Irradiation performance of oxide dispersion strengthened copper alloys to 150 dpa at 415 degree C

International Nuclear Information System (INIS)

Edwards, D.J.; Kumar, A.S.; Anderson, K.R.; Stubbins, J.F.; Garner, F.A.; Hamilton, M.L.

1991-11-01

Results have been obtained on the post-irradiation properties of various oxide dispersion strengthened copper alloys irradiated from 34 to 150 dpa at 415 degrees C in the Fast Flux Test Facility. The GlidCop alloys strengthened by Al 2 O 3 continue to outperform other alloys with respect to swelling resistance, and retention of both electrical conductivity and yield strength. Several castable ODS alloys and a Cr 2 O 3 -strengthened alloy show increasingly poor resistance to radiation, especially in their swelling behavior. A HfO 2 -strengthened alloy retains most of its strength and its electrical conductivity reaches a constant level after 50 dpa, but it exhibits a higher residual radioactivity

Computational design of precipitation-strengthened titanium-nickel-based shape memory alloys

Science.gov (United States)

Bender, Matthew D.

Motivated by performance requirements of future medical stent applications, experimental research addresses the design of novel TiNi-based, superelastic shape-memory alloys employing nanoscale precipitation strengthening to minimize accommodation slip for cyclic stability and to increase output stress capability for smaller devices. Using a thermodynamic database describing the B2 and L21 phases in the Al-Ni-Ti-Zr system, Thermo-Calc software was used to assist modeling the evolution of phase composition during 600°C isothermal evolution of coherent L21 Heusler phase precipitation from supersaturated TiNi-based B2 phase matrix in an alloy experimentally characterized by atomic-scale Local Electrode Atom Probe (LEAP) microanalysis. Based on measured evolution of the alloy hardness (under conditions stable against martensitic transformation) a model for the combined effects of solid solution strengthening and precipitation strengthening was calibrated, and the optimum particle size for efficient strengthening was identified. Thermodynamic modeling of the evolution of measured phase fractions and compositions identified the interfacial capillary energy enabling thermodynamic design of alloy microstructure with the optimal strengthening particle size. Extension of alloy designs to incorporate Pt and Pd for reducing Ni content, enhancing radiopacity, and improving manufacturability were considered using measured Pt and Pd B2/L2 1 partitioning coefficients. After determining that Pt partitioning greatly increases interphase misfit, full attention was devoted to Pd alloy designs. A quantitative approach to radiopacity was employed using mass attenuation as a metric. Radiopacity improvements were also qualitatively observed using x-ray fluoroscopy. Transformation temperatures were experimentally measured as a function of Al and Pd content. Redlich-Kister polynomial modeling was utilized for the dependence of transformation reversion Af temperature on B2 matrix phase

Synergistic alloying effect on microstructural evolution and mechanical properties of Cu precipitation-strengthened ferritic alloys

International Nuclear Information System (INIS)

Wen, Y.R.; Li, Y.P.; Hirata, A.; Zhang, Y.; Fujita, T.; Furuhara, T.; Liu, C.T.; Chiba, A.; Chen, M.W.

2013-01-01

We report the influence of alloying elements (Ni, Al and Mn) on the microstructural evolution of Cu-rich nanoprecipitates and the mechanical properties of Fe–Cu-based ferritic alloys. It was found that individual additions of Ni and Al do not give rise to an obvious strengthening effect, compared with the binary Fe–Cu parent alloy, although Ni segregates at the precipitate/matrix interface and Al partitions into Cu-rich precipitates. In contrast, the co-addition of Ni and Al results in the formation of core–shell nanoprecipitates with a Cu-rich core and a B2 Ni–Al shell, leading to a dramatic improvement in strength. The coarsening rate of the core–shell precipitates is about two orders of magnitude lower than that of monolithic Cu-rich precipitates in the binary and ternary Fe–Cu alloys. Reinforcement of the B2 Ni–Al shells by Mn partitioning further improves the strength of the precipitation-strengthened alloys by forming ultrastable and high number density core–shell nanoprecipitates

Precipitate strengthening of nanostructured aluminium alloy.

Science.gov (United States)

Wawer, Kinga; Lewandowska, Malgorzata; Kurzydlowski, Krzysztof J

2012-11-01

Grain boundaries and precipitates are the major microstructural features influencing the mechanical properties of metals and alloys. Refinement of the grain size to the nanometre scale brings about a significant increase in the mechanical strength of the materials because of the increased number of grain boundaries which act as obstacles to sliding dislocations. A similar effect is obtained if nanoscale precipitates are uniformly distributed in coarse grained matrix. The development of nanograin sized alloys raises the important question of whether or not these two mechanisms are "additive" and precipitate strengthening is effective in nanostructured materials. In the reported work, hydrostatic extrusion (HE) was used to obtain nanostructured 7475 aluminium alloy. Nanosized precipitates were obtained by post-HE annealing. It was found that such annealing at the low temperatures (100 degrees C) results in a significant increase in the microhardness (HV0.2) and strength of the nanostructured 7475 aluminium alloy. These results are discussed in terms of the interplay between the precipitation and deformation of nanocrystalline metals.

Mechanical characterization and constitutive modeling of Mg alloy sheets

International Nuclear Information System (INIS)

Mekonen, M. Nebebe; Steglich, D.; Bohlen, J.; Letzig, D.; Mosler, J.

2012-01-01

Highlights: ► Material characterization of the Mg alloys AZ31 and ZE10 at elevated temperatures. ► Distortion of the yield locus does not depend on the strain rate. ► Novel constitutive model suitable for the analysis of sheet forming of magnesium. ► Strain-dependent r-values are included within the model. ► The model is thermodynamically consistent and accounts for distortional hardening. - Abstract: In this paper, an experimental mechanical characterization of the magnesium alloys ZE10 and AZ31 is performed and a suitable constitutive model is established. The mechanical characterization is based on uniaxial tensile tests. In order to avoid poor formability at room temperature, the tests were conducted at elevated temperature (200 °C). The uniaxial tensile tests reveal sufficient ductility allowing sheet forming processes at this temperature. The differences in yield stresses and plastic strain ratios (r-values) confirm the anisotropic response of the materials under study. The constitutive model is established so that the characteristic mechanical features observed in magnesium alloys such as anisotropy and compression-tension asymmetry can be accommodated. This model is thermodynamically consistent, incorporates rate effect, is formulated based on finite strain plasticity theory and is applicable in sheet forming simulations of magnesium alloys. More precisely, a model originally proposed by Cazacu and Barlat in 2004 and later modified to account for the evolution of the material anisotropy is rewritten in a thermodynamically consistent framework. The calibrated constitutive model is shown to capture the characteristic mechanical features observed in magnesium alloy sheets.

Irradiation creep of dispersion strengthened copper alloy

Energy Technology Data Exchange (ETDEWEB)

Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A. [and others

1997-04-01

Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al{sub 2}O{sub 3}, is very similar to the GlidCop{trademark} alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10{sup 21} n/cm{sup 2} (E>0.1 MeV), which corresponds to {approx}3-5 dpa. The irradiation temperature ranged from 60-90{degrees}C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of {+-}0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as {approx}2 x 10{sup {minus}9}s{sup {minus}1}. These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys.

Irradiation creep of dispersion strengthened copper alloy

International Nuclear Information System (INIS)

Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A.

1997-01-01

Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al 2 O 3 , is very similar to the GlidCop trademark alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10 21 n/cm 2 (E>0.1 MeV), which corresponds to ∼3-5 dpa. The irradiation temperature ranged from 60-90 degrees C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of ±0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as ∼2 x 10 -9 s -1 . These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys

Semi-solid twin-roll casting process of magnesium alloy sheets

International Nuclear Information System (INIS)

Watari, H.; Davey, K.; Rasgado, M.T. Alonso; Haga, T.; Koga, N.

2004-01-01

An experimental approach has been performed to ascertain the effectiveness of semi-solid strip casting using a horizontal twin roll caster. The demand for light-weight products with high strength has grown recently due to the rapid development of automobile and aircraft technology. One key to such development has been utilization of magnesium alloys, which can potentially reduce the total product weight. However, the problems of utilizing magnesium alloys are still mainly related to high manufacturing cost. One of the solutions to this problem is to develop magnesium casting-rolling technology in order to produce magnesium sheet products at competitive cost for commercial applications. In this experiment, magnesium alloy AZ31B was used to ascertain the effectiveness of semi-solid roll strip casting for producing magnesium alloy sheets. The temperature of the molten magnesium, and the roll speeds of the upper and lower rolls, (which could be changed independently), were varied to find an appropriate manufacturing condition. Rolling and heat treatment conditions were changed to examine which condition would be appropriate for producing wrought magnesium alloys with good formability. Microscopic observation of the crystals of the manufactured wrought magnesium alloys was performed. It has been found that a limiting drawing ratio of 2.7 was possible in a warm deep drawing test of the cast magnesium alloy sheets after being hot rolled

Study on Strengthening and Toughening Mechanisms of Aluminum Alloy 2618-Ti at Elevated Temperature

Science.gov (United States)

Kun, Ma; Tingting, Liu; Ya, Liu; Xuping, Su; Jianhua, Wang

2018-01-01

The tensile properties of the alloy 2618 and 2618-Ti were tested using a tensile testing machine. The morphologies of the fracture of tensile samples were observed using scanning electron microscopy. The strengthening and toughening mechanisms of alloy 2618-Ti at elevated temperature were systematically investigated based on the analyses of experimental results. The results showed that the tensile strength of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 250 and 300 °C. But the elongation of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 200 and 300 °C. The equal-strength temperature of intragranular and grain boundary of alloy 2618-Ti is about 235 °C. When the temperature is lower than 235 °C, the strengthening of alloy 2618-Ti is ascribed to the strengthening effect of fine grains and dispersed Al3Ti/Al18Mg3Ti2 phase. When the temperature is higher than 235 °C, the strengthening effect of alloy 2618-Ti is mainly attributed to the load transfer of Al3Ti and Al18Mg3Ti2 particles. The toughening of alloy 2618-Ti at elevated temperature is mainly ascribed to the fine grain microstructure, excellent combination between matrix and dispersed Al3Ti/Al18Mg3Ti2 particles as well as the recrystallization of the alloy at elevated temperature.

Influence of inorganic acid pickling on the corrosion resistance of magnesium alloy AZ31 sheet

DEFF Research Database (Denmark)

Nwaogu, Ugochukwu Chibuzoh; Blawert, C.; Scharnagl, N.

2009-01-01

Surface contaminants as a result of thermo-mechanical processing of magnesium alloys, e.g. sheet rolling, can have a negative effect on the corrosion resistance of magnesium alloys. Especially contaminants such as Fe, Ni and Cu, left on the surface of magnesium alloys result in the formation...... of micro-galvanic couples and can therefore increase corrosion attack on these alloys. Due to this influence they should be removed to obtain good corrosion resistance. In this study, the effect of inorganic acid pickling on the corrosion behaviour of a commercial AZ31 magnesium alloy sheet...... cleaning the AZ31 sheet. However, to obtain reasonable corrosion resistance at least 5 mu m of the surface of AZ31 magnesium alloy sheet have to be removed....

Self-diagnosis of structures strengthened with hybrid carbon-fiber-reinforced polymer sheets

Science.gov (United States)

Wu, Z. S.; Yang, C. Q.; Harada, T.; Ye, L. P.

2005-06-01

The correlation of mechanical and electrical properties of concrete beams strengthened with hybrid carbon-fiber-reinforced polymer (HCFRP) sheets is studied in this paper. Two types of concrete beams, with and without reinforcing bars, are strengthened with externally bonded HCFRP sheets, which have a self-structural health monitoring function due to the electrical conduction and piezoresistivity of carbon fibers. Parameters investigated include the volume fractions and types of carbon fibers. According to the investigation, it is found that the hybridization of uniaxial HCFRP sheets with several different types of carbon fibers is a viable method for enhancing the mechanical properties and obtaining a built-in damage detection function for concrete structures. The changes in electrical resistance during low strain ranges before the rupture of carbon fibers are generally smaller than 1%. Nevertheless, after the gradual ruptures of carbon fibers, the electrical resistance increases remarkably with the strain in a step-wise manner. For the specimens without reinforcing bars, the electrical behaviors are not stable, especially during the low strain ranges. However, the electrical behaviors of the specimens with reinforcing bars are relatively stable, and the whole range of self-sensing function of the HCFRP-strengthened RC structures has realized the conceptual design of the HCFRP sensing models and is confirmed by the experimental investigations. The relationships between the strain/load and the change in electrical resistance show the potential self-monitoring capacity of HCFRP reinforcements used for strengthening concrete structures.

Creep and rupture of an ODS alloy with high stress rupture ductility. [Oxide Dispersion Strengthened

Science.gov (United States)

Mcalarney, M. E.; Arsons, R. M.; Howson, T. E.; Tien, J. K.; Baranow, S.

1982-01-01

The creep and stress rupture properties of an oxide (Y2O3) dispersion strengthened nickel-base alloy, which also is strengthened by gamma-prime precipitates, was studied at 760 and 1093 C. At both temperatures, the alloy YDNiCrAl exhibits unusually high stress rupture ductility as measured by both elongation and reduction in area. Failure was transgranular, and different modes of failure were observed including crystallographic fracture at intermediate temperatures and tearing or necking almost to a chisel point at higher temperatures. While the rupture ductility was high, the creep strength of the alloy was low relative to conventional gamma prime strengthened superalloys in the intermediate temperature range and to ODS alloys in the higher temperature range. These findings are discussed with respect to the alloy composition; the strengthening oxide phases, which are inhomogeneously dispersed; the grain morphology, which is coarse and elongated and exhibits many included grains; and the second phase inclusion particles occurring at grain boundaries and in the matrix. The creep properties, in particular the high stress dependencies and high creep activation energies measured, are discussed with respect to the resisting stress model of creep in particle strengthened alloys.

Formability of Annealed Ni-Ti Shape Memory Alloy Sheet

Science.gov (United States)

Fann, K. J.; Su, J. Y.; Chang, C. H.

2018-03-01

Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its application, this study attempts to investigate the strength and cold formability of its sheet blank, which is annealed at various temperatures, by hardness test and by Erichsen-like cupping test. As a result, the higher the annealing temperature, the lower the hardness, the lower the maximum punch load as the sheet blank fractured, and the lower the Erichsen-like index or the lower the formability. In general, the Ni-Ti sheet after annealing has an Erichsen-like index between 8 mm and 9 mm. This study has also confirmed via DSC that the Ni-Ti shape memory alloy possesses the austenitic phase and shows the superelasticity at room temperature.

Crack Propagation on ESE(T) Specimens Strengthened with CFRP Sheets

DEFF Research Database (Denmark)

Hansen, Christian Skodborg; Jensen, Peter Holmstrøm; Dyrelund, Jens

2009-01-01

In this paper fatigue tests on side notched steel test specimens strengthened with adhesive bonded fibre reinforced polymer (FRP) sheets are presented. The specimens are subject to crack growth both in the steel and bond line. Influence of the load ratio and initial crack length on the overall...

Research on Al-alloy sheet forming formability during warm/hot sheet hydroforming based on elliptical warm bulging test

Science.gov (United States)

Cai, Gaoshen; Wu, Chuanyu; Gao, Zepu; Lang, Lihui; Alexandrov, Sergei

2018-05-01

An elliptical warm/hot sheet bulging test under different temperatures and pressure rates was carried out to predict Al-alloy sheet forming limit during warm/hot sheet hydroforming. Using relevant formulas of ultimate strain to calculate and dispose experimental data, forming limit curves (FLCS) in tension-tension state of strain (TTSS) area are obtained. Combining with the basic experimental data obtained by uniaxial tensile test under the equivalent condition with bulging test, complete forming limit diagrams (FLDS) of Al-alloy are established. Using a quadratic polynomial curve fitting method, material constants of fitting function are calculated and a prediction model equation for sheet metal forming limit is established, by which the corresponding forming limit curves in TTSS area can be obtained. The bulging test and fitting results indicated that the sheet metal FLCS obtained were very accurate. Also, the model equation can be used to instruct warm/hot sheet bulging test.

Response of solute and precipitation-strengthened copper alloys at high neutron exposure

International Nuclear Information System (INIS)

Garner, F.A.; Hamilton, M.L.; Shikama, T.; Edwards, D.J.; Newkirk, J.W.

1991-11-01

A variety of solute and precipitation strengthened copper base alloys have been irradiated to neutron-induced displacement levels of 34 to 150 dpa at 415 degrees C and 32 dpa at 529 degrees C in the Fast Flux Test Facility to assess their potential for high heat flux applications in fusion reactors. Several MZC-type alloys appear to offer the most promise for further study. For low fluence applications CuBeNi and spinodally strengthened CuNiTi alloys may also be suitable. Although Cu-2Be resists swelling, it is not recommended for fusion reactor applications because of its low conductivity

Response of solute and precipitation-strengthened copper alloys at high neutron exposure

Energy Technology Data Exchange (ETDEWEB)

Garner, F.A.; Hamilton, M.L. [Pacific Northwest Lab., Richland, WA (United States); Shikama, T. [Tohoku Univ., Oarai Branch (Japan); Edwards, D.J.; Newkirk, J.W. [Missouri Univ., Rolla, MO (United States)

1991-11-01

A variety of solute and precipitation strengthened copper base alloys have been irradiated to neutron-induced displacement levels of 34 to 150 dpa at 415{degrees}C and 32 dpa at 529{degrees}C in the Fast Flux Test Facility to assess their potential for high heat flux applications in fusion reactors. Several MZC-type alloys appear to offer the most promise for further study. For low fluence applications CuBeNi and spinodally strengthened CuNiTi alloys may also be suitable. Although Cu-2Be resists swelling, it is not recommended for fusion reactor applications because of its low conductivity.

Stretch strength of Al-Li alloy sheet

Energy Technology Data Exchange (ETDEWEB)

Sato, K.; Sawa, Y.; Yokoyama, T.; Fujimoto, S. [Science Univ. of Tokyo (Japan). Dept. of Mech. Eng.; Sakamoto, T. [Kobe Steel Works, Tokyo (Japan)

1998-07-01

Stretch test on Al-Li alloy sheet was carried out in stretch rate of 0.01 to 0.2 mm/sec. The limiting stretch depth was measured in various conditions and the following results were obtained. (1) Stretch rate does not affect the limiting stretch depth of Al-Li alloy. (2) The limiting stretch depth is increased with increase of the profile radius. (3) Strain hardening exponent(n-value) and r-value of Lankford do not affect the limiting stretch depth. (4) Rapture pattern in stretch test of Al is {alpha} type rapture and that of Al-Li alloy is straight line type rapture. (orig.) 4 refs.

Effect of sulphur on the strengthening of a Zr-Nb alloy

International Nuclear Information System (INIS)

Chang, K.I.; Hong, S.I.

2008-01-01

The effect of sulphur on the strengthening and the thermally activated deformation of cold-worked Zr-1 Nb alloy was investigated. In the present study, the sulphur strengthening was observed even at room temperature unlike the previous study of Ferrer et al. The flow stress increased by 65 MPa at room temperature with the addition of sulphur as little as 20 ppm. With further increase of sulphur content up to 300 ppm, negligible change of the flow stress was observed. The additive strengthening behavior in which the entire stress-strain curve shift upward by the friction stress due to the addition of sulphur was observed in the Zr-Nb alloy of the present study. The activation volume decreased slightly (from 110b 3 to 80b 3 ) with the addition of 300 ppm sulphur at room temperature. The rate-controlling mechanism of the deformation can best be explained by the dislocation interaction mechanism in which the segregation of alloying elements such as oxygen and sulphur atoms affects the activation length of dislocations

Plasticity of oxide dispersion strengthened ferritic alloys

International Nuclear Information System (INIS)

Zakine, C.; Prioul, C.; Alamo, A.; Francois, D.

1993-01-01

Two 13%Cr oxide dispersion strengthened (ODS) ferritic alloys, DT and DY, exhibiting different oxide particle size distribution and a χ phase precipitation were studied. Their tensile properties have been tested from 20 to 700 C. Experimental observations during room temperature tensile tests performed in a scanning electronic microscope have shown that the main damage mechanism consists in microcracking of the χ phase precipitates on grain boundaries. These alloys are high tensile and creep resistant between 500 and 700 C. Their strongly stress-sensitive creep behaviour can be described by usual creep laws and incorporating a threshold stress below which the creep rate is negligible. (orig.)

Precipitation Strengthenable NiTiPd High Temperature Shape Memory Alloys

Science.gov (United States)

Bigelow, Glen; Garg, Anita; Benafan, Othmane; Noebe, Ronald; Gaydosh, Darrell; Padula, Santo, II

2017-01-01

In binary NiTi alloys, it has long been known that Ni-rich alloys can be heat treated to produce precipitates which both strengthen the matrix against dislocations and improve the behavior of the material under thermal and mechanical cycling. Within recent years, the same effect has been observed in Ni-rich NiTiHf high temperature shape memory alloys and heat treatment regimens have been defined which will reliably produce improved properties. In NiTiPd alloys, precipitation has also been observed, but studies are still underway to define reliable heat treatments and compositions which will provide a balance of strengthening and good thermomechanical properties. For this study, a series of NiTi-32 at.Pd alloys was produced to determine the effect of changing nickeltitanium content on the transformation behavior and heat treatability of the material. Samples were aged at temperatures between 350C and 450C for times up to 100 hours. Actuation type behavior was evaluated using uniaxial constant force thermal cycling (UCFTC) to determine the effect of composition and aging on the material behavior. TEMSEM was used to evaluate the microstructure and determine the types of precipitates formed. The correlation between composition, heat treat, microstructure, and thermomechanical behavior will be addressed and discussed.

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

International Nuclear Information System (INIS)

Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

2007-01-01

Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model

Fatigue properties of MA 6000E, a gamma-prime strengthened ODS alloy. [Oxide Dispersion Strengthened Ni-base alloy for gas turbine blade applications

Science.gov (United States)

Kim, Y. G.; Merrick, H. F.

1980-01-01

MA 6000E is a corrosion resistant, gamma-prime strengthened ODS alloy under development for advanced turbine blade applications. The high temperature, 1093 C, rupture strength is superior to conventional nickel-base alloys. This paper addresses the fatigue behavior of the alloy. Excellent properties are exhibited in low and high cycle fatigue and also thermal fatigue. This is attributed to a unique combination of microstructural features, i.e., a fine distribution of dispersed oxides and other nonmetallics, and the highly elongated grain structure which advantageously modify the deformation characteristics and crack initiation and propagation modes from that characteristic of conventional gamma-prime hardened superalloys.

Cold Forming of Ni-Ti Shape Memory Alloy Sheet

Science.gov (United States)

Fann, Kaung-Jau; Su, Jhe-Yung

2018-03-01

Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its further application, this study attempts to investigate the feasibility of cold forming its sheet blank especially under a bi-axial tensile stress state. Not only experiments but also a Finite Element Analysis (FEA) with DEFORM 2D was conducted in this study. The material data for FEA was accomplished by the tensile test. An Erichsen-like cupping test was performed as well to determine the process parameter for experiment setup. As a result of the study, the Ni-Ti shape memory alloy sheet has a low formability for cold forming and shows a relative large springback after releasing the forming load.

Connection of crystallographic texture with anisotropy of yield strength of titanium alloy sheets

International Nuclear Information System (INIS)

Serebryannyj, V.N.; Koknaev, R.G.

1983-01-01

Using the programs developed in FORTRAN-4 algorithmic language for the ES-1022 computer the contribution of crystallographic texture to the anisotropy of yield strength in the sheet plane for warm-rolled sheets of α-titanium alloys VT1 and VT5-1, is evaluated. It is established, that experimental and calculation data for the sheet of VT1-0 agree satisfactorily in the angle range phi 40 deg the value anti M (phi) exceeds the experimental values σsub(0.2)(phi./σsub(0.2)(0). The results obtained for the sheet of the VT5-1 alloy show, that calculation and experimental data agree well for narrow angles (phi <= 60 deg) and at wider angles the values anti M(phi) exceed the values σsub(0.2)(phi)/σsub(0.2)(0). Calculation and experimental curves for the VT5-1 alloy on the whole agree better than for the VT1-0 one

Design and screening of nanoprecipitates-strengthened advanced ferritic alloys

Energy Technology Data Exchange (ETDEWEB)

Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chen, Tianyi [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sridharan, K. [Univ. of Wisconsin, Madison, WI (United States); He, Li [Univ. of Wisconsin, Madison, WI (United States)

2016-12-30

Advanced nuclear reactors as well as the life extension of light water reactors require advanced alloys capable of satisfactory operation up to neutron damage levels approaching 200 displacements per atom (dpa). Extensive studies, including fundamental theories, have demonstrated the superior resistance to radiation-induced swelling in ferritic steels, primarily inherited from their body-centered cubic (bcc) structure. This study aims at developing nanoprecipitates strengthened advanced ferritic alloys for advanced nuclear reactor applications. To be more specific, this study aims at enhancing the amorphization ability of some precipitates, such as Laves phase and other types of intermetallic phases, through smart alloying strategy, and thereby promote the crystalline®amorphous transformation of these precipitates under irradiation.

