep of a 20Cr-25Ni austenitic stainless steel

    International Nuclear Information System (INIS)

    Yamane, T.; Takahashi, Y.; Nakagawa, K.

    1984-01-01

    The high temperature creep of an austenitic stainless steel having carbide precipitates, is different from that of the carbide precipitate-free one. Strain rates of the steady state creep d(epsilonsub(s))/dt, or minimum strain rates of the creep in precipitate hardened and dispersion strengthened alloys at the creep temperature T, can be expressed by Sherby-Dorn's equation d(epsilonsub(s))/dt = Aσsup(n) exp (-Qsub(c)/RT). The stress exponent n, and the activation energy for creep Qsub(c), in a power law creep region, are more than those of unstrengthened alloys, where σ is the creep stress, R the gas constant and A the constant. In this research, the influence of carbide precipitates on steady creep rates, is investigated. Experimental details are given. Results are given and discussed. (author)

  18. Influence of energy input in friction stir welding on structure evolution and mechanical behaviour of precipitation-hardening in aluminium alloys (AA2024-T351, AA6013-T6 and Al-Mg-Sc)

    Energy Technology Data Exchange (ETDEWEB)

    Weis Olea, Cesar Afonso [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung

    2008-12-04

    Aluminium alloys AA2024 T351, AA6013 T6 and the recently developed Al-Mg-Sc for aircraft industry applications, which are usually considered difficult to weld by conventional fusion welding processes, demonstrate outstanding performance when joined by friction stir welding (FSW). The main feature of the process is to produce solid-state welds, where the maximum temperatures attained during the process are about 80 % that of the melting temperature of the base material. The process generates substantial plastic deformation, due to the solid-state stirring, and consequently creates a high dislocation density, which is a precursor to dynamic recrystallization, a metallurgical feature that characterizes the stir zone (weld centre). A relevant aspect considered, regarding precipitation-hardening aluminium alloys, is the deterioration of the mechanical properties in the weld zones, which are fundamentally attributed to changes in the characteristics of strengthening precipitates. Among the strengthening mechanisms acting in these aluminium alloys, the most important is basically dependent on the morphology, size and population of the precipitates. The thermal cycle and deformation generated during the FSW process alter the precipitation characteristics previously present in the base material. FSW input energy regulates the magnitude of the thermal cycle and the intensity of deformation taking place during the process, and it can be controlled by the welding parameters, affecting the precipitates evolution and consequently the mechanical properties of the joint. Nevertheless, there remains a lack of knowledge about the substructural evolution of these alloys during FSW, and its correlation with weld energy input and their respective mechanical properties, particularly for the Al-Mg-Sc alloy. The main objective of this work is to explain the micro and substructural evolution (emphasizing precipitates evolution) of AA2024- T351, AA6013-T6 and Al-Mg-Sc alloys in similar

  19. ANISOTROPIC STRAIN-HARDENING IN POLYCRYSTALLINE COPPER AND ALUMINUM

    NARCIS (Netherlands)

    HESS, F

    1993-01-01

    A new viscoplastic model for the plastic stress-strain behaviour of f.c.c. metals is presented. In this model the strain hardening results from increasing dislocation densities. The observed stagnation of strain hardening after strain reversals is explained by a lowering of the increase in

  20. Surface hardening of titanium alloys with melting depth controlled by heat sink

    Science.gov (United States)

    Oden, Laurance L.; Turner, Paul C.

    1995-01-01

    A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

  1. Standard Practice for Exposure of Solar Collector Cover Materials to Natural Weathering Under Conditions Simulating Stagnation Mode

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1992-01-01

    1.1 This practice covers a procedure for the exposure of solar collector cover materials to the natural weather environment at elevated temperatures that approximate stagnation conditions in solar collectors having a combined back and edge loss coefficient of less than 1.5 W/(m2 · °C). 1.2 This practice is suitable for exposure of both glass and plastic solar collector cover materials. Provisions are made for exposure of single and double cover assemblies to accommodate the need for exposure of both inner and outer solar collector cover materials. 1.3 This practice does not apply to cover materials for evacuated collectors, photovoltaic cells, flat-plate collectors having a combined back and edge loss coefficient greater than 1.5 W/(m2 ·° C), or flat-plate collectors whose design incorporates means for limiting temperatures during stagnation. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard t...

  2. Research on SEU hardening of heterogeneous Dual-Core SoC

    Science.gov (United States)

    Huang, Kun; Hu, Keliu; Deng, Jun; Zhang, Tao

    2017-08-01

    The implementation of Single-Event Upsets (SEU) hardening has various schemes. However, some of them require a lot of human, material and financial resources. This paper proposes an easy scheme on SEU hardening for Heterogeneous Dual-core SoC (HD SoC) which contains three techniques. First, the automatic Triple Modular Redundancy (TMR) technique is adopted to harden the register heaps of the processor and the instruction-fetching module. Second, Hamming codes are used to harden the random access memory (RAM). Last, a software signature technique is applied to check the programs which are running on CPU. The scheme need not to consume additional resources, and has little influence on the performance of CPU. These technologies are very mature, easy to implement and needs low cost. According to the simulation result, the scheme can satisfy the basic demand of SEU-hardening.

  3. Hardening and softening mechanisms of pearlitic steel wire under torsion

    International Nuclear Information System (INIS)

    Zhao, Tian-Zhang; Zhang, Shi-Hong; Zhang, Guang-Liang; Song, Hong-Wu; Cheng, Ming

    2014-01-01

    Highlights: • Mechanical behavior of pearlitic steel wire is studied using torsion. • Work hardening results from refinement lamellar pearlitic structure. • Softening results from recovery, shear bands and lamellar fragmentations. • A microstructure based analytical flow stress model is established. - Abstract: The mechanical behaviors and microstructure evolution of pearlitic steel wires under monotonic shear deformation have been investigated by a torsion test and a number of electron microscopy techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an aim to reveal the softening and hardening mechanisms of a randomly oriented pearlitic structure during a monotonic stain path. Significantly different from the remarkable strain hardening in cold wire drawing, the strain hardening rate during torsion drops to zero quickly after a short hardening stage. The microstructure observations indicate that the inter-lamellar spacing (ILS) decreases and the dislocations accumulate with strain, which leads to hardening of the material. Meanwhile, when the strain is larger than 0.154, the enhancement of dynamic recovery, shear bands (SBs) and cementite fragmentations results in the softening and balances the strain hardening. A microstructure based analytical flow stress model with considering the influence of ILS on the mean free path of dislocations and the softening caused by SBs and cementite fragmentations, has been established and the predicted flow shear curve meets well with the measured curve in the torsion test

  4. Quantitative transmission electron microscopy and atom probe tomography study of Ag-dependent precipitation of Ω phase in Al-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song; Ying, Puyou [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2017-02-27

    The close association between the Ω precipitation and various Ag additions is systematically investigated by quantitative transmission electron microscopy and atom probe tomography analysis. Our results suggest that the precipitation of Ω phase is strongly dependent on Ag variations. Increasing the bulk Ag content favors a denser Ω precipitation and hence leads to a greater age-hardening response of Al-Cu-Mg-Ag alloy. This phenomenon, as proposed by proximity histograms, is directly related to the greater abundance of Ag solutes within Ω precursors. This feature lowers its nucleation barrier and increases the nucleation rate of Ω phase, finally contributes to the enhanced Ω precipitation. Also, it is noted that increasing Ag remarkably restricts the precipitation of θ' phase.

  5. EFFECT OF HARDENING TIME ON DEFORMATION-STRENGTH INDICATORS OF CONCRETE FOR INJECTION WITH A TWO-STAGE EXPANSION DURING HARDENING IN WATER

    Directory of Open Access Journals (Sweden)

    Tatjana N. Zhilnikova

    2017-01-01

    Full Text Available Abstract. Objectives Concretes for injection with a two-stage expansion are a kind of selfstressing concrete obtained with the use of self-stressing cement.The aim of the work is to study the influence of the duration of aging on the porosity, strength and self-stress of concrete hardening in water, depending on the expansion value at the first stage. At the first stage, the compacted concrete mixture is expanded to ensure complete filling of the formwork space. At the second stage, the hardening concrete expands due to the formation of an increased amount of ettringite. This process is prolonged in time, with the amount of self-stress and strength dependant on the conditions of hardening. Methods  Experimental evaluation of self-stress, strength and porosity of concretes that are permanently hardened in water, under air-moist and air-dry conditions after different expansion at the first stage. The self-stress of cement stone is the result of superposition of two processes: the hardening of the structure due to hydration of silicates and its expansion as a result of hydration of calcium aluminates with the subsequent formation of ettringite. The magnitude of self-stress is determined by the ratio of these two processes. The self-stress of the cement stone changes in a manner similar to the change in its expansion. The stabilisation of expansion is accompanied by stabilisation of self-stress of cement stone. Results  The relationship of self-stress, strength and porosity of concrete for injection with a two-stage expansion on the duration and humidity conditions of hardening, taking into account the conditions of deformation limitation at the first stage, is revealed. Conclusion During prolonged hardening in an aqueous medium, self-stresses are reduced up to 25% with the exception of expansion at the first stage and up to 20% with an increase in volume up to 5% at the first stage. The increase in compressive strength is up to 28% relative to

  6. The influence of elevated temperature transformation and mechanical properties of a precipitation hardening martensitic stainless steel on its wear behaviour

    International Nuclear Information System (INIS)

    Smith, A.F.

    1989-11-01

    Self wear tests of a martensitic stainless steel in CO 2 in the temperature range 20-300degC showed transitional behaviour at 20 and 300degC. In the mid temperature range a severe wear rate of ∼ 2 x 10 -13 m 3 /Nm persisted for sliding distances up to 2000 m. A possible explanation was that while strain induced transformation of retained austenite at low temperatures provided a sufficiently hardened substrate that allowed inelastic rather than plastic interactions this did not occur at 200degC. Tests were carried out to determine the temperature above which strain no longer transformed austenite into martensite. Although a martensite start temperature of ∼ 150degC was found for the present steel the presence of only ∼ 10% retained austenite in the ''as heat treated'' material suggests that its transformation to martensite at 200degC would not materially affect the extent of subsurface hardening. It is proposed that a surface reaction plays a role in transition behaviour. At 300degC the reaction product is an oxide but at room temperature it is possibly a carbonate. The stability of the carbonate decreases with temperature thus giving an intermediate temperature range where metal/metal contacts prevail leading to the persistent high wear behaviour. (author)

  7. Effect of quenching rate on precipitation kinetics in AA2219 DC cast alloy

    Energy Technology Data Exchange (ETDEWEB)

    Elgallad, E.M., E-mail: eelgalla@uqac.ca; Zhang, Z.; Chen, X.-G.

    2017-06-01

    Slow quenching of direct chill (DC) cast aluminum ingot plates used in large mold applications is often used to decrease quench-induced residual stresses, which can deteriorate the machining performance of these plates. Slow quenching may negatively affect the mechanical properties of the cast plates when using highly quench-sensitive aluminum alloys because of its negative effect on the precipitation hardening behavior of such alloys. The effect of the quenching rate on precipitation kinetics in AA2219 DC cast alloy was systematically studied under water and air quenching conditions using differential scanning calorimetry (DSC) technique. Transmission electron microscopy (TEM) was also used to characterize the precipitate microstructure. The results showed that the precipitation kinetics of the θ′ phase in the air-quenched condition was mostly slower than that in the water-quenched one. Air quenching continuously increased the precipitation kinetics of the θ phase compared to water quenching. These results revealed the contributions of the inadequate precipitation of the strengthening θ′ phase and the increased precipitation of the equilibrium θ phase to the deterioration of the mechanical properties of air-quenched AA2219 DC cast plates. The preexisting GP zones and quenched-in dislocations affected the kinetics of the θ′ phase, whereas the preceding precipitation of the θ′ phase affected the kinetics of the θ phase by controlling its precipitation mechanism.

  8. Comparative and complementary characterization of precipitate microstructures in Al-Mg-Si(-Li) alloys by transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Koshino, Yuki [Department of Mechanical Engineering and Materials Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan); Kozuka, Masaya [Materials Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsukadai, Nishi-ku, Kobe 651-2271 (Japan); Hirosawa, Shoichi, E-mail: hirosawa@ynu.ac.jp [Department of Mechanical Engineering and Materials Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan); Aruga, Yasuhiro [Materials Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsukadai, Nishi-ku, Kobe 651-2271 (Japan)

    2015-02-15

    Highlights: • Microalloying addition of Li enhances the age-hardening response of Al-Mg-Si alloys. • Size and number density of nanoclusters or precipitates are increased by Li addition. • Mg and Si contents within the aggregates are inversely decreased by Li addition. • Microalloying Li accelerates heterogeneous nucleation of such Mg-Si aggregates. - Abstract: In this study, comparative and complementary characterization of precipitate microstructures by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and atom probe tomography (APT) has been performed for Al-0.55 wt%Mg-0.89 wt%Si(-0.043 wt%Li) alloys aged at 433 K for 1.2 ks (under aging) and 36 ks (peak aging). Quantitative estimation of nanometer-scale clusters (nanoclusters) and β″ precipitates by TEM and APT revealed that microalloying addition of Li increases the size and number density of these Mg-Si aggregates, resulting in the enhanced age-hardening response. Positive evidence by APT for the segregation of Li suggests that heterogeneous nucleation of such Mg-Si aggregates with the aid of Li is attributed to the modified precipitate microstructures and thus improved mechanical strength of this alloy system.

  9. Performance assessment of select covers and disposal cell compliance with EPA [Environmental Protection Agency] groundwater standards

    International Nuclear Information System (INIS)

    1989-06-01

    This document describes the technical approach to the assessment of the performance of a full component topslope cover, three sideslope covers, and hence the way in which a Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cell complies with the US Environmental Protection Agency (EPA) groundwater protection standards. 4 refs

  10. The influence of limited kinematic hardening in shakedown analysis

    International Nuclear Information System (INIS)

    Nery, Domingos E.S.; Jospin, Reinaldo R.; Zouain, Nestor

    2009-01-01

    The use of the Design by Analysis concept is a trend in modern pressure vessel and piping calculations. DBA flexibility allow us to deal with unexpected configurations detected at in-service inspections. It is also important, in life extension calculations, when deviations of the original standard hypothesis adopted initially in Design by Formula, can happen. To apply the DBA to structures under variable mechanic and thermal loads, it is necessary that, alternate plasticity and incremental collapse (with instantaneous plastic collapse as a particular case), be precluded. These are two basic failure modes considered by ASME or European Standards in DBA. The shakedown theory is the tool available to achieve this goal. In order to apply it, is necessary only the range of the variable loads and the material properties. Precise, robust and efficient algorithms to solve the very large nonlinear optimization problems generated in numerical applications of the shakedown theory is a recent achievement. Zouain and co-workers developed one of these algorithms for elastic ideally-plastic materials. But, it is necessary to consider more realistic material properties in real practical applications. This paper shows an enhancement of this algorithm to dealing with limited kinematic hardening, a typical property of the usual steels. This is done using internal thermodynamic variables. A discrete algorithm is obtained using a plane stress, mixed finite element, with internal variable. An example, a beam encased in an end, under constant axial force and variable moment is presented to show the importance of considering the limited kinematic hardening in a shakedown analysis. (author)

  11. Radiation hardening of semiconductor parts

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    This chapter is an overview of total-ionizing-dose and single-event hardening techniques and should be used as a guide to a range of research publications. It should be stressed that there is no clear and simple route to a radiation-tolerant silicon integrated circuit. What works for one fabrication process may not work for another, and there are many complex interactions within individual processes and designs. The authors have attempted to highlight the most important factors and those process changes which should bring improved hardness. The main point is that radiation-hardening as a procedure must be approached in a methodical fashion and with a good understanding of the response mechanisms involved

  12. Energetic model of metal hardening

    Directory of Open Access Journals (Sweden)

    Ignatova O.N.

    2011-01-01

    Full Text Available Based on Bailey hypothesis on the link between strain hardening and elastic lattice defect energy this paper suggests a shear strength energetic model that takes into consideration plastic strain intensity and rate as well as softening related to temperature annealing and dislocation annihilation. Metal strain hardening was demonstrated to be determined only by elastic strain energy related to the energy of accumulated defects. It is anticipated that accumulation of the elastic energy of defects is governed by plastic work. The suggested model has a reasonable agreement with the available experimental data for copper up to P = 70 GPa , for aluminum up to P = 10 GPa and for tantalum up to P = 20 GPa.

  13. Comparing the Palmer Drought Index and the Standardized Precipitation Index for Zagreb Gric Observatory

    Science.gov (United States)

    Pandzic, K.; Likso, T.

    2012-04-01

    Conventional Palmer Drought Index (PDI) and recent Standardized Precipitation Index (SPI) for Zagreb Gric Observatory are compared by spectral analysis technique. Data for a period 1862-2010 are used. The results indicate that SPI is simpler for interpretation but PDI more comprehensive index. On the other side, lack of temperature within SPI, make impossible application of it on climate change interpretation. Possible applications of them in irrigation scheduling system is considered as well for drought risk assessment.

  14. Non-isothermal precipitation behaviors of Al-Mg-Si-Cu alloys with different Zn contents

    International Nuclear Information System (INIS)

    Guo, M.X.; Zhang, Y.; Zhang, X.K.; Zhang, J.S.; Zhuang, L.Z.

    2016-01-01

    The non-isothermal precipitation behaviors of Al–Mg–Si–Cu alloys with different Zn contents were investigated by differential scanning calorimetry (DSC) analysis, hardness measurement and high resolution transmission electron microscope characterization. The results show that Zn addition has a significant effect on the GP zone dissolution and precipitation of Al-Mg-Si-Cu alloys. And their activation energies change with the changes of Zn content and aging conditions. Precipitation kinetics can be improved by adding 0.5 wt% or 3.0 wt%Zn, while be suppressed after adding 1.5 wt%Zn. The Mg-Si precipitates (GP zones and β″) are still the main precipitates in the Al-Mg-Si-Cu alloys after heated up to 250 °C, and no Mg-Zn precipitates are observed in the Zn-added alloy due to the occurrence of Mg-Zn precipitates reversion. The measured age-hardening responses of the alloys are corresponding to the predicted results by the established precipitation kinetic equations. Additionally, a double-hump phenomenon of hardness appears in the artificial aging of pre-aged alloy with 3.0 wt% Zn addition, which resulted from the formation of pre-β″ and β″ precipitates. Finally, the precipitation mechanism of Al-Mg-Si-Cu alloys with different Zn contents was proposed based on the microstructure evolution and interaction forces between Mg, Si and Zn atoms.

  15. Standard rules for liability and cover for nuclear installations

    International Nuclear Information System (INIS)

    Pfaffelhuber, J.K.; Kuckuck, B.

    1980-01-01

    To afford full protection for possible victims, the authors of this article are in favour of doing away with the limitation of liability of nuclear operators presently provided under the German Atomic Energy Act, the principle of which is based on the Paris Convention and the Brussels Supplementary Convention. In support of this argument reference is made to the recent accident at Three Mile Island, trends in other national legislation towards unlimited liability as well as high safety standards in German nuclear plants. Finally, possible ways of providing unlimited liability are proposed, in particular increased insurance cover and the constitution of an interest-bearing fund in addition to State intervention in case of a major nuclear incident. (NEA) [fr

  16. Kinetics of niobium carbide precipitation in ferrite

    International Nuclear Information System (INIS)

    Gendt, D.

    2001-01-01

    The aim of this study is to develop a NbC precipitation modelling in ferrite. This theoretical study is motivated by the fact it considers a ternary system and focus on the concurrence of two different diffusion mechanisms. An experimental study with TEP, SANS and Vickers micro-hardening measurements allows a description of the NbC precipitation kinetics. The mean radius of the precipitates is characterized by TEM observations. To focus on the nucleation stage, we use the Tomographic Atom Probe that analyses, at an atomistic scale, the position of the solute atoms in the matrix. A first model based on the classical nucleation theory and the diffusion-limited growth describes the precipitation of spherical precipitates. To solve the set of equations, we use a numerical algorithm that furnishes an evaluation of the precipitated fraction, the mean radius and the whole size distribution of the particles. The parameters that are the interface energy, the solubility product and the diffusion coefficients are fitted with the data available in the literature and our experimental results. It allows a satisfactory agreement as regards to the simplicity of the model. Monte Carlo simulations are used to describe the evolution of a ternary alloy Fe-Nb-C on a cubic centred rigid lattice with vacancy and interstitial mechanisms. This is realized with an atomistic description of the atoms jumps and their related frequencies. The model parameters are fitted with phase diagrams and diffusion coefficients. For the sake of simplicity, we consider that the precipitation of NbC is totally coherent and we neglect any elastic strain effect. We can observe different kinetic paths: for low supersaturations, we find an expected precipitation of NbC but for higher supersaturations, the very fast diffusivity of carbon atoms conducts to the nucleation of iron carbide particles. We establish that the occurrence of this second phenomenon depends on the vacancy arrival kinetics and can be related

  17. Improvements on heap leaching process for a refractory uranium ore and yellow cake precipitation process

    International Nuclear Information System (INIS)

    Feng Jianke

    2013-01-01

    Some problems such as formed harden matrix, ore heap compaction, poor permeability, and agglomeration of absorption resin occur during extracting uranium from a refractory uranium ore by heap leaching process. After some measures were taken, i.e. spraying a new ore heap by low concentration acid, two or more ore heaps in series leaching, turning ores in ore heap, the permeability was improved, acid consumption was reduced. Through precipitate circulation and aging, the yellow cake slurry in amorphous or microlite form was transformed to crystal precipitate, thus uranium content in yellow cake was improved, and water content in yellow cake was lowered with good economic benefits. (author)

  18. Nonlinear kinematic hardening under non-proportional loading

    International Nuclear Information System (INIS)

    Ottosen, N.S.

    1979-07-01

    Within the framework of conventional plasticity theory, it is first determined under which conditions Melan-Prager's and Ziegler's kinematic hardening rules result in identical material behaviour. Next, assuming initial isotropy and adopting the von Mises yield criterion, a nonlinear kinematic hardening function is proposed for prediction of metal behaviour. The model assumes that hardening at a specific stress point depends on the direction of the new incremental loading. Hereby a realistic response is obtained for general reversed loading, and a smooth behaviour is assured, even when loading deviates more and more from proportional loading and ultimately results in reversed loading. The predictions of the proposed model for non-proportional loading under plane stress conditions are compared with those of the classical linear kinematic model, the isotropic model and with published experimental data. Finally, the limitations of the proposaed model are discussed. (author)

  19. An alternative approach to estimate the W/C ratio of hardened concrete using image analysis

    NARCIS (Netherlands)

    Valcke, S.; Nijland, T.G.; Larbi, J.A.

    2009-01-01

    The water cement (w/c) ratio is a typical quality parameter for concrete. The NT Build 361 Nordtest method is a standard for estimating the w/c ratio in hardened concrete and is based on the relationship between the ilc ratio and the capillary porosity in the cement paste. The latter can be

  20. Hardening cookies in web-based systems for better system integrity

    International Nuclear Information System (INIS)

    Mohamad Safuan Sulaiman; Mohd Dzul Aiman Aslan; Saaidi Ismail; Abdul Aziz Mohd Ramli; Abdul Muin Abdul Rahman; Siti Nurbahyah Hamdan; Norlelawati Hashimuddin; Sufian Norazam Mohamed Aris

    2012-01-01

    IT Center (ITC) as technical support and provider for most of web-based systems in Nuclear Malaysia has conducted a study to investigate cookie vulnerability in a system for better integrity. A part of the result has found that cookies in a web-based system in Nuclear Malaysia can be easily manipulated. The main objective of the study is to harden the vulnerability of the cookies. Two levels of security procedures have been used and enforced which consist of 1) Penetration test (Pen Test) 2) Hardening procedure. In one of the system, study has found that 121 attempts threats have been detected after the hardening enforcement from 23 March till 20 September 2012. At this stage, it can be concluded that cookie vulnerability in the system has been hardened and integrity has been assured after the enforcement. This paper describes in detail the penetration and hardening process of cookie vulnerability for better supporting web-based system in Nuclear Malaysia. (author)

  1. Minimizing the Standard Deviation of Spatially Averaged Surface Cross-Sectional Data from the Dual-Frequency Precipitation Radar

    Science.gov (United States)

    Meneghini, Robert; Kim, Hyokyung

    2016-01-01

    For an airborne or spaceborne radar, the precipitation-induced path attenuation can be estimated from the measurements of the normalized surface cross section, sigma 0, in the presence and absence of precipitation. In one implementation, the mean rain-free estimate and its variability are found from a lookup table (LUT) derived from previously measured data. For the dual-frequency precipitation radar aboard the global precipitation measurement satellite, the nominal table consists of the statistics of the rain-free 0 over a 0.5 deg x 0.5 deg latitude-longitude grid using a three-month set of input data. However, a problem with the LUT is an insufficient number of samples in many cells. An alternative table is constructed by a stepwise procedure that begins with the statistics over a 0.25 deg x 0.25 deg grid. If the number of samples at a cell is too few, the area is expanded, cell by cell, choosing at each step that cell that minimizes the variance of the data. The question arises, however, as to whether the selected region corresponds to the smallest variance. To address this question, a second type of variable-averaging grid is constructed using all possible spatial configurations and computing the variance of the data within each region. Comparisons of the standard deviations for the fixed and variable-averaged grids are given as a function of incidence angle and surface type using a three-month set of data. The advantage of variable spatial averaging is that the average standard deviation can be reduced relative to the fixed grid while satisfying the minimum sample requirement.

  2. Stage IV work-hardening related to disorientations in dislocation structures

    DEFF Research Database (Denmark)

    Pantleon, W.

    2004-01-01

    The effect of deformation-induced disorientations on the work-hardening of metals is modelled based on dislocation dynamics. Essentially, Kocks’ dislocation model describing stage III hardening is extended to stage IV by incorporation of excess dislocations related to the disorientations....... Disorientations evolving from purely statistical reasons — leading to a square root dependence of the average disorientation angle on strain — affect the initial work-hardening rate (and the saturation stress) of stage III only slightly. On the other hand, deterministic contributions to the development...... of disorientations, as differences in the activated slip systems across boundaries, cause a linear increase of the flow stress at large strains. Such a constant work-hardening rate is characteristic for stage IV....

  3. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    Science.gov (United States)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  4. Precipitation Processes during Non-Isothermal Ageing of Fine-Grained 2024 Alloy

    Directory of Open Access Journals (Sweden)

    Kozieł J.

    2016-03-01

    Full Text Available Mechanical alloying and powder metallurgy procedures were used to manufacture very fine-grained bulk material made from chips of the 2024 aluminum alloy. Studies of solution treatment and precipitation hardening of as-received material were based on differential scanning calorimetry (DSC tests and TEM/STEM/EDX structural observations. Structural observations complemented by literature data lead to the conclusion that in the case of highly refined structure of commercial 2024 alloys prepared by severe plastic deformation, typical multi-step G-P-B →θ” →θ’ →θ precipitation mechanism accompanied with G-P-B →S” →S’ →S precipitation sequences result in skipping the formation of metastable phases and direct growth of the stable phases. Exothermic effects on DSC characteristics, which are reported for precipitation sequences in commercial materials, were found to be reduced with increased milling time. Moreover, prolonged milling of 2024 chips was found to shift the exothermic peak to lower temperature with respect to the material produced by means of common metallurgy methods. This effect was concluded to result from preferred heterogeneous nucleation of particles at subboundaries and grain boundaries, enhanced by the boundary diffusion in highly refined structures.

  5. 75 FR 76700 - Stainless Steel Sheet and Strip in Coils From Taiwan: Final Results of Antidumping Duty...

    Science.gov (United States)

    2010-12-09

    ... is a trademark of Imphy, S.A. Certain martensitic precipitation-hardenable stainless steel is also... DEPARTMENT OF COMMERCE International Trade Administration [A-583-831] Stainless Steel Sheet and... antidumping duty order on stainless steel sheet and strip in coils (SSSSC) from Taiwan. This review covers...

  6. Application of submerged induction hardening; Ekichu koshuha yakiire no jitsuyoka

    Energy Technology Data Exchange (ETDEWEB)

    Nishimori, Y; Nagai, Y; Amii, Y [Mazda Motor Corp., Hiroshima (Japan); Tanaka, Y [Netsuren Co. Ltd., Tokyo (Japan); Mizuma, T [Toyo Advanced Technologies Co. Ltd., Hiroshima (Japan)

    1997-10-01

    As a cost-cutting measure, the linerless diesel engine was adopted by applying submerged induction hardening process which can harden partial inner surface of cylinder block bore. In applying this process, (1) development of induction coil which can form any shape of quenched pattern and (2) the development of machining technology which can hone precisely the distorted bore after quenching, were important. With these improvements, submerged Induction hardening was made practical. 1 ref., 11 figs.

  7. Influence of cooling rate on the precipitation microstructure in a medium strength Al-Zn-Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Deschamps, A. [SIMAP, INPGrenoble-CNRS-UJF BP 75, 38402 St Martin d' Heres Cedex (France)], E-mail: alexis.deschamps@simap.grenoble-inp.fr; Texier, G.; Ringeval, S. [CEA-DAM centre de Valduc, 21120 Is-Sur-Tille (France); SIMAP, INPGrenoble-CNRS-UJF BP 75, 38402 St Martin d' Heres Cedex (France); Delfaut-Durut, L. [CEA-DAM centre de Valduc, 21120 Is-Sur-Tille (France)

    2009-02-15

    Medium strength Al-Zn-Mg age hardening alloys are widely used when a low quench sensitivity is required, such as in welding applications. In this work we present a detailed characterization of the precipitate microstructures resulting from different quench rates from the solution treatment, and from the subsequent artificial ageing to the T6 state, in an Al-4.5Zn-1Mg (wt%) alloy. This work is carried out using differential scanning calorimetry, transmission electron microscopy and in situ small-angle X-ray scattering. It is shown that for quench rate between 5 and 200 deg. C/min substantial heterogeneous precipitation is observed, nucleated on dispersoids and on grain boundaries, the former being of much larger size than the latter. During subsequent ageing, it is shown that the precipitation kinetics in the material unaffected by the quench-induced precipitates is independent on the quench rate used.

  8. Plastic limit pressure of spherical vessels with combined hardening involving large deformation

    International Nuclear Information System (INIS)

    Leu, S.-Y.; Liao, K.-C.; Lin, Y.-C.

    2014-01-01

    The paper aims to investigate plastic limit pressure of spherical vessels of nonlinear combined isotropic/kinematic hardening materials. The Armstrong-Frederick kinematic hardening model is adopted and the Voce hardening law is incorporated for isotropic hardening behavior. Analytically, we extend sequential limit analysis to deal with combined isotropic/kinematic hardening materials. Further, exact solutions of plastic limit pressure were developed analytically by conducting both static and kinematic limit analysis. The onset of instability was also derived and solved iteratively by Newton's method. Numerically, elastic–plastic analysis is also performed by the commercial finite-element code ABAQUS incorporated with the user subroutine UMAT implemented with user materials of combined hardening. Finally, the problem formulation and the solution derivations presented here are validated by a very good agreement between the numerical results of exact solutions and the results of elastic–plastic finite-element analysis by ABAQUS. -- Highlights: • Sequential limit analysis is extended to consider combined hardening. • Exact solutions of plastic limit pressure are developed. • The onset of instability of a spherical vessel is derived and solved numerically

  9. Process design of press hardening with gradient material property influence

    International Nuclear Information System (INIS)

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-01-01

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  10. Saturation behavior of irradiation hardening in F82H irradiated in the HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Shiba, K.; Tanigawa, H.; Ando, M. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Klueh, R.L. [Oak Ridge National Laboratory, TN (United States); Stoller, R. [ORNL - Oak Ridge National Laboratory, Materials Science and Technology Div., Oak Ridge, AK TN (United States)

    2007-07-01

    Full text of publication follows: Post irradiation tensile tests on reduced activation ferritic/martensitic steel, F82H have been conducted over the past two decades using Japan Materials Testing Reactor (JMTR) of JAEA, and Fast Flux Testing Facility (FFTF) of PNNL and High Flux Isotope Reactor (HFIR) of ORNL, USA, under Japan/US collaboration programs. According to these results, F82H does not demonstrate irradiation hardening above 673 K up to 60 dpa. The current study has been concentrated on hardening behavior at temperature around 573 K. A series of low temperature irradiation experiment has been conducted at the HFIR under the international collaborative research between JAEA/US-DOE. In this collaboration, the irradiation condition is precisely controlled by the well matured capsule designing and instrumentation. This paper summarizes recent results of the irradiation experiments focused on F82H and its modified steels compared with the irradiation properties database on F82H. Post irradiation tensile tests have been conducted on the F82H and its modified steels irradiated at 573 K and the dose level was up to 25 dpa. According to these results, irradiation hardening of F82H is saturated by 9 dpa and the as-irradiated 0.2 % proof stress is less than 1 GPa at ambient temperature. The deterioration of total elongation was also saturated by 9 dpa irradiation. The ductility of some modified steels which showed larger total elongation than that of F82H before irradiation become the same level as that of standard F82H steel after irradiation, even though its magnitude of irradiation hardening is smaller than that of F82H. This suggests that the more ductile steel demonstrates the more ductility loss at this temperature, regardless to the hardening level. The difference in ductility loss behavior between various tensile specimens will be discussed as the ductility could depend on the specimen dimension. (authors)

  11. Paint and binding material to be hardened by ionizing radiations

    International Nuclear Information System (INIS)

    Johnson, O.B.; Labana, S.S.

    1976-01-01

    The invention concerns a paint binding material which can be hardened due to the effect of ionising radiation, consisting of a dispersion of a) an ethylene unsaturated material in b) at least one vinyl monomer. Component (a) is a reaction product of graded rubber particles (0.1 - 4 μm) and an ethylene unsaturated component with a reactive epoxy-, hydroxy- or carbonyl-group, which is connected to the rubber by ester or urethane links. The rubber particles have a core of cross linked elastomer acrylic polymers, an outer shell of reactive groups and an intermediate layer made from the core monomer and the shell. 157 examples explain the manufacturing process. The paint is suitable for covering articles which will later be subject to distortion. (UWI) [de

  12. MEASUREMENTS OF STRAIN FIELDS DUE TO NANOSCALE PRECIPITATES USING THE PHASE IMAGE METHOD

    Directory of Open Access Journals (Sweden)

    Patricia Donnadieu

    2011-05-01

    Full Text Available Owing the phase image method (Hytch, 1998, strain fields can be derived from HREM images. The method is here applied to the nanoscale precipitates responsible for hardening in Aluminum alloys. Since the method is a very sensitive one, we have examined the impact of several aspects of the image quality (noise, fluctuations, distortion. The strain field information derived from the HREM image analysis is further introduced in a simulation of the dislocation motion in the matrix.

  13. Kinematic Hardening: Characterization, Modeling and Impact on Springback Prediction

    International Nuclear Information System (INIS)

    Alves, J. L.; Bouvier, S.; Jomaa, M.; Billardon, R.; Oliveira, M. C.; Menezes, L. F.

    2007-01-01

    The constitutive modeling of the materials' mechanical behavior, usually carried out using a phenomenological constitutive model, i.e., a yield criterion associated to the isotropic and kinematic hardening laws, is of paramount importance in the FEM simulation of the sheet metal forming processes, as well as in the springback prediction. Among others, the kinematic behavior of the yield surface plays an essential role, since it is indispensable to describe the Bauschinger effect, i.e., the materials' answer to the multiple tension-compression cycles to which material points are submitted during the forming process. Several laws are usually used to model and describe the kinematic hardening, namely: a) the Prager's law, which describes a linear evolution of the kinematic hardening with the plastic strain rate tensor b) the Frederick-Armstrong non-linear kinematic hardening, basically a non-linear law with saturation; and c) a more advanced physically-based law, similar to the previous one but sensitive to the strain path changes. In the present paper a mixed kinematic hardening law (linear + non-linear behavior) is proposed and its implementation into a static fully-implicit FE code is described. The material parameters identification for sheet metals using different strategies, and the classical Bauschinger loading tests (i.e. in-plane forward and reverse monotonic loading), are addressed, and their impact on springback prediction evaluated. Some numerical results concerning the springback prediction of the Numisheet'05 Benchmark no. 3 are briefly presented to emphasize the importance of a correct modeling and identification of the kinematic hardening behavior

  14. The Age-Precipitations Structure Of Al-Mg-Ge Alloy Aged At 473K

    Directory of Open Access Journals (Sweden)

    Kawai A.

    2015-06-01

    Full Text Available The Al-Mg-Ge alloy is one of the age-hardening aluminum alloy after solution heat treatment. It has been proposed that the age-precipitation behavior of Al-Mg-Ge alloy is different from that of Al-Mg-Si alloy according to our previous works about the microstructure on Al-Mg-Ge alloy over-aged at 523K. For example, The hardness of peak aged Al-1.0mass%Mg2Ge alloy is higher than that of Al-1.0mass%Mg2Si alloy. The precipitates in the over-aged samples have been classified as some metastable phases, such as the β’-phase and Type-A precipitates and equilibrium phase of β-Mg2Ge by TEM observation. There a few reports about microstructure on Al-Mg-Ge alloys observed by TEM for different aging times. The age-precipitations structure of Al-Mg-Ge alloy has not been became clear. In this work, TEM observation was investigated the microstructure on Al-1.0mass%Mg2Ge alloy for difference aging times aged at 473K.

  15. Kinetic characterization and of recrystallization of the aluminum alloy 6063 after S work hardening treatment

    International Nuclear Information System (INIS)

    Esposito, Iara Maria

    2006-01-01

    The aluminum 6063 alloy possesses a great industrial interest, presenting characteristics that justify its frequent use, when compared to the other aluminum alloys: the precipitation hardening and high cold work capacity. These alloys present high ductility, that allows their use in operations with high deformation degrees, as the cold work. The objective of this work is to show comparative analysis of the hardness Vickers of the commercial aluminum 6063 alloy, after cold work with different area reduction degree and thermal treatment. Considering the frequent utilization aluminium 6063 alloy, this work studies the characterization and recrystallization of this alloy, after the plastic deformation in different area reduction degrees, thermal treatment and convenient treatment times - Thermo mechanic Treatments. (author)

  16. [Microstructural changes in hardened beans (Phaseolus vulgaris)].

    Science.gov (United States)

    Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy

    2015-06-01

    (Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.

  17. ANALISIS ARAH DAN PERLAKUAN SERAT TAPIS SERTA RASIO EPOXY HARDENER TERHADAP SIFAT FISIS DAN MEKANIS KOMPOSIT TAPIS/EPOXY

    Directory of Open Access Journals (Sweden)

    Putu Lokantara

    2012-11-01

    Full Text Available Tapis kelapa (Coconut filter as natural fiber, in this time its resources very copius but no longer be exploited and thrown off hand as waste though in fact its used for other material dissimilar inovatif and high economic valuable that is as one of natural fiber alternative to be composite. The objective of this research is to investigate the behavior changing of physical and mechanical properties of composite tapis kelapa as reinforcement and epoxy 7120 with hardener Versamid 140 as matrix. The fiber is treated with the chemical NaOH and KMnO4 with percentage 0.5%, 1%, and 2% in weight, respectively. The ratio of epoxy and hardener is 7:3 and 6:4, and fiber orientation 0o, 45o, dan 90o. For testing of the speciment in tensile test with ASTM standard D3039 and three point bending test with ASTM standard D790. The result of this research obtained that fiber treatment with KMnO4 give the better effect to machine properties compared to NaOH. Variation of percentage 0.5%, 1%, and 2% NaOH and KMnO4 give the effect in fiber surface which higher percentage make the cleaner of surface, decrease of wax contain, and roughness of fiber surface so that stronger of linkage of fiber and matrix and increase of tensile strength, bending strength, and bending modulus of the composite. The highest tensile strength, modulus of elasticity and bending strength are 70.23 MPa, 446.24 GPa and 97.81 MPa respectively reached at composite with ratio epoxy/hardener 7:3; by 2% KMnO4 and fiber orientation 45o. While the highest modulus of elasticity is 385.48 GPa reached at composite with the ratio epoxy/hardener 6:4; 2% KMnO4 and fiber orientation 90o. Keywords: Tensile Strength, bending strength, ratio of epoxy/hardener, NaOH, KMnO4

  18. Diskette-based database covering standards etc. of relevance to the construction of wind turbines

    International Nuclear Information System (INIS)

    1994-05-01

    The project concerns the development of the database ''Diskettebaseret database med vindmoellestandarder'' (diskette-based database containing wind turbine standards), which contains information about standards, recommendations and other technical documents of relevance for the design, construction and approval of wind mills. The information in the database covers data from Denmark, UK, Germany, Holland and USA together with data from internationally recognized standards and recommendations. The database is contained on a single PC-diskette, which also contains the purpose-built userfriendly serchsoftware. About 5500 records are included in the database. The last edition of the database was updated January 1994. (au)

  19. Climatological determinants of woody cover in Africa

    OpenAIRE

    Good, Stephen P.; Caylor, Kelly K.

    2011-01-01

    Determining the factors that influence the distribution of woody vegetation cover and resolving the sensitivity of woody vegetation cover to shifts in environmental forcing are critical steps necessary to predict continental-scale responses of dryland ecosystems to climate change. We use a 6-year satellite data record of fractional woody vegetation cover and an 11-year daily precipitation record to investigate the climatological controls on woody vegetation cover across the African continent....

  20. Engineered soil covers for management of salt impacted sites

    International Nuclear Information System (INIS)

    Sweeney, D.A.; Tratch, D.J.

    2005-01-01

    The use of engineered soil cover systems to mitigate environmental impacts from tailings and waste rock piles is becoming an accepted practice. This paper presented design concepts for soil covers related to reclamation practices in the mining industry as an effective risk management practice at salt impacted sites. Research and field programs have demonstrated that a layered engineered soil cover can reduce or eliminate infiltration. Key components of the system included re-establishing surface vegetation to balance precipitation fluxes with evapotranspiration potential, and design of a capillary break below the rooting zone to minimize deeper seated infiltration. It was anticipated that the incorporation of a vegetation cover and a capillary break would minimize infiltration into the waste rock or tailing pile and reduce the generation of acid rock drainage (ARD). Design of a layered soil cover requires the incorporation of meteorological data, moisture retention characteristics of the impacted soils, and proposed engineered cover materials. Performance of the soil cover was predicted using a finite element model combined with meteorological data from the site area, unsaturated soil properties of the parent sub-surface soils and potential covered materials. The soil cover design consisted of re-vegetation and a loose clay cover overlying a compacted till layer. The design was conducted for an off site release of salt impacted pasture land adjacent to a former highway maintenance yard. The model predicted minimal infiltration during high precipitation events and no infiltration during low precipitation events. Results indicated that the proposed soil cover would enable re-establishment of a productive agricultural ground cover, as well as minimizing the potential for additional salt migration. It was concluded that further research and development is needed to ensure that the cover system is an acceptable method for long-term risk management. 17 refs., 5 figs

  1. 75 FR 6631 - Stainless Steel Sheet and Strip in Coils from Japan: Final Results of Antidumping Duty...

    Science.gov (United States)

    2010-02-10

    ...\\``Gilphy 36'' is a trademark of Imphy, S.A. Certain martensitic precipitation-hardenable stainless steel is... DEPARTMENT OF COMMERCE International Trade Administration [A-588-845] Stainless Steel Sheet and... antidumping duty order on stainless steel sheet and strip in coils (SSSSC) from Japan. This review covers two...

  2. Study of precipitation in Al–Mg–Si Alloys by atom probe tomography II. Influence of Cu additions

    International Nuclear Information System (INIS)

    Zandbergen, M.W.; Cerezo, A.; Smith, G.D.W.

    2015-01-01

    Atom probe tomography (APT) analysis and hardness measurements have been used to characterise the early stages of precipitation in three Al–Mg–Si alloys with different Cu contents (Al–0.51 at.%Mg–0.94 at.%Si, with 0.01 at.%, 0.06 at.%, or 0.34 at.% Cu). A range of single and multi- stage heat treatments were chosen to evaluate the changes in precipitation processes. Three ageing temperatures were investigated, 298 K (natural ageing), 353 K (pre-ageing) and 453 K (automotive paint-bake conditions). The Cu content had significant effects on the microstructural evolution within the alloy. Formation of clusters which can act as precursors of elongated precipitates during paint-baking was found to be enhanced with increasing Cu content. This improved the paint-bake hardening response and mitigated the deleterious effects of natural ageing. Cu was present in all precipitates in the highest Cu-containing alloy. These precipitates were believed to be precursors to the Q′ phase. Mechanisms for the effects of Cu on precipitation kinetics are proposed.

  3. Radiation-hardened CMOS/SOS LSI circuits

    International Nuclear Information System (INIS)

    Aubuchon, K.G.; Peterson, H.T.; Shumake, D.P.

    1976-01-01

    The recently developed technology for building radiation-hardened CMOS/SOS devices has now been applied to the fabrication of LSI circuits. This paper describes and presents results on three different circuits: an 8-bit adder/subtractor (Al gate), a 256-bit shift register (Si gate), and a polycode generator (Al gate). The 256-bit shift register shows very little degradation after 1 x 10 6 rads (Si), with an increase from 1.9V to 2.9V in minimum operating voltage, a decrease of about 20% in maximum frequency, and little or no change in quiescent current. The p-channel thresholds increase from -0.9V to -1.3V, while the n-channel thresholds decrease from 1.05 to 0.23V, and the n-channel leakage remains below 1nA/mil. Excellent hardening results were also obtained on the polycode generator circuit. Ten circuits were irradiated to 1 x 10 6 rads (Si), and all continued to function well, with an increase in minimum power supply voltage from 2.85V to 5.85V and an increase in quiescent current by a factor of about 2. Similar hardening results were obtained on the 8-bit adder, with the minimum power supply voltage increasing from 2.2V to 4.6V and the add time increasing from 270 to 350 nsec after 1 x 10 6 rads (Si). These results show that large CMOS/SOS circuits can be hardened to above 1 x 10 6 rads (Si) with either the Si gate or Al gate technology. The paper also discusses the relative advantages of the Si gate versus the Al gate technology

  4. Beam hardening correction algorithm in microtomography images

    International Nuclear Information System (INIS)

    Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T.; Assis, Joaquim T. de

    2009-01-01

    Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)

  5. Beam hardening correction algorithm in microtomography images

    Energy Technology Data Exchange (ETDEWEB)

    Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T., E-mail: esales@con.ufrj.b, E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Assis, Joaquim T. de, E-mail: joaquim@iprj.uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Inst. Politecnico. Dept. de Engenharia Mecanica

    2009-07-01

    Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)

  6. Evaluation of hardening by ion irradiation in molybdenum using nanoindentation techniques

    International Nuclear Information System (INIS)

    Iwakiri, Hirotomi; Watanabe, Hideo; Yoshida, Naoaki

    1997-01-01

    As a part of fundamental research on interaction of plasma and wall, some model experiments on loading of particles such as He, H and so forth suffered by plasma facing material were conducted for Mo in high Z material. As an evaluation method for it, nanoindentation technique was proposed. By this method, the hardness evaluation in surface neighboring damage range was conducted. As a result, in the helium irradiated materials, sufficient hardening was observed even at low dpa range impossible to recognize hardening on heavy ion and deuterium irradiated materials, and extreme hardening was established by formation of helium bubble at high dpa region. Furthermore, in the helium irradiated materials, recovery of hardening could not be observed even for annealed materials at 1173 K for 1 hr after irradiation. From such results, hardening promotion work due to helium and extreme thermal stability of the formed defects were elucidated. (B.K.)