Composite sheet made of molybdenum and dispersion-strengthened copper

International Nuclear Information System (INIS)

Nicholson, R.D.; Fusco, R.S.

1990-01-01

This patent describes a roll-bonded composite sheet product having at least one layer of dispersion-strengthened copper and at least one layer of molybdenum. The composite is characterized by a sharply defined, cleavage-resistant interface between the copper and the molybdenum with substantially no detectable diffusion of one metal into the other across the interface. The composite is resistant to delamination and being capable of maintaining structural integrity upon repeated high temperature firings at temperatures up to 900 degrees C

A TEM quantitative evaluation of strengthening in an Mg-RE alloy reinforced with SiC

International Nuclear Information System (INIS)

Cabibbo, Marcello; Spigarelli, Stefano

2011-01-01

Magnesium alloys containing rare earth elements are known to have high specific strength, good creep and corrosion resistance up to 523 K. The addition of SiC ceramic particles strengthens the metal matrix composite resulting in better wear and creep resistance while maintaining good machinability. The role of the reinforcement particles in enhancing strength can be quantitatively evaluated using transmission electron microscopy (TEM). This paper presents a quantitative evaluation of the different strengthening contributions, determined through TEM inspections, in an SiC Mg-RE composite alloy containing yttrium, neodymium, gadolinium and dysprosium. Compression tests at temperatures ranging between 290 and 573 K were carried out. The microstructure strengthening mechanism was studied for all the compression conditions. Strengthening was compared to the mechanical results and the way the different contributions were combined is also discussed and justified. - Research Highlights: → TEM yield strengthening terms evaluation on a Mg-RE SiC alloy. → The evaluation has been extended to different compression temperature conditions. → Linear and Quadratic sum has been proposed and validated. → Hall-Petch was found to be the most prominent strengthening contributions.

Strengthening and elongation mechanism of Lanthanum-doped Titanium-Zirconium-Molybdenum alloy

Energy Technology Data Exchange (ETDEWEB)

Hu, Ping, E-mail: huping1985@126.com [School of Metallurgy Engineering, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Jinduicheng Molybdenum Co., Ltd., Xi’an 710068 (China); Hu, Bo-liang; Wang, Kuai-she; Song, Rui; Yang, Fan [School of Metallurgy Engineering, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Yu, Zhi-tao [Ruifulai Tungsten & Molybdenum Co., Ltd., Xi’an 721914 (China); Tan, Jiang-fei [School of Metallurgy Engineering, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Cao, Wei-cheng; Liu, Dong-xin; An, Geng [Jinduicheng Molybdenum Co., Ltd., Xi’an 710068 (China); Guo, Lei [Ruifulai Tungsten & Molybdenum Co., Ltd., Xi’an 721914 (China); Yu, Hai-liang [School of Mechanical, Materials and Mechatronics Engineering, University of Wollongong, NSW 2522 (Australia)

2016-12-15

The microstructural contributes to understand the strengthening and elongation mechanism in Lanthanum-doped Titanium-Zirconium-Molybdenum alloy. Lanthanum oxide particles not only act as heterogeneous nucleation core, but also act as the second phase to hinder the grain growth during sintering crystallization. The molybdenum substrate formed sub-grain under the effect of second phase when the alloy rolled to plate.

Efficient tunable luminescence of SiGe alloy sheet polymers

International Nuclear Information System (INIS)

Vogg, G.; Meyer, A. J.-P.; Miesner, C.; Brandt, M. S.; Stutzmann, M.

2001-01-01

Crystalline SiGe alloy sheet polymers were topotactically prepared from epitaxially grown calcium germanosilicide Ca(Si 1-x Ge x ) 2 precursor films in the whole composition range. These polygermanosilynes are found to be a well-defined mixture of the known siloxene and polygermyne sheet polymers with the OH groups exclusively bonded to silicon. The optical properties determined by photoluminescence and optical reflection measurements identify the mixed SiGe sheet polymers as direct semiconductors with efficient luminescence tunable in the energy range between 2.4 and 1.3 eV. [copyright] 2001 American Institute of Physics

Design of Helical Self-Piercing Rivet for Joining Aluminum Alloy and High-Strength Steel Sheets

International Nuclear Information System (INIS)

Kim, W. Y.; Kim, D. B.; Park, J. G; Kim, D. H.; Kim, K. H.; Lee, I. H.; Cho, H. Y.

2014-01-01

A self-piercing rivet (SPR) is a mechanical component for joining dissimilar material sheets such as those of aluminum alloy and steel. Unlike conventional rivets, the SPR directly pierces sheets without the need for drilling them beforehand. However, the regular SPR can undergo buckling when it pierces a high-strength steel sheet, warranting the design of a helical SPR. In this study, the joining and forging processes using the helical SPR were simulated using the commercial FEM code, DEFORM-3D. High-tensile-strength steel sheets of different strengths were joined with aluminum alloy sheets using the designed helical SPR. The simulation results were found to agree with the experimental results, validating the optimal design of a helical SPR that can pierce high-strength steel sheets

Design of Helical Self-Piercing Rivet for Joining Aluminum Alloy and High-Strength Steel Sheets

Energy Technology Data Exchange (ETDEWEB)

Kim, W. Y.; Kim, D. B.; Park, J. G; Kim, D. H.; Kim, K. H.; Lee, I. H.; Cho, H. Y. [Chungbuk National University, Cheongju (Korea, Republic of)

2014-07-15

A self-piercing rivet (SPR) is a mechanical component for joining dissimilar material sheets such as those of aluminum alloy and steel. Unlike conventional rivets, the SPR directly pierces sheets without the need for drilling them beforehand. However, the regular SPR can undergo buckling when it pierces a high-strength steel sheet, warranting the design of a helical SPR. In this study, the joining and forging processes using the helical SPR were simulated using the commercial FEM code, DEFORM-3D. High-tensile-strength steel sheets of different strengths were joined with aluminum alloy sheets using the designed helical SPR. The simulation results were found to agree with the experimental results, validating the optimal design of a helical SPR that can pierce high-strength steel sheets.

Strengthening of reinforced concrete beams with basalt-based FRP sheets: An analytical assessment

International Nuclear Information System (INIS)

Nerilli, Francesca; Vairo, Giuseppe

2016-01-01

In this paper the effectiveness of the flexural strengthening of RC beams through basalt fiber-reinforced sheets is investigated. The non-linear flexural response of RC beams strengthened with FRP composites applied at the traction side is described via an analytical formulation. Validation results and some comparative analyses confirm soundness and consistency of the proposed approach, and highlight the good mechanical performances (in terms of strength and ductility enhancement of the beam) produced by basalt-based reinforcements in comparison with traditional glass or carbon FRPs.

Strengthening of reinforced concrete beams with basalt-based FRP sheets: An analytical assessment

Energy Technology Data Exchange (ETDEWEB)

Nerilli, Francesca [Unicusano - Università degli Studi Niccolò Cusano Telematica Roma, 00166 Rome (Italy); Vairo, Giuseppe [Università degli Studi di Roma “Tor Vergata”- (DICII), 00133 Rome (Italy)

2016-06-08

In this paper the effectiveness of the flexural strengthening of RC beams through basalt fiber-reinforced sheets is investigated. The non-linear flexural response of RC beams strengthened with FRP composites applied at the traction side is described via an analytical formulation. Validation results and some comparative analyses confirm soundness and consistency of the proposed approach, and highlight the good mechanical performances (in terms of strength and ductility enhancement of the beam) produced by basalt-based reinforcements in comparison with traditional glass or carbon FRPs.

Strengthening of reinforced concrete beams with basalt-based FRP sheets: An analytical assessment

Science.gov (United States)

Nerilli, Francesca; Vairo, Giuseppe

2016-06-01

In this paper the effectiveness of the flexural strengthening of RC beams through basalt fiber-reinforced sheets is investigated. The non-linear flexural response of RC beams strengthened with FRP composites applied at the traction side is described via an analytical formulation. Validation results and some comparative analyses confirm soundness and consistency of the proposed approach, and highlight the good mechanical performances (in terms of strength and ductility enhancement of the beam) produced by basalt-based reinforcements in comparison with traditional glass or carbon FRPs.

Quantitative prediction of solute strengthening in aluminium alloys.

Science.gov (United States)

Leyson, Gerard Paul M; Curtin, William A; Hector, Louis G; Woodward, Christopher F

2010-09-01

Despite significant advances in computational materials science, a quantitative, parameter-free prediction of the mechanical properties of alloys has been difficult to achieve from first principles. Here, we present a new analytic theory that, with input from first-principles calculations, is able to predict the strengthening of aluminium by substitutional solute atoms. Solute-dislocation interaction energies in and around the dislocation core are first calculated using density functional theory and a flexible-boundary-condition method. An analytic model for the strength, or stress to move a dislocation, owing to the random field of solutes, is then presented. The theory, which has no adjustable parameters and is extendable to other metallic alloys, predicts both the energy barriers to dislocation motion and the zero-temperature flow stress, allowing for predictions of finite-temperature flow stresses. Quantitative comparisons with experimental flow stresses at temperature T=78 K are made for Al-X alloys (X=Mg, Si, Cu, Cr) and good agreement is obtained.

Characterization of Dispersion Strengthened Copper Alloy Prepared by Internal Oxidation Combined with Mechanical Alloying

Science.gov (United States)

Zhao, Ziqian; Xiao, Zhu; Li, Zhou; Zhu, Mengnan; Yang, Ziqi

2017-11-01

Cu-3.6 vol.% Al2O3 dispersion strengthened alloy was prepared by mechanical alloying (MA) of internal oxidation Cu-Al powders. The lattice parameter of Cu matrix decreased with milling time for powders milled in argon, while the abnormal increase of lattice parameter occurred in the air resulting from mechanochemical reactions. With a quantitative analysis, the combined method makes residual aluminum oxidized completely within 10-20 h while mechanical alloying method alone needs longer than 40 h. Lamellar structure formed and the thickness of lamellar structure decreased with milling time. The size of Al2O3 particles decreased from 46 to 22 nm after 40 h milling. After reduction, core-shell structure was found in MAed powders milled in the air. The compacted alloy produced by MAed powders milled in the argon had an average hardness and electrical conductivity of 172.2 HV and 82.1% IACS while the unmilled alloy's were 119.8 HV and 74.1% IACS due to the Al2O3 particles refinement and residual aluminum in situ oxidization.

Investigation of alloying effects in aluminum dispersion strengthened with Al2O3

International Nuclear Information System (INIS)

Copeland, G.L.

1975-10-01

Two types of alloying elements were investigated to determine if the room-temperature strength could be improved and if, through lowering the oxide content, the high-temperature ductility could be improved. Mg was investigated for its solid solution strengthening in one type alloy. The other type alloy involved further dispersion strengthening through adding Fe, Mo, Zr, Cr, V, and Ti which form highly stable intermetallic compounds with Al. Fabrication techniques were developed which produced uniform and reproducible rods for testing. Prealloyed powders were produced by atomizing the molten alloys and collecting the powders in water. This procedure produced uniform powders with a very fine distribution of the intermetallic compounds. Fabrication into rods then included ball-milling, vacuum hot pressing, vacuum heat treating, and hot extrusion. Mg additions improved strengths up to 200 0 C with little effect above that temperature. Room-temperature tensile strengths up to 77,000 psi were obtained which are comparable to the strengths obtained in conventional aluminum alloys. The additional dispersion strengthening of the intermetallic compounds is additive to that of the oxide from room temperature to 450 0 C. No significant improvements in ductility are obtained by reducing the oxide content since even at very low ball-milling times (i.e., low oxide contents) the uniform elongation at 450 0 C is typically 0.5 percent. Good combinations of strength and ductility at 450 0 C were obtained in some of the alloys containing intermetallic compounds with no ball-milling. Typical properties at this temperature were tensile strengths of 7,000 psi, uniform elongation of 3 percent, and total elongation of 35 percent. (21 tables, 33 fig, 43 references) (auth)

Study of laser bending of a preloaded Titanium alloy sheet

Directory of Open Access Journals (Sweden)

Wang Xiufeng

2014-01-01

Full Text Available Laser bending of sheet metals with preload offers some attractive characteristics/merits, comparing to laser free bending without prestressing on the metals. The study reported in this paper was focused on a Titanium alloy which finds widespread applications in aerospace manufacturing. FE simulation of laser bending with prestressing on the Titanium alloy sheet was conducted for the analysis of the bending process and experiment carried out to verify the model and the result. It was shown that the simulation result is close to that measured in the experiment. Based on the computed result, the load-displacement curve was analysed and transmission efficiency of the elastic energy defined to evaluate the bending effect. These enhanced understanding of the mechanism of laser bending with a preload. A method for the optimization on technological parameters was further proposed. Referring to the deformation targeted, the preload value was determined through the FE simulation. The result showed that, on the premise that the specimen surface can be prevented from damaging, transmission efficiency of the elastic energy could reach to the maximum value through adjusting technological parameters of the laser system and deformation accuracy of the specimen could also be improved through this approach. The work presented in this paper may find its application in the manufacture of Titanium alloy sheets with a more cost-effective and a more precise way.

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.

Effect of Intermediate Annealing on Microstructure and Property of 5182 Aluminum Alloy Sheet for Automobile

Directory of Open Access Journals (Sweden)

WANG Yu

2016-09-01

Full Text Available Effect of intermediate annealing on the microstructure and properties of 5182 aluminum alloy sheet with full annealed state (5182-O was investigated by means of optical microscope, scanning electron microscope and universal testing machine. The results indicate that compared with 5182-O sheet without intermediate annealing, 5182-O sheet with intermediate annealing possesses too fine grain size, intermetallic compounds not broken enough, larger size intermetallic particles, less dispersed phase. Yield strength and ultimate tensile strength, work hardening exponent and normal anisotropy of plastic strain ratio decrease but planner anisotropy of plastic strain ratio increases. The mechanical properties and forming ability of 5182-O aluminum alloy sheet and its microstructure are not improved significantly after intermediate annealing.

Evaluation of creep and relaxation data for hastelloy alloy x sheet

International Nuclear Information System (INIS)

Booker, M.K.

1979-02-01

Hastelloy alloy X has been a successful high-temperature structural material for more than two decades. Recently, Hastelloy alloy X sheet has been selected as a prime structural material for the proposed Brayton Isotope Power System (BIPS). The material also sees extensive application in the High-Temperature Gas-Cooled Reactor (HTGR). Design of these systems requires a detailed consideration of the high-temperature creep properties of this material. Therefore, available creep, creep-rupture, and relaxation data for Hastelloy alloy X were collected and analyzed to yield mathematical representations of the behavior for design use

Development of oxide dispersion strengthened W alloys produced by hot isostatic pressing

International Nuclear Information System (INIS)

Martinez, J.; Savoini, B.; Monge, M.A.; Munoz, A.; Pareja, R.

2011-01-01

A powder metallurgy technique has been developed to produce oxide strengthened W-Ti and W-V alloys using elemental powders and nanosized powders of La 2 O 3 or Y 2 O 3 as starting materials. The alloys consolidated by hot isostatic pressing resulted in high-density materials having an ultrafine-grained structure and microhardness values in the range 7-13 GPa. Atom force microscopy studies show a topographic relief in the Ti and V pools that appear in the consolidated alloys. This relief is attributed to the heterogeneous nucleation of martensite plates. The preliminary transmission electron microscopy studies have revealed that a dispersion of nanoparticles can be induced in these alloys produced via the present technique.

The role of solid-solution strengthening in the development of alloys for HTR applications

International Nuclear Information System (INIS)

Dean, A.V.

1978-09-01

In this paper the fundamental factors (lattice distortion, stacking fault energy and diffusion rates) which contribute to solid-solution strengthening are examined and used as a basis for indicating the composition of alloys likely to posses the highest strength at elevated temperatures. Alloys based on Ni-Cr-W-Mo should possess the best properties but alloys based on Ni-Cr-Nb-Ti are also recommended for further study. The effect of alloy composition on corrosion resistance has been excluded from this examination but it should be possible to adjust alloy composition in order to optimise corrosion resistance. (orig./IHOE) [de

Warm Deep Drawing of Rectangular Parts of AZ31 Magnesium Alloy Sheet Adopting Variable Blank Holder Force

International Nuclear Information System (INIS)

Peng Yinghong; Chang Qunfeng; Li Dayong; Zeng Xiaoqin

2007-01-01

AZ31 magnesium alloy sheet with good shape and formability is fabricated by warm cross rolling. Uniaxial tensile tests are conducted using a Gleeble 3500 thermal - mechanical simulator, and the mechanical properties of AZ31 magnesium alloy sheet are analyzed. A warm deep drawing process of square part is also simulated by the finite element method. The influences of blank holder force on the formability are numerically investigated. A double-action hydraulic press that can realize adjustable blank holder forces is developed and its working principle and control system are introduced. Some warm deep drawing experiments of square parts of AZ31 magnesium alloy sheet are also performed. Different variation schemes of the blank holder force with the stroke of the punch are tested, and the experiment results are compared. Results show that the suitable blank holder force variation scheme is a ladder curve with the punch stroke. Adopting the variable blank holder force technique can improve 13.2% of the drawing depth of square parts of AZ31 magnesium alloy sheet

A study on corrosion resistance of electrodeposited Zn-base alloy steel sheet

International Nuclear Information System (INIS)

Park, Hyun Soon

1986-01-01

Effects of electrodeposits of Zn-Ni or Zn-Co alloy with small amounts of Mo or W in sulphate bath on the corrosion resistance of plated steel sheet were studied. 1) The electrodeposition of Zn-Ni and Zn-Co alloy shows both anomalous codeposition behavior. The grade of anomalous codeposition of Zn-Co alloy rises with adding Mo or W in bath. 2) The Ni content in Zn-Ni deposits increases with decreasing cathode current density and with increasing bath temperature. 3) In case of electroplating of Zn-Co, the increase of cathodic current density of bath bring on increasing of the Co content, but on decreasing of the Mo content in deposits. And rising bath temperature increases both Co and Mo deposits. 4) The corrosion resistance of the Zn-Ni electrodeposited steel sheet is shown a maximum at the Ni content of 10-17%. The structure of Zn-Ni of these composition range was finegrained γ-phase. 5) The corrosion resistance of the Zn-Co electrodeposited steel sheet is improved with increasing Co content. The corrosion resistance of the Zn-Co-Mo or Zn-Co-W deposits electroplated by proper plating conditions was improved much more than that of Zn-Co deposits. (Author)

Overview of welding of oxide dispersion strengthened (ODS) alloys for advanced nuclear reactor applications

International Nuclear Information System (INIS)

Kalvala, Prasad Rao; Raja, K.S.; Misra, Manoranjan; Tache, Ricard A.

2009-01-01

Oxide dispersion strengthened (ODS) alloys are very promising materials for Generation IV reactors with a potential to be used at elevated temperatures under severe neutron exposure environment. Welding of the ODS alloys is an understudied problem. In this paper, an overview of welding of the ODS alloys useful for advanced nuclear reactor applications is presented. The microstructural changes and the resultant mechanical properties obtained by various solid state welding processes are reviewed. Based on our results on PM2000, an approach for future work on welding of the ODS alloys is suggested. (author)

Manufacture of a four-sheet complex component from different titanium alloys by superplastic forming

Science.gov (United States)

Allazadeh, M. R.; Zuelli, N.

2017-10-01

A superplastic forming (SPF) technology process was deployed to form a complex component with eight-pocket from a four-sheet sandwich panel sheetstock. Six sheetstock packs were composed of two core sheets made of Ti-6Al-4V or Ti-5Al-4Cr-4Mo-2Sn-2Zr titanium alloy and two skin sheets made of Ti-6Al-4V or Ti-6Al-2Sn-4Zr-2Mo titanium alloy in three different combinations. The sheets were welded with two subsequent welding patterns over the core and skin sheets to meet the required component's details. The applied welding methods were intermittent and continuous resistance seam welding for bonding the core sheets to each other and the skin sheets over the core panel, respectively. The final component configuration was predicted based on the die drawings and finite element method (FEM) simulations for the sandwich panels. An SPF system set-up with two inlet gas pipe feeding facilitated the trials to deliver two pressure-time load cycles acting simultaneously which were extracted from FEM analysis for specific forming temperature and strain rate. The SPF pressure-time cycles were optimized via GOM scanning and visually inspecting some sections of the packs in order to assess the levels of core panel formation during the inflation process of the sheetstock. Two sets of GOM scan results were compared via GOM software to inspect the surface and internal features of the inflated multisheet packs. The results highlighted the capability of the tested SPF process to form complex components from a flat multisheet pack made of different titanium alloys.

Ductility and microstructure of precipitation-strengthened alloys irradiated in HFIR

International Nuclear Information System (INIS)

Yang, W.J.S.; Hamilton, M.L.

1983-08-01

Six γ' and γ'/γ'' strengthened Ni-base alloys have shown near-zero ductility after irradiation at 300 to 600 0 C in HFIR to a peak exposure of 9 dpa. Microstructural examination of the irradiated specimens showed that the loss of ductility in these alloys arises from the simultaneous existence of a strong matrix and weak grain boundaries. The strong matrix is attributed to the irradiation-induced γ' and γ'/γ'' precipitates, the faulted loops and a high density of fine helium bubbles. The weak grain boundaries are attributed to the formation of an unfavorable precipitate, such as eta-plates, recrystallized grains, a thin layer of γ' and helium bubbles

Strengthening mechanisms and deformation behavior of cryomilled Al–Cu–Mg–Ag alloy

Energy Technology Data Exchange (ETDEWEB)

Kurmanaeva, Lilia, E-mail: lkurmanaeva@ucdavis.com [Department of Chemical Engineering & Materials Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); Topping, Troy D. [Department of Chemical Engineering & Materials Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); California State University, Sacramento, 6000 J Street, Sacramento, CA 95819 (United States); Wen, Haiming; Sugahara, Haruka; Yang, Hanry; Zhang, Dalong; Schoenung, Julie M.; Lavernia, Enrique J. [Department of Chemical Engineering & Materials Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States)

2015-05-25

Highlights: • Ultra-fine and coarse grained Al–Cu–Mg–Ag alloy samples were processed by methods of powder metallurgy. • Despite thermal exposure during consolidation,cryomilled materials retain an ultra-fine grained structure due to the presence of nano-dispersoids at grain boundaries. • Cryomilling results in a change in precipitation kinetics, due to the depletion of Mg atoms at the grain interiors and segregation of Mg, Cu and Ag atoms at grain boundaries. • Dominant deformation mechanisms in cryomilled samples were grain boundary strengthening and dispersion strengthening from oxides and nitrides. - Abstract: In the last decade, the commercially available heat-treatable aluminum alloy (AA) 2139 (Al–Cu–Mg–Ag) has generated interest within the aerospace and defense communities because of its high strength and damage tolerance as compared to those of other AA 2XXX alloys. In this work we investigate the possibility of enhancing the performance of AA 2139 via a nanostructuring approach involving the consolidation of cryomilled powders. For comparison purposes, two types of feedstock powders (cryomilled and unmilled, gas-atomized powder), were consolidated via dual mode dynamic forging. Our results show that, following heat treatment (HT), the strength of the cryomilled material increases in the range of ∼25% to ∼200% relative to that of the unmilled counterparts, depending on specific processing parameters. We present microstructural data, including grain size and precipitate chemistry, to provide insight into the underlying strengthening mechanisms. Vickers microhardess tests are used to evaluate peak heat treatments, and tensile testing is performed to characterize mechanical behavior. The kinetics of precipitation, strengthening mechanisms and deformation behavior are discussed. It is proposed that the combination of elemental segregation with the presence of oxides along grain boundaries, both facilitated by enhanced diffusion paths, are

Strengthening behavior of beta phase in lamellar microstructure of TiAl alloys

Science.gov (United States)

Zhu, Hanliang; Seo, D. Y.; Maruyama, K.

2010-01-01

β phase can be introduced to TiAl alloys by the additions of β stabilizing elements such as Cr, Nb, W, and Mo. The β phase has a body-centered cubic lattice structure and is softer than the α2 and γ phases in TiAl alloys at elevated temperatures, and hence is thought to have a detrimental effect on creep strength. However, fine β precipitates can be formed at lamellar interfaces by proper heat treatment conditions and the β interfacial precipitate improves the creep resistance of fully lamellar TiAl alloys, since the phase interface of γ/β retards the motion of dislocations during creep. This paper reviews recent research on high-temperature strengthening behavior of the β phase in fully lamellar TiAl alloys.

Development of oxide dispersion strengthened W alloys produced by hot isostatic pressing

Energy Technology Data Exchange (ETDEWEB)

Martinez, J.; Savoini, B.; Monge, M.A. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Munoz, A., E-mail: angel.munoz@uc3m.es [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

2011-10-15

A powder metallurgy technique has been developed to produce oxide strengthened W-Ti and W-V alloys using elemental powders and nanosized powders of La{sub 2}O{sub 3} or Y{sub 2}O{sub 3} as starting materials. The alloys consolidated by hot isostatic pressing resulted in high-density materials having an ultrafine-grained structure and microhardness values in the range 7-13 GPa. Atom force microscopy studies show a topographic relief in the Ti and V pools that appear in the consolidated alloys. This relief is attributed to the heterogeneous nucleation of martensite plates. The preliminary transmission electron microscopy studies have revealed that a dispersion of nanoparticles can be induced in these alloys produced via the present technique.