  7. Experiment research on grind-hardening of AISI5140 steel based on thermal copensation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiang Ming; Ren, Ying Hui; Zheng, Bo; Zhou, Zhixiong [College of Mechanical and Vehicle Engineering, Hunan University, Changsha, Hunan (China); Deng, Zhao Hui [Key Laboratory for High Efficiency and Precision Machining of Difficult-to-Cut Material of Hunan Province, Hunan (China)

    2016-08-15

    The grind-hardening process utilizes the heat generated to induce martensitic phase transformation. However, the maximum achievable harden layer depth is limited due to high grinding forces, and the tensile residual stress appears on the ground surface in the grind-hardening process. This paper proposes a new grind-hardening technology using thermal compensation. The workpiece of AISI5140 steel is preheated by electric resistance heating, and ground under the condition of the workpiece temperature 25°C, 120°C, 180°C and 240°C. The grinding force, harden layer depth and surface quality including residual stress on ground surface, surface roughness and micro-hardness are investigated. The experimental results show that a deep harden layer with a fine grain martensite can be obtained with the thermal compensation. The ground workpiece surface produces a certain compressive residual stress, and the residual compressive stress value increases with preheating temperature. As the preheating temperature increases, grinding force slightly decreases, while there is slightly increment of surface roughness. Compared with the conventional grind-hardening process, both the harden layer depth and residual stress distribution are significantly improved.

  8. Characterization of the evolution of the volume fraction of precipitates in aged AlMgSiCu alloys using DSC technique

    International Nuclear Information System (INIS)

    Esmaeili, Shahrzad; Lloyd, David J.

    2005-01-01

    Differential scanning calorimetry is used to quantify the evolution of the volume fraction of precipitates during age hardening in AlMgSiCu alloys. The calorimetry tests are run on alloy samples after aging for various times at 180 deg. C and the change in the collective heat effects from the major precipitation and dissolution processes in each run are used to determine the precipitation state of the samples. The method is implemented on alloys with various thermal histories prior to artificial aging, including commercial pre-aging histories. The estimated values for the relative volume fraction of precipitates are compared with the results from a newly developed analytical method using isothermal calorimetry and a related quantitative transmission electron microscopy work. Excellent agreement is obtained between the results from various methods

  9. Evapotranspiration (ET) covers.

    Science.gov (United States)

    Rock, Steve; Myers, Bill; Fiedler, Linda

    2012-01-01

    Evapotranspiration (ET) cover systems are increasingly being used at municipal solid waste (MSW) landfills, hazardous waste landfills, at industrial monofills, and at mine sites. Conventional cover systems use materials with low hydraulic permeability (barrier layers) to minimize the downward migration of water from the surface to the waste (percolation), ET cover systems use water balance components to minimize percolation. These cover systems rely on soil to capture and store precipitation until it is either transpired through vegetation or evaporated from the soil surface. Compared to conventional membrane or compacted clay cover systems, ET cover systems are expected to cost less to construct. They are often aesthetic because they employ naturalized vegetation, require less maintenance once the vegetative system is established, including eliminating mowing, and may require fewer repairs than a barrier system. All cover systems should consider the goals of the cover in terms of protectiveness, including the pathways of risk from contained material, the lifecycle of the containment system. The containment system needs to be protective of direct contact of people and animals with the waste, prevent surface and groundwater water pollution, and minimize release of airborne contaminants. While most containment strategies have been based on the dry tomb strategy of keeping waste dry, there are some sites where adding or allowing moisture to help decompose organic waste is the current plan. ET covers may work well in places where complete exclusion of precipitation is not needed. The U.S. EPA Alternative Cover Assessment Program (ACAP), USDOE, the Nuclear Regulatory Commission, and others have researched ET cover design and efficacy, including the history of their use, general considerations in their design, performance, monitoring, cost, current status, limitations on their use, and project specific examples. An on-line database has been developed with information

  10. Grind hardening process

    CERN Document Server

    Salonitis, Konstantinos

    2015-01-01

    This book presents the grind-hardening process and the main studies published since it was introduced in 1990s.  The modelling of the various aspects of the process, such as the process forces, temperature profile developed, hardness profiles, residual stresses etc. are described in detail. The book is of interest to the research community working with mathematical modeling and optimization of manufacturing processes.

  11. Implementation of Highly-Flowable Strain Hardening Fiber Reinforced Concrete in New RC Beam-Column Joints

    Directory of Open Access Journals (Sweden)

    Liao Wen-Cheng

    2018-01-01

    Full Text Available The purpose of New RC project was aimed to reduce the member sections and increase the available space of high rise buildings by using high strength concrete (f’c > 70 MPa and high strength rebars (fy > 685 MPa. Material consumptions and member section sizes can be further reduced owing to the upgrade of strength. However, the nature of brittleness of high strength may also cause early cover spalling and other ductility issues. Addition of steel fibers is an alternative as transverse reinforcement. Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC has excellent workability in the fresh state and exhibits the strain-hardening and multiple cracking characteristics of high performance fiber reinforced cementitious composites (HPFRCC in their hardened state. The objective of this study is to investigate the feasibility of implementing HF-SHFRC in New RC building systems, particularly for beam-column joints as an alternative of transverse reinforcements. Four full-scale exterior beam-column joints, including two specimens with intensive transverse reinforcements and two specimens made of HF-SHFRC without any stirrup, are tested. Test results show that the HF-SHFRC specimens perform as well as specimens with intensive transverse reinforcements regarding failure mode, ductility, energy dissipation and crack width control. Integration of New RC building systems and HF-SHFRC can assuring construction qualities and further diminish labor work and give infrastructure longer service life, and eventually lower the life-cycle cost.

  12. Effect of precipitate on yield strength of ferritic/martensitic steel exposed to 650 .deg. C liquid sodium

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Yong; Lee, Jeonghyeon; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of); Shin, Sang Hun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Ferritic/martensitic steels(FMS) which are used as one of cladding and structure materials in UCFR, have high creep strength at 600~650°C, low expansion coefficient, and dimensional stability with irradiation-induced void swelling in circumstance of fast neutrons compared to austenitic stainless steel. However, as exposed to high temperature liquid sodium during the design life time (30 to 60 years), the surface of FMS experienced Cr-depletion and decarburization by dissolution of components into sodium and formed oxidations by reacting with sodium. This changes chemical compositions of inter-surface and effects on behavior of precipitations. This change can cause a degradation of mechanical strength of structure material of UCFR. The research about FMS on effects of long term exposure in liquid sodium at 650 °C involve analysis of yield strength by change of microstructure, solid solution hardening and precipitation hardening. It shows how this three parts occupy total yield strength respectively and change over time. In a specific procedure, the microstructure and the surface phenomenon of FMS (Gr. 92) that are exposed to liquid sodium at 650°C, 20 ppm oxygen and are aged in high pure Argon gas environment to express bulk have been investigated by using scanning electron microscope (SEM) and transmission electron microscope (TEM). When specimens were exposed to 650 °C liquid sodium for 1583, 3095 hours and Ar-gas 1601, 2973 hours, mechanical properties of materials were analyzed quantitatively. After experiment, NaCrO{sub 2} oxidation was formed on the surface of Gr.92 at sodium environment. Also, change of microstructure, dissolution of elements, and nucleation and growth of precipitation was raised. During exposed to high temperature at sodium or Ar-gas, annealed lath structure as well as coarsening of tempered martensite structure affects reduction of mechanical properties. And dissolution of elements results in reduction of solid solution hardening. This

  13. Atomistic study of the hardening of ferritic iron by Ni-Cr decorated dislocation loops

    Science.gov (United States)

    Bonny, G.; Bakaev, A.; Terentyev, D.; Zhurkin, E.; Posselt, M.

    2018-01-01

    The exact nature of the radiation defects causing hardening in reactor structural steels consists of several components that are not yet clearly determined. While generally, the hardening is attributed to dislocation loops, voids and secondary phases (radiation-induced precipitates), recent advanced experimental and computational studies point to the importance of solute-rich clusters (SRCs). Depending on the exact composition of the steel, SRCs may contain Mn, Ni and Cu (e.g. in reactor pressure vessel steels) or Ni, Cr, Si, Mn (e.g. in high-chromium steels for generation IV and fusion applications). One of the hypotheses currently implied to explain their formation is the process of radiation-induced diffusion and segregation of these elements to small dislocation loops (heterogeneous nucleation), so that the distinction between SRCs and loops becomes somewhat blurred. In this work, we perform an atomistic study to investigate the enrichment of loops by Ni and Cr solutes and their interaction with an edge dislocation. The dislocation loops decorated with Ni and Cr solutes are obtained by Monte Carlo simulations, while the effect of solute segregation on the loop's strength and interaction mechanism is then addressed by large scale molecular dynamics simulations. The synergy of the Cr-Ni interaction and their competition to occupy positions in the dislocation loop core are specifically clarified.

  14. Analysis of the work-hardening process in spheroidized steels

    International Nuclear Information System (INIS)

    Pacheco, J.L.

    1981-07-01

    An elementary model for the work-hardening process in duplex-structures steels (ferrite - spheroidite) is proposed and tested on low, medium and high carbon content, which seems to give good results concerning the influence of the volume fraction and particle size of the second phase on the work-hardening behaviour. (Author) [pt

  15. Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

    Science.gov (United States)

    Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

  16. Physical and Thermodynamical Properties of Water Phases in Hardening Portland Cement Systems

    DEFF Research Database (Denmark)

    Hansen, T. Bæk

    The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process.......The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process....

  17. Microstructure and high temperature stability of age hardenable AA2219 aluminium alloy modified by Sc, Mg and Zr additions

    Energy Technology Data Exchange (ETDEWEB)

    Naga Raju, P. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)], E-mail: puvvala_nagaraju@yahoo.com; Srinivasa Rao, K. [Metallurgical Engineering Department, Andhra University, Visakapatnam 530003 (India); Reddy, G.M. [Defence Metallurgical Research Laboratory, Hyderabad 500258 (India); Kamaraj, M.; Prasad Rao, K. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)

    2007-08-25

    The present work pertains to the improvement of high temperature stability of age hardenable AA2219 aluminium-copper (6.3%) alloy. Addition of scandium, magnesium and zirconium to the base metal AA2219 was adopted to improve this high temperature stability. These additions were systematically varied by preparing alloys of different composition using gas tungsten arc melting. Long time ageing studies and impression creep technique were used to study the high temperature stability of the alloys. These modified compositions of the alloy resulted in fine equiaxed grains, refined eutectics, large number of high temperature stable and finer precipitates. Among all the compositions, 0.8% Sc + 0.45% Mg + 0.2% Zr addition was found to be significant in improving the high temperature stability of AA2219 alloy. This may be attributed to the possible microstructural changes, solute enrichment of the matrix and pinning of the grain boundaries by the finer precipitates.

  18. Radiation hardening revisited: Role of intracascade clustering

    DEFF Research Database (Denmark)

    Singh, B.N.; Foreman, A.J.E.; Trinkaus, H.

    1997-01-01

    be explained in terms of conventional dispersed-barrier hardening because (a) the grown-in dislocations are not free, and (b) irradiation-induced defect clusters are not rigid indestructible Orowan obstacles. A new model called 'cascade-induced source hardening' is presented where glissile loops produced...... directly in cascades are envisaged to decorate the grown-in dislocations so that they cannot act as dislocation sources. The upper yield stress is related to the breakaway stress which is necessary to pull the dislocation away from the clusters/loops decorating it. The magnitude of the breakaway stress has...

  19. MOULDING MIXTURES HARDENING PROCESS BASED ON LIGNIN-BASE SULPHONATE BINDER

    Directory of Open Access Journals (Sweden)

    V. N. Ektova

    2004-01-01

    Full Text Available Hardening of agglutinant sands on lignosulphonate binding agent is the result of two processes: oxidation-reduction in the system lignosulphonate acids — persulfuric natrium in the early stages of hardening and hydration of cement in the latter stages.

  20. Functional Connectivity of Precipitation Networks in the Brazilian Rainforest-Savanna Transition Zone

    Science.gov (United States)

    Adera, S.; Larsen, L.; Levy, M. C.; Thompson, S. E.

    2016-12-01

    In the Brazilian rainforest-savanna transition zone, vegetation change has the potential to significantly affect precipitation patterns. Deforestation, in particular, can affect precipitation patterns by increasing land surface albedo, increasing aerosol loading to the atmosphere, changing land surface roughness, and reducing transpiration. Understanding land surface-precipitation couplings in this region is important not only for sustaining Amazon and Cerrado ecosystems, but also for cattle ranching and agriculture, hydropower generation, and drinking water management. Simulations suggest complex, scale-dependent interactions between precipitation and land cover. For example, the size and distribution of deforested patches has been found to affect precipitation patterns. We take an empirical approach to ask: (1) what are the dominant spatial and temporal length scales of precipitation coupling in the Brazilian rainforest-savanna transition zone? (2) How do these length scales change over time? (3) How does the connectivity of precipitation change over time? The answers to these questions will help address fundamental questions about the impacts of deforestation on precipitation. We use rain gauge data from 1100 rain gauges intermittently covering the period 1980 - 2013, a period of intensive land cover change in the region. The dominant spatial and temporal length scales of precipitation coupling are resolved using transfer entropy, a metric from information theory. Connectivity of the emergent network of couplings is quantified using network statistics. Analyses using transfer entropy and network statistics reveal the spatial and temporal interdependencies of rainfall events occurring in different parts of the study domain.

  1. Precipitation of {gamma}' phase in {delta}-precipitated Alloy 718 during deformation at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Nalawade, S.A. [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sundararaman, M., E-mail: msraman@barc.gov.in [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, J.B.; Verma, A.; Kishore, R. [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2010-05-15

    Alloy 718 samples aged to precipitate only {delta} particles (with maximum volume fraction) when tensile deformed to fracture at elevated temperatures revealed precipitation of {gamma}' and {gamma}'' phases. The {gamma}' precipitation was found to precede the {gamma}'' phase precipitation unlike in the case of specimens subjected to standard ageing treatment where both the {gamma}' and the {gamma}'' phases precipitate simultaneously. This sequence is explained on the basis of the relative concentration of Al, Ti and Nb in the matrix of {delta} precipitated Alloy 718 microstructure. The precipitation sequence was consistent with the Cozar and Pineau's model that predicts such sequences on the basis of (Al + Ti) to Nb atom ratios.

  2. Radiation-hardened optoelectronic components: detectors

    International Nuclear Information System (INIS)

    Wiczer, J.J.

    1986-01-01

    In this talk, we will survey recent research in the area of radiation hardened optical detectors. We have studied conventional silicon photodiode structures, special radiation hardened silicon photodiodes, and special double heterojunction AlGaAs/GaAs photodiodes in neutron, gamma, pulsed x-ray and charged particle environments. We will present results of our work and summarize other research in this area. Our studies have shown that detectors can be made to function acceptably after exposures to neutron fluences of 10 15 n/cm 2 , total dose gamma exposures of 10 8 rad (Si), and flash x-ray environments of 10 8 rad/sec (Si). We will describe detector structures that can operate through these conditions, pre-rad and post-rad operational characteristics, and experimental conditions that produced these results. 23 refs., 10 figs., 1 tab

  3. Strong work-hardening behavior induced by the solid solution strengthening of dendrites in TiZr-based bulk metallic glass matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Ma, D.Q. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Jiao, W.T. [College of Education, Hebei Normal University of Science and Technology, Qinhuangdao 066004 (China); Zhang, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Vocational and Technical College of Building Materials, Qinhuangdao 066004 (China); Wang, B.A.; Li, J.; Zhang, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma, M.Z., E-mail: mz550509@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-03-05

    Highlights: • Hardness of dendrite of TiZr-based BMGMCs increases. • Strong work-hardening behavior is obtained after solid solution strengthening. • Lattice distortions of dendrite suffering from rapid cooling are detected. - Abstract: A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti{sub 38.8}Zr{sub 28.8}Cu{sub 6.2}Be{sub 16.2}Nb{sub 10} as the basic composition, denoted as Ta{sub 0.0}–Ta{sub 8.0}). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta{sub 8.0}. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallic elements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta{sub 0.5} possesses the largest plastic strain (ε{sub p}) at 20.3% and ultimate strength (σ{sub max}) of 2613 MPa during compressive loading. In addition, the sample of Ta{sub 0.5} exhibits work-hardening up to an ultrahigh tensile strength of 1680 MPa during the tensile process, and then progressively

  4. Radiation hardening of metals irradiated by heavy ions

    International Nuclear Information System (INIS)

    Didyk, A.Yu.; Skuratov, V.A.; Mikhajlova, N.Yu.; Regel', V.R.

    1988-01-01

    The damage dose dependence in the 10 -4 -10 -2 dpa region of radiation hardening of Al, V, Ni, Cu irradiated by xenon ions with 124 MeV energy is investigated using the microhardness technique and transmission electron microscope. It is shown that the pure metals radiation hardening is stimulated for defects clusters with the typical size less than 5 nm, as in the case of neutron and the light charge ion irradiation

  5. idRHa+ProMod - Rail Hardening Control System

    International Nuclear Information System (INIS)

    Ferro, L

    2016-01-01

    idRHa+ProMod is the process control system developed by Primetals Technologies to foresee the thermo-mechanical evolution and micro-structural composition of rail steels subjected to slack quenching into idRHa+ Rail Hardening equipments in a simulation environment. This tool can be used both off-line or in-line, giving the user the chance to test and study the best cooling strategies or letting the automatic control system free to adjust the proper cooling recipe. Optimization criteria have been tailored in order to determine the best cooling conditions according to the metallurgical requirements imposed by the main rail standards and also taking into account the elastoplastic bending phenomena occurring during all stages of the head hardening process. The computational core of idRHa+ProMod is a thermal finite element procedure coupled with special algorithms developed to work out the main thermo-physical properties of steel, to predict the non-isothermal austenite decomposition into all the relevant phases and subsequently to evaluate the amount of latent heat of transformation released, the compound thermal expansion coefficient and the amount of plastic deformation in the material. Air mist and air blades boundary conditions have been carefully investigated by means of pilot plant tests aimed to study the jet impingement on rail surfaces and the cooling efficiency at all working conditions. Heat transfer coefficients have been further checked and adjusted directly on field during commissioning. idRHa+ is a trademark of Primetals Technologies Italy Srl (paper)

  6. idRHa+ProMod - Rail Hardening Control System

    Science.gov (United States)

    Ferro, L.

    2016-03-01

    idRHa+ProMod is the process control system developed by Primetals Technologies to foresee the thermo-mechanical evolution and micro-structural composition of rail steels subjected to slack quenching into idRHa+ Rail Hardening equipments in a simulation environment. This tool can be used both off-line or in-line, giving the user the chance to test and study the best cooling strategies or letting the automatic control system free to adjust the proper cooling recipe. Optimization criteria have been tailored in order to determine the best cooling conditions according to the metallurgical requirements imposed by the main rail standards and also taking into account the elastoplastic bending phenomena occurring during all stages of the head hardening process. The computational core of idRHa+ProMod is a thermal finite element procedure coupled with special algorithms developed to work out the main thermo-physical properties of steel, to predict the non-isothermal austenite decomposition into all the relevant phases and subsequently to evaluate the amount of latent heat of transformation released, the compound thermal expansion coefficient and the amount of plastic deformation in the material. Air mist and air blades boundary conditions have been carefully investigated by means of pilot plant tests aimed to study the jet impingement on rail surfaces and the cooling efficiency at all working conditions. Heat transfer coefficients have been further checked and adjusted directly on field during commissioning. idRHa+ is a trademark of Primetals Technologies Italy Srl

  7. Nuclear effects hardened shelters

    International Nuclear Information System (INIS)

    Lindke, P.

    1990-01-01

    This paper reports on the Houston Fearless 76 Government Projects Group that has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8 foot by 8 foot x 22 foot nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Compartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters

  8. Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

    Science.gov (United States)

    Gao, Guangyao; Zhang, Jianjun; Liu, Yu; Ning, Zheng; Fu, Bojie; Sivapalan, Murugesu

    2017-09-01

    Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures since the 1950s aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield, and sediment concentration have all decreased considerably. Human-induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, whereas the contribution of precipitation was less than 30 %. In this study, we use 50-year time series data (1961-2011), showing decreasing trends in the annual sediment loads of 15 catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space-time variability of sediment yield was expressed notionally as a product of two factors representing (i) the effect of precipitation and (ii) the fraction of treated land surface area. Under minimal LUCC, the square root of annual sediment yield varied linearly with precipitation, with the precipitation-sediment load relationship showing coherent spatial patterns amongst the catchments. As the LUCC increased and took effect, the changes in sediment yield pattern depended more on engineering measures and vegetation restoration campaign, and the within-year rainfall patterns (especially storm events) also played an important role. The effect of LUCC is expressed in terms of a sediment coefficient, i.e., the ratio of annual sediment yield to annual precipitation. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

  9. The effect of Cu on mechanical and precipitation properties of Al-Zn-Mg alloys

    International Nuclear Information System (INIS)

    Chinh, N.Q.; Lendvai, J.; Ping, D.H.; Hono, K.

    2004-01-01

    The effect of Cu on the mechanical and precipitation properties of a high strength Al-2.4 at.% Zn-2.1 at.% Mg alloy was investigated by compression and indentation tests, as well as by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and three-dimensional atom probe field ion microscopy (3DAPFIM). The addition of 0.5 at.% Cu introduces significant changes in the precipitation process and consequently in the age-hardening behavior of the alloy. Microstructural measurements reveal that the addition of Cu changes the density of GP zones, but it also changes partly the shape and composition of the particles. Mechanical and microstructural results together lead to the conclusion that clustering of solute atoms and vacancies during or immediately after water quenching plays an important role in the nucleation of intermediate phase precipitates in one-step aging and the addition of Cu to ternary Al-Zn-Mg leads to changes also in the initial clustering process

  10. Increase of resistance to cracking on stress relieving of hardened steel

    International Nuclear Information System (INIS)

    Velichko, V.V.; Zabil'skij, V.V.; Mikheev, G.M.

    1995-01-01

    Regularities of increase of resistance to cracking during stress relieving of hardened low-alloyed steels were studied, using complex of methods. Effect of carbon, stress concentrator radius, duration and temperature of stress relieving was studies in particular. Results of investigating kinetics of change of physicomechanical properties, hydrogen desorption from hardened specimens showed, that increase of resistance to cracking was caused by desorption from grain boundaries of diffusion-mobile hydrogen, formed during hardening. 18 refs., 8 figs

  11. Tensile testing study of dynamic interactions between dislocations and precipitate in vanadium alloys

    International Nuclear Information System (INIS)

    Tougou, Kouichi; Nogiwa, Kimihiro; Tachikawa, Kazuhiro; Fukumoto, Ken-ichi

    2013-01-01

    To investigate the hardening of fine Ti(OCN) precipitate, we performed in situ transmission electron microscopy (TEM) observations during tensile testing of dislocations gliding through fine Ti(OCN) precipitates in thermally aged V–4Cr–4Ti alloys. The obstacle strength parameter was estimated from the critical bow-out angle, ϕ, of the dislocation lines from the microstructural change during tensile deformation observed in the TEM images. From image processing analysis of the dislocation motion, the value of the obstacle strength parameter of Ti(OCN) precipitates of 4-nm size was determined to be 0.30. The increase in yield stress calculated from the measured dislocation behavior pinned around precipitates was Δσ in situ = 43 MPa, and the increase in yield stress measured by the micro-Vickers hardness test was Δσ HV = 49.5 MPa. Data from in situ TEM observations during tensile testing and from micro-Vickers hardness tests were in good agreement; thus, the obstacle strength parameter of the Ti(OCN) precipitates of 4-nm size was successfully obtained experimentally. The obstacle strength parameter also was compared with data from a previous study, and there was also quite good agreement. Therefore, the obstacle strength parameter obtained from this study is measurable and is a reliable measure of mechanical property changes following precipitation in V–4Cr–4Ti alloys

  12. Plasticity of alloys strengthened with nano-precipitation

    International Nuclear Information System (INIS)

    Praud, M.

    2012-01-01

    As part of the development of the new generation of nuclear power plant, especially sodium-cooled fast reactors (SFR), oxide dispersion strengthened (ODS) steels are considered as potential candidates for cladding materials. Their main advantages are their excellent dimensional stability under irradiation, thanks to their body centered cubic structure, and their high thermal creep resistance due to the nano-particles. The aim of this work is to understand the plasticity of such materials through a multiscale approach. First, the microstructure of 9% and 14% Cr ODS steels has been finely characterized. Then, their mechanical behavior has been studied through tensile tests and creep tests. In addition, in situ Transmission Electron Microscopy straining experiments have been carried out to observe the dynamic behavior at a finer scale. This work emphasizes an evolution of the deformation and damage mechanisms with temperature. At room temperature, a mechanism with a strong intragranular contribution is noticed. At high temperature, an increase in the intergranular component has been pointed out. Consequently, it leads to more severe damage. Finally, the hardening role of the precipitates on the mechanical properties and the plasticity has been evaluated thanks to a 'model' material, without precipitate. (author) [fr

  13. Some aspects of plasticity in hardened face-centred cubic metals

    International Nuclear Information System (INIS)

    Jackson, P.J.; Nathanson, P.D.K.

    1978-01-01

    The plasticity of crystals of f.c.c. metals hardened by solute atoms, neutron irradiation, quenching and by dislocation distributions not characteristic of the active mode of testing is reviewed, with emphasis being placed on the simiularity of slip after various hardening treatments. Normal work hardening is not treated. The reasons for this exclusion are discussed. It is concluded that correlated slip is a normal aspect of deformation, and that diffuse uncorrelated slip occurs only when secondary dislocation multiplication is promoted, e.g. by obstacles introduced by prior slip, or by the presence of hard impenetrable obstacles of another material or phase [af

  14. Work hardening behavior study of structural alloys for cryogenic applications

    International Nuclear Information System (INIS)

    Chu, D.; Morris, J.W. Jr.

    1992-01-01

    Previous investigation on aluminum-lithium alloys have indicated different dependencies of the work hardening behavior on temperature. This variation in temperature dependence is attributed to differences in microstructure rather than composition. An understanding of the microstructural effect on the observed thermal dependency is important as it may allow the tailoring of deformation properties through mechanical processing. Work hardening analyses on other aluminum alloys and a number of structural steels have been performed to better elucidate the role played by microstructure in determining the work hardening behavior. In the paper correlations between the differences in mechanical behavior and the various microstructures observed are presented

  15. General analytical shakedown solution for structures with kinematic hardening materials

    Science.gov (United States)

    Guo, Baofeng; Zou, Zongyuan; Jin, Miao

    2016-09-01

    The effect of kinematic hardening behavior on the shakedown behaviors of structure has been investigated by performing shakedown analysis for some specific problems. The results obtained only show that the shakedown limit loads of structures with kinematic hardening model are larger than or equal to those with perfectly plastic model of the same initial yield stress. To further investigate the rules governing the different shakedown behaviors of kinematic hardening structures, the extended shakedown theorem for limited kinematic hardening is applied, the shakedown condition is then proposed, and a general analytical solution for the structural shakedown limit load is thus derived. The analytical shakedown limit loads for fully reversed cyclic loading and non-fully reversed cyclic loading are then given based on the general solution. The resulting analytical solution is applied to some specific problems: a hollow specimen subjected to tension and torsion, a flanged pipe subjected to pressure and axial force and a square plate with small central hole subjected to biaxial tension. The results obtained are compared with those in literatures, they are consistent with each other. Based on the resulting general analytical solution, rules governing the general effects of kinematic hardening behavior on the shakedown behavior of structure are clearly.

  16. Radiation hardening techniques for rare-earth based optical fibers and amplifiers

    International Nuclear Information System (INIS)

    Girard, Sylvain; Marcandella, Claude; Vivona, Marilena; Prudenzano, Luciano Mescia F.; Laurent, Arnaud; Robin, Thierry; Cadier, Benoit; Pinsard, Emmanuel; Ouerdane, Youcef; Boukenter, Aziz; Cannas, Marco; Boscaino, Roberto

    2012-01-01

    Er/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern the fiber composition, some possible pre-treatments and the interest of simulation tools used to harden by design the amplifiers. We showed that adding cerium inside the fiber phospho-silicate-based core strongly decreases the fiber radiation sensitivity compared to the standard fiber. For both fibers, a pre-treatment with hydrogen permits to enhance again the fiber resistance. Furthermore, simulations tools can also be used to improve the tolerance of the fiber amplifier by helping identifying the best amplifier configuration for operation in the radiative environment. (authors)

  17. Inorganic nitrogen in precipitation and atmospheric sediments

    Energy Technology Data Exchange (ETDEWEB)

    Matheson, D H

    1951-01-01

    In an investigation covering 18 months, daily determinations were made of the inorganic nitrogen contained in precipitation and atmospheric sediments collected at Hamilton, Ont. The nitrogen fall for the whole period averaged 5.8 lb. N per acre per year. Sixty-one per cent of the total nitrogen was collected on 25% of the days when precipitation occurred. The balance, occurring on days without precipitation, is attributable solely to the sedimentation of dust. Ammonia nitrogen averaged 56% of the total, but the proportion for individual days varied widely.

  18. Effects of distributed and centralized stormwater best management practices and land cover on urban stream hydrology at the catchment scale

    Science.gov (United States)

    Loperfido, J. V.; Noe, Gregory B.; Jarnagin, S. Taylor; Hogan, Dianna M.

    2014-11-01

    Urban stormwater runoff remains an important issue that causes local and regional-scale water quantity and quality issues. Stormwater best management practices (BMPs) have been widely used to mitigate runoff issues, traditionally in a centralized manner; however, problems associated with urban hydrology have remained. An emerging trend is implementation of BMPs in a distributed manner (multi-BMP treatment trains located on the landscape and integrated with urban design), but little catchment-scale performance of these systems have been reported to date. Here, stream hydrologic data (March, 2011-September, 2012) are evaluated in four catchments located in the Chesapeake Bay watershed: one utilizing distributed stormwater BMPs, two utilizing centralized stormwater BMPs, and a forested catchment serving as a reference. Among urban catchments with similar land cover, geology and BMP design standards (i.e. 100-year event), but contrasting placement of stormwater BMPs, distributed BMPs resulted in: significantly greater estimated baseflow, a higher minimum precipitation threshold for stream response and maximum discharge increases, better maximum discharge control for small precipitation events, and reduced runoff volume during an extreme (1000-year) precipitation event compared to centralized BMPs. For all catchments, greater forest land cover and less impervious cover appeared to be more important drivers than stormwater BMP spatial pattern, and caused lower total, stormflow, and baseflow runoff volume; lower maximum discharge during typical precipitation events; and lower runoff volume during an extreme precipitation event. Analysis of hydrologic field data in this study suggests that both the spatial distribution of stormwater BMPs and land cover are important for management of urban stormwater runoff. In particular, catchment-wide application of distributed BMPs improved stream hydrology compared to centralized BMPs, but not enough to fully replicate forested

  19. Effects of distributed and centralized stormwater best management practices and land cover on urban stream hydrology at the catchment scale

    Science.gov (United States)

    Loperfido, John V.; Noe, Gregory B.; Jarnagin, S. Taylor; Hogan, Dianna M.

    2014-01-01

    Urban stormwater runoff remains an important issue that causes local and regional-scale water quantity and quality issues. Stormwater best management practices (BMPs) have been widely used to mitigate runoff issues, traditionally in a centralized manner; however, problems associated with urban hydrology have remained. An emerging trend is implementation of BMPs in a distributed manner (multi-BMP treatment trains located on the landscape and integrated with urban design), but little catchment-scale performance of these systems have been reported to date. Here, stream hydrologic data (March, 2011–September, 2012) are evaluated in four catchments located in the Chesapeake Bay watershed: one utilizing distributed stormwater BMPs, two utilizing centralized stormwater BMPs, and a forested catchment serving as a reference. Among urban catchments with similar land cover, geology and BMP design standards (i.e. 100-year event), but contrasting placement of stormwater BMPs, distributed BMPs resulted in: significantly greater estimated baseflow, a higher minimum precipitation threshold for stream response and maximum discharge increases, better maximum discharge control for small precipitation events, and reduced runoff volume during an extreme (1000-year) precipitation event compared to centralized BMPs. For all catchments, greater forest land cover and less impervious cover appeared to be more important drivers than stormwater BMP spatial pattern, and caused lower total, stormflow, and baseflow runoff volume; lower maximum discharge during typical precipitation events; and lower runoff volume during an extreme precipitation event. Analysis of hydrologic field data in this study suggests that both the spatial distribution of stormwater BMPs and land cover are important for management of urban stormwater runoff. In particular, catchment-wide application of distributed BMPs improved stream hydrology compared to centralized BMPs, but not enough to fully replicate forested

  20. Skin hardening effect in patients with polymorphic light eruption: comparison of UVB hardening in hospital with a novel home UV-hardening device.

    Science.gov (United States)

    Franken, S M; Genders, R E; de Gruijl, F R; Rustemeyer, T; Pavel, S

    2013-01-01

    An effective prophylactic treatment of patients with polymorphic light eruption (PLE) consists of repeated low, gradually increasing exposures to UVB radiation. This so-called UV(B) hardening induces better tolerance of the skin to sunlight. SunshowerMedical company (Amsterdam) has developed an UV (B) source that can be used during taking shower. The low UV fluence of this apparatus makes it an interesting device for UV hardening. In a group of PLE patients, we compared the effectiveness of the irradiation with SunshowerMedical at home with that of the UVB treatment in the hospital. The PLE patients were randomized for one of the treatments. The hospital treatment consisted of irradiations with broad-band UVB (Waldmann 85/UV21 lamps) twice a week during 6 weeks. The home UV-device was used each day with the maximal irradiation time of 6 min. The outcome assessment was based on the information obtained from patients' dermatological quality of life (DLQI) questionnaires, the ability of both phototherapies to reduce the provocation reaction and from the patients' evaluation of the long-term benefits of their phototherapies. Sixteen patients completed treatment with SunshowerMedical and thirteen completed treatment in hospital. Both types of phototherapy were effective. There was a highly significant improvement in DLQI with either treatment. In most cases, the hardening reduced or even completely suppressed clinical UV provocation of PLE. The patients using SunshowerMedical at home were, however, much more content with the treatment procedure than the patients visiting the dermatological units. Both treatments were equally effective in the induction of skin tolerance to sunlight in PLE patients. However, the home treatment was much better accepted than the treatment in the hospital. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

  1. Effects of solute elements on irradiation hardening and microstructural evolution in low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Katsuhiko, E-mail: fujiik@inss.co.jp [Institute of Nuclear Safety System Inc., 64 Sata, Mihama 919-1205 (Japan); Ohkubo, Tadakatsu, E-mail: OHKUBO.Tadakatsu@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Fukuya, Koji, E-mail: fukuya@inss.co.jp [Institute of Nuclear Safety System Inc., 64 Sata, Mihama 919-1205 (Japan)

    2011-10-01

    The effects of the elements Mn, Ni, Si and Cu on irradiation hardening and microstructural evolution in low alloy steels were investigated in ion irradiation experiments using five kinds of alloys prepared by removing Mn, Ni and Si from, and adding 0.05 wt.%Cu to, the base alloy (Fe-1.5Mn-0.5Ni-0.25Si). The alloy without Mn showed less hardening and the alloys without Ni or Si showed more hardening. The addition of Cu had hardly any influence on hardening. These facts indicated that Mn enhanced hardening and that Ni and Si had some synergetic effects. The formation of solute clusters was not confirmed by atom probe (AP) analysis, whereas small dislocation loops were identified by TEM observation. The difference in hardening between the alloys with and without Mn was qualitatively consistent with loop formation. However, microstructural components that were not detected by the AP and TEM were assumed to explain the hardening level quantitatively.

  2. OCCUPATIONAL ASTHMA CAUSED BY A HARDENER CONTAINING AN ALIPHATIC AND A CYCLOALIPHATIC DIAMINE

    NARCIS (Netherlands)

    ALEVA, RM; AALBERS, R; KOETER, GH; DEMONCHY, JGR

    An otherwise healthy 44-yr-old man experienced a serious attack of bronchial obstruction after working with resins and hardeners, releasing fumes of a mixture of an aliphatic and a cycloaliphatic diamine hardener. Eight hours after deliberate challenge with the hardener a large increase of airway

  3. Effect of aging and cold working on the high-temperature low-cycle fatigue behavior of alloy 800H. Part I. The effect of hardening processes on the initial stress--strain curve

    International Nuclear Information System (INIS)

    Villagrana, R.E.; Kaae, J.L.; Ellis, J.R.; Gantzel, P.K.

    1978-01-01

    The individual and combined effects of cold working (5 and 10%) and aging (4000 and 8000 h at 538 to 760 0 C) on the microstructure and high-temperature yield strength of alloy 800H have been investigated. The specimens were tested at the aging temperatures. During testing some of the specimens showed the phenomenon of serrated yielding. In order of importance, the principal hardening agents observed in this work were: cold work, the precipitation of Cr 23 C 6 at the grain boundaries, and, in some cases, the precipitation of a Perovskite-type γ' phase in the grain interiors

  4. Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

    Directory of Open Access Journals (Sweden)

    M. Stachowicz

    2010-07-01

    Full Text Available Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.

  5. Generation Mechanism of Work Hardened Surface Layer in Metal Cutting

    Science.gov (United States)

    Hikiji, Rikio; Kondo, Eiji; Kawagoishi, Norio; Arai, Minoru

    Finish machining used to be carried out in grinding, but it is being replaced by cutting with very small undeformed chip thickness. In ultra precision process, the effects of the cutting conditions and the complicated factors on the machined surface integrity are the serious problems. In this research, work hardened surface layer was dealt with as an evaluation of the machined surface integrity and the effect of the mechanical factors on work hardening was investigated experimentally in orthogonal cutting. As a result, it was found that work hardened surface layer was affected not only by the shear angle varied under the cutting conditions and the thrust force of cutting resistance, but also by the thrust force acting point, the coefficient of the thrust force and the compressive stress equivalent to the bulk hardness. Furthermore, these mechanical factors acting on the depth of the work hardened surface layer were investigated with the calculation model.

  6. Microstructural evolution and hardening of GH3535 alloy under energetic Xe ion irradiation at room temperature and 650 °C

    Science.gov (United States)

    Huang, Hefei; Gao, Jie; Radiguet, Bertrand; Liu, Renduo; Li, Jianjian; Lei, Guanhong; Huang, Qing; Liu, Min; Xie, Ruobing

    2018-02-01

    The GH3535 alloy was irradiated with 7 MeV Xe26+ ions to a dose of 10 dpa at room temperature (RT) and 650 °C, and subsequently examined using Transmission Electron Microscopy (TEM) and nanoindentation. High numbers of nano-sized black dots, identified as dislocation loops were observed in both irradiated samples. The dislocation loops detected at the high temperature irradiated sample (size/number density: 9.5 nm/1.9 × 1021 m-3) were found to be larger in size but less in amount as compared to that of the case of RT irradiation (6.9 nm/18.7 × 1021 m-3). In addition, the large-sized Mo-Cr rich precipitates (16.4 nm/3.7 × 1021 m-3) were observed in the sample irradiated at 650 °C. Moreover, the Xe bubbles, with smaller size (2.9 nm) but higher number density (77.8 × 1021 m-3) among the irradiated induced defects, were also detected in the case of high temperature irradiated sample via the diffusion and aggregation of Xe atoms. Nanoindentaion measurements showed a hardening phenomenon for the irradiated sample, and the hardness increment is higher in the case of high temperature irradiated sample. Dispersed barrier-hardening (DBH) model was applied to predict the hardening produced from the irradiation induced defects. The yield strength increment calculated based on TEM observations and the nanohardness increment measured using nanoindentation are in excellent agreement.

  7. The Use of Fuzzy Systems for Forecasting the Hardenability of Steel

    Directory of Open Access Journals (Sweden)

    Sitek W.

    2016-06-01

    Full Text Available The goal of the research carried out was to develop the fuzzy systems, allowing the determination of the Jominy hardenability curve based on the chemical composition of structural steels for quenching and tempering. Fuzzy system was created to calculate hardness of the steel, based on the alloying elements concentrations, and to forecast the hardenability curves. This was done based on information from the PN-EN 10083-3: 2008. Examples of hardenability curves calculated for exemplar steels were presented. Results of the research confirmed that fuzzy systems are a useful tool in evaluation the effect of alloying elements on the properties of materials compared to conventional methods. It has been demonstrated the practical usefulness of the developed models which allows forecasting the steels’ Jominy hardenability curve.

  8. Unit rupture work as a criterion for quantitative estimation of hardenability in steel

    International Nuclear Information System (INIS)

    Kramarov, M.A.; Orlov, E.D.; Rybakov, A.B.

    1980-01-01

    Shown is possible utilization of high sensitivity of resistance to fracture of structural steel to the hardenability degree in the course of hardening to find the quantitative estimation of the latter one. Proposed is a criterion kappa, the ratio of the unit rupture work in the case of incomplete hardenability (asub(Tsub(ih))) under investigation, and the analoguc value obtained in the case of complete hardenability Asub(Tsub(Ch)) at the testing temperature corresponding to the critical temperature Tsub(100(M). Confirmed is high criterion sensitivity of the hardened steel structure on the basis of experimental investigation of the 40Kh, 38KhNM and 38KhNMFA steels after isothermal hold-up at different temperatures, corresponding to production of various products of austenite decomposition

  9. Determination of the strain hardening rate of metals and alloys by X ray diffraction

    International Nuclear Information System (INIS)

    Cadalbert, Robert

    1977-01-01

    This report for engineering graduation is based on the study of X ray diffraction line profile which varies with the plastic strain rate of the metal. After some generalities of strain hardening (consequence of a plastic deformation on the structure of a polycrystalline metal, means to study a strain hardened structure, use of X ray diffraction to analyse the strain hardened crystalline structure), the author reports the strain hardening rate measurement by using X ray diffraction. Several aspects are addressed: principles, experimental technique, apparatus, automation and programming of the measurement cycle, method sensitivity and precision. In the next part, the author reports applications: measurement of the strain hardening rate in different materials (tubes with hexagonal profile, cylindrical tubes in austenitic steel), and study of the evolution of strain hardening with temperature [fr

  10. DMILL circuits. The hardened electronics decuples its performances

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Thanks to the DMILL (mixed logic-linear hardening) technology under development at the CEA, MHS, a French company specialized in the fabrication of integrated circuits now produces hardened electronic circuits ten times more resistant to radiations than its competitors. Outside the initial market (several thousands of circuits for the LHC particle accelerator of Geneva), a broad choice of applications is opened to this technology: national defense, space, civil nuclear and medical engineering, and high temperature applications. Short paper. (J.S.)

  11. Study of the mechanisms involved in the laser superficial hardening process of metallic alloys; Estudo dos mecanismos envolvidos no processo de endurecimento superficial a laser de ligas metalicas

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Edmara Marques Rodrigues da

    2001-07-01

    The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO{sub 2} laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the

  12. Development of production methods of volume source by the resinous solution which has hardening

    CERN Document Server

    Motoki, R

    2002-01-01

    Volume sources is used for standard sources by radioactive measurement using Ge semiconductor detector of environmental sample, e.g. water, soil and etc. that require large volume. The commercial volume source used in measurement of the water sample is made of agar-agar, and that used in measurement of the soil sample is made of alumina powder. When the plastic receptacles of this two kinds of volume sources were damaged, the leakage contents cause contamination. Moreover, if hermetically sealing performance of volume source made of agar-agar fell, volume decrease due to an evaporation off moisture gives an error to radioactive measurement. Therefore, we developed the two type methods using unsaturated polyester resin, vinilester resin, their hardening agent and acrylicresin. The first type is due to dispersing the hydrochloric acid solution included the radioisotopes uniformly in each resin and hardening the resin. The second is due to dispersing the alumina powder absorbed the radioisotopes in each resin an...

  13. Assessing the impact of climate variability on catchment water balance and vegetation cover

    Directory of Open Access Journals (Sweden)

    X. Xu

    2012-01-01

    Full Text Available Understanding the interactions among climate, vegetation cover and the water cycle lies at the heart of the study of watershed ecohydrology. Recently, considerable attention is being paid to the effect of climate variability on catchment water balance and also associated vegetation cover. In this paper, we investigate the general pattern of long-term water balance and vegetation cover (as reflected by fPAR among 193 study catchments in Australia through statistical analysis. We then employ the elasticity analysis approach for quantifying the effects of climate variability on hydrologic partitioning (including total, surface and subsurface runoff and on vegetation cover (including total, woody and non-woody vegetation cover. Based on the results of statistical analysis, we conclude that annual runoff (R, evapotranspiration (E and runoff coefficient (R/P increase with vegetation cover for catchments in which woody vegetation is dominant and annual precipitation is relatively high. Control of water available on annual evapotranspiration in non-woody dominated catchments is relatively stronger compared to woody dominated ones. The ratio of subsurface runoff to total runoff (Rg/R also increases with woody vegetation cover. Through the elasticity analysis of catchment runoff, it is shown that precipitation (P in current year is the most important factor affecting the change in annual total runoff (R, surface runoff (Rs and subsurface runoff (Rg. The significance of other controlling factors is in the order of annual precipitation in previous years (P−1 and P−2, which represents the net effect of soil moisture and annual mean temperature (T in current year. Change of P by +1% causes a +3.35% change of R, a +3.47% change of Rs and a +2.89% change of

  14. Residual stresses relaxation in surface-hardened half-space under creep conditions

    Directory of Open Access Journals (Sweden)

    Vladimir P. Radchenko

    2015-09-01

    Full Text Available We developed the method for solving the problem of residual stresses relaxation in surface-hardened layer of half-space under creep conditions. At the first stage we made the reconstruction of stress-strain state in half-space after plastic surface hardening procedure based on partial information about distribution for one residual stress tensor component experimentally detected. At the second stage using a numerical method we solve the problem of relaxation of self-balanced residual stresses under creep conditions. To solve this problem we introduce the following Cartesian system: x0y plane is aligned with hardened surface of half-space and 0z axis is directed to the depth of hardened layer. We also introduce the hypotheses of plane sections parallel to x0z and y0z planes. Detailed analysis of the problem has been done. Comparison of the calculated data with the corresponding test data was made for plane specimens (rectangular parallelepipeds made of EP742 alloy during T=650°C after the ultrasonic hardening with four hardening modes. We use half-space to model these specimens because penetration's depth of residual stresses is less than specimen general size in two digit exponent. There is enough correspondence of experimental and calculated data. It is shown that there is a decay (in modulus of pressing residual stresses under creep in 1.4–1.6 times.

  15. On the mechanism of dispersion hardening in molybdenum-carbide alloy systems

    International Nuclear Information System (INIS)

    Shulepov, V.I.; Yudkovskij, S.I.; Batenina, O.I. et al.

    1975-01-01

    The effect of heat treatment of the forming alloys of the Mo-Ti-C and Mo-Ti-Zr-C systems (at the temperatures below the recrystallization temperature) on the structure, distribution of carbon and mechanical properties of the alloys is studied. It is shown that the dispersion-strengthened state of the molybdenum alloys may be obtained on the account of the deformation ageing effect, rather than through the use of the standard heat-treatment procedure (hardening plus ageing). On the basis of the experimental results a theoretical explanation of strengthening of the high-alloy molybdenum-titanum-carbon system is given

  16. Ion irradiation-induced swelling and hardening effect of Hastelloy N alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.J. [Key Laboratory of Artificial Micro-and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, D.H.; Chen, H.C.; Lei, G.H.; Huang, H.F.; Zhang, W.; Wang, C.B. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Yan, L., E-mail: yanlong@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Fu, D.J. [Key Laboratory of Artificial Micro-and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Tang, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2017-06-15

    The volumetric swelling and hardening effect of irradiated Hastelloy N alloy were investigated in this paper. 7 MeV and 1 MeV Xe ions irradiations were performed at room temperature (RT) with irradiation dose ranging from 0.5 to 27 dpa. The volumetric swelling increases with increasing irradiation dose, and reaches up to 3.2% at 27 dpa. And the irradiation induced lattice expansion is also observed. The irradiation induced hardening initiates at low ion dose (≤1dpa) then saturates with higher ion dose. The irradiation induced volumetric swelling may be ascribed to excess atomic volume of defects. The irradiation induced hardening may be explained by the pinning effect where the defects can act as obstacles for the free movement of dislocation lines. And the evolution of the defects' size and number density could be responsible for the saturation of hardness. - Highlights: •Irradiation Swelling: The irradiation induced volumetric swelling increases with ion dose. •Irradiation Hardening: The irradiation hardening initiates below 1 dpa, then saturates with higher ion dose (1–10 dpa). •Irradiation Mechanism: The irradiation phenomena are ascribed to the microstructural evolution of the irradiation defects.