Semi-quantitative evaluation of texture components and anisotropy of the yield strength in 2524 T3 alloy sheets

International Nuclear Information System (INIS)

Shen, Fanghua; Yi, Danqing; Wang, Bin; Liu, Huiqun; Jiang, Yong; Tang, Cong; Jiang, Bo

2016-01-01

Decreasing the anisotropy of 2524 alloys is a key factor for their use in applications such as high-performance inertial components or space robots. Studying the interaction between sheet textures and anisotropy is a key factor to overcome this problem. In this study, the semi-quantitative approach to estimate the relation between texture and in-plane anisotropy (IPA) of yield strength has been developed. The intensity ratio between Cube and Brass texture components (F CGB ) was used as an effective variable for this purpose. This approach has been tested in 2524 T3 aluminum alloy sheets, which were investigated using X-Ray diffraction, scanning electron microscopy, optical microscopy and tensile tests. The results show that F CGB decreased with an increase in cold reduction. The 2524 T3 sheet, dominated by Cube texture grains, possesses the lowest in-plane anisotropy for the yield strength of all texture components investigated. The alloy sheet dominated by Brass texture exhibits the highest anisotropy, while the Goss texture-led sheets fall in between them. These results agree with the trends seen in the factor F CGB , suggesting that is suited to evaluate the anisotropy of yield strength in 2524 T3 alloy sheets semi-quantitatively.

Semi-quantitative evaluation of texture components and anisotropy of the yield strength in 2524 T3 alloy sheets

Energy Technology Data Exchange (ETDEWEB)

Shen, Fanghua [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yi, Danqing, E-mail: yioffice@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Light Alloy Research Institute, Central South University, Changsha, Hunan 410083 (China); National Collaborative Innovation Center of Advanced Nonferrous Structural Materials and Manufacturing, Central South University, Changsha 410083 (China); Wang, Bin; Liu, Huiqun; Jiang, Yong; Tang, Cong; Jiang, Bo [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

2016-10-15

Decreasing the anisotropy of 2524 alloys is a key factor for their use in applications such as high-performance inertial components or space robots. Studying the interaction between sheet textures and anisotropy is a key factor to overcome this problem. In this study, the semi-quantitative approach to estimate the relation between texture and in-plane anisotropy (IPA) of yield strength has been developed. The intensity ratio between Cube and Brass texture components (F{sub CGB}) was used as an effective variable for this purpose. This approach has been tested in 2524 T3 aluminum alloy sheets, which were investigated using X-Ray diffraction, scanning electron microscopy, optical microscopy and tensile tests. The results show that F{sub CGB} decreased with an increase in cold reduction. The 2524 T3 sheet, dominated by Cube texture grains, possesses the lowest in-plane anisotropy for the yield strength of all texture components investigated. The alloy sheet dominated by Brass texture exhibits the highest anisotropy, while the Goss texture-led sheets fall in between them. These results agree with the trends seen in the factor F{sub CGB}, suggesting that is suited to evaluate the anisotropy of yield strength in 2524 T3 alloy sheets semi-quantitatively.

Ferritic oxide dispersion strengthened alloys by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Allahar, Kerry N., E-mail: KerryAllahar@boisestate.edu [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Burns, Jatuporn [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Jaques, Brian [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Wu, Y.Q. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Charit, Indrajit [Department of Chemical and Materials Engineering, University of Idaho, McClure Hall Room 405D, Moscow, ID 83844 (United States); Cole, James [Idaho National Laboratory, Idaho Falls, ID 83401 (United States); Butt, Darryl P. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States)

2013-11-15

Spark plasma sintering (SPS) was used to consolidate a Fe–16Cr–3Al (wt.%) powder that was mechanically alloyed with Y{sub 2}O{sub 3} and Ti powders to produce 0.5 Y{sub 2}O{sub 3} and 0.5 Y{sub 2}O{sub 3}–1Ti powders. The effects of mechanical alloying and sintering conditions on the microstructure, relative density and hardness of the sintered oxide dispersion strengthened (ODS) alloys are presented. Scanning electron microscopy indicated a mixed fine-grain and coarse-grain microstructure that was attributed to recrystallization and grain growth during sintering. Analysis of the transmission electron microscopy (TEM) and atom probe tomography (APT) data identified Y–O and Y–O–Ti nanoclusters. Elemental ratios of these nanoclusters were consistent with that observed in hot-extruded ODS alloys. The influence of Ti was to refine the grains as well as the nanoclusters with there being greater number density and smaller sizes of the Y–O–Ti nanoclusters as compared to the Y–O nanoclusters. This resulted in the Ti-containing samples being harder than the Ti-free alloys. The hardness of the alloys with the Y–O–Ti nanoclusters was insensitive to sintering time while smaller hardness values were associated with longer sintering times for the alloys with the Y–O nanoclusters. Pressures greater than 80 MPa are recommended for improved densification as higher sintering temperatures and longer sintering times at 80 MPa did not improve the relative density beyond 97.5%.

Effect of material flow on joint strength in activation spot joining of Al alloy and steel sheets

International Nuclear Information System (INIS)

Watanabe, Goro; Yogo, Yasuhiro; Takao, Hisaaki

2014-01-01

A new joining method for dissimilar metal sheets was developed where a rotated consumable rod of Al alloy is pressed onto an Al alloy sheet at the part overlapped with a mild steel sheet. The metal flow in the joining region is increased by the through-hole in the Al sheet and consumable Al rod. The rod creates the joint interface and pads out of the thinly joined parts through pressing. This produces a higher joint strength than that of conventional friction stir spot welding. Measurements of the joint interface showed the presence of a 5-10 nm thick amorphous layer consisting of Al and Mg oxides

Plasticity of oxide dispersion strengthened ferritic alloys; Plasticite des alliages ferritiques renforces par dispersion d`oxydes

Energy Technology Data Exchange (ETDEWEB)

Zakine, C

1994-07-05

The object of this work is to study the plasticity mechanisms of two oxide dispersion strengthened ferritic alloys, DT and DY. Microstructural characterisation has been performed on DT and DY alloys by optical, scanning and transmission electron microscopy. These materials, strengthened by an oxide dispersion, contain an intermetallic {chi} phase precipitated on grain boundaries. The {chi} phase, stable up to 900 deg, can be dissolved into the matrix by heat treatment beyond 1 000 deg. Between 20 and 700 deg, according to tensile tests, the DY alloy which is strengthened by a fine dispersion of yttria particles is more resistant and less ductile than DT alloy, strengthened by titanium oxides. Tensile tests performed at room temperature, in the chamber of a SEM, have shown that micro-cracking of the {chi} phase coincides with the first stage of the macroscopic yielding. The cavities initiated by the {chi} phase micro-cracking induce a ductile fracture of the matrix. A dynamic strain ageing mechanism has been observed around 400 deg, which is attributed to the Mo contribution. Between 20 and 700 deg, comparison of tensile properties of alloys with or without {chi} phase has shown that the intermetallic phase has a detrimental effect on the ductility, but has no influence on the mechanical strength. Creep tests have been performed between 500 and 700 deg. Thermally activated plasticity mechanisms are observed in this temperature range. The {chi} phase, which is always micro-cracked after tensile testing, is not damaged after creep testing below a critical stress. This behaviour is explained by the influence of strain rate through the competition between strain hardening and relaxation of the matrix. (author).

Dispersion strengthened ferritic alloy for use in liquid-metal fast breeder reactors (LMFBRS)

International Nuclear Information System (INIS)

Fischer, J.J.

1978-01-01

A dispersion-strengthened ferritic alloy is provided which has high-temperature strength and is readily fabricable at ambient temperatures, and which is useful as structural elements of liquid-metal fast breeder reactors. 4 tables

The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy

Science.gov (United States)

Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J.; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai

2017-01-01

A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process. PMID:28772747

The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy

Directory of Open Access Journals (Sweden)

Chao Yang

2017-04-01

Full Text Available A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt % were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA route followed by spark plasma sintering (SPS and rapid cooling. Neutron Powder Diffraction (NPD, Electron Back Scattering Diffraction (EBSD, and Transmission Electron Microscopy (TEM were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process.

The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy.

Science.gov (United States)

Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai

2017-04-06

A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5-2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni₃Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo₂C particles during sintering. The amount of grain boundaries greatly increases the Hall-Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process.

Strengthening of Zircaloy-4 using Oxide Particles by Laser Beam Treatment

Energy Technology Data Exchange (ETDEWEB)

Jung, Yang-Il; Park, Dong-Jun; Park, Jung-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

Oxide particles such as Y{sub 2}O{sub 3} and CeO{sub 2} were dispersed homogeneously in a Zircaloy-4 plate surface using an LBS method. From the tensile test at 380 .deg. C, the strength of laser ODS alloying on the Zircaloy-4 sheet was increased more than 50% when compared to the initial state of the sheet, although the ODS alloyed layer was less than 20% of the specimen thickness. This technology showed a good opportunity to increase the strength without major changes in the substrates of zirconium-based alloys. Accident tolerant fuel (ATF) cladding is being developed globally after the Fukushima accident with the demands for the nuclear fuel having higher safety at normal operation conditions as well as even in a severe accident conditions. Korea Atomic Energy Research Institute (KAERI) is one of the leading organizations for developing ATF claddings. One concept is to form an oxidation-resistant layer on Zr cladding surface. The other is to increase high-temperature mechanical strength of Zr tube. The oxide dispersion strengthened (ODS) zirconium was proposed to increase the strength of the Zr-based alloy up to high temperatures.

First-principles investigations of solid solution strengthening in Al alloys

OpenAIRE

Ma, Duancheng

2012-01-01

Any material properties, in principle, can be reproduced or predicted by performing firstprinciples calculations. Nowadays, however, we are dealing with complex alloy compositions and processes. The complexities cannot be fully described by first-principles, because of the limited computational power. The primary objective of this study is to investigate an important engineering problem, solid solution strengthening, in a simplified manner. The simplified scheme should allow fast and reliable...

Enhanced Age Strengthening of Mg-Nd-Zn-Zr Alloy via Pre-Stretching

Directory of Open Access Journals (Sweden)

Erjun Guo

2016-08-01

Full Text Available Pre-stretching was carried out to modify the microstructure of Mg-Nd-Zn-Zr alloy to enhance its age strengthening. The results indicated that more heterogeneous nucleation sites can be provided by the high density of dislocations caused by the plastic pre-stretching deformation, as well as speeding up the growth rate of precipitates. Comparison of microstructure in non-pre-stretched specimens after artificial aging showed that pre-stretched specimens exhibited a higher number density of precipitates. The fine and coarse plate-shaped precipitates were found in the matrix. Due to an increase in the number density of precipitates, the dislocation slipping during the deformation process is effectively hindered, and the matrix is strengthened. The yield strength stabilizes at 4% pre-stretching condition, and then the evolution is stable within the error bars. The 8% pre-stretched specimens can achieve an ultimate tensile strength of 297 MPa. However, further pre-stretching strains after 8% cannot supply any increase in strength. Tensile fracture surfaces of specimens subjected to pre-stretching strain mainly exhibit a trans-granular cleavage fracture. This work indicated that a small amount of pre-stretching strain can further increase strength of alloy and also effectively enhance the formation of precipitates, which can expand the application fields of this alloy.

Enhanced age-strengthening by two-step progressive solution treatment in an Mg–Zn–Al–Re alloy

International Nuclear Information System (INIS)

Zhang, Jing; Yuan, Fuqing; Du, Yong

2013-01-01

Highlights: • A two-step progressive solution treatment schedule was proposed. • The treatment enhanced dissolution of ternary eutectic phases in Mg–Zn–Al alloy. • Solution temperature could break the limit of the ternary eutectic temperature. • There was no microstructural over-heating defect during the progressive heating. • The τ precipitates have a remarkable dispersion strengthening effect. - Abstract: A two-step progressive solution treatment was designed and performed on an as-extruded Mg–7Zn–3Al–0.7Er alloy. The resultant microstructure and mechanical properties were examined by means of scanning electron microscopy, X-ray diffractometer, differential scanning calorimetry and hardness testing. The results showed that the two-step progressive solution treatment could enhance the dissolution of the ternary eutectic phases in the Mg–Zn–Al system without the formation of microstructure over-heating defects. After homogenization for 50 h at 325 °C, the volume fraction of the undissolved particles in the Mg–7Zn–3Al–0.7Er alloy ingot was ∼4.1%. Two-step progressive solution treatment performed on the as-extruded alloy could further dissolve the particles. Only 1.5% undissolved particles remained after the treatment. The supersaturated degree of both the dissolved solute atoms and vacancies in the α-Mg matrix was expected to be increased, resulting in an enhanced age-strengthening, compared with normal solution and aging treatments. Moreover, the processed alloy exhibited a homogenous and stable fine grain structure. Remarkable dispersion strengthening effect of ternary τ (Mg 32 (Al,Zn) 49 ) precipitates occurred in Mg–Zn–Al alloy was also identified

Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

Science.gov (United States)

Trivedi, Shefali; Ravi Kumar, D.; Aravindan, S.

2016-10-01

Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1-0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.

Heat transfer modeling in asymmetrical sheet rolling of aluminium alloys with ultra high shear strain

Directory of Open Access Journals (Sweden)

Pesin Alexander

2016-01-01

Full Text Available Asymmetrical sheet rolling is a method of severe plastic deformation (SPD for production of aluminium alloys with UFG structure. Prediction of sheet temperature during SPD is important. The temperature of sheet is changed due to the conversion of mechanical work into heat through sliding on contact surfaces and high shear strain. Paper presents the results of FEM simulation of the effect of contact friction, rolling speed and rolls speed ratio on the heating of aluminium sheets during asymmetrical rolling.

Strengthening mechanisms of Fe nanoparticles for single crystal Cu–Fe alloy

International Nuclear Information System (INIS)

Shi, Guodong; Chen, Xiaohua; Jiang, Han; Wang, Zidong; Tang, Hao; Fan, Yongquan

2015-01-01

A single crystal Cu–Fe alloy with finely dispersed precipitate Fe nanoparticles was fabricated in this study. The interface relationship of iron nanoparticle and copper matrix was analyzed with a high-resolution transmission electron microscope (HRTEM), and the effect of Fe nanoparticles on mechanical properties of single crystal Cu–Fe alloy was discussed. Results show that, the finely dispersed Fe nanoparticles can be obtained under the directional solidification condition, with the size of 5–50 nm and the coherent interface between the iron nanoparticle and the copper matrix. Single crystal Cu–Fe alloy possesses improved tensile strength of 194.64 MPa, and total elongation of 44.72%, respectively, at room temperature, in contrast to pure Cu sample. Nanoparticles which have coherent interface with matrix can improve the dislocation motion state. Some dislocations can slip through the nanoparticle along the coherent interface and some dislocations can enter into the nanoparticles. Thus to improve the tensile strength of single crystal Cu–Fe alloy without sacrificing the ductility simultaneously. Based on the above analyses, strengthening mechanisms of Fe nanoparticles for single crystal Cu–Fe alloy was described

Effects of organic acid pickling on the corrosion resistance of magnesium alloy AZ31 sheet

DEFF Research Database (Denmark)

Nwaogu, Ugochukwu Chibuzoh; Blawert, C.; Scharnagl, N.

2010-01-01

mu m of the contaminated surface was required to reach corrosion rates less than 1 mm/year in salt spray condition. Among the three organic acids examined, acetic acid is the best choice. Oxalic acid can be an alternative while citric acid is not suitable for cleaning AZ31 sheet, because......Organic acids were used to clean AZ31 magnesium alloy sheet and the effect of the cleaning processes on the surface condition and corrosion performance of the alloy was investigated. Organic acid cleanings reduced the surface impurities and enhanced the corrosion resistance. Removal of at least 4...

Stamping of Thin-Walled Structural Components with Magnesium Alloy AZ31 Sheets

International Nuclear Information System (INIS)

Chen, F.-K.; Chang, C.-K.

2005-01-01

In the present study, the stamping process for manufacturing cell phone cases with magnesium alloy AZ31 sheets was studied using both the experimental approach and the finite element analysis. In order to determine the proper forming temperature and set up a fracture criterion, tensile tests and forming limit tests were first conducted to obtain the mechanical behaviors of AZ31 sheets at various elevated temperatures. The mechanical properties of Z31 sheets obtained from the experiments were then adopted in the finite element analysis to investigate the effects of the process parameters on the formability of the stamping process of cell phone cases. The finite element simulation results revealed that both the fracture and wrinkle defects could not be eliminated at the same time by adjusting blank-holder force or blank size. A drawbead design was then performed using the finite element simulations to determine the size and the location of drawbead required to suppress the wrinkle defect. An optimum stamping process, including die geometry, forming temperature, and blank dimension, was then determined for manufacturing the cell phone cases. The finite element analysis was validated by the good agreement between the simulation results and the experimental data. It confirms that the cell phone cases can be produced with magnesium alloy AZ31 sheet by the stamping process at elevated temperatures

Microscopy of Alloy Formation on Arc Plasma Sintered Oxide Dispersion Strengthen (ODS) Steel

Science.gov (United States)

Bandriyana, B.; Sujatno, A.; Salam, R.; Dimyati, A.; Untoro, P.

2017-07-01

The oxide dispersed strengthened (ODS) alloys steel developed as structure material for nuclear power plants (NPP) has good resistant against creep due to their unique microstructure. Microscopy investigation on the microstructure formation during alloying process especially at the early stages was carried out to study the correlation between structure and property of ODS alloys. This was possible thanks to the arc plasma sintering (APS) device which can simulate the time dependent alloying processes. The ODS sample with composition of 88 wt.% Fe and 12 wt.% Cr powder dispersed with 1 wt.% ZrO2 nano powder was mixed in a high energy milling, isostatic compressed to form sample coins and then alloyed in APS. The Scanning Electron Microscope (SEM) with X-ray Diffraction Spectroscopy (EDX) line scan and mapping was used to characterize the microstructure and elemental composition distribution of the samples. The alloying process with unification of each Fe and Cr phase continued by the alloying formation of Fe-Cr by inter-diffusion of both Fe and Cr and followed by the improvement of the mechanical properties of hardness.

Microstructural and magnetic properties study of Fe–P rolled sheet alloys

International Nuclear Information System (INIS)

Jafari, S.; Beitollahi, A.; EftekhariYekta, B.; Kanada, Keiu; Ohkubo, T.; Gopalan, R.; Herzer, Giselher; Hono, K.

2014-01-01

In the work presented here, the soft magnetic properties of Fe 1−x P x (x=0.36, 0.7, 1.1 at%) rolled sheet alloys were investigated. In this respect, the as-rolled sheets were subjected to a two steps annealing processes; the first one between 800 and 1000 °C for 1 h referred as first stage annealing and the second one at lower temperatures (500 and 600 °C) for 30 min, referred as second step annealing. BH tracer measurements at 50 Hz showed that for all of the phosphorous containing alloys, in general, the magnitude of coercivity decreased by applying these two annealing steps compared to those of as-rolled samples. For all of the studied samples, the B 50 values measured at 50 Hz were in the range of 1.6–1.7 tesla (T). Samples having highest amount of phosphorous (1.1 at%) exhibited lower eddy current loss compared to the rest of the specimens due to the increased electrical resistivity. Besides, microstructural studies revealed that the prepared samples were free from Fe 3 P phase precipitation and the average grain size increased (∼three times) with increasing the phosphorous content giving rise to the decrease of hysteresis losses. Further, amongst the whole prepared samples, the alloy containing 1.1 at% P showed the lowest hysteresis loss (6.99 W/kg), eddy current loss (9.25 W/kg) as well as the highest magnetic induction (1.7 T) at 5000 A/M (B 50 ). - Highlights: • We have studied magnetic properties and microstructure of Fe 1−x P x rolled sheet alloys. • Increasing phosphorous content increases the B 50 from 1.65 to 1.70 T. • Increasing phosphorous content causes the decline of the eddy current loss. • The grain size increases about 3 times with increasing phosphorous concentration. • The hysteresis loss decreases with increasing the phosphorous content (88%)

Microstructural and magnetic properties study of Fe–P rolled sheet alloys

Energy Technology Data Exchange (ETDEWEB)

Jafari, S. [Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Beitollahi, A., E-mail: beitolla@iust.ac.ir [Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); EftekhariYekta, B. [Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Kanada, Keiu [Toyota Motor Corporation, Aichi Prefecture, Toyota (Japan); Ohkubo, T.; Gopalan, R. [Magnetic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Herzer, Giselher [Vacuumschmelze GmBH, D-63450 Hanau (Germany); Hono, K. [Magnetic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2014-05-01

In the work presented here, the soft magnetic properties of Fe{sub 1−x}P{sub x} (x=0.36, 0.7, 1.1 at%) rolled sheet alloys were investigated. In this respect, the as-rolled sheets were subjected to a two steps annealing processes; the first one between 800 and 1000 °C for 1 h referred as first stage annealing and the second one at lower temperatures (500 and 600 °C) for 30 min, referred as second step annealing. BH tracer measurements at 50 Hz showed that for all of the phosphorous containing alloys, in general, the magnitude of coercivity decreased by applying these two annealing steps compared to those of as-rolled samples. For all of the studied samples, the B{sub 50} values measured at 50 Hz were in the range of 1.6–1.7 tesla (T). Samples having highest amount of phosphorous (1.1 at%) exhibited lower eddy current loss compared to the rest of the specimens due to the increased electrical resistivity. Besides, microstructural studies revealed that the prepared samples were free from Fe{sub 3}P phase precipitation and the average grain size increased (∼three times) with increasing the phosphorous content giving rise to the decrease of hysteresis losses. Further, amongst the whole prepared samples, the alloy containing 1.1 at% P showed the lowest hysteresis loss (6.99 W/kg), eddy current loss (9.25 W/kg) as well as the highest magnetic induction (1.7 T) at 5000 A/M (B{sub 50}). - Highlights: • We have studied magnetic properties and microstructure of Fe{sub 1−x}P{sub x} rolled sheet alloys. • Increasing phosphorous content increases the B{sub 50} from 1.65 to 1.70 T. • Increasing phosphorous content causes the decline of the eddy current loss. • The grain size increases about 3 times with increasing phosphorous concentration. • The hysteresis loss decreases with increasing the phosphorous content (88%)

Strengthening Hadfield steel welds by nitrogen alloying

International Nuclear Information System (INIS)

Efstathiou, C.; Sehitoglu, H.

2009-01-01

Strengthening Hadfield steel weld repairs by introducing nitrogen into the weld region was proven to be feasible via two welding techniques. The first technique required a pure Hadfield steel filler material to be diffusion treated in a high pressure nitrogen gas environment, and subsequently used during tungsten inert gas welding with a pure argon shielding gas. The second technique used a Hadfield steel filler material, and a 10% nitrogen containing argon shielding gas during tungsten inert gas welding. Both techniques increased the yield strength, the hardening rate, and the ultimate strength of the weld region. Using optical microscopy, scanning electron microscopy, and Auger spectroscopy, we determined that the increased strength of the weld region resulted from a combination of nitrogen alloying and microstructural refinement

Hot mechanical behaviour of dispersion strengthened Cu alloys

International Nuclear Information System (INIS)

Garcia G, Jose; Espinoza G, Rodrigo; Palma H, Rodrigo; Sepulveda O, Aquiles

2003-01-01

This work is part of a research project which objective is the improvement of the high-temperature mechanical properties of copper, without an important decrease of the electrical or thermal conduction properties. The general hypothesis is that this will be done by the incorporation of nanometric ceramic dispersoids for hindering the dislocation and grain boundaries movement. In this context, the object of the present work is the study of the resistance to hot deformation of dispersion-strengthened copper alloys which have prepared by reactive milling. Two different alloys, Cu-2,39wt.%Ti-0.56wt.%C and Cu-1.18wt.%Al, were prepared so as obtain a copper matrix reinforced with nanometric TiC y Al 2 O 3 particles with a nominal total amount of 5 vol.%. The particles were developed by an in-situ formation process during milling. The materials were prepared in an attritor mill, and consolidated by extrusion at 750 o C, with an area reduction rate of 10:1. The resistance to hot deformation was evaluated by hot compression tests at 500 and 850 o C, at initial strain rates of 10 -3 and 10 -4 s-1. To evaluate the material softening due temperature, annealing at 400, 650 y 900 o C during 1h were applied; after that, hardness was measured at room temperature. Both studies alloys presented a higher resistance to hot deformation than pure copper, with or without milling. Moreover, the Cu-Ti-C alloy presented a mechanical resistance higher than that of the Cu-Al one. Both alloys presented strain-stress compression curves with a typical hot-work shape: an initial maximum followed by a stationary plateau. The Cu-Ti-C alloy had a higher hardness and did not present a hardness decay even after annealings at the higher temperature imposed (900 o C), while the Cu-Al alloy did exhibit a strong decay of hardness after the annealing at 900 o C. The best behaviour exhibited by the Cu-Ti C alloy, was attributed to the formation of a major quantity of dispersoids that in the Cu-Al alloy. In

Initial Development in Joining of ODS Alloys Using Friction Stir Welding

Energy Technology Data Exchange (ETDEWEB)

Ren, Weiju [ORNL; Feng, Zhili [ORNL

2007-08-01

Solid-state welding of oxide-dispersion-strengthened (ODS) alloy MA956 sheets using friction stir welding (FSW) was investigated. Butt weld was successfully produced. The weld and base metals were characterized using optical microscopy, scanning electronic microscopy, transmission electronic microscopy, and energy dispersion x-ray spectrum. Microhardness mapping was also conducted over the weld region. Analyses indicate that the distribution of the strengthening oxides was preserved in the weld. Decrease in microhardness of the weld was observed but was insignificant. The preliminary results seem to confirm the envisioned feasibility of FSW application to ODS alloy joining. For application to Gen IV nuclear reactor heat exchanger, further investigation is suggested.