  17. Helium-induced hardening effect in polycrystalline tungsten

    Science.gov (United States)

    Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

    2017-09-01

    In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

  18. Influence of Solution-Annealing Parameters on the Continuous Cooling Precipitation of Aluminum Alloy 6082

    Directory of Open Access Journals (Sweden)

    Hannes Fröck

    2018-04-01

    Full Text Available We use a systematic approach to investigate the influence of the specific solution condition on quench-induced precipitation of coarse secondary phase particles during subsequent cooling for a wide range of cooling rates. Commercially produced plate material of aluminum alloy EN AW-6082 was investigated and the applied solution treatment conditions were chosen based on heating differential scanning calorimetry experiments of the initial T651 condition. The kinetics of the quench-induced precipitation were investigated by in situ cooling differential scanning calorimetry for a wide range of cooling rates. The nature of those quench-induced precipitates was analyzed by electron microscopy. The experimental data was evaluated with respect to the detrimental effect of incomplete dissolution on the age-hardening potential. We show that if the chosen solution temperature and soaking duration are too low or short, the solution treatment results in an incomplete dissolution of secondary phase particles. This involves precipitation during subsequent cooling to start concurrently with the onset of cooling, which increases the quench sensitivity. However, if the solution conditions allow the formation of a complete solid solution, precipitation will start after a certain degree of undercooling, thus keeping the upper critical cooling rate at the usual alloy-specific level.

  19. Global Precipitation Analyses at Time Scales of Monthly to 3-Hourly

    Science.gov (United States)

    Adler, Robert F.; Huffman, George; Curtis, Scott; Bolvin, David; Nelkin, Eric; Einaudi, Franco (Technical Monitor)

    2002-01-01

    Global precipitation analysis covering the last few decades and the impact of the new TRMM precipitation observations are discussed. The 20+ year, monthly, globally complete precipitation analysis of the World Climate Research Program's (WCRP/GEWEX) Global Precipitation Climatology Project (GPCP) is used to explore global and regional variations and trends and is compared to the much shorter TRMM (Tropical Rainfall Measuring Mission) tropical data set. The GPCP data set shows no significant trend in precipitation over the twenty years, unlike the positive trend in global surface temperatures over the past century. Regional trends are also analyzed. A trend pattern that is a combination of both El Nino and La Nina precipitation features is evident in the Goodyear data set. This pattern is related to an increase with time in the number of combined months of El Nino and La Nina during the Goodyear period. Monthly anomalies of precipitation are related to ENRON variations with clear signals extending into middle and high latitudes of both hemispheres. The GPCP daily, 1 degree latitude-longitude analysis, which is available from January 1997 to the present is described and the evolution of precipitation patterns on this time scale related to El Nino and La Nina is described. Finally, a TRMM-based Based analysis is described that uses TRMM to calibrate polar-orbit microwave observations from SSM/I and geosynchronous OR observations and merges the various calibrated observations into a final, Baehr resolution map. This TRMM standard product will be available for the entire TRMM period (January Represent). A real-time version of this merged product is being produced and is available at 0.25 degree latitude-longitude resolution over the latitude range from 50 deg. N -50 deg. S. Examples will be shown, including its use in monitoring flood conditions.

  20. Precipitated iron. A limit on gettering efficacy in multicrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Fenning, D.P.; Hofstetter, J.; Bertoni, M.I.; Buonassisi, T. [Massachusetts Institute of Technology MIT, Cambridge, Massachusetts 02139 (United States); Coletti, G. [ECN Solar Energy, Westerduinweg 3, NL-1755 LE Petten (Netherlands); Lai, B. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Del Canizo, C. [Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid (Spain)

    2013-01-31

    A phosphorus diffusion gettering model is used to examine the efficacy of a standard gettering process on interstitial and precipitated iron in multicrystalline silicon. The model predicts a large concentration of precipitated iron remaining after standard gettering for most as-grown iron distributions. Although changes in the precipitated iron distribution are predicted to be small, the simulated post-processing interstitial iron concentration is predicted to depend strongly on the as-grown distribution of precipitates, indicating that precipitates must be considered as internal sources of contamination during processing. To inform and validate the model, the iron distributions before and after a standard phosphorus diffusion step are studied in samples from the bottom, middle, and top of an intentionally Fe-contaminated laboratory ingot. A census of iron-silicide precipitates taken by synchrotron-based X-ray fluorescence microscopy confirms the presence of a high density of iron-silicide precipitates both before and after phosphorus diffusion. A comparable precipitated iron distribution was measured in a sister wafer after hydrogenation during a firing step. The similar distributions of precipitated iron seen after each step in the solar cell process confirm that the effect of standard gettering on precipitated iron is strongly limited as predicted by simulation. Good agreement between the experimental and simulated data supports the hypothesis that gettering kinetics is governed by not only the total iron concentration but also by the distribution of precipitated iron. Finally, future directions based on the modeling are suggested for the improvement of effective minority carrier lifetime in multicrystalline silicon solar cells.

  1. Virginia Standards of Learning (Grades 6 through 12) That Are Covered When Students Attend Live Performances of Shakespeare's Plays.

    Science.gov (United States)

    Brookshire, Cathy A.

    This paper outlines Standards of Learning for grades 6-12 students in Virginia that are covered when they attend live performances of William Shakespeare's plays. The paper details separate standards for each grade in English, subdivided into standards which fulfill requirements in Oral Language, Reading/Literature, Writing, and Research, along…

  2. Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rojacz, H., E-mail: rojacz@ac2t.at [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria); Mozdzen, G. [Aerospace & Advanced Composites GmbH, Viktor-Kaplan-Straße 2F, 2700 Wiener Neustadt (Austria); Weigel, F.; Varga, M. [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria)

    2016-08-15

    Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

  3. Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

    International Nuclear Information System (INIS)

    Rojacz, H.; Mozdzen, G.; Weigel, F.; Varga, M.

    2016-01-01

    Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

  4. Work-hardening of dual-phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Rieger, Florian

    2016-07-01

    Exhibiting good mechanical properties for cold-sheet forming, low-alloyed dual-phase (DP) steels are nowadays widely used for automotive applications. The composite-like microstructure of DP steels is composed of a low-carbon ductile ferrite-matrix and 10 - 60 vol.% hard martensitic inclusions. A nonlinear mean-field model and full-field finite-element simulations are applied to investigate three major topics: the influence of grain-size distribution, grain-level plasticity and derivation of an original material-model. The plastic behavior of polycrystals is assumed to be grain-size dependent in this work. The distribution of grain-sizes is taken to be lognormal. It is found that grain-size dispersion leads to a decrease of the material strength, in particular for small mean diameters around one micron. The numerical results from the mean-field model are confirmed notably well by means of a simple analytical expression. The micromechanical behavior of DP steels is investigated by full-field RVE simulations with a crystal-plasticity based ferrite-matrix and von Mises-type martensite inclusions. To examine the martensite influence, full-field simulation results of DP steels have been compared to an RVE in which martensite is substituted by ferrite. After quenching, a higher grain-boundary area covered by martensite facilitates an increased average dislocation-density. For uniaxial deformations above ∝10%, however, the grain-size dependent relation reverses. With more surrounding martensite, the local crystal-plasticity material-model exhibits hardening at a slower rate. A nonlinear mean-field model of Hashin-Shtrikman type is employed as framework for the original material-model for DP steels. The model incorporates the interaction of ferrite and martensite via incompatibility-induced long-range stresses in an averaged sense. The proposed model combines works of Ashby (1970) and Brown and Stobbs (1971a) to simulate the ferrite behavior. Based on the composite model

  5. CASE-HARDENING OF STAINLESS STEEL

    DEFF Research Database (Denmark)

    2004-01-01

    The invention relates to case-hardening of a stainless steel article by means of gas including carbon and/or nitrogen, whereby carbon and/or nitrogen atoms diffuse through the surface into the article. The method includes activating the surface of the article, applying a top layer on the activated...

  6. Role of grain refinement in hardening of structural steels at preliminary thermomechanical treatment

    International Nuclear Information System (INIS)

    Bukhvalov, A.B.; Grigor'eva, E.V.; Davydova, L.S.; Degtyarev, M.V.; Levit, V.I.; Smirnova, N.A.; Smirnov, L.V.

    1981-01-01

    The hardening mechanism during preliminary thermomechanical treatment with deformation by cold rolling or hydroextrusion is studied on structural 37KhN3M1 and 38KhN3MFA steels. Specimens have been tested on static tension, impact strength and fracture toughness. It is shown that hydroextrusion application instead of rolling does not change the hardening effect of preliminary thermomechanical treatment (PTMT). It is established that the increase of preliminary deformation degree and the use of accelerated short term hardening heating provides a bett er grain refinement and the increase of PTMT hardening effect [ru

  7. Environmental hardening of a mobile-manipulator system for nuclear environments

    International Nuclear Information System (INIS)

    Jones, S.L.; Cable, T.; Tulenko, J.S.; Toshkov, S.; Sias, F.R. Jr.

    1993-01-01

    This research report discusses the radiation hardening of a commercially available mobile robot, the REMOTEC ANDROS. This hardening effort is culminating in the availability of a megarad hardened mobile platform to access areas in nuclear facilities with extremely high levels of radiation (0.1 to 1 Mrad). These radiation levels may be encountered both during routine repair and monitoring activities and accident situations. The project has completed a phase-I U.S. Department of Energy Small Business Innovative Research contract and is now in a phase-II effort with completion scheduled in early 1995. The research involves the evaluation of the material and electrical components of an ANDROS robot to determine the anticipated radiation hardness of the current production version and evaluation of the components that must be replaced or modified to harden the system to higher radiation levels. The work being reported is based on an evaluation of the complete list of all electronic, electrical, and mechanical parts used in the robot and includes initial experimental radiation evaluations performed at the University of Florida

  8. Determinants of woody cover in African savannas

    Science.gov (United States)

    Sankaran, M.; Hanan, N.P.; Scholes, Robert J.; Ratnam, J.; Augustine, D.J.; Cade, B.S.; Gignoux, J.; Higgins, S.I.; Le, Roux X.; Ludwig, F.; Ardo, J.; Banyikwa, F.; Bronn, A.; Bucini, G.; Caylor, K.K.; Coughenour, M.B.; Diouf, A.; Ekaya, W.; Feral, C.J.; February, E.C.; Frost, P.G.H.; Hiernaux, P.; Hrabar, H.; Metzger, K.L.; Prins, H.H.T.; Ringrose, S.; Sea, W.; Tews, J.; Worden, J.; Zambatis, N.

    2005-01-01

    Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties 1-3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1,2,4,5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ???650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ???650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation 6 may considerably affect their distribution and dynamics. ?? 2005 Nature Publishing Group.

  9. Climatological determinants of woody cover in Africa.

    Science.gov (United States)

    Good, Stephen P; Caylor, Kelly K

    2011-03-22

    Determining the factors that influence the distribution of woody vegetation cover and resolving the sensitivity of woody vegetation cover to shifts in environmental forcing are critical steps necessary to predict continental-scale responses of dryland ecosystems to climate change. We use a 6-year satellite data record of fractional woody vegetation cover and an 11-year daily precipitation record to investigate the climatological controls on woody vegetation cover across the African continent. We find that-as opposed to a relationship with only mean annual rainfall-the upper limit of fractional woody vegetation cover is strongly influenced by both the quantity and intensity of rainfall events. Using a set of statistics derived from the seasonal distribution of rainfall, we show that areas with similar seasonal rainfall totals have higher fractional woody cover if the local rainfall climatology consists of frequent, less intense precipitation events. Based on these observations, we develop a generalized response surface between rainfall climatology and maximum woody vegetation cover across the African continent. The normalized local gradient of this response surface is used as an estimator of ecosystem vegetation sensitivity to climatological variation. A comparison between predicted climate sensitivity patterns and observed shifts in both rainfall and vegetation during 2009 reveals both the importance of rainfall climatology in governing how ecosystems respond to interannual fluctuations in climate and the utility of our framework as a means to forecast continental-scale patterns of vegetation shifts in response to future climate change.

  10. Investigation of magnesium oxychloride cement at the initial hardening stage

    Directory of Open Access Journals (Sweden)

    Averina Galina

    2018-01-01

    Full Text Available The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.

  11. Modeling Precipitation Dependent Forest Resilience in India

    Science.gov (United States)

    Das, P.; Behera, M. D.; Roy, P. S.

    2018-04-01

    The impact of long term climate change that imparts stress on forest could be perceived by studying the regime shift of forest ecosystem. With the change of significant precipitation, forest may go through density change around globe at different spatial and temporal scale. The 100 class high resolution (60 meter spatial resolution) Indian vegetation type map was used in this study recoded into four broad categories depending on phrenology as (i) forest, (ii) scrubland, (iii) grassland and (iv) treeless area. The percentage occupancy of forest, scrub, grass and treeless were observed as 19.9 %, 5.05 %, 1.89 % and 7.79 % respectively. Rest of the 65.37 % land area was occupied by the cropland, built-up, water body and snow covers. The majority forest cover were appended into a 5 km × 5 km grid, along with the mean annual precipitation taken from Bioclim data. The binary presence and absence of different vegetation categories in relates to the annual precipitation was analyzed to calculate their resilience expressed in probability values ranging from 0 to 1. Forest cover observed having resilience probability (Pr) < 0.3 in only 0.3 % (200 km2) of total forest cover in India, which was 4.3 % < 0.5 Pr. Majority of the scrubs and grass (64.92 % Pr < 0.5) from North East India which were the shifting cultivation lands showing low resilience, having their high tendency to be transform to forest. These results have spatial explicitness to highlight the resilient and non-resilient distribution of forest, scrub and grass, and treeless areas in India.

  12. Dissolution of hardened wood ash in forest soils. Studies in a column experiment

    International Nuclear Information System (INIS)

    Eriksson, Jan

    1996-01-01

    Dissolution of hardened and crushed ashes was studied in a column experiment during leaching with artificial rain water corresponding to 5 year-precipitations. The ashes studied were a CFB ash from Perstorp and a bottom ash from Ljungby that were added in amounts corresponding to 4 tonnes per hectare. Assuming that the studied ashes are representative and that the results can be transferred to field conditions, the most important conclusions that can be drawn are summarized in the following way: Hardened and crushed ashes are broken down relatively slowly, which particularly applies to the coarse fraction. The fine fraction of the Perstorp ashes has a good liming effect at the same time as the risk for large pH-increases appears to be small. As regards the macro-nutrients Ca and K (not the Ljungby ashes), the amounts released are probably sufficient from a forest vitalization viewpoint. As regards Mg and P, this is less certain. The heavy metals appear to be released relatively slowly and most of them are bound in non-exchangeable form in the mor layer. The exception is Cd that tends to be absorbed in the mor layer to a minor extent but which, on the other hand, is not released from the ashes in any greater amounts. The greatest risk for increased concentrations of soluble heavy metals appears to be the mobilization of part of the mor layer's reserve as a result of the salt effect of the ashes. However, this is a temporary effect. 17 refs, 18 figs, 6 tabs Figs and tabs with text in English

  13. Structure of hardened alloys of Sr-Rh system

    International Nuclear Information System (INIS)

    Dobromyslov, A.V.; Taluth, N.I.

    1997-01-01

    Methods of X-ray diffraction analysis, optical metallography, transmission electron microscopy and hardness measurement were applied to study the structure of hardened zirconium-rhodium system alloys with rhodium contents up to 4.5 at.%. It is shown that in hardening alloys with rhodium concentration lower 2.2 at.% the eutectoid decomposition takes place and bainite-like structure is formed. A metastable ω-phase is formed in alloys with rhodium concentration equal to 2.65 at.% and above. The formation of ω-phase suppresses the process of eutectoid decomposition

  14. Introduction and application of non-stationary standardized precipitation index considering probability distribution function and return period

    Science.gov (United States)

    Park, Junehyeong; Sung, Jang Hyun; Lim, Yoon-Jin; Kang, Hyun-Suk

    2018-05-01

    The widely used meteorological drought index, the Standardized Precipitation Index (SPI), basically assumes stationarity, but recent changes in the climate have led to a need to review this hypothesis. In this study, a new non-stationary SPI that considers not only the modified probability distribution parameter but also the return period under the non-stationary process was proposed. The results were evaluated for two severe drought cases during the last 10 years in South Korea. As a result, SPIs considered that the non-stationary hypothesis underestimated the drought severity than the stationary SPI despite that these past two droughts were recognized as significantly severe droughts. It may be caused by that the variances of summer and autumn precipitation become larger over time then it can make the probability distribution wider than before. This implies that drought expressions by statistical index such as SPI can be distorted by stationary assumption and cautious approach is needed when deciding drought level considering climate changes.

  15. Study of the early stages of precipitation of molybdenum in steelwelds

    International Nuclear Information System (INIS)

    Choudhary, H.U.

    2001-01-01

    The addition of molybdenum to steel welds in quite small concentrations leads to a variety of anomalous microstructural and mechanical property effects. In some cases, the effects manifest even there are no obvious changes in microstructure at the resolution of a transmission electron microscope. It has been reported in the published literature, that an increase in the molybdenum concentration leads to a corresponding increase in the proportion of primary microstructure in multipass welds. Another striking anomaly with molybdenum containing welds, identified in the published literature, is that the strength of such welds is much higher than is estimated using normally reliable models for he prediction of mechanical properties. The surprising feature of this anomaly is that it is present even for the as-deposited microstructure, which has not been deliberately or otherwise tempered. The anomaly cannot therefore be attributed to easily observed secondary hardening effects, and indeed precipitates such a molybdenum carbides are not found to occur in the as-deposited state at the resolution of a conventional transmission electron microscope. An investigation has been carried out to study the possible existence of the early stages of precipitation/clustering of molybdenum atoms, using the atomic resolution method know as APFIM (Atom Probe Field Ion Microscopy). The results has given a strong indication that the anomalous strengthening in the as deposited welds is due to sub-microscopic effects, arising from the fine scale clustering of molybdenum atoms. This clustering appears to occur in the ferrite as the weld cools to ambient temperature after solidification. The effect is essentially secondary hardening, but at the very early stages. (author)

  16. Optimization of hardening/softening behavior of plane frame structures using nonlinear normal modes

    DEFF Research Database (Denmark)

    Dou, Suguang; Jensen, Jakob Søndergaard

    2016-01-01

    Devices that exploit essential nonlinear behavior such as hardening/softening and inter-modal coupling effects are increasingly used in engineering and fundamental studies. Based on nonlinear normal modes, we present a gradient-based structural optimization method for tailoring the hardening...... involving plane frame structures where the hardening/softening behavior is qualitatively and quantitatively tuned by simple changes in the geometry of the structures....

  17. Micromilling of hardened tool steel for mould making applications

    DEFF Research Database (Denmark)

    Bissacco, Giuliano; Hansen, Hans Nørgaard; De Chiffre, Leonardo

    2005-01-01

    geometries as those characterizing injection moulding moulds. The realization of the micromilling process in connection with hardened tool steel as workpiece material is particularly challenging. The low strength of the miniaturized end mills implies reduction and accurate control of the chip load which...... wear. This paper presents the micromilling process applied to the manufacturing of micro injection moulding moulds in hardened tool steel, presenting experimental evidence and possible solutions to the above-mentioned issues....

  18. High precipitation and seeded species competition reduce seeded shrub establishment during dryland restoration.

    Science.gov (United States)

    Rinella, Matthew J; Hammond, Darcy H; Bryant, Ana-Elisa M; Kozar, Brian J

    2015-06-01

    Drylands comprise 40% of Earth's land mass and are critical to food security, carbon sequestration, and threatened and endangered wildlife. Exotic weed invasions, overgrazing, energy extraction, and other factors have degraded many drylands, and this has placed an increased emphasis on dryland restoration. The increased restoration focus has generated a wealth of experience, innovations and empirical data, yet the goal of restoring diverse, native, dryland plant assemblages composed of grasses, forbs, and shrubs has generally proven beyond reach. Of particular concern are shrubs, which often fail to establish or establish at trivially low densities. We used data from two Great Plains, USA coal mines to explore factors regulating shrub establishment. Our predictor data related to weather and restoration (e.g., seed rates, rock cover) variables, and our response data described shrub abundances on fields of the mines. We found that seeded non-shrubs, especially grasses, formed an important competitive barrier to shrub establishment: With every one standard deviation increase in non-shrub seed rate, the probability shrubs were present decreased ~0.1 and shrub cover decreased ~35%. Since new fields were seeded almost every year for > 20 years, the data also provided a unique opportunity to explore effects of stochastic drivers (i.e., precipitation, year effects). With every one standard deviation increase in precipitation the first growing season following seeding, the probability shrubs were present decreased ~0.07 and shrub cover decreased ~47%. High precipitation appeared to harm shrubs by increasing grass growth/competition. Also, weak evidence suggested shrub establishment was better in rockier fields where grass abundance/competition was lower. Multiple lines of evidence suggest reducing grass seed rates below levels typically used in Great Plains restoration would benefit shrubs without substantially impacting grass stand development over the long term. We used

  19. Improved daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed

    International Nuclear Information System (INIS)

    Grimm, J.W.; Lynch, J.A.

    2005-01-01

    Daily precipitation nitrate and ammonium concentration models were developed for the Chesapeake Bay Watershed (USA) using a linear least-squares regression approach and precipitation chemistry data from 29 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. Only weekly samples that comprised a single precipitation event were used in model development. The most significant variables in both ammonium and nitrate models included: precipitation volume, the number of days since the last event, a measure of seasonality, latitude, and the proportion of land within 8 km covered by forest or devoted to industry and transportation. Additional variables included in the nitrate model were the proportion of land within 0.8 km covered by water and/or forest. Local and regional ammonia and nitrogen oxide emissions were not as well correlated as land cover. Modeled concentrations compared very well with event chemistry data collected at six NADP/AirMoN sites within the Chesapeake Bay Watershed. Wet deposition estimates were also consistent with observed deposition at selected sites. Accurately describing the spatial distribution of precipitation volume throughout the watershed is important in providing critical estimates of wet-fall deposition of ammonium and nitrate. - A linear least-squares regression approach was used to develop daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed

  20. Orowan strengthening and forest hardening superposition examined by dislocation dynamics simulations

    International Nuclear Information System (INIS)

    Queyreau, Sylvain; Monnet, Ghiath; Devincre, Benoit

    2010-01-01

    Rule of mixtures are an essential feature of the modeling of plastic deformation in complex materials in which more than one strain-hardening mechanism is involved. In this work, use is made of dislocation dynamics simulations to characterize the individual and the superposed contributions of two major mechanisms of crystal plasticity, i.e. Orowan strengthening and forest hardening. Based on a formal description of each hardening mechanism, evidence is presented to show that a quadratic rule of mixtures has the ability to predict quantitatively the flow stress of complex materials such as reactor pressure vessel steel.

  1. Water Resources Response to Climate and Land-Cover Changes in a Semi-Arid Watershed, New Mexico, USA

    Directory of Open Access Journals (Sweden)

    Joonghyeok Heo

    2015-01-01

    Full Text Available This research evaluates a climate-land cover-water resources interconnected system in a semi-arid watershed with minimal human impact from 1970 - 2009. We found _ increase in temperature and 10.9% decrease in precipitation. The temperature exhibited a lower increase trend and precipitation showed a similar decrease trend compared to previous studies. The dominant land-cover change trend was grass and forest conversion into bush/shrub and developed land and crop land into barren and grass land. These alterations indicate that changes in temperature and precipitation in the study area may be linked to changes in land cover, although human intervention is recognized as the major land-cover change contributor for the short term. These alterations also suggest that decreasing human activity in the study area leads to developed land and crop land conversion into barren and grass land. Hydrological responses to climate and land-cover changes for surface runoff, groundwater discharge, soil water content and evapotranspiration decreased by 10.2, 10.0, 4.1, and 10.5%, respectively. Hydrological parameters generally follow similar trends to that of precipitation in semi-arid watersheds with minimal human development. Soil water content is sensitive to land-cover change and offset relatively by the changes in precipitation.

  2. 75 FR 22469 - National Emission Standards for Hazardous Air Pollutants: Gold Mine Ore Processing and Production...

    Science.gov (United States)

    2010-04-28

    ... facilities use a different, zinc precipitate process, which is described later in this preamble. At all the... zinc powder (discussed below). Separation of gold through electrowinning is achieved by using an... poured into bars, and any flux slag that hardens on the bars is removed with a mechanical chipper. The...

  3. Strain hardening of aluminium alloy 3004 in the deep drawing and ironing processes

    International Nuclear Information System (INIS)

    Courbon, J.; Duval, J.L.

    1993-01-01

    The evolution of material hardening resulting from the canmaking operations on aluminium beverage cans has been investigated. Tensile tests in cup walls revealed that deep drawing induced softening in the hoop direction and hardening in the meridian direction. This anisotropy is retained in the ironing operation. Changes in strain path on a heavily cold-rolled material probably cause such a complex behaviour. To determine hardening laws for deep drawing, simple shear tests were thus performed because of the strain path similarity. They allowed to determine hardening laws over larger strains than tension could reach and revealed a saturation of stress. Altogether they proved adapted to the understanding of deep drawing. (orig.)

  4. Work hardening correlation for monotonic loading based on state variables

    International Nuclear Information System (INIS)

    Huang, F.H.; Li, C.Y.

    1977-01-01

    An absolute work hardening correlation in terms of the hardness parameter and the internal stress based on the state variable approach was developed. It was found applicable to a variety of metals and alloys. This correlation predicts strain rate insensitive work hardening properties at low homologous temperatures and produces strain rate effects at higher homologous temperatures without involving thermally induced recovery processes

  5. Induction hardening of tool steel for heavily loaded aircraft engine components

    Directory of Open Access Journals (Sweden)

    Rokicki P.

    2017-03-01

    Full Text Available Induction hardening is an innovative process allowing modification of the materials surface with more effective, cheaper and more reproducible way to compare with conventional hardening methods used in the aerospace industry. Unfortunately, high requirements and strict regulation concerning this branch of the industry force deep research allowing to obtain results that would be used for numerical modelling of the process. Only by this way one is able to start the industrial application of the process. The main scope of presented paper are results concerning investigation of microstructure evolution of tool steel after single-frequency induction hardening process. The specimens that aim in representing final industrial products (as heavily loaded gears, were heat- -treated with induction method and subjected to metallographic preparation, after which complex microstructure investigation was performed. The results obtained within the research will be a basis for numerical modelling of the process of induction hardening with potential to be introduced for the aviation industrial components.

  6. The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions

    International Nuclear Information System (INIS)

    Totik, Y.; Sadeler, R.; Altun, H.; Gavgali, M.

    2002-01-01

    Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy and X-ray diffraction. The wear tests using a pin-on-disc machine showed that the induction hardening treatments improved the wear behaviour of AISI 4140 steel specimens compared to normalised AISI 4140 steel as a result of residual stresses and hardened surfaces. The wear coefficients in normalised specimens are greater than that in the induction hardened samples. The lowest coefficient of the friction was obtained in specimens induction-hardened at 875 deg. C for 27 s

  7. The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions

    Energy Technology Data Exchange (ETDEWEB)

    Totik, Y.; Sadeler, R.; Altun, H.; Gavgali, M

    2002-02-15

    Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy and X-ray diffraction. The wear tests using a pin-on-disc machine showed that the induction hardening treatments improved the wear behaviour of AISI 4140 steel specimens compared to normalised AISI 4140 steel as a result of residual stresses and hardened surfaces. The wear coefficients in normalised specimens are greater than that in the induction hardened samples. The lowest coefficient of the friction was obtained in specimens induction-hardened at 875 deg. C for 27 s.

  8. Simulating the influence of scatter and beam hardening in dimensional computed tomography

    Science.gov (United States)

    Lifton, J. J.; Carmignato, S.

    2017-10-01

    Cone-beam x-ray computed tomography (XCT) is a radiographic scanning technique that allows the non-destructive dimensional measurement of an object’s internal and external features. XCT measurements are influenced by a number of different factors that are poorly understood. This work investigates how non-linear x-ray attenuation caused by beam hardening and scatter influences XCT-based dimensional measurements through the use of simulated data. For the measurement task considered, both scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, only beam hardening is found to influence dimensional measurements when evaluated using an advanced surface determination method. Based on the results presented, recommendations on the use of beam hardening and scatter correction for dimensional XCT are given.

  9. CLIMATIC CHARACTERISTICS OF TYPHOON PRECIPITATION OVER CHINA

    Institute of Scientific and Technical Information of China (English)

    WANG Yong-mei; REN Fu-min; LI Wei-jing; WANG Xiao-ling

    2008-01-01

    The spatio-temporal characteristics of typhoon precipitation over China are analyzed in this study. The results show that typhoon precipitation covers most of central-eastern China. Typhoon precipitation gradually decreases from the southeastern coastal regions to the northwestern mainland. The maximum annual typhoon precipitation exceeds 700 mm in central-eastern Taiwan and part of Hainan, while the minimum annual typhoon precipitation occurs in parts of Inner Mongolia, Shanxi, Shaanxi and Sichuan, with values less than 10 mm. Generally, typhoons produce precipitation over China during April - December with a peak in August. The annual typhoon precipitation time series for observation stations are examined for long-term trends. The results show that decreasing trends exist in most of the stations from 1957 to 2004 and are statistically significant in parts of Taiwan, Hainan, coastal Southeast China and southern Northeast China. The anomaly of typhoon precipitation mainly results from that of the general circulation over Asia and the Walker Cell circulation over the equatorial central and eastern Pacific. Typhoon torrential rain is one of the extreme rainfall events in the southeastern coastal regions and parts of central mainland. In these regions, torrential rains are mostly caused by typhoons.

  10. GRAVITY PIPELINE TRANSPORT FOR HARDENING FILLING MIXTURES

    Directory of Open Access Journals (Sweden)

    Leonid KROUPNIK

    2015-12-01

    Full Text Available In underground mining of solid minerals becoming increasingly common development system with stowing hardening mixtures. In this case the natural ore array after it is replaced by an artificial excavation of solidified filling mixture consisting of binder, aggregates and water. Such a mixture is prepared on the surface on special stowing complexes and transported underground at special stowing pipelines. However, it is transported to the horizons of a few kilometers, which requires a sustainable mode of motion of such a mixture in the pipeline. Hardening stowing mixture changes its rheological characteristics over time, which complicates the calculation of the parameters of pipeline transportation. The article suggests a method of determining the initial parameters of such mixtures: the status coefficient, indicator of transportability, coefficient of hydrodynamic resistance to motion of the mixture. These indicators characterize the mixture in terms of the possibility to transport it through pipes. On the basis of these indicators is proposed methodology for calculating the parameters of pipeline transport hardening filling mixtures in drift mode when traffic on the horizontal part of the mixture under pressure column of the mixture in the vertical part of the backfill of the pipeline. This technique allows stable operation is guaranteed to provide pipeline transportation.

  11. Effect of ethephon on hardening of Pachystroma longifolium seedlings

    Directory of Open Access Journals (Sweden)

    João Alexandre Lopes Dranski

    2013-06-01

    Full Text Available Immediately after planting, tree seedlings face adverse environmental and biotic stresses that must be overcome to ensure survival and to yield a desirable growth. Hardening practices in the nursery may help improve seedling stress resistance through reduction of aboveground plant tissues and increased root volume and biomass. We conducted an assay to quantify changes in the morphogenesis following application of ethephon on seedlings of Pachystroma longifolium (Ness I. M. Johnst.during hardening. The results showed no effect of the ethephon treatments on the number of leaves but a reduction of up to 50% in seedling height increment, and an increase in stem diameter increment of up to 44% with the 600 mg L-1 ethephon treatment, which consequently altered seedling Dickson Quality Index. Our results indicate that ethephon may help to promote desired morphological changes that occur during seedling hardening in nurseries.

  12. Designing of the chemical composition of steels basing on the hardenability of constructional steels

    International Nuclear Information System (INIS)

    Dobrzanski, L.A.; Sitek, W.

    2003-01-01

    The paper presents the original method of modelling of the relationships between chemical composition of alloy constructional steel and its hardenability, employing neural networks. Basing on the experimental results of the hardenability investigations, which employed Jominy method, the model of the neural networks was developed and fully verified experimentally. The model makes it possible to obtain Jominy hardenability curves basing on the steel chemical composition. The model of neural networks, making it possible to design the steel chemical composition, basing on the known Jominy hardenability curve shape, was developed also and fully verified numerically. (author)

  13. Improved daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed.

    Science.gov (United States)

    Grimm, J W; Lynch, J A

    2005-06-01

    Daily precipitation nitrate and ammonium concentration models were developed for the Chesapeake Bay Watershed (USA) using a linear least-squares regression approach and precipitation chemistry data from 29 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. Only weekly samples that comprised a single precipitation event were used in model development. The most significant variables in both ammonium and nitrate models included: precipitation volume, the number of days since the last event, a measure of seasonality, latitude, and the proportion of land within 8km covered by forest or devoted to industry and transportation. Additional variables included in the nitrate model were the proportion of land within 0.8km covered by water and/or forest. Local and regional ammonia and nitrogen oxide emissions were not as well correlated as land cover. Modeled concentrations compared very well with event chemistry data collected at six NADP/AirMoN sites within the Chesapeake Bay Watershed. Wet deposition estimates were also consistent with observed deposition at selected sites. Accurately describing the spatial distribution of precipitation volume throughout the watershed is important in providing critical estimates of wet-fall deposition of ammonium and nitrate.

  14. Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    G. Gao

    2017-09-01

    Full Text Available Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures since the 1950s aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield, and sediment concentration have all decreased considerably. Human-induced land use/cover change (LUCC was the dominant factor, contributing over 70 % of the sediment load reduction, whereas the contribution of precipitation was less than 30 %. In this study, we use 50-year time series data (1961–2011, showing decreasing trends in the annual sediment loads of 15 catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space–time variability of sediment yield was expressed notionally as a product of two factors representing (i the effect of precipitation and (ii the fraction of treated land surface area. Under minimal LUCC, the square root of annual sediment yield varied linearly with precipitation, with the precipitation–sediment load relationship showing coherent spatial patterns amongst the catchments. As the LUCC increased and took effect, the changes in sediment yield pattern depended more on engineering measures and vegetation restoration campaign, and the within-year rainfall patterns (especially storm events also played an important role. The effect of LUCC is expressed in terms of a sediment coefficient, i.e., the ratio of annual sediment yield to annual precipitation. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

  15. Effects of Cu and Ag additions on age-hardening behavior during multi-step aging in Al--Mg--Si alloys

    International Nuclear Information System (INIS)

    Kim, JaeHwang; Daniel Marioara, Calin; Holmestad, Randi; Kobayashi, Equo; Sato, Tatsuo

    2013-01-01

    Low Cu and Ag additions (≤0.10 at%) were found to strongly affect the age-hardening behavior in Al--Mg--Si alloys with Mg+Si>1.5 at%. The hardness increased during aging at 170 °C and the formation of β ″ precipitates was kinetically accelerated. The activation energy of the formation of the β ″ phase was calculated to 127, 105, 108 and 99 KJmol −1 in the base, Cu-added, Ag-added and Cu--Ag-added alloys, respectively using the Kissinger method. The negative effect of two-step aging caused by the formation of Cluster (1) during natural aging was not overcome by the addition of microalloying elements. However, it was suppressed by the formation of Cluster (2) through a pre-aging at 100 °C. Quantitative analysis of the precipitate microstructure was performed using a transmission electron microscope equipped with a parallel electron energy loss spectrometer for the determination of specimen thickness. The formation of Cluster (2) was found to increase the number density of β ″ precipitates, whereas the formation of Cluster (1) decreased the number density and increased the needle length. The effects of low Cu and Ag additions in combination with multi-step aging are discussed based on microstructure observations and hardness and resistivity measurements.

  16. Global Precipitation Climatology Project (GPCP) Climate Data Record (CDR), Version 2.3 (Monthly)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Global Precipitation Climatology Project (GPCP) consists of monthly satellite-gauge and associated precipitation error estimates and covers the period January...

  17. Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship.

    Science.gov (United States)

    Estiarte, Marc; Vicca, Sara; Peñuelas, Josep; Bahn, Michael; Beier, Claus; Emmett, Bridget A; Fay, Philip A; Hanson, Paul J; Hasibeder, Roland; Kigel, Jaime; Kröel-Dulay, Gyorgy; Larsen, Klaus Steenberg; Lellei-Kovács, Eszter; Limousin, Jean-Marc; Ogaya, Romà; Ourcival, Jean-Marc; Reinsch, Sabine; Sala, Osvaldo E; Schmidt, Inger Kappel; Sternberg, Marcelo; Tielbörger, Katja; Tietema, Albert; Janssens, Ivan A

    2016-07-01

    Well-defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with

  18. Effect of combined addition of N and Nb on the high temperature behavior of a 25Cr-20Ni stainless steel

    International Nuclear Information System (INIS)

    Park, In Duck; Nam, Ki Woo

    2002-01-01

    In order to clarify the effect of precipitates on creep strength at high temperature in 25Cr-20Ni stainless steels, threshold stress and void-hardening stress have been measured and compared each others. The value of threshold stress for high temperature, measured by stress abruptly loading test, is about 130 MPa. Threshold stress must be measured by the function of stress loading time in the combination hardening steel of solution hardening and precipitate hardening. Average diameter and inter-partial distance of precipitates from TEM microstructure can determine void-hardening stress. The value of void-hardening stress, evaluated by using Scattergood and Bacon's equation, was from 101 to 130 MPa. The ratio of average void hardening to threshold stress is 1.13 and both values are not equal. The result from analyzing the electron diffraction pattern shows that the dispersed precipitates in SUS310J1TB is NbCrN nitrides. Mechanism of the interaction between dislocations and precipitate particles in SUS310J1TB is Srolovitz mechanism, which is a gravitation-type interaction

  19. The capability of pulsed laser radiation for cutting band saws hardening

    Directory of Open Access Journals (Sweden)

    Marinin Evgeny

    2017-01-01

    Full Text Available The article deals with the possibilities of pulsed laser radiation for hardening the band saws. The regimes of pulsed laser hardening the band saws of 1 mm thick made of tool steel 9CrV are grounded theoretically and experimentally tested. Selected and justified modes of treatment harden in the autohardening mode without additional heat removal. The results of the experimental research of microhardness are presented and formed as a result of processing of the microstructure. Selected modes increase the microhardness of the surface to 8500 MPa and form ultra highly dispersed structure in the surface layer characterized by high resistance to abrasion.

  20. EFFECT OF HARDENER ON MECHANICAL PROPERTIES OF CARBON FIBRE REINFORCED PHENOLIC RESIN COMPOSITES

    Directory of Open Access Journals (Sweden)

    S. SULAIMAN

    2008-04-01

    Full Text Available In this paper the effect of hardener on mechanical properties of carbon reinforced phenolic resin composites is investigated. Carbon fibre is one of the most useful reinforcement materials in composites, its major use being the manufacture of components in the aerospace, automotive, and leisure industries. In this study, carbon fibres are hot pressed with phenolic resin with various percentages of carbon fibre and hardener contents that range from 5-15%. Composites with 15% hardener content show an increase in flexural strength, tensile strength and hardness. The ultimate tensile strength (UTS, flexural strength and hardness for 15% hardener are 411.9 MPa, 51.7 MPa and 85.4 HRR respectively.

  1. MODELING PRECIPITATION DEPENDENT FOREST RESILIENCE IN INDIA

    Directory of Open Access Journals (Sweden)

    P. Das

    2018-04-01

    Full Text Available The impact of long term climate change that imparts stress on forest could be perceived by studying the regime shift of forest ecosystem. With the change of significant precipitation, forest may go through density change around globe at different spatial and temporal scale. The 100 class high resolution (60 meter spatial resolution Indian vegetation type map was used in this study recoded into four broad categories depending on phrenology as (i forest, (ii scrubland, (iii grassland and (iv treeless area. The percentage occupancy of forest, scrub, grass and treeless were observed as 19.9 %, 5.05 %, 1.89 % and 7.79 % respectively. Rest of the 65.37 % land area was occupied by the cropland, built-up, water body and snow covers. The majority forest cover were appended into a 5 km × 5 km grid, along with the mean annual precipitation taken from Bioclim data. The binary presence and absence of different vegetation categories in relates to the annual precipitation was analyzed to calculate their resilience expressed in probability values ranging from 0 to 1. Forest cover observed having resilience probability (Pr < 0.3 in only 0.3 % (200 km2 of total forest cover in India, which was 4.3 % < 0.5 Pr. Majority of the scrubs and grass (64.92 % Pr < 0.5 from North East India which were the shifting cultivation lands showing low resilience, having their high tendency to be transform to forest. These results have spatial explicitness to highlight the resilient and non-resilient distribution of forest, scrub and grass, and treeless areas in India.

  2. Radiation hardening and embrittlement of some refractory metals and alloys

    International Nuclear Information System (INIS)

    Fabritsiev, S.; Pokrovskyb

    2007-01-01

    Tungsten is proposed for application in the ITER divertor and limiter as plasma facing material. The tungsten operation temperature in the ITER divertor is relatively high. Hence, the ductile properties of tungsten will be controlled by the low temperature radiation embrittlement. The mechanism of radiation hardening and embrittlement under neutron irradiation at low temperature is well studied for FCC metals, in particular for copper. At the same time, low-temperature radiation hardening of BCC materials, in particular for refractory metals, is less studied. This study presents the results of investigation into radiation hardening and embrittlement of pure metals: W, Mo and Nb, and W-Re and Ta-4W alloys. The materials were in the annealed conditions. The specimens were irradiated in the SM-2 reactor to doses of 10 -4 -10 -1 dpa at 80 C and then tested for tension at 80 C. The study of the stress-strain curves of unirradiated specimens revealed a yield drop for W, Mo, Nb, Ta-4W, W-Re. After the yield drop some metals (Mo,Nb) retain their capability for strain hardening and demonstrate a high elongation (20-50%). Radiation hardening is maximum in Mo (∝400MPa) and minimum in Nb (∝100 MPa). In this case the dependence slope for Nb is similar to that for pure copper irradiated in SM-2 under the same conditions. Ii and Ta-4W have a higher slope. Measurement of electrical resistivity of irradiated specimens showed that for all materials it is increased monotonously with an increase in the irradiation dose. A minimum gain in electrical resistivity with a dose was observed for Nb (∝3% at 0.1 dpa). As for Mo it was essentially higher, i.e. ∝ 30%. The gain was maximum for W-Re alloy. Comparison of radiation hardening dose dependencies obtained in this study with the data for FCC metals (Cu) showed that in spite of the quantitative difference the qualitative behavior of these two classes of metals is similar. (orig.)

  3. Effect of bainitic transformation on bake hardening in TRIP assisted steel

    International Nuclear Information System (INIS)

    Das, S.; Timokhina, I.; Singh, S.B.; Pereloma, E.; Mohanty, O.N.

    2012-01-01

    Highlights: ► Bainitic transformation in TRIP-assisted steel can lead to a very good bake hardening response as demonstrated by other researchers also. ► No extra deformation is needed. Dislocations can be generated in situ during the transformation itself. ► Detail characterisation and theoretical treatments showed bainite plates are sufficiently enriched with extra carbon atoms which can migrate and lock the dislocations. - Abstract: Bake hardening is a phenomenon where freshly generated dislocations get pinned down by the migrating carbon atoms under the influence of temperature employed in paint baking shop. Experimentally, a minimal 2% deformation is given to generate such new dislocations. On the other hand, after bainitic transformation, steel contains a large number of dislocations as well as excess carbon atoms in bainite, a combination of which is capable of producing bake hardening effect. In the current analysis, one grade of transformation induced plasticity aided steel was chosen to study the effect of isothermal bainitic transformation on subsequent bake hardening response, without giving any deformation assuming that the previous treatment would have generated sufficient dislocations which could be pinned down by the migrating carbon atoms under the influence of thermal treatment of the bake hardening process. The final microstructure was characterised by many techniques, using Thermo-Calc, optical microscopy, XRD analysis and 3-DAP. A good agreement was observed amongst all the techniques employed.

  4. Two Back Stress Hardening Models in Rate Independent Rigid Plastic Deformation

    Science.gov (United States)

    Yun, Su-Jin

    In the present work, the constitutive relations based on the combination of two back stresses are developed using the Armstrong-Frederick, Phillips and Ziegler’s type hardening rules. Various evolutions of the kinematic hardening parameter can be obtained by means of a simple combination of back stress rate using the rule of mixtures. Thus, a wide range of plastic deformation behavior can be depicted depending on the dominant back stress evolution. The ultimate back stress is also determined for the present combined kinematic hardening models. Since a kinematic hardening rule is assumed in the finite deformation regime, the stress rate is co-rotated with respect to the spin of substructure obtained by incorporating the plastic spin concept. A comparison of the various co-rotational rates is also included. Assuming rigid plasticity, the continuum body consists of the elastic deformation zone and the plastic deformation zone to form a hybrid finite element formulation. Then, the plastic deformation behavior is investigated under various loading conditions with an assumption of the J2 deformation theory. The plastic deformation localization turns out to be strongly dependent on the description of back stress evolution and its associated hardening parameters. The analysis for the shear deformation with fixed boundaries is carried out to examine the deformation localization behavior and the evolution of state variables.

  5. Regionalization of precipitation characteristics in Iran's Lake Urmia basin

    Science.gov (United States)

    Fazel, Nasim; Berndtsson, Ronny; Uvo, Cintia Bertacchi; Madani, Kaveh; Kløve, Bjørn

    2018-04-01

    Lake Urmia in northwest Iran, once one of the largest hypersaline lakes in the world, has shrunk by almost 90% in area and 80% in volume during the last four decades. To improve the understanding of regional differences in water availability throughout the region and to refine the existing information on precipitation variability, this study investigated the spatial pattern of precipitation for the Lake Urmia basin. Daily rainfall time series from 122 precipitation stations with different record lengths were used to extract 15 statistical descriptors comprising 25th percentile, 75th percentile, and coefficient of variation for annual and seasonal total precipitation. Principal component analysis in association with cluster analysis identified three main homogeneous precipitation groups in the lake basin. The first sub-region (group 1) includes stations located in the center and southeast; the second sub-region (group 2) covers mostly northern and northeastern part of the basin, and the third sub-region (group 3) covers the western and southern edges of the basin. Results of principal component (PC) and clustering analyses showed that seasonal precipitation variation is the most important feature controlling the spatial pattern of precipitation in the lake basin. The 25th and 75th percentiles of winter and autumn are the most important variables controlling the spatial pattern of the first rotated principal component explaining about 32% of the total variance. Summer and spring precipitation variations are the most important variables in the second and third rotated principal components, respectively. Seasonal variation in precipitation amount and seasonality are explained by topography and influenced by the lake and westerly winds that are related to the strength of the North Atlantic Oscillation. Despite using incomplete time series with different lengths, the identified sub-regions are physically meaningful.

  6. Branching structure and strain hardening of branched metallocene polyethylenes

    International Nuclear Information System (INIS)

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M.

    2015-01-01

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers

  7. Branching structure and strain hardening of branched metallocene polyethylenes

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M., E-mail: john.dealy@mcgill.ca [Department of Chemical Engineering, McGill University, Montreal, Quebec H3A 0C4 (Canada)

    2015-09-15

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers.