High-temperature deformation of dispersion-strengthened Cu-Zr-Ti-C alloys

International Nuclear Information System (INIS)

Palma, Rodrigo H.; Sepulveda, Aquiles; Espinoza, Rodrigo; Dianez, M. Jesus; Criado, Jose M.; Sayagues, M. Jesus

2005-01-01

The hot mechanical behaviour and microstructure of Cu-5 vol.% TiC, Cu-5 vol.% ZrO 2 and Cu-2.5 vol.% TiC-2.5 vol.% ZrO 2 alloys prepared by reaction milling were studied. After a test of 1 h annealing at 1173 K, the Cu-5 vol.% ZrO 2 alloy presented the lower softening resistance to annealing, while the other two ones kept their initial room-temperature hardness (about 2 GPa). Hot-compression tests at 773 and 1123 K, at initial true strain rates of 0.85 x 10 -3 and 0.85 x 10 -4 s -1 were performed. The Cu-2.5 vol.% TiC-2.5 vol.% ZrO 2 and the Cu-5 vol.% ZrO 2 alloys were the strongest and softest materials, respectively. Moreover, by electron microscopy, nanometric TiC and micrometric particles were detected in the Cu-5 vol.% TiC and Cu-5 vol.% ZrO 2 alloys, respectively. A possible explanation for the observed behaviour of these materials is proposed. In the compression tests, it was also found that strain rate has a low effect on flow stress, as it has been previously observed by various authors in dispersion-strengthened alloys deformed at high temperatures

Summary of Prior Work on Joining of Oxide Dispersion-Strengthened Alloys

Energy Technology Data Exchange (ETDEWEB)

Wright, Ian G [ORNL; Tatlock, Gordon J [ORNL; Badairy, H. [University of Liverpool; Chen, C-L. [University of Liverpool

2009-08-01

There is a range of joining techniques available for use with ODS alloys, but care should be exercised in matching the technique to the final duty requirements of the joint. The goal for joining ODS alloys is a joint with no local disruption of the distribution of the oxide dispersion, and no significant change in the size and orientation of the alloy microstructure. Not surprisingly, the fusion welding processes typically employed with wrought alloys produce the least satisfactory results with ODS alloys, but some versions, such as fusion spot welding, and the laser and electron-beam welding technologies, have demonstrated potential for producing sound joints. Welds made using solid-state spot welding reportedly have exhibited parent metal properties. Thus, it is possible to employ processes that result in significant disruption of the alloy microstructure, as long as the processing parameters are adjustment to minimize the extent of or influence of the changes in the alloy microstructure. Selection among these joining approaches largely depends on the particular application and component configuration, and an understanding of the relationships among processing, alloy microstructure, and final properties is key. Recent developments have resulted in friction welding evolving to be a prime method for joining ODS sheet products, and variants of brazing/diffusion bonding have shown excellent promise for use with tubes and pipes. The techniques that come closest to the goal defined above involve solid-state diffusion bonding and, in particular, it has been found that secondary recrystallization of joints made by pulsed plasma-assisted diffusion can produce the desired, continuous, large alloy grain structure through the joint. Such joints have exhibited creep rupture failure at >82% of the load needed to fail the monolithic parent alloy at 1000 C.

Properties of Rolled AZ31 Magnesium Alloy Sheet Fabricated by Continuous Variable Cross-Section Direct Extrusion

Science.gov (United States)

Liu, Yang; Li, Feng; Li, Xue Wen; Shi, Wen Yong

2018-03-01

Rolling is currently a widely used method for manufacturing and processing high-performance magnesium alloy sheets and has received widespread attention in recent years. Here, we combined continuous variable cross-section direct extrusion (CVCDE) and rolling processes. The microstructure and mechanical properties of the resulting sheets rolled at different temperatures from CVCDE extrudate were investigated by optical microscopy, scanning electron microscope, transmission electron microscopy and electron backscatter diffraction. The results showed that a fine-grained microstructure was present with an average grain size of 3.62 μm in sheets rolled from CVCDE extrudate at 623 K. Dynamic recrystallization and a large strain were induced by the multi-pass rolling, which resulted in grain refinement. In the 573-673 K range, the yield strength, tensile strength and elongation initially increased and then declined as the CVCDE temperature increased. The above results provide an important scientific basis of processing, manufacturing and the active control on microstructure and property for high-performance magnesium alloy sheet.

Microstructure and mechanical properties of Mg-Al-Mn-Ca alloy sheet produced by twin roll casting and sequential warm rolling

International Nuclear Information System (INIS)

Wang Yinong; Kang, Suk Bong; Cho, Jaehyung

2011-01-01

Research highlights: → This work, taking AM30 + 0.2Ca alloy as experimental material, will provide some new information as follows: one is microstructural difference between twin roll cast and ingot cast AM31-0.2Ca alloy. The other is the comparison of tensile properties after warm rolling and annealing. Suggesting the possibility of the development of wrought magnesium alloy sheets by strip casting. - Abstract: Microstructural evolution and mechanical properties of twin roll cast (TRC) Mg-3.3 wt.%Al-0.8 wt.%Mn-0.2 wt.%Ca (AM31 + 0.2Ca) alloy strip during warm rolling and subsequent annealing were investigated in this paper. The as-TRC alloy strip shows columnar dendrites in surface and equiaxed dendrites in center regions, as well as finely dispersed primary Al 8 Mn 5 particles on interdendritic boundaries which result in the beneficial effect on microstructural refinement of strip casting. The warm rolled sheets show intensively deformed band or shear band structures, as well as finely and homogeneously dispersed Al-Mn particles. No evident dynamic recrystallization (DRX) takes place during warm rolling process, which is more likely attributed to the finely dispersed particle and high solid solution of Al and Mn atoms in α-Mg matrix. After annealing at 350 deg. C for 1 h, the warm rolled TRC sheets show fine equiaxed grains around 7.8 μm in average size. It has been shown that the present TRC alloy sheet has superior tensile strength and comparative elongation compared to commercial ingot cast (IC) one, suggesting the possibility of the development of wrought magnesium alloy sheets by twin roll strip casting processing. The microstructural evolution during warm rolling and subsequent annealing as well as the resulting tensile properties were analyzed and discussed.

Prediction of Precipitation Strengthening in the Commercial Mg Alloy AZ91 Using Dislocation Dynamics

Science.gov (United States)

Aagesen, L. K.; Miao, J.; Allison, J. E.; Aubry, S.; Arsenlis, A.

2018-03-01

Dislocation dynamics simulations were used to predict the strengthening of a commercial magnesium alloy, AZ91, due to β-Mg17Al12 formed in the continuous precipitation mode. The precipitate distributions used in simulations were determined based on experimental characterization of the sizes, shapes, and number densities of the precipitates for 10-hour aging and 50-hour aging. For dislocations gliding on the basal plane, which is expected to be the dominant contributor to plastic deformation at room temperature, the critical resolved shear stress to bypass the precipitate distribution was 3.5 MPa for the 10-hour aged sample and 16.0 MPa for the 50-hour aged sample. The simulation results were compared to an analytical model of strengthening in this alloy, and the analytical model was found to predict critical resolved shear stresses that were approximately 30 pct lower. A model for the total yield strength was developed and compared with experiment for the 50-hour aged sample. The predicted yield strength, which included the precipitate strengthening contribution from the DD simulations, was 132.0 MPa, in good agreement with the measured yield strength of 141 MPa.

Development and Characterization of Improved NiTiPd High-Temperature Shape-Memory Alloys by Solid-Solution Strengthening and Thermomechanical Processing

Science.gov (United States)

Bigelow, Glen; Noebe, Ronald; Padula, Santo, II; Garg, Anita; Olson, David

2006-01-01

The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently motivating research in high-temperature shape-memory alloys (HTSMA) with transformation temperatures greater than 100 C. One of the basic high-temperature alloys investigated to fill this need is Ni(19.5)Ti(50.5)Pd30. Initial testing has indicated that this alloy, while having acceptable work characteristics, suffers from significant permanent deformation (or ratcheting) during thermal cycling under load. In an effort to overcome this deficiency, various solid-solution alloying and thermomechanical processing schemes were investigated. Solid-solution strengthening was achieved by substituting 5at% gold or platinum for palladium in Ni(19.5)Ti(50.5)Pd30, the so-called baseline alloy, to strengthen the martensite and austenite phases against slip processes and improve thermomechanical behavior. Tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared. The relative difference in yield strength between the martensite and austenite phases and the dimensional stability of the alloy were improved by the quaternary additions, while work output was only minimally impacted. The three alloys were also thermomechanically processed by cycling repeatedly through the transformation range under a constant stress. This so-called training process dramatically improved the dimensional stability in these samples and also recovered the slight decrease in work output caused by quaternary alloying. An added benefit of the solid-solution strengthening was maintenance of enhanced dimensional stability of the trained material to higher temperatures compared to the baseline alloy, providing a greater measure of over-temperature capability.

On the superposition of strengthening mechanisms in dispersion strengthened alloys and metal-matrix nanocomposites: Considerations of stress and energy

Science.gov (United States)

Ferguson, J. B.; Schultz, Benjamin F.; Venugopalan, Dev; Lopez, Hugo F.; Rohatgi, Pradeep K.; Cho, Kyu; Kim, Chang-Soo

2014-03-01

Yield strength improvement in dispersion strengthened alloys and nano particle-reinforced composites by well-known strengthening mechanisms such as solid solution, grain refinement, coherent and incoherent dispersed particles, and increased dislocation density resulting from work-hardening can all be described individually. However, there is no agreed upon description of how these mechanisms combine to determine the yield strength. In this work, we propose an analytical yield strength prediction model combining arithmetic and quadratic addition approaches based on the consideration of two types of yielding mechanisms; stress-activated and energy-activated. Using data available in the literature for materials of differing grain sizes, we consider the cases of solid solutions and coherent precipitates to show that they follow stress-activated behavior. Then, we applied our model with some empirical parameters to precipitationhardenable materials of various grain sizes in both coherent and incoherent precipitate conditions, which demonstrated that grain boundary and Orowan-strengthening can be treated as energy-activated mechanisms.

Preparation of Si and O co-solution strengthened Ti alloys by using rice husks as SiO2 resource and quantitative descriptions on their strengthening effects

Science.gov (United States)

Jia, Lei; Chen, Jiang-xian; Lu, Zhen-lin; Li, Shu-feng; Umeda, Junko; Kondoh, Katsuyoshi

2018-04-01

Ti alloys strengthened by both Si and O solutes were prepared by powder metallurgy method from pure Ti and amorphous SiO2 powder obtained by combusting rice husks. At the same time, Ti alloys singly strengthened by Si or O were also prepared for studying the strengthening effect of Si and O solutes. Results showed that amorphous SiO2 powder originated from rice husks could almost fully dissolve into pure Ti matrix when the content was not higher than 1.0 wt%, while higher content of SiO2 addition resulted in the formation of Ti5Si3 intermetallics. Si and O elements leaded to negative and positive distortion of Ti lattice, and the influencing degrees were ‑0.02 and +0.014 Å/wt% for lattice constant a, while ‑0.05 and +0.046 Å/wt% for constant c, respectively. Solid solution of Si and O would also result in the increase of hardness, which was 98.5 and 209.43 HV/wt%, respectively. When Si and O were co-exsited in Ti matrix, the negative and positive distortion cancelled each other, while the strengthening effect did not cancel but enhance each other.

Study on the fabrication of Al matrix composites strengthened by combined in-situ alumina particle and in-situ alloying elements

International Nuclear Information System (INIS)

Huang Zanjun; Yang Bin; Cui Hua; Zhang Jishan

2003-01-01

A new idea to fabricate aluminum matrix composites strengthened by combined in-situ particle strengthening and in-situ alloying has been proposed. Following the concept of in-situ alloying and in-situ particle strengthening, aluminum matrix composites reinforced by Cu and α-Al 2 O 3 particulate (material I) and the same matrix reinforced by Cu, Si alloying elements and α-Al 2 O 3 particulate (material II) have been obtained. SEM observation, EDS and XRD analysis show that the alloy elements Cu and Si exist in the two materials, respectively. In-situ Al 2 O 3 particulates are generally spherical and their mean size is less than 0.5 μm. TEM observation shows that the in-situ α-Al 2 O 3 particulates have a good cohesion with the matrix. The reaction mechanism of the Al 2 O 3 particulate obtained by this method was studied. Thermodynamic considerations are given to the in-situ reactions and the distribution characteristic of in-situ the α-Al 2 O 3 particulate in the process of solidification is also discussed

Improving significantly the failure strain and work hardening response of LPSO-strengthened Mg-Y-Zn-Al alloy via hot extrusion speed control

Science.gov (United States)

Tan, Xinghe; Chee, Winston; Chan, Jimmy; Kwok, Richard; Gupta, Manoj

2017-07-01

The effect of hot extrusion speed on the microstructure and mechanical properties of MgY1.06Zn0.76Al0.42 (at%) alloy strengthened by the novel long-period stacking ordered (LPSO) phase was systematically investigated. Increase in the speed of extrusion accelerated dynamic recrystallization of α-Mg via particle-stimulated nucleation and grain growth in the alloy. The intensive recrystallization and grain growth events weakened the conventional basal texture and Hall-Petch strengthening in the alloy which led to significant improvement in its failure strain from 4.9% to 19.6%. The critical strengthening contribution from LPSO phase known for attributing high strength to the alloy was observed to be greatly undermined by the parallel competition from texture weakening and the adverse Hall-Petch effect when the alloy was extruded at higher speed. Absence of work hardening interestingly observed in the alloy extruded at lower speed was discussed in terms of its ultra-fine grained microstructure which promoted the condition of steady-state defect density in the alloy; where dislocation annihilation balances out the generation of new dislocations during plastic deformation. One approach to improve work hardening response of the alloy to prevent unstable deformation and abrupt failure in service is to increase the grain diameter in the alloy by judiciously increasing the extrusion speed.

Grinding as an approach to the production of high-strength, dispersion-strengthened nickel-base alloys

Science.gov (United States)

Orth, N. W.; Quatinetz, M.; Weeton, J. W.

1970-01-01

Mechanical process produces dispersion-strengthened metal alloys. Power surface contamination during milling is removed by a cleaning method that involves heating thin shapes or partially-compacted milled powder blends in hydrogen to carefully controlled temperature schedules.

The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

International Nuclear Information System (INIS)

Li, Yinghong; Zhou, Liucheng; He, Weifeng; He, Guangyu; Wang, Xuede; Nie, Xiangfan; Wang, Bo; Luo, Sihai; Li, Yuqin

2013-01-01

We investigated the strengthening mechanism of laser shock processing (LSP) at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30–200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa; the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation. (paper)

Weld Growth Mechanisms and Failure Behavior of Three-Sheet Resistance Spot Welds Made of 5052 Aluminum Alloy

Science.gov (United States)

Li, Yang; Yan, Fuyu; Luo, Zhen; Chao, Y. J.; Ao, Sansan; Cui, Xuetuan

2015-06-01

This paper investigates the weld nugget formation in three-sheet aluminum alloy resistance spot welding. The nugget formation process in three equal thickness sheets and three unequal thickness sheets of 5052 aluminum alloy were studied. The results showed that the nugget was initially formed at the workpiece/workpiece interfaces (i.e., both upper interface and lower interface). The two small nuggets then grew along the radial direction and axial direction (welding direction) as the welding time increased. Eventually, the two nuggets fused into one large nugget. During the welding process, the Peltier effect between the Cu-Al caused the shift of the nugget in the welding direction. In addition, the mechanical strength and fracture mode of the weld nuggets at the upper and lower interfaces were also studied using tensile shear specimen configuration. Three failure modes were identified, namely interfacial, mixed, and pullout. The critical welding time and critical nugget diameter corresponding to the transitions of these modes were investigated. Finally, an empirical failure load formula for three-sheet weld similar to two-sheet spot weld was developed.

Texture and mechanical properties of Al-0.5Mg-1.0Si-0.5Cu alloy sheets manufactured via a cross rolling method

Science.gov (United States)

Jeon, Jae-Yeol; Son, Hyeon-Taek; Woo, Kee-Do; Lee, Kwang-Jin

2012-04-01

The relationship between the texture and mechanical properties of 6xxx aluminum alloy sheets processed via cross rolling was investigated. The microstructures of the conventional rolled and cross rolled sheets after annealing were analyzed using optical micrographs (OM). The texture distribution across the thickness in the Al-Mg-Si-Cu alloy, conventional rolled sheets, and cross rolled sheets both before and after annealing was investigated via X-ray texture measurements. The texture was analyzed in three layers from the surface to the center of the sheet. The β-fiber texture of the conventional rolled sheet was typical of the texture obtained using aluminumoll ring. After annealing, the typical β-fiber orientations were changed to recrystallization textures: cube{001} and normal direction (ND)-rotated cubes. However, the texture of the cross rolled sheet was composed of an asymmetrical, rolling direction (RD)-rotated cubes. After annealing, the asymmetrical orientations in the cross rolled sheet were changed to a randomized texture. The average R-value of the annealed cross rolled sheets was higher than that of the conventional rolled sheets. The limit dome height (LDH) test results demonstrated that cross rolling is effective in improving the formability of the Al-Mg-Si-Cu alloy sheets.

Evaluation of Sc-Bearing Aluminum Alloy C557 for Aerospace Applications

Science.gov (United States)

Domack, Marcia S.; Dicus, Dennis L.

2002-01-01

The performance of the Al-Mg-Sc alloy C557 was evaluated to assess its potential for a broad range of aerospace applications, including airframe and launch vehicle structures. Of specific interest were mechanical properties at anticipated service temperatures and thermal stability of the alloy. Performance was compared with conventional airframe aluminum alloys and with other emerging aluminum alloys developed for specific service environments. Mechanical properties and metallurgical structure were evaluated for commercially rolled sheet in the as-received H116 condition and after thermal exposures at 107 C. Metallurgical analyses were performed to de.ne grain morphology and texture, strengthening precipitates, and to assess the effect of thermal exposure.

Method of thermally processing superplastically formed aluminum-lithium alloys to obtain optimum strengthening

Science.gov (United States)

Anton, Claire E. (Inventor)

1993-01-01

Optimum strengthening of a superplastically formed aluminum-lithium alloy structure is achieved via a thermal processing technique which eliminates the conventional step of solution heat-treating immediately following the step of superplastic forming of the structure. The thermal processing technique involves quenching of the superplastically formed structure using static air, forced air or water quenching.

Crystal Plasticity Finite Element Analysis of Loading-Unloading Behaviour in Magnesium Alloy Sheet

International Nuclear Information System (INIS)

Hama, Takayuki; Fujimoto, Hitoshi; Takuda, Hirohiko

2010-01-01

Magnesium alloy sheets exhibit strong inelastic response during unloading. In this study crystal plasticity finite element analysis of loading-unloading behaviour during uniaxial tension in a rolled magnesium alloy sheet was carried out, and the mechanism of this inelastic response was examined in detail in terms of macroscopic and mesoscopic deformations. The unloading behaviour obtained by the simulation was in good agreement with the experiment in terms of variation with stress of instantaneous tangent modulus during unloading. Variations of activities of each family of slip systems during the deformation showed that the activation of basal slip systems is the largest during unloading, and the slip direction during unloading is opposite from during loading. These results indicated that one of the factors of the inelastic behaviour during unloading is the fact that the basal slip systems are easily activated during unloading because of their low strengths.

Zr-based conversion layer on Zn-Al-Mg alloy coated steel sheets: insights into the formation mechanism

International Nuclear Information System (INIS)

Lostak, Thomas; Maljusch, Artjom; Klink, Björn; Krebs, Stefan; Kimpel, Matthias; Flock, Jörg; Schulz, Stephan; Schuhmann, Wolfgang

2014-01-01

Zr-based conversion layers are considered as environmentally friendly alternatives replacing trication phosphatation in the automotive industry. Based on excellent electronic barrier properties they provide an effective corrosion protection of the metallic substrate. In this work, thin protective layers were grown on novel Zn-Al-Mg alloy coated steel sheets by increasing the local pH-value at the sample surface leading to deposition of a Zr-based conversion layer. For this purpose Zn-Al-Mg alloy (ZM) coated steel sheets were treated in an aqueous model conversion solution containing well-defined amounts of hexafluorozirconic acid (H 2 ZrF 6 ) and characterized after different immersion times with SKPFM and field emission SEM (FE-SEM)/EDX techniques. A deposition mechanism of Zr-based conversion coatings on microstructural heterogeneous Zn-Al-Mg alloy surfaces was proposed

Some new characteristics of the strengthening phase in β-phase magnesium-lithium alloys containing aluminum and beryllium

International Nuclear Information System (INIS)

Song Guangsheng; Staiger, Mark; Kral, Milo

2004-01-01

Hardness, optical-microscopy and X-ray diffraction studies on the strengthening phase in β-phase magnesium-lithium alloys containing different content of aluminum were carried out to give some new characteristics of the strengthening phase affecting lattice distortion and α-Mg precipitation in the β-matrix. In the presence of the strengthening-phase precipitates, the matrix lattice undergoes substantial strain characterized by peak broadening. The peak width in the β-matrix phase pattern can provide an indication of lattice strain caused by the strengthening-phase precipitates. The origin of α-Mg precipitation resulting from the decomposition of the strengthening phase into stable AlLi compound is also explained in the present work

Development of Fe-Ni and Ni-base alloys without {gamma}' strengthening for advanced USC boilers

Energy Technology Data Exchange (ETDEWEB)

Semba, Hiroyuki; Okada, Hirokazu; Igarashi, Masaaki; Hirata, Hiroyuki [Sumitomo Metal Industries, Ltd., Amagasaki, Hyogo (Japan). Corporate Research and Development Labs.; Yoshizawa, Mitsuru [Sumitomo Metal Industries Ltd., Amagasaki, Hyogo (Japan). Steel Tube Works

2010-07-01

An Fe-Ni base alloy, 23Cr-45Ni-7W alloy (HR6W) strengthened by Fe{sub 2}W-type Laves phase is one of the candidate materials for the piping application. Stability of long-term creep strength and superior creep rupture ductility have been proved by creep rupture tests up to 60000h at 650-800 C. The 10{sup 5}h extrapolated creep rupture strength at 700 C approved by TUV is 85MPa. It has also been confirmed that HR6W has excellent microstructural stability by means of microstructural observations after term creep tests and aging. A thick wall pipe of HR6W, which is 457mm in diameter and 60mm in wall thickness, has successfully been manufactured by the Erhart Push Bench press method. This trial production has shown that hot workability of HR6W is sufficient for manufacturing thick wall piping for A-USC plants. A new Ni-base alloy, 30r-50Ni-4W alloy (HR35) has been proposed for piping application having comparable creep rupture strength with Alloy 617 at 700 C. This alloy is not strengthened by {gamma}' phase but mainly by {alpha}-Cr phase. The 10{sup 5}h extrapolated creep rupture strength is estimated to be 114 MPa at 700 C. It has sufficient creep rupture ductility compared with Alloy 617. A thick wall pipe of HR35 has also been successfully manufactured. Capability of HR6W and HR35 as structural materials for A-USC plants has been examined in detail. They have high resistance to relaxation cracking after welding. It is, therefore, concluded that both the alloys are promising candidates especially for thick wall piping in A-USC power plants. (orig.)

Modelling and optimization of cut quality during pulsed Nd:YAG laser cutting of thin Al-alloy sheet for straight profile

Science.gov (United States)

Sharma, Amit; Yadava, Vinod

2012-02-01

Thin sheets of aluminium alloys are widely used in aerospace and automotive industries for specific applications. Nd:YAG laser beam cutting is one of the most promising sheetmetal cutting process for cutting sheets for any profile. Al-alloy sheets are difficult to cut by laser beam because of its highly reflective nature. This paper presents modelling and optimization of cut quality during pulsed Nd:YAG laser cutting of thin Al-alloy sheet for straight profile. In the present study, four input process parameters such as oxygen pressure, pulse width, pulse frequency, and cutting speed and two output parameters such as average kerf taper ( Ta) and average surface roughness ( Ra) are considered. The hybrid approach comprising of Taguchi methodology (TM) and response surface methodology (RSM) is used for modelling whereas multi-objective optimization is performed using hybrid approach of TM and grey relational analysis (GRA) coupled with entropy measurement methodology. The entropy measurement methodology is employed for the calculation of weight corresponding to each quality characteristic. The results indicate that the hybrid approaches applied for modelling and optimization of the LBC process are reasonable.