  8. Strengthening effect of nano-scale precipitates in a die-cast Mg–4Al–5.6Sm–0.3Mn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qiang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Bu, Fanqiang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Qiu, Xin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Yangzhou Hongfu Aluminium Co. Ltd, Yangzhou 100049 (China); Li, Yangde; Li, Weirong [E-ande Scientific & Technology Co. Ltd, Dongguan 523000 (China); Sun, Wei [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Liu, Xiaojuan, E-mail: lxjuan@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng, Jian, E-mail: jmeng@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2016-04-25

    In this paper we report a quantitative study of the age-hardening in the high-pressure die-cast Mg–4Al−5.6Sm−0.3Mn alloy. The results indicate that a number of nano-scale spherical precipitates identified as Al{sub 3}Sm using high-angle annular dark-field scanning transmission electron microscopy, precipitated in Mg matrix after aging at 150–225 °C, with no obvious changes on grain sizes, intermetallic phases formed during solidification, and dislocation densities. From the existing strengthening theory equations in which some lacking parameters were taken from the first-principles density functional theory (DFT) calculations, a quantitative insight into the strengthening mechanisms of the nano-scale precipitate was formulated. The results are in reasonable agreement with the experimental values, and the operative mechanism of precipitation strengthening was revealed as Orowan dislocation bypassing. - Highlights: • The yield strength of Mg–Al–Sm alloy was improved by aging treatment. • A number of nano-scale precipitates formed in matrix after aging treatments. • The nanoscale precipitate was confirmed as Al{sub 3}Sm based on the data of HAADF-STEM study. • The strengthening mechanisms of the nano-scale precipitate were quantitatively formulated. • The operative mechanism of precipitate strengthening is Orowan dislocation bypassing.

  9. Precipitation structures and mechanical properties of Al-Li-Zr alloy containing V

    International Nuclear Information System (INIS)

    Ying, J.K.; Ohashi, T.

    1999-01-01

    It is known that Al-Li alloys possess high elastic modulus and low density, and the metastable δ' (Al 3 Li) precipitate in these alloys affords considerable strengthening effect. However, with the strengthening resulting from the precipitation of δ' which is coherent with the matrix, these alloys suffer from low ductility and fracture toughness. It seems that the loss of ductility is the slip localization which occurs as a result of slip planes during deformation in connection with the specific hardening mechanism. As a result it indicates typical intergranular fracture. On the one hand, zirconium is used in many aluminum alloys to inhibit recrystallization during alloy processing. When zirconium is present in the alloy grain refinement occurs, which consequently, is considered as a factor that reduces the slip distance, and lowers the stress concentration across grain boundaries and at grain boundary triple points. Nevertheless, if only zirconium is added in Al-Li alloy it still shows intergranular fracture. By Zedaris et al., equilibrium phase Al 3 (Zr,V) in Al-Zr alloy containing V reduces the lattice mismatch along the c-axis with Al and, the L1 2 -structure metastable precipitates Al 3 (Zr,V) in Al-Zr-V alloys are stable at elevated temperature. Therefore, it is interesting to elucidate the effect of V in Al-Li-Zr alloy at the precipitation structures and mechanical properties of these alloys

  10. Elasto-plastic hardening models adjustment to ferritic, austenitic and austenoferritic Rebar

    International Nuclear Information System (INIS)

    Hortigóna, B.; Gallardo, J.M.; Nieto-García, E.J.; López, J.A.

    2017-01-01

    The elastoplastic behaviour of steel used for structural member fabrication has received attention to facilitate a mechanical-resistant design. New Zealand and South African standards have adopted various theoretical approaches to describe such behaviour in stainless steels. With respect to the building industry, describing the tensile behaviour of steel rebar used to produce reinforced concrete structures is of interest. Differences compared with the homogenous material described in the above mentioned standards and related literatures are discussed in this paper. Specifically, the presence of ribs and the TEMPCORE® technology used to produce carbon steel rebar may alter the elastoplastic model. Carbon steel rebar is shown to fit a Hollomon model giving hardening exponent values on the order of 0.17. Austenitic stainless steel rebar behaviour is better described using a modified Rasmussen model with a free fitted exponent of 6. Duplex stainless steel shows a poor fit to any previous model. [es

  11. THE DEVELOPMENT OF TECHNOLOGY OF THE CORE THERMO-MECHANICALLY HARDENED REINFORC-ING STEEL OF GRADE A700HW OF DIE-ROLLED SECTION NO 12, 14, 16 PRODUCTION ACCORDING TO REQUIREMENT OF FINNISH STANDARDS SFST1216 IN CONDITIONS OF SMALL-SECTION MILL 320 OF RUP «BMZ»

    Directory of Open Access Journals (Sweden)

    A. V. Rusalenko

    2009-01-01

    Full Text Available The development of technology of the core thermomechanically hardened reinforcing steel of grade А700HW of die-rolled section No 12, 14, 16 production according to requirement of Finnish standards SFST1216 in conditions of small-section mill 320 of RUP «BMZ» is given.

  12. Influence of cyclic temperature changes on the microstructure of AISI 4140 after laser surface hardening

    International Nuclear Information System (INIS)

    Miokovic, T.; Schulze, V.; Voehringer, O.; Loehe, D.

    2007-01-01

    In recent years laser surface hardening using pulsed laser sources has become an increasingly established technology in engineering industry and has opened up wider possibilities for the application of selective surface hardening. However, the choice of the process parameters is generally based on experience rather than on their empirical influence on the resulting microstructure, and for hardening processes with cyclic temperature changes, almost no correlations between process parameters and hardening results are known. Therefore, some problems regarding the choice of the process parameters and their influence on the resulting microstructure still remain. In particular, there is a lack of data concerning the effect of cyclic temperature changes on hardening. To facilitate process optimization, this paper deals with a detailed characterization of the microstructures created in quenched and tempered AISI 4140 (German grade 42CrMo4) steel following a temperature-dependent laser surface hardening treatment. The structure properties were obtained from microhardness measurements, scanning electron microscopy investigations and X-ray diffraction analysis of retained austenite

  13. Influence of cyclic temperature changes on the microstructure of AISI 4140 after laser surface hardening

    Energy Technology Data Exchange (ETDEWEB)

    Miokovic, T. [Institute of Materials Science and Engineering I, University of Karlsruhe, 76131 Karlsruhe (Germany); Schulze, V. [Institute of Materials Science and Engineering I, University of Karlsruhe, 76131 Karlsruhe (Germany)]. E-mail: volker.schulze@mach.uni-karlsruhe.de; Voehringer, O. [Institute of Materials Science and Engineering I, University of Karlsruhe, 76131 Karlsruhe (Germany); Loehe, D. [Institute of Materials Science and Engineering I, University of Karlsruhe, 76131 Karlsruhe (Germany)

    2007-01-15

    In recent years laser surface hardening using pulsed laser sources has become an increasingly established technology in engineering industry and has opened up wider possibilities for the application of selective surface hardening. However, the choice of the process parameters is generally based on experience rather than on their empirical influence on the resulting microstructure, and for hardening processes with cyclic temperature changes, almost no correlations between process parameters and hardening results are known. Therefore, some problems regarding the choice of the process parameters and their influence on the resulting microstructure still remain. In particular, there is a lack of data concerning the effect of cyclic temperature changes on hardening. To facilitate process optimization, this paper deals with a detailed characterization of the microstructures created in quenched and tempered AISI 4140 (German grade 42CrMo4) steel following a temperature-dependent laser surface hardening treatment. The structure properties were obtained from microhardness measurements, scanning electron microscopy investigations and X-ray diffraction analysis of retained austenite.

  14. The surface fatigue life of contour induction hardened AISI 1552 gears

    Science.gov (United States)

    Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

    1995-07-01

    Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

  15. Precipitation Indices Low Countries

    Science.gov (United States)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  16. Radiation hardening coating material

    International Nuclear Information System (INIS)

    McDonald, W.H.; Prucnal, P.J.; DeMajistre, Robert.

    1977-01-01

    This invention concerns a radiation hardening coating material. First a resin is prepared by reaction of bisphenol diglycidylic ether with acrylic or methacrylic acids. Then the reactive solvent is prepared by reaction of acrylic or methacrylic acids with epichlorhydrine or epibromhydrine. Then a solution consisting of the resin dissolved in the reactive solvent is prepared. A substrate (wood, paper, polyesters, polyamines etc.) is coated with this composition and exposed to ionizing radiations (electron beams) or ultraviolet radiations [fr

  17. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    La Cruz, P. de.

    1990-01-01

    In the present work the effect of ion nitriding, laser hardening and hot dip galvanizing upon the fatigue limit and notch sensitivity of a B-Mn Swedish steel SS 2131 have been investigated. The fatigue tests were performed in plane reverse bending fatigue (R=1). The quenched and tempered condition was taken as the reference condition. The microstructure, microhardness, fracture surface and coating appearance of the fatigue surface treated specimens were studied. Residual stress and retained austenite measurements were also carried out. It was found that ion nitriding improves the fatigue limit by 53 % for smooth specimens and by 115 % for notched specimens. Laser hardening improves the fatigue limit by 18 % and 56 % for smooth and notched specimen respectively. Hot dip galvanizing gives a slight deterioration of the fatigue limit (9 % and 10 % for smooth and notched specimen respectively). Ion nitriding and laser hardening decrease the value of the notch sensitivity factor q by 78 % and 65 % respectively. Hot dip galvanizing does not modify it. A simple schematic model based on a residual stress distribution, has been used to explain the different effects. It seems that the presence of the higher compressive residual stresses and the higher uniformity of the microstructure may be the causes of the better fatigue performance of ion nitrided specimens. (119 refs.) (author)

  18. Effect of ferrite-martensite interface morphology on bake hardening response of DP590 steel

    International Nuclear Information System (INIS)

    Chakraborty, Arnab; Adhikary, Manashi; Venugopalan, T.; Singh, Virender; Nanda, Tarun; Kumar, B. Ravi

    2016-01-01

    The effect of martensite spatial distribution and its interface morphology on the bake hardening characteristics of a dual phase steel was investigated. In one case, typical industrial continuous annealing line parameters were employed to anneal a 67% cold rolled steel to obtain a dual phase microstructure. In the other case, a modified annealing process with changed initial heating rates and peak annealing temperature was employed. The processed specimens were further tensile pre-strained within 1–5% strain range followed by a bake hardening treatment at 170 °C for 20 min. It was observed that industrial continuous annealing line processed specimen showed a peak of about 70 MPa in bake-hardening index at 2% pre-strain level. At higher pre-strain values a gradual drop in bake-hardening index was observed. On the contrary, modified annealing process showed near uniform bake-hardening response at all pre-strain levels and a decrease could be noted only above 4% pre-strain. The evolving microstructure at each stage of annealing process and after bake-hardening treatment was studied using field emission scanning electron microscope. The microstructure analysis distinctly revealed differences in martensite spatial distribution and interface morphologies between each annealing processes employed. The modified process showed predominant formation of martensite within the ferrite grains with serrated lath martensite interfaces. This nature of the martensite was considered responsible for the observed improvement in the bake-hardening response. Furthermore, along with improved bake-hardening response negligible loss in tensile ductility was also noted. This behaviour was correlated with delayed micro-crack initiation at martensite interface due to serrated nature.

  19. Precipitation Strengthening by Induction Treatment in High Strength Low Carbon Microalloyed Hot-Rolled Plates

    Science.gov (United States)

    Larzabal, G.; Isasti, N.; Rodriguez-Ibabe, J. M.; Uranga, P.

    2018-03-01

    The use of microalloyed steels in the production of thick plates is expanding due to the possibility of achieving attractive combinations of strength and toughness. As market requirements for high strength plates are increasing and new applications require reduced weight and innovative designs, novel approaches to attaining cost-effective grades are being developed. The mechanism of precipitation strengthening has been widely used in thin strip products, since the optimization of the coiling strategy offers interesting combinations in terms of final properties and microalloying additions. Precipitation strengthening in thick plates, however, is less widespread due to the limitation of interphase precipitation during continuous cooling after hot rolling. With the main objective of exploring the limits of this strengthening mechanism, laboratory thermomechanical simulations that reproduced plate hot rolling mill conditions were performed using low carbon steels microalloyed with Nb, NbMo, and TiMo additions. After continuous cooling to room temperature, a set of heat treatments using fast heating rates were applied simulating the conditions of induction heat treatments. An important increase of both yield and tensile strengths was measured after induction treatment without any important impairment in toughness properties. A significant precipitation hardening is observed in Mo-containing grades under specific heat treatment parameters.

  20. THE MECHANISM OF HARDENING OF ALLOYED STEELS IN IMPULSE MAGNETIC FIELD

    Directory of Open Access Journals (Sweden)

    A. V. Alifanov

    2012-01-01

    Full Text Available In this paper, a model describing the mechanism of hardening steels in a pulsed magnetic field is provided. The model is based on the consideration of induction currents in the grain bulk ferrite, on the surface of the workpiece near the inductor. The influence of doping efficiency of the process of hardening is established.

  1. A unified theoretical and experimental study of anisotropic hardening

    International Nuclear Information System (INIS)

    Boehler, J.P.; Raclin, J.

    1981-01-01

    The purpose of this work is to develop a consistent formulation of the constitutive relations regarding anisotropic hardening materials. Attention is focused on the appearance and the evolution of mechanical anisotropies during irreversible processes, such as plastic forming and inelastic deformation of structures. The representation theorems for anisotropic tensor functions constitute a theoretical basis, allowing to reduce arbitrariness and to obtain a unified formulation of anisotropic hardening. In this approach, a general three-dimensional constitutive law is developed for prestrained initially orthotropic materials. Introduction of the plastic behavior results in the general forms of both the flow-law and the yield criterion. The developed theory is then specialized for the case of plane stress and different modes of anisotropic hardening are analyzed. A new generalization of the Von Mises criterion is proposed, in considering a homogeneous form of order two in stress and employing the simplest combinations of the basic invariants entering the general form of the yield condition. The proposed criterion involves specific terms accounting for the initial anisotropy, the deformation induced anisotropy and correlative terms between initial and induced anisotropy. The effects of prestrainings result in both isotropic and anisotropic hardening. An adequate experimental program, consisting of uniaxial tensile tests on oriented specimens of prestrained sheet-metal, was performed, in order to determine the specific form and the evolution of the anisotropic failure criterion for soft-steel subjected to different irreversible prestrainings. (orig.)

  2. Tem Observation Of Precipitate Structures In Al-Zn-Mg Alloys With Additions Of Cu/Ag

    Directory of Open Access Journals (Sweden)

    Watanabe K.

    2015-06-01

    Full Text Available Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg alloy, were prepared to compare the effect of the additional elements on the aging behavior. The content of Ag and Cu were 0.2at.% and the same as, respectively. Ag or Cu added alloy showed higher maximum hardness than base alloy. The particle shape and rod shape precipitates were observed in all alloys peak-aged at 423K. According to addition of Ag or Cu, the number density of the precipitates increased higher than that of base alloy.

  3. Influence of coolant motion on structure of hardened steel element

    Directory of Open Access Journals (Sweden)

    A. Kulawik

    2008-08-01

    Full Text Available Presented paper is focused on volumetric hardening process using liquid low melting point metal as a coolant. Effect of convective motion of the coolant on material structure after hardening is investigated. Comparison with results obtained for model neglecting motion of liquid is executed. Mathematical and numerical model based on Finite Element Metod is described. Characteristic Based Split (CBS method is used to uncouple velocities and pressure and finally to solve Navier-Stokes equation. Petrov-Galerkin formulation is employed to stabilize convective term in heat transport equation. Phase transformations model is created on the basis of Johnson-Mehl and Avrami laws. Continuous cooling diagram (CTPc for C45 steel is exploited in presented model of phase transformations. Temporary temperatures, phases participation, thermal and structural strains in hardening element and coolant velocities are shown and discussed.

  4. Structural characterisation of oxygen diffusion hardened alpha-tantalum PVD-coatings on titanium.

    Science.gov (United States)

    Hertl, C; Koll, L; Schmitz, T; Werner, E; Gbureck, U

    2014-08-01

    Titanium substrates were coated with tantalum layers of 5 μm thickness using physical vapour deposition (PVD). The tantalum layers showed a (110)-preferred orientation. The coated samples were hardened by oxygen diffusion. Using X-ray diffraction the crystallographic structure of the tantalum coatings was characterised, comparing untreated and diffusion hardened specimen conditions. Oxygen depth profiles were determined by glow discharge spectrometry. The hardening effect of the heat treatment was examined by Vickers microhardness testing. The increase of surface hardness caused by oxygen diffusion was at least 50%. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. On the Spectral Hardening at gsim300 keV in Solar Flares

    Science.gov (United States)

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-05-01

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.

  6. Effects of solute elements on hardening of thermally-aged RPV model alloys

    International Nuclear Information System (INIS)

    Dohi, Kenji; Nishida, Kenji; Nomoto, Akiyoshi; Soneda, Naoki; Liu, Li; Sekimura, Naoto; Li Zhengcao

    2012-01-01

    The investigation of effects of solute elements on the copper-enriched cluster, which is a cause of radiation embrittlement of reactor pressure vessel steels, is needed in order to understand the mechanism of the hardening and the cluster formation. The dependence of the hardness change and the formation of thermally-aged Fe-Cu model alloys doped Ni, Si and Mn on aging time are investigated using Vickers harness tester and three dimensional atom probe. Ni addition suppresses hardening, and Si addition accelerates hardening slightly at the initial stage of the aging. Mn addition accelerates hardening much more but does not almost affect the peak hardness. Ni and Si addition increase the number density and the size of the cluster, while Mn addition remarkably increases the number density and the size of the cluster at the initial stage of the aging. In addition, there is no clear correlation between the square root of the volume fraction of the clusters and the hardness change for all of the alloys. The reasons are considered to be the decrease in the solute hardening caused by the cluster formation and the difference in the shear modulus of the cluster due to the difference in the chemical composition of the cluster. (author)

  7. Effect of bainitic transformation on bake hardening in TRIP assisted steel

    Energy Technology Data Exchange (ETDEWEB)

    Das, S., E-mail: sourav.das@tatasteel.com [Research and Development, Tata Steel Limited, Jamshedpur (India); Timokhina, I. [Centre for Material and Fibre Innovation/Science and Technology, Deakin University (Australia); Singh, S.B. [Metallurgical and Materials Engineering, IIT Kharagpur (India); Pereloma, E. [BlueScope Steel Metallurgy Centre, University of Wollongong (Australia); Mohanty, O.N. [RSB Metaltech, RSB Group, Jamshedpur (India)

    2012-02-01

    Highlights: Black-Right-Pointing-Pointer Bainitic transformation in TRIP-assisted steel can lead to a very good bake hardening response as demonstrated by other researchers also. Black-Right-Pointing-Pointer No extra deformation is needed. Dislocations can be generated in situ during the transformation itself. Black-Right-Pointing-Pointer Detail characterisation and theoretical treatments showed bainite plates are sufficiently enriched with extra carbon atoms which can migrate and lock the dislocations. - Abstract: Bake hardening is a phenomenon where freshly generated dislocations get pinned down by the migrating carbon atoms under the influence of temperature employed in paint baking shop. Experimentally, a minimal 2% deformation is given to generate such new dislocations. On the other hand, after bainitic transformation, steel contains a large number of dislocations as well as excess carbon atoms in bainite, a combination of which is capable of producing bake hardening effect. In the current analysis, one grade of transformation induced plasticity aided steel was chosen to study the effect of isothermal bainitic transformation on subsequent bake hardening response, without giving any deformation assuming that the previous treatment would have generated sufficient dislocations which could be pinned down by the migrating carbon atoms under the influence of thermal treatment of the bake hardening process. The final microstructure was characterised by many techniques, using Thermo-Calc, optical microscopy, XRD analysis and 3-DAP. A good agreement was observed amongst all the techniques employed.

  8. Exploration of a radiation hardening stabilized voltage power supply

    International Nuclear Information System (INIS)

    Xie Zeyuan; Xu Xianguo

    2014-01-01

    This paper mainly introduces the design method of radiation hardening stabilized voltage power supply that makes use of commercial radiation resistant electronic devices and the test results of radiation performance of the power supply and devices are presented in detail. The experiment results show that the hardened power supply can normally work until 1000 Gy (Si) total dose and 1 × 10 14 n/cm 2 neutron radiation, and it doesn't latchup at about 1 × l0 9 Gy (Si)/s gamma transient dose rate. (authors)

  9. Hardening and softening analysis of pure titanium based on the dislocation density during torsion deformation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Han; Li, Fuguo, E-mail: fuguolx@nwpu.edu.cn; Li, Jinghui; Ma, Xinkai; Li, Jiang; Wan, Qiong

    2016-08-01

    The hardening and softening phenomena during torsion deformation are studied based on the Taylor dislocation model for pure titanium. The hardening and softening phenomena are observed through the hardness analysis during micro-indentation test and micro-hardness test. Besides, the variations of indentation size also verify the existence of hardening and softening phenomena during torsion. The variations of geometric necessary dislocations (GNDs) and statistic store dislocations (SSDs) state that the positions of high dislocation density and low dislocation density correspond to the positions of hardening and softening. The results from the microstructure, grain boundaries evolution and twins analysis indicate the twins play an important role in appearance of hardening and softening phenomena. The appearance of hardening and softening phenomena are attributed to the combination of different slip systems and twinning systems combining with the Schmid Factor (SF) analysis and the transmission electron microscope (TEM). The appearance of hardening and softening phenomena can be explained by the Taylor dislocation theory based on TEM analysis. - Highlights: • The phenomena can be characterized by Taylor dislocation model. • The variation of GNDs leads to the phenomena. • The phenomena are proved by micro-hardness, indentation hardness. • The {10-12} twin and {11-24} twin play an important role in the phenomena.

  10. The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

    Directory of Open Access Journals (Sweden)

    F. S. E. Vamborg

    2011-02-01

    Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr−1 for the pre-industrial simulation and by about 80 mm yr−1 for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

  11. Beam-hardening correction in CT based on basis image and TV model

    International Nuclear Information System (INIS)

    Li Qingliang; Yan Bin; Li Lei; Sun Hongsheng; Zhang Feng

    2012-01-01

    In X-ray computed tomography, the beam hardening leads to artifacts and reduces the image quality. It analyzes how beam hardening influences on original projection. According, it puts forward a kind of new beam-hardening correction method based on the basis images and TV model. Firstly, according to physical characteristics of the beam hardening an preliminary correction model with adjustable parameters is set up. Secondly, using different parameters, original projections are operated by the correction model. Thirdly, the projections are reconstructed to obtain a series of basis images. Finally, the linear combination of basis images is the final reconstruction image. Here, with total variation for the final reconstruction image as the cost function, the linear combination coefficients for the basis images are determined according to iterative method. To verify the effectiveness of the proposed method, the experiments are carried out on real phantom and industrial part. The results show that the algorithm significantly inhibits cup and strip artifacts in CT image. (authors)

  12. Literature survey on phase composition of hardened cement paste containing fly ash

    International Nuclear Information System (INIS)

    Otsuka, Taku; Yamamoto, Takeshi

    2015-01-01

    The purpose of this literature survey is to collect the knowledge on the effect of fly ash in hardened cement paste and the information about evaluation of physicochemical performance based on phase composition of hardened cement paste. The performance of hardened cement paste containing fly ash is affected by the property of fly ash, hydration of cement and pozzolanic reaction of fly ash. Some properties of fly ash such as density and chemical composition are reflected in phase composition, showing the progress of cement hydration and pozzolanic reaction. Therefore clarification of the relationship of phase composition and performance will lead to appropriate evaluation of the property of fly ash. The amount of pore, chemical shrinkage, pore solution, compressive strength, Young modulus and alkali silica reaction have relations to the phase composition of hardened cement paste. It is considered as future subject to clarify the relationship of phase composition and performance for various properties of fly ash. (author)

  13. 40 CFR 434.63 - Effluent limitations for precipitation events.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Effluent limitations for precipitation... SOURCE PERFORMANCE STANDARDS Miscellaneous Provisions § 434.63 Effluent limitations for precipitation... discharge or increase in the volume of a discharge caused by precipitation within any 24 hour period less...