Solid state welding processes for an oxide dispersion strengthened nickel-chromium-aluminum alloy

Science.gov (United States)

Moore, T. J.

1975-01-01

Solid-state welding processes were evaluated for joining TD-NiCrAl (Ni-16Cr-4Al-2ThO2) alloy sheet. Both hot-press and resistance spot welding techniques were successfully applied in terms of achieving grain growth across the bond line. Less success was achieved with a resistance seam welding process. In stress-rupture shear and tensile shear tests of lap joints at 1100 C, most failures occurred in the parent material, which indicates that the weld quality was good and that the welds were not a plane of weakness. The overall weld quality was not as good as previously attained with TD-NiCr, probably because the presence of alumina at the faying surfaces and the developmental TD-NiCrAl sheet, which was not of the quality of the TD-NiCr sheet in terms of surface flatness and dimensional control.

Enhanced mechanical properties of ARB-processed aluminum alloy 6061 sheets by subsequent asymmetric cryorolling and ageing

International Nuclear Information System (INIS)

Yu, Hailiang; Su, Lihong; Lu, Cheng; Tieu, Kiet; Li, Huijun; Li, Jintao; Godbole, Ajit; Kong, Charlie

2016-01-01

Grain size and precipitations affect the strength and ductility of ultrafine-grained materials. In this study, aluminum alloy 6061 sheets were fabricated using the accumulative roll bonding (ARB) technique. The ARB-processed sheets were subsequently subjected to cryorolling and asymmetric cryorolling. The sheets were further aged at 100 °C for 48 h. Mechanical tests show that a combination of asymmetric cryorolling and ageing results in significant improvement in both the ductility and the strength of the ARB-processed sheets. The microstructures of the sheets at different stages of the process were also analyzed using optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction in order to correlate the mechanical properties with the microstructure.

Enhanced mechanical properties of ARB-processed aluminum alloy 6061 sheets by subsequent asymmetric cryorolling and ageing

Energy Technology Data Exchange (ETDEWEB)

Yu, Hailiang, E-mail: hailiang@uow.edu.au [State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083 (China); School of Mechanical, Materials & Mechatronics Engineering, University of Wollongong, NSW 2500 (Australia); Su, Lihong; Lu, Cheng; Tieu, Kiet [School of Mechanical, Materials & Mechatronics Engineering, University of Wollongong, NSW 2500 (Australia); Li, Huijun, E-mail: huijun@uow.edu.au [School of Mechanical, Materials & Mechatronics Engineering, University of Wollongong, NSW 2500 (Australia); Li, Jintao; Godbole, Ajit [School of Mechanical, Materials & Mechatronics Engineering, University of Wollongong, NSW 2500 (Australia); Kong, Charlie [Electron Microscope Unit, University of New South Wales, Sydney, NSW 2052 (Australia)

2016-09-30

Grain size and precipitations affect the strength and ductility of ultrafine-grained materials. In this study, aluminum alloy 6061 sheets were fabricated using the accumulative roll bonding (ARB) technique. The ARB-processed sheets were subsequently subjected to cryorolling and asymmetric cryorolling. The sheets were further aged at 100 °C for 48 h. Mechanical tests show that a combination of asymmetric cryorolling and ageing results in significant improvement in both the ductility and the strength of the ARB-processed sheets. The microstructures of the sheets at different stages of the process were also analyzed using optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction in order to correlate the mechanical properties with the microstructure.

Creep and residual mechanical properties of cast superalloys and oxide dispersion strengthened alloys

Science.gov (United States)

Whittenberger, J. D.

1981-01-01

Tensile, stress-rupture, creep, and residual tensile properties after creep testing were determined for two typical cast superalloys and four advanced oxide dispersion strengthened (ODS) alloys. The superalloys examined included the nickel-base alloy B-1900 and the cobalt-base alloy MAR-M509. The nickel-base ODS MA-757 (Ni-16CR-4Al-0.6Y2O3 and the iron-base ODS alloy MA-956 (Fe-20Cr-5Al-0.8Y2O3) were extensively studied, while limited testing was conducted on the ODS nickel-base alloys STCA (Ni-16Cr-4.5Al-2Y2O3) with a without Ta and YD-NiCrAl (Ni-16Cr-5Al-2Y2O3). Elevated temperature testing was conducted from 114 to 1477 K except for STCA and YD-NiCrAl alloys, which were only tested at 1366 K. The residual tensile properties of B-1900 and MAR-M509 are not reduced by prior creep testing (strains at least up to 1 percent), while the room temperature tensile properties of ODS nickel-base alloys can be reduced by small amounts of prior creep strain (less than 0.5 percent). The iron-base ODS alloy MA-956 does not appear to be susceptible to creep degradation at least up to strains of about 0.25 percent. However, MA-956 exhibits unusual creep behavior which apparently involves crack nucleation and growth.

Effects of Zr Addition on Strengthening Mechanisms of Al-Alloyed High-Cr ODS Steels.

Science.gov (United States)

Ren, Jian; Yu, Liming; Liu, Yongchang; Liu, Chenxi; Li, Huijun; Wu, Jiefeng

2018-01-12

Oxide dispersion strengthened (ODS) steels with different contents of zirconium (denoted as 16Cr ODS, 16Cr-0.3Zr ODS and 16Cr-0.6Zr ODS) were fabricated to investigate the effects of Zr on strengthening mechanism of Al-alloyed 16Cr ODS steel. Electron backscatter diffraction (EBSD) results show that the mean grain size of ODS steels could be decreased by Zr addition. Transmission electron microscope (TEM) results indicate that Zr addition could increase the number density but decrease the mean diameter and inter-particle spacing of oxide particles. Furthermore, it is also found that in addition to Y-Al-O nanoparticles, Y-Zr-O oxides with finer size were observed in 16Cr-0.3Zr ODS and 16Cr-0.6Zr ODS steels. These changes in microstructure significantly increase the yield strength (YS) and ultimate tensile strength (UTS) of ODS steels through mechanisms of grain boundary strengthening and dispersion strengthening.

Characterization of zinc alloy by sheet bulging test with analytical models and digital image correlation

Science.gov (United States)

Vitu, L.; Laforge, N.; Malécot, P.; Boudeau, N.; Manov, S.; Milesi, M.

2018-05-01

Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal forming community. Different theoretical models of the literature for the evaluation of thickness and radius of the deformed sheet in SBT have been studied in order to get the hardening curve of different materials. These theoretical models present the advantage that the experimental procedure is very simple. But Koç et al. showed their limitation, since the combination of thickness and radius evaluations depend on the material. As Zinc alloys are strongly anisotropic with a special crystalline structure, a procedure is adopted for characterizing the hardening curve of a Zinc alloy. The anisotropy is first studied with tensile test, and SBT with elliptical dies is also investigated. Parallel to this, Digital Image Correlation (DIC) measures are carried out. The results obtained from theoretical models and DIC measures are compared. Measures done on post-mortem specimens complete the comparisons. Finally, DIC measures give better results and the resulting hardening curve of the studied zinc alloy is provided.

Strengthening Mechanisms in Microtruss Metals

Science.gov (United States)

Ng, Evelyn K.

Microtrusses are hybrid materials composed of a three-dimensional array of struts capable of efficiently transmitting an externally applied load. The strut connectivity of microtrusses enables them to behave in a stretch-dominated fashion, allowing higher specific strength and stiffness values to be reached than conventional metal foams. While much attention has been given to the optimization of microtruss architectures, little attention has been given to the strengthening mechanisms inside the materials that make up this architecture. This thesis examines strengthening mechanisms in aluminum alloy and copper alloy microtruss systems with and without a reinforcing structural coating. C11000 microtrusses were stretch-bend fabricated for the first time; varying internal truss angles were selected in order to study the accumulating effects of plastic deformation and it was found that the mechanical performance was significantly enhanced in the presence of work hardening with the peak strength increasing by a factor of three. The C11000 microtrusses could also be significantly reinforced with sleeves of electrodeposited nanocrystalline Ni-53wt%Fe. It was found that the strength increase from work hardening and electrodeposition were additive over the range of structures considered. The AA2024 system allowed the contribution of work hardening, precipitation hardening, and hard anodizing to be considered as interacting strengthening mechanisms. Because of the lower formability of AA2024 compared to C11000, several different perforation geometries in the starting sheet were considered in order to more effectively distribute the plastic strain during stretch-bend fabrication. A T8 condition was selected over a T6 condition because it was shown that the plastic deformation induced during the final step was sufficient to enhance precipitation kinetics allowing higher strengths to be reached, while at the same time eliminating one annealing treatment. When hard anodizing

Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final Report Ph.D. Thesis

Science.gov (United States)

Ellis, David L.; Michal, Gary M.

1989-01-01

A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

Post irradiation fracture properties of precipitation-strengthened alloy D21

International Nuclear Information System (INIS)

Huang, F.H.

1986-03-01

The precipitation strengthened alloys have the potential for use in fuel cladding and duct applications for liquid metal reactors due to their high strength and low swelling rate. Unfortunately, these high strength alloys tend to exhibit poor fracture toughness, and the effects of neutron irradiation on the fracture properties of the material are of concern. Compact tension specimens of alloy D21 were irradiated in the Experimental Breeder Reactor II to a fluence of 2.7 x 10 22 n/cm 2 (E > 0.1 MeV) at 425, 500, 550 and 600 0 C. Fracture toughness tests on these specimens wre performed using electric potential techniques at temperatures ranging from 205 to 425 C. The material exhibited low postirradiation fracture toughness which increased with either increasing test or irradiation temperature. The tearing modulus, however, increased with increasing irradiation temperature but decreased with increasing test temperature. Results wre analyzed using the J-integral approach. The fracture toughness of irradiated D21 was evaluated essentially following the procedure recommended in ASTM Test Method E813. It was found that the data elimination limits illustrated in E813 were too large for the specimens tested, although the thickness criterion was satisfied. The precautions needed to determine J/sub 1c/ based on a reduced data qualification range were disussed

Microstructural influences on strengthening in a naturally aged and overaged Al–Cu–Li–Mg based alloy

International Nuclear Information System (INIS)

Ovri, Henry; Jägle, Eric A.; Stark, Andreas; Lilleodden, Erica T.

2015-01-01

A combination of transmission electron microscopy, atom probe tomography and high-energy X-ray diffraction was employed to investigate the influence of local microstructural changes on strengthening in a commercial Al–Cu–Li–Mg based alloy, AA2198, in the stretched and naturally aged, and overaged states. Strengthening in the stretched and naturally aged temper was shown to be governed by a combination of Cu–Cu clusters, δ′/β′ phase and solution strengthening. This is in contrast to another report which suggests that strength in this temper is only due to Cu-rich clusters [B. Decreus, et al., Acta Mater., 61 (2013) 2207]. On the other hand, although large volume fractions of equilibrium phases such as T B , and θ were present in the overaged temper, its strengthening was largely governed by order hardening, which is the strengthening mechanism associated with the δ′/β′ phase. The δ′/β′ phase remained in the matrix even after extensive overaging

Microstructural influences on strengthening in a naturally aged and overaged Al–Cu–Li–Mg based alloy

Energy Technology Data Exchange (ETDEWEB)

Ovri, Henry, E-mail: henry.ovri@hzg.de [Helmholtz Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, 21502 Geesthacht (Germany); Jägle, Eric A. [Max-Planck-Institut für Eisenforschung GmbH, Department of Microstructure Physics and Alloy Design, 40237 Düsseldorf (Germany); Stark, Andreas [Helmholtz Zentrum Geesthacht, Institute of Materials Research, Materials Physics, 21502 Geesthacht (Germany); Lilleodden, Erica T. [Helmholtz Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, 21502 Geesthacht (Germany)

2015-06-18

A combination of transmission electron microscopy, atom probe tomography and high-energy X-ray diffraction was employed to investigate the influence of local microstructural changes on strengthening in a commercial Al–Cu–Li–Mg based alloy, AA2198, in the stretched and naturally aged, and overaged states. Strengthening in the stretched and naturally aged temper was shown to be governed by a combination of Cu–Cu clusters, δ′/β′ phase and solution strengthening. This is in contrast to another report which suggests that strength in this temper is only due to Cu-rich clusters [B. Decreus, et al., Acta Mater., 61 (2013) 2207]. On the other hand, although large volume fractions of equilibrium phases such as T{sub B}, and θ were present in the overaged temper, its strengthening was largely governed by order hardening, which is the strengthening mechanism associated with the δ′/β′ phase. The δ′/β′ phase remained in the matrix even after extensive overaging.

Experimental Characterization and Material Modelling of an AZ31 Magnesium Sheet Alloy at Elevated Temperatures under Consideration of the Tension-Compression Asymmetry

Science.gov (United States)

Behrens, B.-A.; Bouguecha, A.; Bonk, C.; Dykiert, M.

2017-09-01

Magnesium sheet alloys have a great potential as a construction material in the aerospace and automotive industry. However, the current state of research regarding temperature dependent material parameters for the description of the plastic behaviour of magnesium sheet alloys is scarce in literature and accurate statements concerning yield criteria and appropriate characterization tests to describe the plastic behaviour of a magnesium sheet alloy at elevated temperatures in deep drawing processes are to define. Hence, in this paper the plastic behaviour of the well-established magnesium sheet alloy AZ31 has been characterized by means of convenient mechanical tests (e. g. tension, compression and biaxial tests) at temperatures between 180 and 230 °C. In this manner, anisotropic and hardening behaviour as well as differences between the tension-compression asymmetry of the yield locus have been estimated. Furthermore, using the evaluated data from the above mentioned tests, two different yield criteria have been parametrized; the commonly used Hill’48 and an orthotropic yield criterion, CPB2006, which was developed especially for materials with hexagonal close packed lattice structure and is able to describe an asymmetrical yielding behaviour regarding tensile and compressive stress states. Numerical simulations have been finally carried out with both yield functions in order to assess the accuracy of the material models.

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies.

Science.gov (United States)

Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K

2017-04-07

The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2 TiAl/NiAl or single-Ni 2 TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.

Strengthening Aluminum Alloys for High Temperature Applications Using Nanoparticles of Al203 and Al3-X Compounds (X= Ti, V, Zr)

Science.gov (United States)

Lee, Jonathan A.

2007-01-01

In this paper the effect of nanoparticles A12O3 and A13-X compounds (X= Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their chemical stability and low diffusions rates in aluminum matrix at high temperatures. The strengthening mechanism for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. Samples were prepared from A12O3 nanoparticle preforms, which were produced using ceramic injection molding process and pressure infiltrated by molten aluminum. A12O3 nanoparticles can also be homogeneously mixed with aluminum powder and consolidated into samples through hot pressing and sintering. On the other hand, the Al3-X nanoparticles are produced as precipitates via in situ reactions with molten aluminum alloys using conventional casting techniques. The degree of alloy strengthening using nanoparticles will depend on the materials, particle size, shape, volume fraction, and mean inter-particle spacing.

Contribution of Lattice Distortion to Solid Solution Strengthening in a Series of Refractory High Entropy Alloys

Science.gov (United States)

Chen, H.; Kauffmann, A.; Laube, S.; Choi, I.-C.; Schwaiger, R.; Huang, Y.; Lichtenberg, K.; Müller, F.; Gorr, B.; Christ, H.-J.; Heilmaier, M.

2018-03-01

We present an experimental approach for revealing the impact of lattice distortion on solid solution strengthening in a series of body-centered-cubic (bcc) Al-containing, refractory high entropy alloys (HEAs) from the Nb-Mo-Cr-Ti-Al system. By systematically varying the Nb and Cr content, a wide range of atomic size difference as a common measure for the lattice distortion was obtained. Single-phase, bcc solid solutions were achieved by arc melting and homogenization as well as verified by means of scanning electron microscopy and X-ray diffraction. The atomic radii of the alloying elements for determination of atomic size difference were recalculated on the basis of the mean atomic radii in and the chemical compositions of the solid solutions. Microhardness (μH) at room temperature correlates well with the deduced atomic size difference. Nevertheless, the mechanisms of microscopic slip lead to pronounced temperature dependence of mechanical strength. In order to account for this particular feature, we present a combined approach, using μH, nanoindentation, and compression tests. The athermal proportion to the yield stress of the investigated equimolar alloys is revealed. These parameters support the universality of this aforementioned correlation. Hence, the pertinence of lattice distortion for solid solution strengthening in bcc HEAs is proven.

Development of powder metallurgy 2XXX series Al alloy plate and sheet materials for high temperature aircraft structural applications, FY 1983/1984

Science.gov (United States)

Chellman, D. J.

1985-01-01

The objective of this investigation is to fabricate and evaluate PM 2124 Al alloy plate and sheet materials according to NASA program goals for damage tolerance and fatigue resistance. Previous research has indicated the outstanding strength-toughness relationship available with PM 2124 Al-Zr modified alloy compositions in extruded product forms. The range of processing conditions was explored in the fabrication of plate and sheet gage materials, as well as the resultant mechanical and metallurgical properties. The PM composition based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.60 wt. pct. Zr was selected. Flat rolled material consisting of 0.250 in. thick plate was fabricated using selected thermal mechanical treatments (TMT). The schedule of TMT operations was designed to yield the extreme conditions of grain structure normally encountered in the fabrication of flat rolled products, specifically recrystallized and unrecrystallized. The PM Al alloy plate and sheet materials exhibited improved strength properties at thin gages compared to IM Al alloys, as a consequence of their enhanced ability to inhibit recrystallization and grain growth. In addition, the PM 2124 Al alloys offer much better combinations of strength and toughnessover equivalent IM Al. The alloy microstructures were examined by optical metallographic texture techniques in order to establish the metallurgical basis for these significant property improvements.

Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix

DEFF Research Database (Denmark)

Zhang, Zhenbo; Pantleon, Wolfgang

2017-01-01

Oxide nanoparticles are quintessential for ensuring the extraordinary properties of oxide dispersion strengthened (ODS) steels. In this study, the crystallographic structure of oxide nanoparticles, and their interface with the ferritic steel matrix in an Al-alloyed ODS steel, i.e. PM2000, were...

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.

Study of microstructure evolution and strengthening mechanisms in novel TiZrAlB alloy

Energy Technology Data Exchange (ETDEWEB)

Liu, S.G.; Feng, Z.H.; Xia, C.Q.; Zhang, Z.G.; Zhang, X.; Zhang, X.Y., E-mail: xyzhang@ysu.edu.cn; Ma, M.Z.; Liu, R.P., E-mail: riping@ysu.edu.cn

2017-04-24

In this paper, the microstructural evolution and mechanical properties of the as-cast Ti-χZr-4Al-0.005B (TχZAB and χ=0, 10, 20, 30, 40 wt%) alloys were systematically investigated. Only the α phase was detected from the X-ray diffraction patterns of the as-cast TχZAB quaternary alloy series. As the Zr content increased, the average size and length-diameter ratio of the α grains were decreased from 69.8 μm to 17.1 µm and 37.5 to 8.4, respectively. The analysis of the results from the tensile and microhardness tests demonstrated that both the strength and hardness increased significantly as the Zr content increased (from 0 wt% to 40 wt%). Nevertheless, the ductility exhibited an opposite trend. The fracture mode of the ductile-brittle transfer was consistent with the ductility alteration. The as-cast Ti-40Zr-4Al-0.005B alloys demonstrated the highest tensile strength (σ{sub b}=1134 MPa), which increased by 53% compared to the Ti-4Al-0.005B alloys, whereas the lowest elongation-to-failure was of 6.77%. The mechanical properties of the TχZAB alloy series were discussed based on the microstructural evolution and the solid solution strengthening mechanisms.

Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

OpenAIRE

Wang, Dan; Li, Heng; Yang, He; Ma, Jun; Li, Guangjun

2014-01-01

The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods (c...

Analysis of Strengthening Mechanisms in an Artificially Aged Ultrafine Grain 6061 Aluminum Alloy

Directory of Open Access Journals (Sweden)

Mohammad Reza Rezaei

2017-12-01

Full Text Available The current study adopted a quantitative approach to investigating the mechanical properties, and their relationship to the microstructural features, of precipitation-strengthened 6061 aluminum alloy processed through accumulative roll bonding (ARB and aging heat treatment.  To serve this purpose, the contributions of different strengthening mechanisms including grain refinement, precipitation, dislocation and solid-solution strengthening to the yield strength of five-cycle ARB samples processed under pre-aged (ARBed and aged (ARBed+Aged conditions were examined and compared. Microstructural characterizations were performed on the samples through the transmission electron microscope (TEM and X-ray diffraction (XRD. Also, the mechanical properties of the samples were investigated through the tensile test. The obtained results showed that an equiaxed ultrafine grain structure with nano-sized precipitates was created in the both ARBed and ARBed+Aged samples. The grain refinement was the predominant strengthening mechanism which was estimated to contribute 151 and 226 MPa to the ARBed and ARBed+Aged samples, respectively, while the dislocation and Orowan strengthening mechanisms were ranked second with regard to their contributions to the ARBed and ARBed+Aged samples, respectively. The overall yield strength, calculated through the root mean square summation method, was found to be in good agreement with the experimentally determined yield strength. It was also found that the presence of non-shearable precipitates, which interfered with the movement of the dislocations, would be effective for the simultaneous improvement of the strength and ductility of the ARBed+Agedsample .

Investigation and modeling of Al3(Sc, Zr) precipitation strengthening in the presence of enhanced supersaturation and within Al-Cu binary alloys

Science.gov (United States)

Deane, Kyle

Diffuse Al-Sc and Al-Zr alloys have been demonstrated in literature to be relatively coarsening resistant at higher temperatures when compared with commonly used precipitation strengthening alloys (e.g. 2000 series, 6000 series). However, because of a limited strengthening due to the low solubility of scandium and zirconium in aluminum, and owing to the scarcity and therefore sizeable price tag attached to scandium, little research has been done in the way of optimizing these alloys for commercial applications. With this in mind, this dissertation describes research which aims to tackle several important areas of Al-Sc-Zr research that have been yet unresolved. In Chapter 4, rapid solidification was utilized to enhance the achievable supersaturation of the alloy in an effort to increase the achievable precipitate strengthening. In Chapter 5, Additive Friction Stir processing (AFS), a novel method of mechanically combining materials without melting, was employed in an attempt to pass the benefits of supersaturation from melt spun ribbon into a more structurally useful bulk material. In Chapter 6, a Matlab program written to predict precipitate nucleation, growth, and coarsening with a modified Kampmann and Wagner Numerical (KWN) model, was used to predict heat treatment regimens for more efficient strengthening. Those predictions were then tested experimentally to test the validity of the results. And lastly, in Chapter 7, the effect of zirconium on Al-Cu secondary precipitates was studied in an attempt to increase their thermal stability, as much higher phase fractions of Al-Cu precipitates are achievable than Al-Zr precipitates.

A kinematic hardening constitutive model for the uniaxial cyclic stress-strain response of magnesium sheet alloys at room temperature

Science.gov (United States)

He, Zhitao; Chen, Wufan; Wang, Fenghua; Feng, Miaolin

2017-11-01

A kinematic hardening constitutive model is presented, in which a modified form of von Mises yield function is adopted, and the initial asymmetric tension and compression yield stresses of magnesium (Mg) alloys at room temperature (RT) are considered. The hardening behavior was classified into slip, twinning, and untwinning deformation modes, and these were described by two forms of back stress to capture the mechanical response of Mg sheet alloys under cyclic loading tests at RT. Experimental values were obtained for AZ31B-O and AZ31B sheet alloys under both tension-compression-tension (T-C-T) and compression-tension (C-T) loadings to calibrate the parameters of back stresses in the proposed model. The predicted parameters of back stresses in the twinning and untwinning modes were expressed as a cubic polynomial. The predicted curves based on these parameters showed good agreement with the tests.

Microstructure characterization and strengthening mechanisms of oxide dispersion strengthened (ODS) Fe-9%Cr and Fe-14%Cr extruded bars

Science.gov (United States)

Chauhan, A.; Bergner, F.; Etienne, A.; Aktaa, J.; de Carlan, Y.; Heintze, C.; Litvinov, D.; Hernandez-Mayoral, M.; Oñorbe, E.; Radiguet, B.; Ulbricht, A.

2017-11-01

The collaborative study is focused on the relationship between microstructure and yield stress for an ODS Fe-9%Cr-based transformable alloy and an ODS Fe-14%Cr-based ferritic alloy. The contributions to the total room temperature yield stress arising from various strengthening mechanisms are addressed on the basis of a comprehensive description of the microstructures uncovered by means of transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), small-angle neutron scattering (SANS) and atom probe tomography (APT). While these methods provide a high degree of complementarity, a reasonable agreement was found in cases of overlap of information. The derived set of microstructure parameters along with reported strengthening equations was used to calculate the room temperature yield stress. The estimates were critically compared with the measured yield stress for an extended set of alloys including data reported for Fe-Cr model alloys and steels thus covering one order of magnitude or more in grain size, dislocation density, particle density and yield stress. The comparison shows that particle strengthening, dislocation forest strengthening, and Hall-Petch strengthening are the major contributions and that a mixed superposition rule reproduces the measured yield stress within experimental scatter for the whole extended set of alloys. The wide variation of microstructures additionally underpins the conclusions and goes beyond previous work, in which one or few ODS steels and narrow microstructure variations were typically covered.