  14. RHOBOT: Radiation hardened robotics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, P.C.; Posey, L.D. [Sandia National Labs., Albuquerque, NM (United States)

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  15. RHOBOT: Radiation hardened robotics

    International Nuclear Information System (INIS)

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program

  16. Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

    Science.gov (United States)

    Li, H.; Liu, Y. H.

    2008-11-01

    The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

  17. Mouse-resistant insulated covers keep pipes from freezing

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2010-01-15

    Fabric wellhead covers and insulated blankets are commonly used at well sites in the Wyoming coalbed methane field to keep surface pipes from freezing. These materials are often chewed up by mice who build nests close to the warm pipes. The mice attract rattlesnakes, a potentially serious problem for the workmen who check the wells daily. Kennon Products of Sheridan, Wyoming solved this problem by making a flexible covering material that has a coating of hardened guard plates that prevents mice from chewing through it. More than a hundred of Kennon's mouse-resistant wellhead covers have been used successfully in the gas fields for over a year. They can be installed in less than 30 minutes and cost only a fraction of what a fiberglass hut costs to purchase and install. Huts are being discouraged for use on federal lands because they alter the nesting patterns of eagles, who perch upon them to hunt rodents. Huts also trap methane gas, which is a potential safety hazard. Kennon's mouse-resistant wellhead covers are lower than the fiberglass huts and blend into the landscape. The company is working on camouflage colours to make wellheads less noticeable. In the future, the company plans to insulate water pipes. 1 fig.

  18. Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments.

    Science.gov (United States)

    Wilcox, Kevin R; Shi, Zheng; Gherardi, Laureano A; Lemoine, Nathan P; Koerner, Sally E; Hoover, David L; Bork, Edward; Byrne, Kerry M; Cahill, James; Collins, Scott L; Evans, Sarah; Gilgen, Anna K; Holub, Petr; Jiang, Lifen; Knapp, Alan K; LeCain, Daniel; Liang, Junyi; Garcia-Palacios, Pablo; Peñuelas, Josep; Pockman, William T; Smith, Melinda D; Sun, Shanghua; White, Shannon R; Yahdjian, Laura; Zhu, Kai; Luo, Yiqi

    2017-10-01

    Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change

  19. Impacts of land use/cover classification accuracy on regional climate simulations

    Science.gov (United States)

    Ge, Jianjun; Qi, Jiaguo; Lofgren, Brent M.; Moore, Nathan; Torbick, Nathan; Olson, Jennifer M.

    2007-03-01

    Land use/cover change has been recognized as a key component in global change. Various land cover data sets, including historically reconstructed, recently observed, and future projected, have been used in numerous climate modeling studies at regional to global scales. However, little attention has been paid to the effect of land cover classification accuracy on climate simulations, though accuracy assessment has become a routine procedure in land cover production community. In this study, we analyzed the behavior of simulated precipitation in the Regional Atmospheric Modeling System (RAMS) over a range of simulated classification accuracies over a 3 month period. This study found that land cover accuracy under 80% had a strong effect on precipitation especially when the land surface had a greater control of the atmosphere. This effect became stronger as the accuracy decreased. As shown in three follow-on experiments, the effect was further influenced by model parameterizations such as convection schemes and interior nudging, which can mitigate the strength of surface boundary forcings. In reality, land cover accuracy rarely obtains the commonly recommended 85% target. Its effect on climate simulations should therefore be considered, especially when historically reconstructed and future projected land covers are employed.

  20. Radiation hardening of oxygen-doped niobium by 14-MeV neutrons

    International Nuclear Information System (INIS)

    Bradley, E.R.; Jones, R.H.

    1983-09-01

    The flow properties of niobium containing 185 and 480 wt ppM oxygen have been studied following irradiation at 300K with T(d,n) neutrons to fluence levels ranging from 6 x 10 20 to 2 x 10 22 m -2 . Two hardening stages connected by a plateau region were observed in the niobium containing 185 wt ppM oxygen. Increasing the oxygen content by 300 wt ppM oxygen shifted the beginning of the high-fluence hardening stage from 6 x 10 21 to 1 x 10 21 m -2 , thereby eliminating the plateau region. This shift resulted in 1.5 times more hardening in the oxygen-doped niobium irradiated to fluence levels above 5 x 10 21 m -2

  1. Characterization of the work hardening structure of austenitic steels by X-ray diffraction. Application to the determination of work hardening gradients and the study of recovery

    International Nuclear Information System (INIS)

    Cadalbert, Robert; Baron, J.L.

    1977-01-01

    A method has been developed to determine quantitatively the work hardening of austenitic steels by measurement of the broadening of X-ray diffraction lines. This simple, rapid, accurate and sensible method enables to determine work hardening variations in the thickness of a material. The complete automation of the measurement cycle using a small computer enables to carry out numerous determinations and to process data with accuracy. The unit developed is well adapted to the testing of metallic materials. It is also possible with this method to study the evolution of work hardening in a metal as a function of heat treatments. For instance, the determination of the recovery curves of the crystal lattice in austenitic steels allows to investigate the influence of additions (Mo, Ti) on the recovery kinetics [fr

  2. DEVELOPMENT AND RESEARCH OF ULTRASONIC OSCILLATORY SYSTEM FOR HARDENING OF SPRING PLATE BILLETS

    Directory of Open Access Journals (Sweden)

    V. A. Tomilo

    2015-01-01

    Full Text Available Various schemes of ultrasonic oscillatory system are developed: with a «force nonsensitive» support, with a «force sensitive» support, with the deforming steel balls in bulk. Results of the ultrasonic treatment showed that hardening of a surface of the samples took place when the vibration amplitude of a radiator exceeds a certain level. The level of hardening increases with increase in amplitude of fluctuations of a radiator. Higher level of hardening is registered when the surface is treated by steel balls.

  3. Spatio-Temporal Analysis of the Accuracy of Tropical Multisatellite Precipitation Analysis 3B42 Precipitation Data in Mid-High Latitudes of China

    Science.gov (United States)

    Cai, Yancong; Jin, Changjie; Wang, Anzhi; Guan, Dexin; Wu, Jiabing; Yuan, Fenghui; Xu, Leilei

    2015-01-01

    Satellite-based precipitation data have contributed greatly to quantitatively forecasting precipitation, and provides a potential alternative source for precipitation data allowing researchers to better understand patterns of precipitation over ungauged basins. However, the absence of calibration satellite data creates considerable uncertainties for The Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B42 product over high latitude areas beyond the TRMM satellites latitude band (38°NS). This study attempts to statistically assess TMPA V7 data over the region beyond 40°NS using data obtained from numerous weather stations in 1998–2012. Comparative analysis at three timescales (daily, monthly and annual scale) indicates that adoption of a monthly adjustment significantly improved correlation at a larger timescale increasing from 0.63 to 0.95; TMPA data always exhibits a slight overestimation that is most serious at a daily scale (the absolute bias is 103.54%). Moreover, the performance of TMPA data varies across all seasons. Generally, TMPA data performs best in summer, but worst in winter, which is likely to be associated with the effects of snow/ice-covered surfaces and shortcomings of precipitation retrieval algorithms. Temporal and spatial analysis of accuracy indices suggest that the performance of TMPA data has gradually improved and has benefited from upgrades; the data are more reliable in humid areas than in arid regions. Special attention should be paid to its application in arid areas and in winter with poor scores of accuracy indices. Also, it is clear that the calibration can significantly improve precipitation estimates, the overestimation by TMPA in TRMM-covered area is about a third as much as that in no-TRMM area for monthly and annual precipitation. The systematic evaluation of TMPA over mid-high latitudes provides a broader understanding of satellite-based precipitation estimates, and these data are

  4. Spatio-temporal analysis of the accuracy of tropical multisatellite precipitation analysis 3B42 precipitation data in mid-high latitudes of China.

    Directory of Open Access Journals (Sweden)

    Yancong Cai

    Full Text Available Satellite-based precipitation data have contributed greatly to quantitatively forecasting precipitation, and provides a potential alternative source for precipitation data allowing researchers to better understand patterns of precipitation over ungauged basins. However, the absence of calibration satellite data creates considerable uncertainties for The Tropical Rainfall Measuring Mission (TRMM Multisatellite Precipitation Analysis (TMPA 3B42 product over high latitude areas beyond the TRMM satellites latitude band (38°NS. This study attempts to statistically assess TMPA V7 data over the region beyond 40°NS using data obtained from numerous weather stations in 1998-2012. Comparative analysis at three timescales (daily, monthly and annual scale indicates that adoption of a monthly adjustment significantly improved correlation at a larger timescale increasing from 0.63 to 0.95; TMPA data always exhibits a slight overestimation that is most serious at a daily scale (the absolute bias is 103.54%. Moreover, the performance of TMPA data varies across all seasons. Generally, TMPA data performs best in summer, but worst in winter, which is likely to be associated with the effects of snow/ice-covered surfaces and shortcomings of precipitation retrieval algorithms. Temporal and spatial analysis of accuracy indices suggest that the performance of TMPA data has gradually improved and has benefited from upgrades; the data are more reliable in humid areas than in arid regions. Special attention should be paid to its application in arid areas and in winter with poor scores of accuracy indices. Also, it is clear that the calibration can significantly improve precipitation estimates, the overestimation by TMPA in TRMM-covered area is about a third as much as that in no-TRMM area for monthly and annual precipitation. The systematic evaluation of TMPA over mid-high latitudes provides a broader understanding of satellite-based precipitation estimates, and these

  5. A Thermodynamic Mixed-Solid Asphaltene Precipitation Model

    DEFF Research Database (Denmark)

    Lindeloff, Niels; Heidemann, R.A.; Andersen, Simon Ivar

    1998-01-01

    A simple model for the prediction of asphaltene precipitation is proposed. The model is based on an equation of state and uses standard thermodynamics, thus assuming that the precipitation phenomenon is a reversible process. The solid phase is treated as an ideal multicomponent mixture. An activity...

  6. Temperature dependence of work hardening in sparsely twinning zirconium

    International Nuclear Information System (INIS)

    Singh, Jaiveer; Mahesh, S.; Roy, Shomic; Kumar, Gulshan; Srivastava, D.; Dey, G.K.; Saibaba, N.; Samajdar, I.

    2017-01-01

    Fully recrystallized commercial Zirconium plates were subjected to uniaxial tension. Tests were conducted at different temperatures (123 K - 623 K) and along two plate directions. Both directions were nominally unfavorable for deformation twinning. The effect of the working temperature on crystallographic texture and in-grain misorientation development was insignificant. However, systematic variation in work hardening and in the area fraction and morphology of deformation twins was observed with temperature. At all temperatures, twinning was associated with significant near boundary mesoscopic shear, suggesting a possible linkage with twin nucleation. A binary tree based model of the polycrystal, which explicitly accounts for grain boundary accommodation and implements the phenomenological extended Voce hardening law, was implemented. This model could capture the measured stress-strain response and twin volume fractions accurately. Interestingly, slip and twin system hardness evolution permitted multiplicative decomposition into temperature-dependent, and accumulated strain-dependent parts. Furthermore, under conditions of relatively limited deformation twinning, the work hardening of the slip and twin systems followed two phenomenological laws proposed in the literature for non-twinning single-phase face centered cubic materials.

  7. Residual stress analysis of drive shafts after induction hardening

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Guilherme Vieira Braga; Rocha, Alexandre da Silva; Nunes, Rafael Menezes, E-mail: lemos_gl@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Algre, RS (Brazil); Hirsch, Thomas Karl [Stiftung Institut für Werkstofftechnik (IWT), Bremen (Germany)

    2014-08-15

    Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable diffractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected. (author)

  8. The effect of Ag and Ca additions on the age hardening response of Mg–Zn alloys

    International Nuclear Information System (INIS)

    Bhattacharjee, T.; Mendis, C.L.; Oh-ishi, K.; Ohkubo, T.; Hono, K.

    2013-01-01

    The effect of sole and combined additions of Ag and Ca in enhancing the age hardening response in a Mg–2.4Zn (at%) alloy have been studied by systematic microstructure investigations using transmission electron microscopy (TEM) and three dimensional atom probe (3DAP). In the early aging stage of a Mg–2.4Zn–0.1Ag–0.1Ca (at%) alloy at 160 °C, Zn-rich Guinier Preston (G.P.) zones form with Ag and Ca enrichment. Further aging lead to the formation of fine β′ 1 precipitates with Ag and Ca enrichment. We confirmed that the G.P. zones do not form in the Mg–2.4Zn (at%) binary alloy at 160 °C, but form after a prolonged aging at 70 °C. This suggests that the combined addition of Ag and Ca shifts the metastable solvus for the G.P. zones to a higher temperature, thereby making it possible to form G.P. zones even at the artificial aging temperature of 160 °C. Since G.P. zones act as nucleation sites for the β′ 1 precipitates, the peak-aged microstructure is refined substantially by the addition of Ag and Ca

  9. The variation of work hardening characteristics of Al-5 wt% Mg alloy during phase transition

    International Nuclear Information System (INIS)

    Mahmoud, M.A.; Sobhy, M.; Abd El-Rehim, A.F.; Abdel Rahman, R.M.

    2010-01-01

    The aim of this study is to investigate the effect of aging conditions on the stress-strain behavior along with microstructure changes of the Al-5 wt% Mg alloy. Following solid solution treatment and aging of specimens at temperatures ranging from 373 to 573 K for various aging times (1/4 to 4 h), stress-strain tests were performed at different testing temperatures (313-343 K). The work hardening parameters (σ y , σ f , χ p and Y) were found to decrease continuously with pre-aging times at all aging and testing temperatures, where the softening parameters (ε f and L) oppose this behavior. The variation in stress-strain parameters with increasing aging temperatures and aging times was explained on the basis of structural transformations taking place in the Al-Mg alloy. A precipitate-dislocation intersections mechanism was assumed as the rate-controlling mechanism for alloy.

  10. BUSFET - A Novel Radiation-Hardened SOI Transistor

    International Nuclear Information System (INIS)

    Dodd, P.E.; Draper, B.L.; Schwank, J.R.; Shaneyfelt, M.R.

    1999-01-01

    A partially-depleted SOI transistor structure has been designed that does not require the use of specially-processed hardened buried oxides for total-dose hardness and maintains the intrinsic SEU and dose rate hardness advantages of SOI technology

  11. Hardening in AlN induced by point defects

    International Nuclear Information System (INIS)

    Suematsu, H.; Mitchell, T.E.; Iseki, T.; Yano, T.

    1991-01-01

    Pressureless-sintered AIN was neutron irradiated and the hardness change was examined by Vickers indentation. The hardness was increased by irradiation. When the samples were annealed at high temperature, the hardness gradually decreased. Length was also found to increase and to change in the same way as the hardness. A considerable density of dislocation loops still remained, even after the hardness completely recovered to the value of the unirradiated sample. Thus, it is concluded that the hardening in AIN is caused by isolated point defects and small clusters of point defects, rather than by dislocation loops. Hardness was found to increase in proportion to the length change. If the length change is assumed to be proportional to the point defect density, then the curve could be fitted qualitatively to that predicted by models of solution hardening in metals. Furthermore, the curves for three samples irradiated at different temperatures and fluences are identical. There should be different kinds of defect clusters in samples irradiated at different conditions, e.g., the fraction of single point defects is the highest in the sample irradiated at the lowest temperature. Thus, hardening is insensitive to the kind of defects remaining in the sample and is influenced only by those which contribute to length change

  12. ON THE SPECTRAL HARDENING AT ∼>300 keV IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-01-01

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies ∼>300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ∼k –2.7 . A ∼k –2.7 dissipation range spectrum is consistent with recent solar wind observations.

  13. Work hardening and plastic equation of state of tantalum

    International Nuclear Information System (INIS)

    Gypen, L.A.; Aernoudt, E.; Deruyttere, A.

    1983-01-01

    The influence of cold deformation on the thermal and athermal components of the flow stress of tantalum was investigated. Up to high deformation levels the strain hardening is due only to the development of internal stress fields; the effective stress remains almost constant. The athermal strain hardening of tantalum is parabolic at low deformation levels (epsilon < 0.5) and linear at high deformation levels, as for other bcc metals. Hart's plastic equation of state is shown to be valid for tantalum at room temperature in the whole deformation range investigated (from epsilon = 0.005 to epsilon = 2.8). (author)

  14. Copper precipitation behavior and mechanical properties of Cu-bearing 316L austenitic stainless steel: A comprehensive cross-correlation study

    International Nuclear Information System (INIS)

    Xi, Tong; Babar Shahzad, M.; Xu, Dake; Zhao, Jinlong; Yang, Chunguang; Qi, Min; Yang, Ke

    2016-01-01

    The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 °C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38±0.46 nm to 2.39±0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels.

  15. Copper precipitation behavior and mechanical properties of Cu-bearing 316L austenitic stainless steel: A comprehensive cross-correlation study

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Tong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Babar Shahzad, M.; Xu, Dake; Zhao, Jinlong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Yang, Chunguang, E-mail: cgyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Qi, Min [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2016-10-15

    The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 °C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38±0.46 nm to 2.39±0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels.

  16. TH-CD-202-02: A Preliminary Study Evaluating Beam-Hardening Artifact Reduction On CT Direct Electron-Density Images

    Energy Technology Data Exchange (ETDEWEB)

    Li, H; Dolly, S; Zhao, T; Anastasio, M; Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Ritter, A; Colombo, V; Raupach, R; Huenemohr, N [Siemens Healthcare GmbH, Deutschland (Germany); Mistry, N [Siemens Medical Solutions USA, Malvern, PA (United States); Yu, L [Mayo Clinic, Rochester, MN (United States)

    2016-06-15

    Purpose: A prototype reconstruction algorithm that can provide direct electron density (ED) images from single energy CT scans is being currently developed by Siemens Healthcare GmbH. This feature can eliminate the need for kV specific calibration curve for radiation treatemnt planning. An added benefit is that beam-hardening artifacts are also reduced on direct-ED images due to the underlying material decomposition. This study is to quantitatively analyze the reduction of beam-hardening artifacts on direct-ED images and suggest additional clinical usages. Methods: HU and direct-ED images were reconstructed on a head phantom scanned on a Siemens Definition AS CT scanner at five tube potentials of 70kV, 80kV, 100kV, 120kV and 140kV respectively. From these images, mean, standard deviation (SD), and local NPS were calculated for regions of interest (ROI) of same locations and sizes. A complete analysis of beam-hardening artifact reduction and image quality improvement was conducted. Results: Along with the increase of tube potentials, ROI means and SDs decrease on both HU and direct-ED images. The mean value differences between HU and direct-ED images are up to 8% with absolute value of 2.9. Compared to that on HU images, the SDs are lower on direct-ED images, and the differences are up to 26%. Interestingly, the local NPS calculated from direct-ED images shows consistent values in the low spatial frequency domain for images acquired from all tube potential settings, while varied dramatically on HU images. This also confirms the beam -hardening artifact reduction on ED images. Conclusions: The low SDs on direct-ED images and relative consistent NPS values in the low spatial frequency domain indicate a reduction of beam-hardening artifacts. The direct-ED image has the potential to assist in more accurate organ contouring, and is a better fit for the desired purpose of CT simulations for radiotherapy.

  17. Precipitation Behavior of Carbides in H13 Hot Work Die Steel and Its Strengthening during Tempering

    Directory of Open Access Journals (Sweden)

    Angang Ning

    2017-02-01

    Full Text Available The properties of carbides, such as morphology, size, and type, in H13 hot work die steel were studied with optical microscopy, transmission electron microscopy, electron diffraction, and energy dispersive X-ray analysis; their size distribution and quantity after tempering, at different positions within the ingot, were analyzed using Image-Pro Plus software. Thermodynamic calculations were also performed for these carbides. The microstructures near the ingot surface were homogeneous and had slender martensite laths. Two kinds of carbide precipitates have been detected in H13: (1 MC and M6C, generally smaller than 200 nm; and (2 M23C6, usually larger than 200 nm. MC and M6C play the key role in precipitation hardening. These are the most frequent carbides precipitating at the halfway point from the center of the ingot, and the least frequent at the surface. From the center of the ingot to its surface, the size and volume fraction of the carbides decrease, and the toughness improves, while the contribution of the carbides to the yield strength increases.

  18. Ferrous arrowheads and their oil quench hardening: Some early Indian evidence

    Science.gov (United States)

    Dube, R. K.

    2008-05-01

    A wide variety of ferrous arrowheads were in use in ancient India. Several typical chemical analyses of arrowheads found from archaeological excavation carried out at Kaushambi are reported in this paper. The average carbon content of these arrowheads varied from as low as 0.1 wt.% to approximately 0.9 wt.%. Literary evidence for oil quench hardening of ferrous arrowheads, as reported in famous Sanskrit epics—the Rāmāyana and the Mahābhārata—have been discussed in this paper. This type of quench hardening was intentionally adopted as it helped in preventing distortion and formation of quench cracks in arrowheads. The oil quench-hardened arrowheads were rubbed on stones to sharpen them, which also brought about tempering of martensite due to frictional heat.

  19. Strain hardening behavior and microstructural evolution during plastic deformation of dual phase, non-grain oriented electrical and AISI 304 steels

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Guilherme Corrêa; Gonzalez, Berenice Mendonça; Arruda Santos, Leandro de, E-mail: leandro.arruda@demet.ufmg.br

    2017-01-27

    Strain hardening behavior and microstructural evolution of non-grain oriented electrical, dual phase, and AISI 304 steels, subjected to uniaxial tensile tests, were investigated in this study. Tensile tests were performed at room temperature and the strain hardening behavior of the steels was characterized by three different parameters: modified Crussard–Jaoul stages, strain hardening rate and instantaneous strain hardening exponent. Optical microscopic analysis, X-ray diffraction measurements, phase quantification by Rietveld refinement and hardness tests were also carried out in order to correlate the microstructural and mechanical responses to plastic deformation. Distinct strain hardening stages were observed in the steels in terms of the instantaneous strain hardening exponent and the strain hardening rate. The dual phase and non-grain oriented steels exhibited a two-stage strain hardening behavior while the AISI 304 steel displayed multiple stages, resulting in a more complex strain hardening behavior. The dual phase steels showed a high work hardening capacity in stage 1, which was gradually reduced in stage 2. On the other hand, the AISI 304 steel showed high strain hardening capacity, which continued to increase up to the tensile strength. This is a consequence of its additional strain hardening mechanism, based on a strain-induced martensitic transformation, as shown by the X-ray diffraction and optical microscopic analyses.

  20. Spatio-temporal variations in climate, primary productivity and efficiency of water and carbon use of the land cover types in Sudan and Ethiopia.

    Science.gov (United States)

    Khalifa, Muhammad; Elagib, Nadir Ahmed; Ribbe, Lars; Schneider, Karl

    2018-05-15

    The impact of climate variability on the Net Primary Productivity (NPP) of different land cover types and the reaction of NPP to drought conditions are still unclear, especially in Sub-Saharan Africa. This research utilizes public-domain data for the period 2000 through 2013 to analyze these aspects for several land cover types in Sudan and Ethiopia, as examples of data-scarce countries. Spatio-temporal variation in NPP, water use efficiency (WUE) and carbon use efficiency (CUE) for several land covers were correlated with variations in precipitation, temperature and drought at different time scales, i.e. 1, 3, 6 and 12months using Standardized Precipitation Evapotranspiration Index (SPEI) datasets. WUE and CUE were estimated as the ratios of NPP to actual evapotranspiration and NPP to Gross Primary Productivity (GPP), respectively. Results of this study revealed that NPP, WUE and CUE of the different land cover types in Ethiopia have higher magnitudes than their counterparts in Sudan. Moreover, they exhibit higher sensitivity to drought and variation in precipitation. Whereas savannah represents the most sensitive land cover to drought, croplands and permanent wetlands are the least sensitive ones. The inter-annual variation in NPP, WUE and CUE in Ethiopia is likely to be driven by a drought of time scale of three months. No statistically significant correlation was found for Sudan between the inter-annual variations in these indicators with drought at any of the time scales considered in the study. Our findings are useful from the view point of both food security for a growing population and mitigation to climate change as discussed in the present study. Copyright © 2017 Elsevier B.V. All rights reserved.