Enhancement of tensile ductility and stretch formability of AZ31 magnesium alloy sheet processed by cross-wavy bending

International Nuclear Information System (INIS)

Huo, Qinghuan; Yang, Xuyue; Sun, Huan; Li, Bin; Qin, Jia; Wang, Jun; Ma, Jijun

2013-01-01

Highlights: •The AZ31 Mg alloy sheet is deformed to 4 passes at 673 K by cross-wavy bending. •A fine-grained microstructure and a weak and random texture are achieved. •Different softening mechanisms significantly affect the microstructure evolution. •The tensile ductility and stretch formability enhance dramatically. -- Abstract: The microstructure and texture evolution in the sheets of AZ31 magnesium alloy was studied by means of cross-wavy bending for 4 passes at 673 K. The bended samples were examined by optical microscopy and electron backscatter diffraction analysis. Finite element analysis suggested an inhomogeneous deformation at each pass. Following cross-wavy bending, a fine-grained microstructure with an average grain size of ∼8 μm and a weak and random basal texture were achieved. Accumulative effective strain was almost equal in the whole sheet at the end. Different work softening mechanisms significantly affected the evolution of the microstructure. Dynamic recovery played an important role during the first three bending passes whereas, in contrast, dynamic recrystallization dominated the evident grain refinement during the last pass. The tensile ductility and stretch formability of the 4-pass sheet at room temperature were distinctly enhanced compared to the initial sheet (1.55 and 2 times larger, respectively). These prominent increases were mainly attributed to texture randomizing rather than texture weakening alone

Studies of the AA2519 Alloy Hot Rolling Process and Cladding with EN AW-1050A Alloy

Directory of Open Access Journals (Sweden)

Płonka B.

2016-03-01

Full Text Available The objective of the study was to determine the feasibility of plastic forming by hot rolling of the AA2519 aluminium alloy sheets and cladding these sheets with a layer of the EN AW-1050A alloy. Numerous hot-rolling tests were carried out on the slab ingots to define the parameters of the AA2519 alloy rolling process. It has been established that rolling of the AA2519 alloy should be carried out in the temperature range of 400-440°C. Depending on the required final thickness of the sheet metal, appropriate thickness of the EN AW-1050A alloy sheet, used as a cladding layer, was selected. As a next step, structure and mechanical properties of the resulting AA2519 alloy sheets clad with EN AW-1050A alloy was examined. The thickness of the coating layer was established at 0,3÷0,5mm. Studies covered alloy grain size and the core alloy-cladding material bond strength.

Influence of the Aluminium Alloy Type on Defects Formation in Friction Stir Lap Welding of Thin Sheets

Directory of Open Access Journals (Sweden)

M. I. Costa

Full Text Available Abstract The weldability in Friction Stir Lap Welding (FSLW of heat and non-heat treatable aluminium alloys, the AA6082-T6 and the AA5754-H22 aluminium alloys, respectively, are compared. For both alloys, welds were produced in very thin sheets, using the same welding parameters and procedures, and strong differences in welds morphology were found. The strength of the welds was evaluated by performing tensile-shear tests under monotonic and cyclic loading conditions. As-welded and heat-treated samples of the AA6082- T6 were tested. It was found that the heat-treatable alloy is more sensitive to defects formation, in lap welding, than the non-heat-treatable alloy. The presence of defects has a strong influence on the monotonic and fatigue behaviour of the welds. In spite of this, for very high-applied stresses, the heat-treatable alloy welds perform better in fatigue than the non-heat-treatable alloy welds.

Strengthening effect of nano-scaled precipitates in Ta alloying layer induced by high current pulsed electron beam

Energy Technology Data Exchange (ETDEWEB)

Tang, Guangze; Luo, Dian; Fan, Guohua [School of Material Science & Engineering, Harbin Institute of Technology, Harbin 150001 (China); Ma, Xinxin, E-mail: maxin@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Liqin [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2017-05-01

Highlights: • Ta alloying layer are fabricated by magnetron sputtering and high current pulsed electron beam. • Nano-scaled TaC precipitates forms within the δ-Fe grain after tempering treatment. • The mean diameter of TaC particles is about 5–8 nm. • The hardness of alloying layer increased by over 50% after formation of nano-scaled TaC particle. - Abstract: In this study, the combination of magnetron sputtering and high current pulsed electron beam are used for surface alloying treatment of Ta film on high speed steel. And the Ta alloying layer is about 6 μm. After tempering treatment, TaC phase forms in Ta alloying layer when the treated temperature is over 823 K. Through the TEM and HRTEM observation, a large amount of nano-scaled precipitates (mean diameter 5–8 nm) form within the δ-Fe grain in Ta alloying layer after tempering treatment and these nano-scaled precipitates are confirmed as TaC particles, which contribute to the strengthening effect of the surface alloying layer. The hardness of tempered alloying layer can reach to 18.1 GPa when the treated temperature is 823 K which increase by 50% comparing with the untreated steel sample before surface alloying treatment.

Effects of nano-particles strengthening activating flux on the microstructures and mechanical properties of TIG welded AZ31 magnesium alloy joints

International Nuclear Information System (INIS)

Xie, Xiong; Shen, Jun; Cheng, Liang; Li, Yang; Pu, Yayun

2015-01-01

Highlights: • Increased nano-particles strengthening activating flux degraded TIGed seams. • The reaction between SiC particles and Mg alloy produced Al 4 C 3 and Mg 2 Si phases. • Al 4 C 3 and SiC particles promoted the nucleation and suppressed the growth of α-Mg. • Refined α-Mg grains, precipitated phase and SiC particles enhanced TIGed joints. - Abstract: In this paper, AZ31 magnesium alloy joints were processed by nano-particles strengthening activating flux tungsten inert gas (NSA-TIG) welding, which was achieved by the mixed TiO 2 and nano-SiC particles coated on the samples before welding tests. The macro/micro structural observation and mechanical properties evaluation of the welding joints were conducted by using optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction and tension and microhardness tests. The results showed that nano-particles strengthening activating flux effective improved the microstructure, microhardness in fusion zone, ultimate tensile strength of the TIG welding joints. In addition, the chemical reaction between part of SiC particles and AZ31 magnesium alloy produced Al 4 C 3 and Mg 2 Si in the joints. The Al 4 C 3 performed as nucleating agents for α-Mg and the dispersed Mg 2 Si and SiC particles enhanced the mechanical properties of the NSA-TIG welding joints. However, large heat input induced by the increase of the surface coating density of the nano-particles strengthening activating flux, increased the α-Mg grain sizes and weakened the mechanical properties of the welded joints. Therefore, the grain size of α-Mg, distribution of β-Mg 17 Al 12 , Mg 2 Si and SiC particles together influenced the evolution of the mechanical properties of the NSA-TIG welded AZ31 magnesium alloy joints

Numerical modelling in friction lap joining of aluminium alloy and carbon-fiber-reinforced-plastic sheets

Science.gov (United States)

Das, A.; Bang, H. S.; Bang, H. S.

2018-05-01

Multi-material combinations of aluminium alloy and carbon-fiber-reinforced-plastics (CFRP) have gained attention in automotive and aerospace industries to enhance fuel efficiency and strength-to-weight ratio of components. Various limitations of laser beam welding, adhesive bonding and mechanical fasteners make these processes inefficient to join metal and CFRP sheets. Friction lap joining is an alternative choice for the same. Comprehensive studies in friction lap joining of aluminium to CFRP sheets are essential and scare in the literature. The present work reports a combined theoretical and experimental study in joining of AA5052 and CFRP sheets using friction lap joining process. A three-dimensional finite element based heat transfer model is developed to compute the temperature fields and thermal cycles. The computed results are validated extensively with the corresponding experimentally measured results.

Punchless Drawing of Magnesium Alloy Sheet under Cold Condition and its Computation

International Nuclear Information System (INIS)

Yamashita, Minoru; Hattori, Toshio; Sato, Joji

2011-01-01

The punchless drawing with Maslennikov's technique was applied to the circular cup drawing of magnesium alloy AZ31B sheet under cold condition. The elastic rubber ring was used instead of the 'hard' punch, where the compressed ring dragged the sheet inward the die cavity. Attainable circumferential strain of the blank was increased by this technique with repetitive drawing operation. Thickness of the rubber pad affected little the attainable strain. The shape appearance became better when a harder rubber was used. The cup forming by single drawing operation was also tested using a small die shoulder radius. The LDR of 1.250 was obtained with the straight cup wall. Further, the computation of the punchless drawing was also conducted for the single drawing operation. The computed deformation pattern was well consistent with the corresponding experimental result.

Microstructure strengthening mechanisms in an Al–Mg–Si–Sc–Zr equal channel angular pressed aluminium alloy

Energy Technology Data Exchange (ETDEWEB)

Cabibbo, Marcello, E-mail: m.cabibbo@univpm.it [Dipartimento di Ingegneria Meccanica e Scienze Matematiche (DIISM), Università Politecnica delle Marche, 60131 Ancona (Italy)

2013-09-15

Microstructure dislocation strengthening mechanisms in severely deformed aluminium strongly depend on the different boundary evolutions. Thereafter, models of proof stress determination should take into account the different nature of the boundaries that form during severe plastic deformation. In the last few decades, Hall–Petch modified relationship and other proof stress modelling were extensively discussed. This paper deals with further insights into the Hansen's and other authors approach to the modelling of aluminium poof stress after equal channel angular pressing. The present model is based on a detailed transmission electron microscopy microstructure characterization of the different strengthening contributions in an age-hardened Al–Mg–Si–Sc–Zr alloy.

Microstructure strengthening mechanisms in an Al–Mg–Si–Sc–Zr equal channel angular pressed aluminium alloy

International Nuclear Information System (INIS)

Cabibbo, Marcello

2013-01-01

Microstructure dislocation strengthening mechanisms in severely deformed aluminium strongly depend on the different boundary evolutions. Thereafter, models of proof stress determination should take into account the different nature of the boundaries that form during severe plastic deformation. In the last few decades, Hall–Petch modified relationship and other proof stress modelling were extensively discussed. This paper deals with further insights into the Hansen's and other authors approach to the modelling of aluminium poof stress after equal channel angular pressing. The present model is based on a detailed transmission electron microscopy microstructure characterization of the different strengthening contributions in an age-hardened Al–Mg–Si–Sc–Zr alloy.

Non-contact sheet forming using lasers applied to a high strength aluminum alloy

Directory of Open Access Journals (Sweden)

Rafael Humberto Mota Siqueira

2016-07-01

Full Text Available Laser beam forming (LBF is a contactless mechanical process accomplished by the introduction of thermal stresses on the surface of a material using a laser in order to induce plastic deformation. In this work, LBF was performed on 1.6 mm thick sheets of a high strength aluminum alloy, AA6013-T4 class by using a defocused continuous Yb-fiber laser beam of 0.6 mm in diameter on the sheet top surface. The laser power and process speed were varied from 200 W to 2000 W and from 3 to 30 mm/s, respectively. For these experimental conditions, the bending angle of the sheet ranged from 0.1° to 2.5° per run. In the highest bending angle condition, 1000 W and 30 mm/s, the depth of remelted pool was 0.6 mm and the microstructure near the plate bottom surface remained unaltered. For the whole set of experimental conditions, the hardness remained constant at approximately 100 HV, which is similar to the base material. In order to verify the applicability of the method, some previously T-welded sheets were straightened. The method was efficient in correcting the distortion of the sheets with a bending angle up to 5°.

Composites Strengthened with Graphene Platelets and Formed in Semisolid State Based on α and α/β MgLiAl Alloys

Science.gov (United States)

Dutkiewicz, Jan; Rogal, Łukasz; Fima, Przemyslaw; Ozga, Piotr

2018-05-01

MgLiAl base composites strengthened with graphene platelets were prepared by semisolid processing of ball-milled alloy chips with 2% of graphene platelets. Composites strengthened with graphene platelets show higher hardness and yield stress than the cast alloys, i.e., 160 MPa as compared to 90 MPa for as-cast alloy MgLi9Al1.5. Mechanical properties for MgLiAl-based composites were similar or higher than for composites based on conventional AZ91 or WE43 alloys. The strengthening however was not only due to the presence of graphene, but also phases resulting from the reaction between carbon and lithium, i.e., Li2C2 carbide. Graphene platelets were located at globules boundaries resulting from semisolid processing for all investigated composites. Graphene platelets were in agglomerates forming continuous layers at grain boundaries in the composite based on the alloy MgLi4.5Al1.5. The shape of agglomerates was more complex and wavy in the composite based on MgLi9Al1.5 alloy most probably due to lithium-graphene reaction. Electron diffraction from the two-phase region α + β in MgLi9Al1.5 indicated that [001]α and [110]β directions are rotated about 4° from the ideal relationship [001] hex || [110] bcc phases. It showed higher lattice rotation than in earlier studies what is most probably caused by lattice slip and rotation during semisolid pressing causing substantial deformation particularly within the β phase. Raman spectroscopy studies confirmed the presence of graphene platelets within agglomerates and in addition the presence mainly of Li2C2 carbides in composites based on MgLi4.5Al1.5 and Mg9Li1.5Al alloys. From the character of Raman spectra refinement of graphene platelets was found in comparison with their initial size. The graphene areas without carbides contain graphene nanoplatelets with lateral dimension close to initial graphene sample. Electron diffraction allowed to confirm the presence of Li2C2 carbide at the surface of agglomerates found from

Effect of Strengthening Mechanism on Strain-Rate Related Tensile Properties of Low-Carbon Sheet Steels for Automotive Application

Science.gov (United States)

Das, Anindya; Biswas, Pinaki; Tarafder, S.; Chakrabarti, D.; Sivaprasad, S.

2018-05-01

In order to ensure crash resistance of the steels used in automotive components, the ensile deformation behavior needs to be studied and predicted not only under quasi-static condition, but also under dynamic loading rates. In the present study, tensile tests have been performed on four different automobile grade sheet steels, namely interstitial free steel, dual-phase 600 and 800, and a carbon manganese steel over the strain rate regime of 0.001-800/s. Apart from the variation in strength (which always increased with strain rate), the effect of strengthening mechanism on strain rate sensitivity and strain hardening behavior has been evaluated. Strain rate sensitivity was found to increase at high-strain rate regime for all the steels. Contribution of solid solution hardening on strain rate sensitivity at lower plastic strains was found to be higher compared to dislocation strengthening and second-phase hardening. However, precipitation hardening coupled with solid solution hardening produced the highest strain rate sensitivity, in C-Mn-440 steel at high strain rates. Different strain-rate-sensitive models which take into account the change in yield stress and strain hardening behavior with strain rate for ductile materials were used to predict the flow behavior of these sheet steels at strain rates up to 800/s.

B2-ordered iron-aluminium alloys strengthening. Influence of additions (Ni and B) and microstructure

International Nuclear Information System (INIS)

Colas, David

2004-01-01

We study the effects of additions (Ni and B) and microstructure on the mechanical behaviour of 40 at. % Al iron-aluminium alloys. From a macroscopic point of view, we show that nickel reinforces FeAl alloys over the whole temperature range, but that it simultaneously leads to emphasize the room temperature brittleness of these alloys through a cleavage stress decrease. We confirm powder metallurgy grain refining interest to enhance yield stress as well as fracture resistance. We show that nickel-induced yield stress effect is additive to 'Hall-Petch' one. Also, we point out that the strengthening phenomena (nickel or grain size) cause the yield stress anomaly, which these alloys usually present, to be hidden. Through a dislocation structures analysis of deformed materials we precise that low temperature nickel-induced solid solution hardening (SSH) cannot be explained on the basis of classical SSH theories but more probably through nickel influence upon the Peierls stress. Moreover, we show that the APB tubes dragging model may be compatible with our microscopic and macroscopic results about the anomaly. Eventually, we put into relation a dynamic super-dislocations multiplication process observation (in situ transmission microscopy) with the nickel-containing alloys tendency to cleavage. (author) [fr

Nanosized-Particle Dispersion-Strengthened Al Matrix Composites Fabricated by the Double Mechanical Alloying Process.

Science.gov (United States)

Kim, Chungseok

2018-03-01

The objective of this study was to fabricate an Al metal matrix composite strengthened by nanosized Al3Ti particles via double mechanical alloying process. Several Al-xTi alloys were fabricated, including Al-12%Ti, Al-15%Ti, and Al-12%Ti-1%Y2O3. The lattice parameter of as-milled state was calculated to be 4.0485 Å; after a milling time of 540 min, it was 4.0401 Å. This decrease was induced by Ti solutionizing into the Al matrix. The equivalent size of a coarse Al3Ti particle was 200-500 nm after the heat treatment; however, the particles were uniformly distributed and were refined through the MA2 process. The particle size of a Al3Ti phase was 30 nm or less, and the particles were uniformly distributed. These particles remained in a fine state in the matrix without growth and coarsening, even after the hot extrusion process. The microstructure of hot extruded alloys consisted of a uniform distribution of Al3Ti particles and other dispersoids in the Al matrix.

Texture and structure of VT-19 alloy thin sheets and their welded joints

International Nuclear Information System (INIS)

Ehgiz, I.V.; Babarehko, A.A.; Khorev, M.A.

1986-01-01

The phase content and texture of VT-19 alloys in all zones of welded joints (weld, a heat affected zone a base metal) after different heat treatments and the effect of the latter on mechanical properties of the welded joint are studied. It is characteristic of a 2.5 mm sheet of the VT-19 alloy rolled in the β → α phase transformation temperature range the development of β-phase plane deformation textures with (001), (112), (111) orientations in the rolling plane that compose 56% of the β-phase material volume. In this case a texture of univariant phase transformation of the above β-phase components { 1120 } - { 1122 } - { 1124 }, as well as that of α-phase plane deformation } 1014 } - { 1015 } are formed in the α-phase. Hardening with subsequent ageing of the rolled sheet leads to increasing the fraction of textured material in the β-phase up to 95% with expanding the volume with the (111) orientation, but as a whole the β-phase texture type remains the same. The α-phase texture type corresponds to the univariant β → α phase transformation, the material having the α-phase texture accounts for 70%. In the weld zone the and axes with orientation spreading to 20 deg are the β-phase crystallization axes in the trans verse direction. The textured material accounts for ∼ 70%. The same texture is observed along the normal to the sheet plane. The α-phase texture after hardening and ageing corresponds to the univariant phase transformation of the above-mentionedβ-phase orientations, the material volume with the α-phase texture is ∼80%

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

Forming characteristics of artificial aging Al-Mg-Si-Cu sheet alloys

Science.gov (United States)

Klos, Artur; Kellner, Sven; Wortberg, Daniel; Walter, Philipp; Bassi, Corrado; Merklein, Marion

2017-10-01

AA6111 is a commonly used aluminum alloy for body-in-white (BIW) components with good bake-hardening response, high strength and excellent formability. For industrial applications various process strategies are considered to reach strength of about 250 MPa in the final body part with that type of alloy. The purpose of this paper is to discuss recent process strategies of high-strength AA6111 sheets to evaluate the forming characteristics, precipitation kinetics dissolution and mechanical properties in the final condition. The forming behavior is investigated by four potential process chains after single-stage or multi-stage heat treatment including T4 (pre-aged at > 80 °C after quenching), T61 (T4 + artificial aged at 120-150 °C for 10-18 h), T6 (T4 + artificial aged at 180-220°C up to 12 h) and PFHT (T4 + post form heat treatment at 205°C for 30 min). The experimental input for characterization of the formability consists of tensile tests, bending tests and drawing tests. Differential Scanning Calorimetry (DSC) is used, to correlate the forming behavior with the precipitation distribution in the advanced stages of aging. The study shows that the forming behavior is strongly dependent on the condition the alloy.

High-temperature deformation of B2 NiAl-base alloys

International Nuclear Information System (INIS)

Lee, I.G.; Ghosh, A.K.

1994-01-01

The high-temperature deformation behavior of three rapidly solidified and processed NiAl-base alloys--NiAl, NiAl containing 2 pct TiB 2 , and NiAl containing 4 pct HfC--have been studied and their microstructural and textural changes during deformation characterized. Compressions tests were conducted at 1,300 and 1,447 K at strain rates ranging from 10 -6 to 10 -2 s -1 . HfC-containing material showed dispersion strengthening as well as some degree of grain refinement over NiAl, while TiB 2 dispersoid-containing material showed grain refinement as well as secondary recrystallization and did not improve high-temperature strength. Hot-pack rolling was also performed to develop thin sheet materials (1.27-mm thick) and from these alloys. Without dispersoids, NiAl rolled easily at 1,223 K and showed low flow stress and good ductility during the hot-rolling operation. Rolling of dispersoid-containing alloys was difficult due to strain localization and edge-cracking effects, resulting partly from the high flow stress at the higher strain rate during the rolling operation. Sheet rolling initially produced a {111} texture, which eventually broke into multiple-texture components with severe deformation

Oxide Dispersion Strengthened Fe(sub 3)Al-Based Alloy Tubes: Application Specific Development for the Power Generation Industry

Energy Technology Data Exchange (ETDEWEB)

Kad, B.K.

1999-07-01

A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe3Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100C in the power generation industry. A particular 'in service application' anomaly of Fe3Al-based alloys is that the environmental resistance is maintained up to 1200C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism.

Design of Fatigue Resistant Heusler-strengthened PdTi-based Shape Memory Alloys for Biomedical Applications

Science.gov (United States)

Frankel, Dana J.

The development of non-surgical transcatheter aortic valve implantation (TAVI) techniques, which utilize collapsible artificial heart valves with shape memory alloy (SMA)-based frames, pushes performance requirements for biomedical SMAs beyond those for well-established vascular stent applications. Fatigue life for these devices must extend into the ultra-high cycle fatigue (UHCF) regime (>600M cycles) with zero probability of failure predicted at applied strain levels. High rates of Ni-hypersensitivity raise biocompatibility concerns, driving the development of low-Ni and Ni-free SMAs. This work focuses on the development of biocompatible, precipitation-strengthened, fatigue-resistant PdTi-based SMAs for biomedical applications. Functional and structural fatigue are both manifestations of cyclic instability resulting in accumulation of slip and eventual structural damage. While functional fatigue is easily experimentally evaluated, structural fatigue is more difficult to measure without the proper equipment. Therefore, in this work a theoretical approach using a model well validated in steels is utilized to investigate structural fatigue behavior in NiTi in the UHCF regime, while low cycle functional fatigue is evaluated in order to monitor the core phenomena of the cyclic instability. Results from fatigue simulations modeling crack nucleation at non-metallic inclusions in commercial NiTi underscore the importance of increasing yield strength for UHCF performance. Controlled precipitation of nanoscale, low-misfit, L21 Heusler aluminides can provide effective strengthening. Phase relations, precipitation kinetics, transformation temperature, transformation strain, cyclic stability, and mechanical properties are characterized in both Ni-free (Pd,Fe)(Ti,Al) and low-Ni high-strength "hybrid" (Pd,Ni)(Ti,Zr,Al) systems. Atom probe tomography is employed to measure phase compositions and particle sizes used to calibrate LSW models for coarsening kinetics and Gibbs

Residual-stress-induced grain growth of twinned grains and its effect on formability of magnesium alloy sheet at room temperature

Energy Technology Data Exchange (ETDEWEB)

Kim, Se-Jong [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Kim, Daeyong, E-mail: daeyong@kims.re.kr [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Lee, Keunho; Cho, Hoon-Hwe; Han, Heung Nam [Department of Materials Science and Engineering and RIAM, Seoul National University, Seoul 151-744 (Korea, Republic of)

2015-11-15

A magnesium alloy sheet was subjected to in-plane compression along with a vertical load to avoid buckling during compression. Pre-compressed specimens machined from the sheet were annealed at different temperatures and the changes in microstructure and texture were observed using electron back scattered diffraction (EBSD). Twinned grains preferentially grew during annealing at 300 °C, so that a strong texture with the < 0001 > direction parallel to the transverse direction developed. EBSD analysis confirmed that the friction caused by the vertical load induced inhomogeneous distribution of residual stress, which acted as an additional driving force for preferential grain growth of twinned grain during annealing. The annealed specimen showed excellent formability. - Highlights: • A magnesium alloy sheet subjected to in-plane compression under a vertical load • The vertical load induced inhomogeneous distribution of the residual stress. • The residual stress acted as an additional driving force for grain growth. • The annealed specimen with strong non-basal texture showed excellent formability.

Strengthening of Cu–Ni–Si alloy using high-pressure torsion and aging

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); Matsunaga, Hirotaka [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Sauvage, Xavier [University of Rouen, CNRS UMR 6634, Groupe de Physique des Matériaux, Faculté des Sciences, BP 12, 76801 Saint-Etienne du Rouvray (France); 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)

2014-04-01

An age-hardenable Cu–2.9%Ni–0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ∼ 150 nm and the Vickers microhardness was significantly increased through the HPT processing. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis including high-resolution transmission electron microscopy revealed that nanosized precipitates having compositions of a metastable Cu{sub 3}Ni{sub 5}Si{sub 2} phase and a stable NiSi phase were formed in the Cu matrix by aging of the HPT-processed samples and these particles are responsible for the additional increase in strength after the HPT processing. - Highlights: • Grain refinement is achieved in Corson alloy the size of ∼150nm by HPT. • Aging at 300°C after HPT leads to further increase in the mechanical property. • Electrical conductivity reaches 40% IACS after aging for 100 h. • 3D-APT revealed the formation of nanosized-precipitates during aging treatment. • Simultaneous hardening in both grain refinement and precipitation is achieved.

Study of microstructural evolution in friction-stir welded thin-sheet Al-Cu-Li alloy using transmission-electron microscopy

International Nuclear Information System (INIS)

Shukla, A.K.; Baeslack, W.A.

2007-01-01

Microstructure evolution in friction-stir welded thin-sheet Al-Cu-Li alloy was studied using transmission-electron microscopy (TEM) and the dissolution and coarsening of T 1 and θ' precipitates were related to the microhardness profile of the weld

Material Behavior Based Hybrid Process for Sheet Draw-Forging Thin Walled Magnesium Alloys

International Nuclear Information System (INIS)

Sheng, Z.Q.; Shivpuri, R.

2005-01-01

Magnesium alloys are conventionally formed at the elevated temperatures. The thermally improved formability is sensitive to the temperature and strain rate. Due to limitations in forming speeds, tooling strength and narrow processing windows, complex thin walled parts cannot be made by traditional warm drawing or hot forging processes. A hybrid process, which is based on the deformation mechanism of magnesium alloys at the elevated temperature, is proposed that combines warm drawing and hot forging modes to produce an aggressive geometry at acceptable forming speed. The process parameters, such as temperatures, forming speeds etc. are determined by the FEM modeling and simulation. Sensitivity analysis under the constraint of forming limits of Mg alloy sheet material and strength of tooling material is carried out. The proposed approach is demonstrated on a conical geometry with thin walls and with bottom features. Results show that designed geometry can be formed in about 8 seconds, this cannot be formed by conventional forging while around 1000s is required for warm drawing. This process is being further investigated through controlled experiments

Chitosan coatings crosslinked with genipin for corrosion protection of AZ31 magnesium alloy sheets.

Science.gov (United States)

de Y Pozzo, Ludmila; da Conceição, Thiago F; Spinelli, Almir; Scharnagl, Nico; Pires, Alfredo T N

2018-02-01

In this study, coatings of chitosan crosslinked with genipin were prepared on sheets of AZ31 magnesium alloy and their corrosion protection properties were characterized by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The coatings were also characterized by means of FTIR and XPS. It was observed that the crosslinking process decreases the corrosion current and shifts the corrosion potential of the alloy to less negative values. The EIS analysis demonstrated that the crosslinking process increases the maximum impedance after short and long exposure times. The superior performance of the crosslinked coatings is related to a lower degree of swelling, as observed in the swelling tests carried out on free-standing films. Copyright © 2017 Elsevier Ltd. All rights reserved.

Low-cycle fatigue of sheet elements with ''soft'' surface layer

International Nuclear Information System (INIS)

Luk'yanov, V.F.; Kharchenko, V.Ya.; Berezutskij, V.I.; Ovsyannikov, V.G.

1978-01-01

Investigated are regularities of low-cycle fatigue of bimetallic sheet constructions made of chrome-nickel-molybdenum steel, plated with a low-alloyed steel with a reduced yield limit. Static repeated bending tests have been carried out using two-layer samples. The surface layer has been shown to increase resistance to nucleation and propagation of cracks under pulsating load if stresses are not more than 2 times higher than the yield limit. Increase in stresses leads to elastoplastic deformation and reduces durability. The positive effect of the surface layer is advisable to be used when welding-up surface defects and strengthening welded joints of high-strength steels

Strengthening mechanisms in a high-strength bulk nanostructured Cu–Zn–Al alloy processed via cryomilling and spark plasma sintering

International Nuclear Information System (INIS)

Wen, Haiming; Topping, Troy D.; Isheim, Dieter; Seidman, David N.; Lavernia, Enrique J.

2013-01-01

A bulk nanostructured alloy with the nominal composition Cu–30Zn–0.8Al wt.% (commercial designation brass 260) was fabricated by cryomilling of brass powders and subsequent spark plasma sintering (SPS) of the cryomilled powders, yielding a compressive yield strength of 950 MPa, which is significantly higher than the yield strength of commercial brass 260 alloys (∼200–400 MPa). Transmission electron microscopy investigations revealed that cryomilling results in an average grain diameter of 26 nm and a high density of deformation twins. Nearly fully dense bulk samples were obtained after SPS of cryomilled powders, with average grain diameter 110 nm. After SPS, 10 vol.% of twins is retained with average twin thickness 30 nm. Three-dimensional atom-probe tomography studies demonstrate that the distribution of Al is highly inhomogeneous in the sintered bulk samples, and Al-containing precipitates including Al(Cu,Zn)–O–N, Al–O–N and Al–N are distributed in the matrix. The precipitates have an average diameter of 1.7 nm and a volume fraction of 0.39%. Quantitative calculations were performed for different strengthening contributions in the sintered bulk samples, including grain boundary, twin boundary, precipitate, dislocation and solid-solution strengthening. Results from the analyses demonstrate that precipitate and grain boundary strengthening are the dominant strengthening mechanisms, and the calculated overall yield strength is in reasonable agreement with the experimentally determined compressive yield strength

Complementary AES and AEM of grain boundary regions in irradiated γ'-strengthened alloys

International Nuclear Information System (INIS)

Farrell, K.; Kishimoto, N.; Clausing, R.E.; Heatherly, L.; Lehman, G.L.

1986-01-01

Two microchemical analysis techniques are used to measure solute segregation at grain boundaries in two γ'-strengthened, fcc Fe-Ni-Cr alloys that display radiation-induced intergranular fracture. Scanning Auger electron spectroscopy (AES) of grain boundary fracture surfaces and analytical electron microscopy (AEM) of intact grain boundaries using energy-dispersive x-ray spectroscopy show good agreement on the nature and extent of segregation. The elements Ni, Si, Ti, and Mo are found to accumulate in G, Laves and γ' phases on the grain boundaries. Segregation of P is detected by AES. The complementary features of the two analytical techniques are discussed briefly

Controlling microstructure and texture in magnesium alloy sheet by shear-based deformation processing

Science.gov (United States)

Sagapuram, Dinakar

Application of lightweight Mg sheet is limited by its low workability, both in production of sheet (typically by multistep hot and cold-rolling) and forming of sheet into components. Large strain extrusion machining (LSEM), a constrained chip formation process, is used to create Mg alloy AZ31B sheet in a single deformation step. The deformation in LSEM is shown to be intense simple shear that is confined to a narrow zone, which results in significant deformation-induced heating up to ~ 200°C and reduces the need for pre-heating to realize continuous sheet forms. This study focuses on the texture and microstructure development in the sheet processed by LSEM. Interestingly, deep, highly twinned steady-state layer develops in the workpiece subsurface due to the compressive field ahead of the shear zone. The shear deformation, in conjunction with this pre-deformed twinned layer, results in tilted-basal textures in the sheet with basal planes tilted well away from the surface. These textures are significantly different from those in rolled sheet, where basal planes are nearly parallel to the surface. By controlling the strain path, the basal plane inclination from the surface could be varied in the range of 32-53°. B-fiber (basal plane parallel to LSEM shear plane), associated with basal slip, is the major texture component in the sheet. An additional minor C2-fiber component appears above 250°C due to the thermal activation of pyramidal slip. Together with these textures, microstructure ranges from severely cold-worked to (dynamically) recrystallized type, with the corresponding grain sizes varying from ultrafine- (~ 200 nm) to fine- (2 mum) grained. Small-scale limiting dome height (LDH) confirmed enhanced formability (~ 50% increase in LDH) of LSEM sheet over the conventional rolled sheet. Premature, twinning-driven shear fractures are observed in the rolled sheet with the basal texture. In contrast, LSEM sheet with a tilted-basal texture favorably oriented for

Tribological properties of Al 7075 alloy based composites strengthened with Al2O3 fibres

Directory of Open Access Journals (Sweden)

K. Naplocha

2011-04-01

Full Text Available Wear resistance of 7075 aluminium alloy based composite materials reinforced with Al2O3 Saffil fibres was investigated. The measurementsof wear were performed applying the pin-on-disc method at dry friction conditions with the gray iron counterpart. The effects ofpressure of composite samples on the counterpart made of gray iron and the orientation of fibers in relation to the friction surface on wear rate were determined. The materials were produced by squeeze casting method where 80-90% porous ceramic preform were infiltrated.After T6 heat treatment hardness increased about 50-60% both for unreinforced alloy and composites containing strengthening Saffilfibres. Wear resistance of composite materials in relation to the unreinforced 7075 alloy was slightly worse at lower pressure of 0.8 MPa. Under higher pressure of 1.2 MPa wear resistance of unreinforced 7075 alloy was even better whereas no effect of orientation of fibers on wear in composite materials was observed. Additionally, significant wear of counterface in the presence of debris with fragmented Al2O3 fibres as abrasives was observed. Wear resistance improvement of composite materials was obtained when with alumina Saffil fibres Carbon C fibres in the preforms were applied.

Structural improvement of strengthened deck panels with externally bonded plates

International Nuclear Information System (INIS)

Sim, Jongsung; Oh, Hongseob

2005-01-01

Concrete bridge decks require eventual replacement and rehabilitation due to decreasing load-carrying capacity. This paper compares different strengthening design procedures that improve the usability and structural performance of bridge decks. The failure characteristics of bridge decks strengthened with various materials such as carbon fiber sheet, glass fiber sheet, steel plate, and grid CFRP and GFRP are analyzed, and the theoretical load-carrying capacities are evaluated using traditional beam and yield line theory, and punching shear analysis. The strengthening materials increase the punching shear strength of the deck and change the failure mode of the strengthened panel

Effect of Al and Mg Contents on Wettability and Reactivity of Molten Zn-Al-Mg Alloys on Steel Sheets Covered with MnO and SiO2 Layers

Science.gov (United States)

Huh, Joo-Youl; Hwang, Min-Je; Shim, Seung-Woo; Kim, Tae-Chul; Kim, Jong-Sang

2018-05-01

The reactive wetting behaviors of molten Zn-Al-Mg alloys on MnO- and amorphous (a-) SiO2-covered steel sheets were investigated by the sessile drop method, as a function of the Al and Mg contents in the alloys. The sessile drop tests were carried out at 460 °C and the variation in the contact angles (θc) of alloys containing 0.2-2.5 wt% Al and 0-3.0 wt% Mg was monitored for 20 s. For all the alloys, the MnO-covered steel substrate exhibited reactive wetting whereas the a-SiO2-covered steel exhibited nonreactive, nonwetting (θc > 90°) behavior. The MnO layer was rapidly removed by Al and Mg contained in the alloys. The wetting of the MnO-covered steel sheet significantly improved upon increasing the Mg content but decreased upon increasing the Al content, indicating that the surface tension of the alloy droplet is the main factor controlling its wettability. Although the reactions of Al and Mg in molten alloys with the a-SiO2 layer were found to be sluggish, the wettability of Zn-Al-Mg alloys on the a-SiO2 layer improved upon increasing the Al and Mg contents. These results suggest that the wetting of advanced high-strength steel sheets, the surface oxide layer of which consists of a mixture of MnO and SiO2, with Zn-Al-Mg alloys could be most effectively improved by increasing the Mg content of the alloys.

New concept of composite strengthening in Co-Re based alloys for high temperature applications in gas turbines

Energy Technology Data Exchange (ETDEWEB)

Mukherji, D.; Roesler, J.; Fricke, T.; Schmitz, F. [Technische Univ. Braunschweig (DE). Inst. fuer Werkstoffkunde (IfW); Piegert, S. [Siemens AG, Berlin (DE). Energy Sector (F PR GT EN)

2010-07-01

High temperature material development is mainly driven by gas turbine needs. Today, Ni-based superalloys are the dominant material class in the hot section of turbines. Material development will continue to push the maximum service temperature of Ni-superalloys upwards. However, this approach has a fundamental limit and can not be sustained indefinitely, as the Ni-superalloys are already used very close to their melting point. Within the frame work of a DFG Forschergruppe program (FOR 727) - ''Beyond Ni-base Superalloys'' - Co-Re based alloys are being developed as a new generation of high temperature materials that can be used at +100 C above single crystal Ni-superalloys. Along with other strengthening concepts, hardening by second phase is explored to develop a two phase composite alloy. With quaternary Co-Re-Cr-Ni alloys we demonstrate this development concept, where Co{sub 2}Re{sub 3}-type {sigma} phase is used in a novel way as the hardening phase. Thermodynamic calculation was used for designing model alloy compositions. (orig.)

Preparation of a high strength Al–Cu–Mg alloy by mechanical alloying and press-forming

International Nuclear Information System (INIS)

Tang Huaguo; Cheng Zhiqiang; Liu Jianwei; Ma Xianfeng

2012-01-01

Highlights: ► A high strength aluminum alloy of Al–2 wt.%Mg–2 wt.%Cu has been prepared by mechanical alloying and press-forming. ► The alloy only consists of solid solution α-Al. ► The grains size of α-Al was about 300 nm–5 μm. ► The solid solution strengthening and the grain refinement strengthening are the main reasons for such a high strength. - Abstract: A high strength aluminum alloy, with the ratio of 96 wt.%Al–2 wt.%Mg–2 wt.%Cu, has been prepared by mechanical alloying and press-forming. The alloy exhibited a high tensile strength of 780 MPa and a high microhardness of 180 HV. X-ray diffraction characterizations confirmed that the alloy only consists of a solid solution α-Al. Microstructure characterizations revealed that the grain size of α-Al was about 300 nm–5 μm. The solid solution strengthening and the grain refinement strengthening were considered to be the reason for such a high strength.

Preparation of a high strength Al-Cu-Mg alloy by mechanical alloying and press-forming

Energy Technology Data Exchange (ETDEWEB)

Tang Huaguo [State Key Laboratory of Rare Earth Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Cheng Zhiqiang [College of Resources and Environment, Jilin Agricultural University, Changchun 130118 (China); Liu Jianwei [State Key Laboratory of Rare Earth Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Ma Xianfeng, E-mail: xfma@ciac.jl.cn [State Key Laboratory of Rare Earth Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2012-07-30

Highlights: Black-Right-Pointing-Pointer A high strength aluminum alloy of Al-2 wt.%Mg-2 wt.%Cu has been prepared by mechanical alloying and press-forming. Black-Right-Pointing-Pointer The alloy only consists of solid solution {alpha}-Al. Black-Right-Pointing-Pointer The grains size of {alpha}-Al was about 300 nm-5 {mu}m. Black-Right-Pointing-Pointer The solid solution strengthening and the grain refinement strengthening are the main reasons for such a high strength. - Abstract: A high strength aluminum alloy, with the ratio of 96 wt.%Al-2 wt.%Mg-2 wt.%Cu, has been prepared by mechanical alloying and press-forming. The alloy exhibited a high tensile strength of 780 MPa and a high microhardness of 180 HV. X-ray diffraction characterizations confirmed that the alloy only consists of a solid solution {alpha}-Al. Microstructure characterizations revealed that the grain size of {alpha}-Al was about 300 nm-5 {mu}m. The solid solution strengthening and the grain refinement strengthening were considered to be the reason for such a high strength.

Comparison of Ductile-to-Brittle Transition Behavior in Two Similar Ferritic Oxide Dispersion Strengthened Alloys

Science.gov (United States)

Chao, Jesus; Rementeria, Rosalia; Aranda, Maria; Capdevila, Carlos; Gonzalez-Carrasco, Jose Luis

2016-01-01

The ductile-to-brittle transition (DBT) behavior of two similar Fe-Cr-Al oxide dispersion strengthened (ODS) stainless steels was analyzed following the Cottrell–Petch model. Both alloys were manufactured by mechanical alloying (MA) but by different forming routes. One was manufactured as hot rolled tube, and the other in the form of hot extruded bar. The two hot forming routes considered do not significantly influence the microstructure, but cause differences in the texture and the distribution of oxide particles. These have little influence on tensile properties; however, the DBT temperature and the upper shelf energy (USE) are significantly affected because of delamination orientation with regard to the notch plane. Whereas in hot rolled material the delaminations are parallel to the rolling surface, in the hot extruded material, they are randomly oriented because the material is transversally isotropic. PMID:28773764

Comparison of Ductile-to-Brittle Transition Behavior in Two Similar Ferritic Oxide Dispersion Strengthened Alloys.

Science.gov (United States)

Chao, Jesus; Rementeria, Rosalia; Aranda, Maria; Capdevila, Carlos; Gonzalez-Carrasco, Jose Luis

2016-07-29

The ductile-to-brittle transition (DBT) behavior of two similar Fe-Cr-Al oxide dispersion strengthened (ODS) stainless steels was analyzed following the Cottrell-Petch model. Both alloys were manufactured by mechanical alloying (MA) but by different forming routes. One was manufactured as hot rolled tube, and the other in the form of hot extruded bar. The two hot forming routes considered do not significantly influence the microstructure, but cause differences in the texture and the distribution of oxide particles. These have little influence on tensile properties; however, the DBT temperature and the upper shelf energy (USE) are significantly affected because of delamination orientation with regard to the notch plane. Whereas in hot rolled material the delaminations are parallel to the rolling surface, in the hot extruded material, they are randomly oriented because the material is transversally isotropic.

Irradiation-assisted stress corrosion cracking in HTH Alloy X-750 and Alloy 625

International Nuclear Information System (INIS)

Bajaj, R.; Mills, W.J.; Lebo, M.R.; Hyatt, B.Z.; Burke, M.G.

1995-01-01

In-reactor testing of bolt-loaded compact tension specimens was performed in 360 C water to determine the irradiation-assisted stress corrosion cracking (IASCC) behavior of HTH Alloy X-750 and direct-aged Alloy 625. New data confirm previous results showing that high irradiation levels reduce SCC resistance in Alloy X-750. Heat-to-heat variability correlates with boron content, with low boron heats showing improved IASCC properties. Alloy 625 is resistant to IASCC, as no cracking was observed in any Alloy 625 specimens. Microstructural, microchemical and deformation studies were performed to characterize the mechanisms responsible for IASCC in Alloy X-750 and the lack of an effect in Alloy 625. The mechanisms under investigation are: boron transmutation effects, radiation-induced changes in microstructure and deformation characteristics, and radiation-induced segregation. Irradiation of Alloy X-750 caused significant strengthening and ductility loss that was associated with the formation of cavities and dislocation loops. High irradiation levels did not cause significant segregation of alloying or trace elements in Alloy X-750. Irradiation of Alloy 625 resulted in the formation of small dislocation loops and a fine body-centered-orthorhombic phase. The strengthening due to the loops and precipitates was apparently offset by a partial dissolution of γ double-prime precipitates, as Alloy 625 showed no irradiation-induced strengthening or ductility loss. In the nonirradiated condition, an IASCC susceptible HTH heat containing 28 ppm B showed grain boundary segregation of boron, whereas a nonsusceptible HTH heat containing 2 ppm B and Alloy 625 with 20 ppm B did not show significant boron segregation. Transmutation of boron to helium at grain boundaries, coupled with matrix strengthening, is believed to be responsible for IASCC in Alloy X-750, and the absence of these two effects results in the superior IASCC resistance displayed by Alloy 625

Quantification of oxide particle composition in model oxide dispersion strengthened steel alloys

Energy Technology Data Exchange (ETDEWEB)

London, A.J., E-mail: andrew.london@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Lozano-Perez, S.; Moody, M.P. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Amirthapandian, S.; Panigrahi, B.K.; Sundar, C.S. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Grovenor, C.R.M. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

2015-12-15

Oxide dispersion strengthened ferritic steels (ODS) are being considered for structural components of future designs of fission and fusion reactors because of their impressive high-temperature mechanical properties and resistance to radiation damage, both of which arise from the nanoscale oxide particles they contain. Because of the critical importance of these nanoscale phases, significant research activity has been dedicated to analysing their precise size, shape and composition (Odette et al., Annu. Rev. Mater. Res. 38 (2008) 471–503 [1]; Miller et al., Mater. Sci. Technol. 29(10) (2013) 1174–1178 [2]). As part of a project to develop new fuel cladding alloys in India, model ODS alloys have been produced with the compositions, Fe–0.3Y{sub 2}O{sub 3}, Fe–0.2Ti–0.3Y{sub 2}O{sub 3} and Fe–14Cr–0.2Ti–0.3Y{sub 2}O{sub 3}. The oxide particles in these three model alloys have been studied by APT in their as-received state and following ion irradiation (as a proxy for neutron irradiation) at various temperatures. In order to adequately quantify the composition of the oxide clusters, several difficulties must be managed, including issues relating to the chemical identification (ranging and variable peak-overlaps); trajectory aberrations and chemical structure; and particle sizing. This paper presents how these issues can be addressed by the application of bespoke data analysis tools and correlative microscopy. A discussion follows concerning the achievable precision in these measurements, with reference to the fundamental limiting factors.

Quantification of oxide particle composition in model oxide dispersion strengthened steel alloys.

Science.gov (United States)

London, A J; Lozano-Perez, S; Moody, M P; Amirthapandian, S; Panigrahi, B K; Sundar, C S; Grovenor, C R M

2015-12-01

Oxide dispersion strengthened ferritic steels (ODS) are being considered for structural components of future designs of fission and fusion reactors because of their impressive high-temperature mechanical properties and resistance to radiation damage, both of which arise from the nanoscale oxide particles they contain. Because of the critical importance of these nanoscale phases, significant research activity has been dedicated to analysing their precise size, shape and composition (Odette et al., Annu. Rev. Mater. Res. 38 (2008) 471-503 [1]; Miller et al., Mater. Sci. Technol. 29(10) (2013) 1174-1178 [2]). As part of a project to develop new fuel cladding alloys in India, model ODS alloys have been produced with the compositions, Fe-0.3Y2O3, Fe-0.2Ti-0.3Y2O3 and Fe-14Cr-0.2Ti-0.3Y2O3. The oxide particles in these three model alloys have been studied by APT in their as-received state and following ion irradiation (as a proxy for neutron irradiation) at various temperatures. In order to adequately quantify the composition of the oxide clusters, several difficulties must be managed, including issues relating to the chemical identification (ranging and variable peak-overlaps); trajectory aberrations and chemical structure; and particle sizing. This paper presents how these issues can be addressed by the application of bespoke data analysis tools and correlative microscopy. A discussion follows concerning the achievable precision in these measurements, with reference to the fundamental limiting factors. Copyright © 2015 Elsevier B.V. All rights reserved.

Alloying principles for magnesium base heat resisting alloys

International Nuclear Information System (INIS)

Drits, M.E.; Rokhlin, L.L.; Oreshkina, A.A.; Nikitina, N.I.

1982-01-01

Some binary systems of magnesium-base alloys in which solid solutions are formed, are considered for prospecting heat resistant alloys. It is shown that elements having essential solubility in solid magnesium strongly decreasing with temperature should be used for alloying maqnesium base alloys with high strength properties at increased temperatures. The strengthening phases in these alloys should comprise essential quantity of magnesium and be rather refractory

Material characterization and finite element simulations of aluminum alloy sheets during non-isothermal forming process

Science.gov (United States)

Zhang, Nan

The utilization of more non-ferrous materials is one of the key factors to succeed out of the constantly increasing demand for lightweight vehicles in automotive sector. Aluminum-magnesium alloys have been identified as the most promising substitutions to the conventional steel without significant compromise in structural stiffness and strength. However, the conventional forming methods to deform the aluminum alloy sheets are either costly or insufficient in formability which limit the wide applications of aluminum alloy sheets. A recently proposed non-isothermal hot stamping approach, which is also referred as Hot Blank - Cold Die (HB-CD) stamping, aims at fitting the commercial grade aluminum alloy sheets, such as AA5XXX and AA7XXX, into high-volume and cost-effective production for automotive sector. In essence, HB-CD is a mutation of the conventional hot stamping approach for boron steel (22MnB5) which deforms the hot blank within the cold tool set. By elevating the operation temperature, the formability of aluminum alloy sheets can be significantly improved. Meanwhile, heating the blank only and deforming within the cold tool sets allow to reduce the energy and time consumed. This research work aims at conducting a comprehensive investigation of HB-CD with particular focuses on material characterization, constitutive modeling and coupled thermo-mechanical finite element simulations with validation. The material properties of AA5182-O, a popular commercial grade of aluminum alloy sheet in automotive sector, are obtained through isothermal tensile testing at temperatures from 25° to 300°, covering a quasi-static strain-rate range (0.001--0.1s-1). As the state-of-the-art non-contact strain measurement technique, digital image correlation (DIC) system is utilized to evaluate the stress-strain curves as well as to reveal the details of material deformation with full-field and multi-axis strain measurement. Material anisotropy is characterized by extracting the

Novel strip-cast Mg/Al clad sheets with excellent tensile and interfacial bonding properties.

Science.gov (United States)

Kim, Jung-Su; Lee, Dong Ho; Jung, Seung-Pill; Lee, Kwang Seok; Kim, Ki Jong; Kim, Hyoung Seop; Lee, Byeong-Joo; Chang, Young Won; Yuh, Junhan; Lee, Sunghak

2016-06-01

In order to broaden industrial applications of Mg alloys, as lightest-weight metal alloys in practical uses, many efforts have been dedicated to manufacture various clad sheets which can complement inherent shortcomings of Mg alloys. Here, we present a new fabrication method of Mg/Al clad sheets by bonding thin Al alloy sheet on to Mg alloy melt during strip casting. In the as-strip-cast Mg/Al clad sheet, homogeneously distributed equi-axed dendrites existed in the Mg alloy side, and two types of thin reaction layers, i.e., γ (Mg17Al12) and β (Mg2Al3) phases, were formed along the Mg/Al interface. After post-treatments (homogenization, warm rolling, and annealing), the interfacial layers were deformed in a sawtooth shape by forming deformation bands in the Mg alloy and interfacial layers, which favorably led to dramatic improvement in tensile and interfacial bonding properties. This work presents new applications to multi-functional lightweight alloy sheets requiring excellent formability, surface quality, and corrosion resistance as well as tensile and interfacial bonding properties.

Fatigue and creep–fatigue deformation of an ultra-fine precipitate strengthened advanced austenitic alloy

International Nuclear Information System (INIS)

Carroll, M.C.; Carroll, L.J.

2012-01-01

An advanced austenitic alloy, HT-UPS (high-temperature ultrafine-precipitation-strengthened), has been identified as an ideal candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS alloys demonstrate improved creep resistance relative to 316 stainless steel (SS) through additions of Ti and Nb, which precipitate to form a widespread dispersion of stable nanoscale metallic carbide (MC) particles in the austenitic matrix. To investigate the behavior in more representative conditions than are offered by uniaxial creep tests, the low-cycle continuous fatigue and combined creep–fatigue response of an HT-UPS alloy have been investigated at 650 °C and 1.0% total strain, with an R-ratio of −1 and hold times at peak tensile strain of up to 150 min. The cyclic deformation response of HT-UPS is directly compared to that of standard 316 SS. The measured values for total cycles to failure between the two alloys are similar, despite differences in peak stress profiles and in qualitative observations of the deformed microstructures. Crack propagation is primarily transgranular in both fatigue and creep–fatigue of each alloy at the investigated conditions. Internal grain boundary damage in the form of fine cracks resulting from the tensile hold is present following the application of hold times of 60 min and longer, and considerably more internal cracks are quantifiable in 316 SS than in HT-UPS. The dislocation substructures observed in the deformed material differ substantially; an equiaxed cellular structure is observed in the microstructure of 316 SS, whereas HT-UPS exhibits widespread and relatively homogenous tangles of dislocations pinned by the nanoscale MC precipitates. The significant effect of the fine distribution of precipitates on observed fatigue and creep–fatigue response is described in three distinct behavioral regions as the microstructure evolves with continued cycling.

Fatigue and creep-fatigue deformation of an ultra-fine precipitate strengthened advanced austenitic alloy

Energy Technology Data Exchange (ETDEWEB)

Carroll, M.C., E-mail: Mark.Carroll@INL.gov [Idaho National Laboratory, 1955 Fremont, PO Box 1625, Idaho Falls, ID 83415-2218 (United States); Carroll, L.J. [Idaho National Laboratory, 1955 Fremont, PO Box 1625, Idaho Falls, ID 83415-2218 (United States)

2012-10-30

An advanced austenitic alloy, HT-UPS (high-temperature ultrafine-precipitation-strengthened), has been identified as an ideal candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS alloys demonstrate improved creep resistance relative to 316 stainless steel (SS) through additions of Ti and Nb, which precipitate to form a widespread dispersion of stable nanoscale metallic carbide (MC) particles in the austenitic matrix. To investigate the behavior in more representative conditions than are offered by uniaxial creep tests, the low-cycle continuous fatigue and combined creep-fatigue response of an HT-UPS alloy have been investigated at 650 Degree-Sign C and 1.0% total strain, with an R-ratio of -1 and hold times at peak tensile strain of up to 150 min. The cyclic deformation response of HT-UPS is directly compared to that of standard 316 SS. The measured values for total cycles to failure between the two alloys are similar, despite differences in peak stress profiles and in qualitative observations of the deformed microstructures. Crack propagation is primarily transgranular in both fatigue and creep-fatigue of each alloy at the investigated conditions. Internal grain boundary damage in the form of fine cracks resulting from the tensile hold is present following the application of hold times of 60 min and longer, and considerably more internal cracks are quantifiable in 316 SS than in HT-UPS. The dislocation substructures observed in the deformed material differ substantially; an equiaxed cellular structure is observed in the microstructure of 316 SS, whereas HT-UPS exhibits widespread and relatively homogenous tangles of dislocations pinned by the nanoscale MC precipitates. The significant effect of the fine distribution of precipitates on observed fatigue and creep-fatigue response is described in three distinct behavioral regions as the microstructure evolves with continued cycling.

Failure analysis of fusion clad alloy system AA3003/AA6xxx sheet under bending

Energy Technology Data Exchange (ETDEWEB)

Shi, Y., E-mail: shiyh@mcmaster.ca [Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Jin, H. [Novelis Global Technology Center, P.O. Box 8400, Kingston, Ontario, Canada K7L 5L9 (Canada); Wu, P.D. [Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Lloyd, D.J. [Aluminum Materials Consultants, 106 Nicholsons Point Road, Bath, Ontario, Canada K0H 1G0 (Canada); Embury, D. [Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada)

2014-07-29

An ingot of AA6xxx Al–Si–Mg–Cu alloy clad with AA3003 Al–Mn alloy was co-cast by Fusion technology. Bending tests and numerical modeling were performed to investigate the potential for sub-surface cracking for this laminate system. To simulate particle-induced crack initiation and growth, both random and stringer particles have been selected to mimic the particle distribution in the tested samples. The morphology of cracking in the model was similar to that observed in clad sheet tested in the Cantilever bend test. The crack initiated in the core close to the clad-core interface where the strain in the core is highest, between particles or near particles and propagates along local shear bands in the core, while the clad layer experiences extreme thinning before failure.

Characterization of the deformation texture after tensile test and cold rolling of a Ti-6Al-4V sheet alloy

International Nuclear Information System (INIS)

Mehdi, B; Badji, R; Azzeddine, H; Alili, B; Bradai, D; Ji, V

2015-01-01

The deformation texture after cold rolling and tensile test of an industrial Ti-6Al-4V sheet alloy was studied using X-ray diffraction. The alloy was subjected to a cold rolling to different thickness reductions (from 20% to 60%) and then tensile tests have been carried out along three directions relatively to the rolling direction (0°, 45° and 90°). The experimental results were compared to the existing literature and discussed in terms of active plastic deformation mechanisms. (paper)

Effect of Low-Temperature Thermomechanical Treatment on the Structure and Mechanical, Fatigue and Corrosion Characteristics of Sheets from an Alloy of the Al - Mg - Si - Cu - Zn System

Science.gov (United States)

Makhsidov, V. V.; Kolobnev, N. I.; Kochubey, A. Ya.; Fomina, M. A.; Zamyatin, V. M.; Pushin, V. G.

2014-11-01

The effect of deformation on the structure, strength and fatigue properties, stresses on the surface and sensitivity to intercrystalline corrosion of sheets from alloy 1370 of the Al -Mg - Si - Cu - Zn system with one-side cladding is investigated. Application of deformation to sheets of alloy 1370 between the stages of artificial aging lowers the depth of penetration of ICC (≤ 0.10 mm) and raises the fatigue characteristics (by up to a factor of 2) at a high level of mechanical properties.

The Mechanisms of Dispersion Strengthening and Fracture in Al-based XD (TM) Alloys

Science.gov (United States)

Aiken, R. M., Jr.

1990-01-01

The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength, and the fracture toughness of metal matrix composites of both pure aluminum and Al(4 percent)Cu(1.5 percent)Mg with 0 to 15 vol percent TiB2 were examined. Higher TiB2 volume fractions increased the tensile yield strength both at room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. The fracture toughness of the Al(4 percent)Cu(1.5 percent)Mg alloys decreased rapidly with TiB2 additions of 0 to 5 vol percent and more slowly with TiB2 additions of 5 to 15 vol percent. Fracture toughness appears to be independent of TiB2 particle size. The isothermal-aging response of the precipitation strengthened Al(4 percent)Cu(1.5 percent)Mg alloys was not altered by the presence of TiB2.

Strengthening mechanisms in ultrafine grained Al-Mg-Si alloy processed by hydrostatic extrusion – Influence of ageing temperature

Energy Technology Data Exchange (ETDEWEB)

Chrominski, Witold, E-mail: wichr@inmat.pw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Wenner, Sigurd [Department of Physics, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Marioara, Calin D. [SINTEF Materials and Chemistry, 7465 Trondheim (Norway); Holmestad, Randi [Department of Physics, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Lewandowska, Malgorzata [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

2016-07-04

Microstructure of hydrostatically extruded Al-Mg-Si alloy was studied by the combination of electron backscattered diffraction and transmission electron microscopy. Three different grain types which feature various defects arrangements were detected. Post deformation ageing at two temperatures caused different precipitation phenomena which were strongly dependent on type of grain boundaries in the considered grain types. Thus, a combination of plastic deformation and ageing resulted in a material with complex microstructure. Based on transmission electron microscopy observations, contributions of different strengthening mechanisms were estimated and compared to experimental results. A good agreement between obtained data points confirmed that depending on grain type, different strengthening mechanisms are operative and the overall strength is a sum of hardening given by each of them. Ageing of ultrafine grain structure results in efficient precipitation strengthening. On the other hand ageing causes annihilation of low and high angle grains boundaries in which leads to softening of investigated material. This effect cannot be compensated by precipitation hardening.

Effect of alumina strengthening particles on brazed joints of GlidCop Al-15 copper alloy

International Nuclear Information System (INIS)

Chen, S.; Liu, J.Y.; Chin, B.A.

1994-01-01

Brazed joints of the alumina dispersion-strengthened copper alloy were developed using resistance heating brazing with BCuP-3 braze alloy. Experimental results show that tensile strength and fatigue properties are a function of the brazing process temperature cycle. Maximum tensile and fatigue properties can be obtained by choice of an optimal braze time and temperature. However, in both tensile and fatigue tests the brazed joints exhibited low ductility. Metallography of the fractured tensile and fatigue samples showed that cracks always initiated in and propagated along the interface between the transition layer and the braze metal. EDS analysis across the joint showed that P diffused very quickly into base metal along grain boundaries. A strong Al peak (associated with the detection of Al 2 O 3 ) was found that corresponded with the transition layer. Fractography showed an intergranular fracture pattern across this transition zone indicating that the observed segregation of alumina particles reduces the ductility of this region. ((orig.))

Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

Science.gov (United States)

Royster, D. M.; Thomas, J. R.; Singleton, O. R.

1993-01-01

Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

Novel twin-roll-cast Ti/Al clad sheets with excellent tensile properties.

Science.gov (United States)

Kim, Dae Woong; Lee, Dong Ho; Kim, Jung-Su; Sohn, Seok Su; Kim, Hyoung Seop; Lee, Sunghak

2017-08-14

Pure Ti or Ti alloys are recently spot-lighted in construction industries because they have excellent resistance to corrosions, chemicals, and climates as well as various coloring characteristics, but their wide applications are postponed by their expensiveness and poor formability. We present a new fabrication process of Ti/Al clad sheets by bonding a thin Ti sheet on to a 5052 Al alloy melt during vertical-twin-roll casting. This process has merits of reduced production costs as well as improved tensile properties. In the as-twin-roll-cast clad sheet, the homogeneously cast microstructure existed in the Al alloy substrate side, while the Ti/Al interface did not contain any reaction products, pores, cracks, or lateral delamination, which indicated the successful twin-roll casting. When this sheet was annealed at 350 °C~600 °C, the metallurgical bonding was expanded by interfacial diffusion, thereby leading to improvement in tensile properties over those calculated by a rule of mixtures. The ductility was also improved over that of 5052-O Al alloy (25%) or pure Ti (25%) by synergic effect of homogeneous deformation due to excellent Ti/Al bonding. This work provides new applications of Ti/Al clad sheets to lightweight-alloy clad sheets requiring excellent formability and corrosion resistance as well as alloy cost saving.

Characterization of dispersion strengthened copper with 3wt%Al2O3 by mechanical alloying

Directory of Open Access Journals (Sweden)

Rajković Višeslava

2004-01-01

Full Text Available The copper matrix has been dispersion strengthened with 3wt.%Al2O3 by mechanical alloying. Commercial alumina powder with an average particle size of 0.75mm was used for alloying. The mechanical alloying process was performed in a planetary ball mill up to 20h in air. After milling all powders were treated in H2 at 4000C for 1h, and finally hot pressing was used for compaction (800oC, 3h, Ar. Structure observations revealed a lamellar structure (Al2O3 particles largely restricted to interlamellar planes between adjacent copper lamellae accompanied also by structure refinement. These structural changes were mostly completed in the early stage of milling, and retained after compaction. Micro hardness was found to progressively increase with milling time. So, after 5h of milling the micro hardness of the Cu+3twt%Al2O3 compact was 1540MPa, i.e. 2.5 times greater than for the as-received electrolytic copper powder (638MPa compacted under identical conditions, while after 20h of milling it was 2370 MPa. However after exposing the tested compact at 800oC up to 5h, the achieved hardening effect vanished.

The mechanisms of dispersion strengthening and fracture in Al-based XD(tm) alloys, part 1

Science.gov (United States)

Aikin, R. M., Jr.

1990-01-01

The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength; the fracture toughness; and the fatigue crack growth rate of metal matrix composites of Al-4(pct)Cu-1.5(pct)Mg with TiB2 were examined. The influence of reinforcement volume fraction was also examined for pure aluminum with TiB2. Higher TiB2 volume fractions increased the tensile yield strength at both room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. Interparticle spacing appears to be the factor that controls the strength of these alloys, with the exact nature of the dependence relying on the nature of dislocation slip in the matrix (planar vs. diffuse). The isothermal aging response of the precipitation strengthened Al-4(pct)Cu-1.5(pct)Mg alloys was not accelerated by the presence of TiB2. Cold work prior to artificial aging created additional geometrically necessary dislocations which serve as heterogeneous nucleation sites leading to accelerated aging, a finer precipitate size, and an increase in the strength of the alloy.

A technology to improve formability for aluminum alloy thin-wall corrugated sheet component hydroforming

Directory of Open Access Journals (Sweden)

Lang Lihui

2015-01-01

Full Text Available The explosively forming projectile (EFP had been traditional adopted for the aluminum thin-walled corrugated sheet, whose deformation range is large but the formability is poor, and this process usually has problems of poor surface quality, long manufacturing cycle and high cost. The active hydroforming process was suggested to solve these issues during EFP. A new technology named as blank bulging by turning the upside down active hydroforming technology was proposed to overcome difficulties in non-uniform thickness distribution and cracking failure of corrugated sheet during the conventional hydroforming process. Both numerical simulations and experiments were conducted for this new technology. The result show that the deformation capacity of aluminum alloys can be improved effectively, and the more uniform distribution of wall thickness was obtained by this new method. It is conducted that the new method is universal for thin-walled, shallow drawing parts with complex section.

Effect of TMP variables upon structure and properties in ODS alloy HDA 8077 sheet. [ThermoMechanical Processing of Oxide Dispersion Strengthened nickel alloy

Science.gov (United States)

Rothman, M. F.; Tawancy, H. M.

1980-01-01

The effects of oxide content level and variations in thermomechanical processing upon the final structure and properties of HDA 8077 sheet have been systematically examined. It was found that creep strength and formability are substantially influenced by both oxide content and TMP schedule. Variations in creep properties obtained appear to correlate with observed microstructures.

Fabrication technological development of the oxide dispersion strengthened alloy MA957 for fast reactor applications

International Nuclear Information System (INIS)

ML Hamilton; DS Gelles; RJ Lobsinger; GD Johnson; WF Brown; MM Paxton; RJ Puigh; CR Eiholzer; C Martinez; MA Blotter

2000-01-01

A significant amount of effort has been devoted to determining the properties and understanding the behavior of the alloy MA957 to define its potential usefulness as a cladding material, in the fast breeder reactor program. The numerous characterization and fabrication studies that were conducted are documented in this report. The alloy is a ferritic stainless steel developed by International Nickel Company specifically for structural reactor applications. It is strengthened by a very fine, uniformly distributed yttria dispersoid. Its fabrication involves a mechanical alloying process and subsequent extrusion, which ultimately results in a highly elongated grain structure. While the presence of the dispersoid produces a material with excellent strength, the body centered cubic structure inherent to the material coupled with the high aspect ratio that results from processing operations produces some difficulties with ductility. The alloy is very sensitive to variations in a number of processing parameters, and if the high strength is once lost during fabrication, it cannot be recovered. The microstructural evolution of the alloy under irradiation falls into two regimes. Below about 550 C, dislocation development, αprime precipitation and void evolution in the matrix are observed, while above about 550 C damage appears to be restricted to cavity formation within oxide particles. The thermal expansion of the alloy is very similar to that of HT9 up to the temperature where HT9 undergoes a phase transition to austenitic. Pulse magnetic welding of end caps onto MA957 tubing can be accomplished in a manner similar to that in which it is performed on HT9, although the welding parameters appear to be very sensitive to variations in the tubing that result from small changes in fabrication conditions. The tensile and stress rupture behavior of the alloy are acceptable in the unirradiated condition, being comparable to HT9 below about 700 C and exceeding those of HT9 at

Friction stir welding of T joints of dissimilar aluminum alloy: A review

Science.gov (United States)

Thakare, Shrikant B.; Kalyankar, Vivek D.

2018-04-01

Aluminum alloys are preferred in the mechanical design due to their advantages like high strength, good corrosion resistance, low density and good weldability. In various industrial applications T joints configuration of aluminum alloys are used. In different fields, T joints having skin (horizontal sheet) strengthen by stringers (vertical sheets) were used to increase the strength of structure without increasing the weight. T joints are usually carried out by fusion welding which has limitations in joining of aluminum alloy due to significant distortion and metallurgical defects. Some aluminum alloys are even non weldable by fusion welding. The friction stir welding (FSW) has an excellent replacement of conventional fusion welding for T joints. In this article, FSW of T joints is reviewed by considering aluminum alloy and various joint geometries for defect analysis. The previous experiments carried out on T joints shows the factors such as tool geometry, fixturing device and joint configurations plays significant role in defect free joints. It is essential to investigate the material flow during FSW to know joining mechanism and the formation of joint. In this study the defect occurred in the FSW are studied for various joint configurations and parameters. Also the effect of the parameters and defects occurs on the tensile strength are studied. It is concluded that the T-joints of different joint configurations can be pretended successfully. Comparing to base metal some loss in tensile strength was observed in the weldments as well as overall reduction of the hardness in the thermos mechanically affected zone also observed.

Corrosion resistance and protection mechanism of hot-dip Zn-Al-Mg alloy coated steel sheet under accelerated corrosion environment; Yoyu Zn-Al-Mg kei gokin mekki koban no sokushin fushoku kankyoka ni okeru taishokusei toi boshoku kiko

Energy Technology Data Exchange (ETDEWEB)

Komatsu, A.; Izutani, H.; Tsujimura, T.; Ando, A.; Kittaka, T. [NKK Corp., Tokyo (Japan)

2000-08-01

Corrosion behavior of hot-dip Zn-6%Al 0-3%Mg alloy coated steel sheets in cyclic corrosion test (CCT) has been investigated. The corrosion resistance was improved with increasing Mg content in the coating layer, and the highest corrosion resistance was observed at 3% Mg. In Zn-6%Al-3%Mg alloy coated steel sheet, the formations of zinc carbonate hydroxide and zinc oxide were suppressed for longer duration compared with Zn-0.2%Al and Zn-4.5%Al-0.l%Mg alloy coated steel sheets. As a result, zinc chloride hydroxide existed stable on the surface of the coating layer. From the polarization behaviors in 5% NaCl aqueous solution after CCT, it was found that the corrosion current density of Zn-6%At-3%Mg alloy coated steel sheet was much smaller than those of Zn-0.2%Al and Zn-4.5%Al-0.1%Mg alloy coated steel sheets. As zinc carbonate hydroxide and zinc oxide had poor adhesion to the coating layer and had porous structures, these corrosion products were considered to have little protective action for the coating layer. Therefore, it was concluded that Mg suppressed the formation of such nonprotective corrosion products. resulting in the remarkable improvement of corrosion resistance. (author)

Characteristics of Resistance Spot Welded Ti6Al4V Titanium Alloy Sheets

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Xinge Zhang

2017-10-01

Full Text Available Ti6Al4V titanium alloy is applied extensively in the aviation, aerospace, jet engine, and marine industries owing to its strength-to-weight ratio, excellent high-temperature properties and corrosion resistance. In order to extend the application range, investigations on welding characteristics of Ti6Al4V alloy using more welding methods are required. In the present study, Ti6Al4V alloy sheets were joined using resistance spot welding, and the weld nugget formation, mechanical properties (including tensile strength and hardness, and microstructure features of the resistance spot-welded joints were analyzed and evaluated. The visible indentations on the weld nugget surfaces caused by the electrode force and the surface expulsion were severe due to the high welding current. The weld nugget width at the sheets’ faying surface was mainly affected by the welding current and welding time, and the welded joint height at weld nugget center was chiefly associated with electrode force. The maximum tensile load of welded joint was up to 14.3 kN in the pullout failure mode. The hardness of the weld nugget was the highest because of the coarse acicular α′ structure, and the hardness of the heat-affected zone increased in comparison to the base metal due to the transformation of the β phase to some fine acicular α′ phase.

Evaluation of oxide dispersion strengthened (ODS) molybdenum and molybdenum-rhenium alloys

International Nuclear Information System (INIS)

Mueller, A.J.; Bianco, R.; Buckman, R.W. Jr.

1999-01-01

Oxide dispersion strengthened (ODS) molybdenum alloys being developed for high temperature applications possess excellent high temperature strength and creep resistance. In addition they exhibit a ductile-to-brittle transition temperature (DBIT) in the worked and stress-relieved condition under longitudinal tensile load well below room temperature. However, in the recrystallized condition, the DBTT maybe near or above room temperature, depending on the volume fraction of oxide dispersion and the amount of prior work. Dilute rhenium additions (7 and 14 wt.%) to ODS molybdenum were evaluated to determine their effect on low temperature ductility. The addition of 7 wt.% rhenium to the ODS molybdenum did not significantly enhance the mechanical properties. However, the addition of 14 wt.% rhenium to the ODS molybdenum resulted in a DBTT well below room temperature in both the stress-relieved and recrystallized condition. Additionally, the tensile strength of ODS Mo-14Re is greater than the base ODS molybdenum at 1,000 to 1,250 C

Numerical models for the prediction of failure for multilayer fusion Al-alloy sheets

International Nuclear Information System (INIS)

Gorji, Maysam; Berisha, Bekim; Hora, Pavel; Timm, Jürgen

2013-01-01

Initiation and propagation of cracks in monolithic and multi-layer aluminum alloys, called “Fusion”, is investigated. 2D plane strain finite element simulations are performed to model deformation due to bending and to predict failure. For this purpose, fracture strains are measured based on microscopic pictures of Nakajima specimens. In addition to, micro-structure of materials is taken into account by introducing a random grain distribution over the sheet thickness as well as a random distribution of the measured yield curve. It is shown that the performed experiments and the introduced FE-Model are appropriate methods to highlight the advantages of the Fusion material, especially for bending processes

Laser beam welding and friction stir welding of 6013-T6 aluminium alloy sheet

International Nuclear Information System (INIS)

Braun, R.; Dalle Donne, C.; Staniek, G.

2000-01-01

Butt welds of 1.6 mm thick 6013-T6 sheet were produced using laser beam welding and friction stir welding processes. Employing the former joining technique, filler powders of the alloys Al-5%Mg and Al-12%Si were used. Microstructure, hardness profiles, tensile properties and the corrosion behaviour of the welds in the as-welded condition were investigated. The hardness in the weld zone was lower compared to that of the base material in the peak-aged temper. Hardness minima were measured in the fusion zone and in the thermomechanically affected zone for laser beam welded and friction stir welded joints, respectively. Metallographic and fractographic examinations revealed pores in the fusion zone of the laser beam welds. Porosity was higher in welds made using the filler alloy Al-5%Mg than using the filler metal Al-12%Si. Transmission electron microscopy indicated that the β '' (Mg 2 Si) hardening precipitates were dissolved in the weld zone due to the heat input of the joining processes. Joint efficiencies achieved for laser beam welds depended upon the filler powders, being about 60 and 80% using the alloys Al-5%Mg and Al-12%Si, respectively. Strength of the friction stir weld approached over 80% of the ultimate tensile strength of the 6013-T6 base material. Fracture occurred in the region of hardness minima unless defects in the weld zone led to premature failure. The heat input during welding did not cause a degradation of the corrosion behaviour of the welds, as found in continuous immersion tests in an aqueous chloride-peroxide solution. In contrast to the 6013-T6 parent material, the weld zone was not sensitive to intergranular corrosion. Alternate immersion tests in 3.5% NaCl solution indicated high stress corrosion cracking resistance of the joints. For laser beam welded sheet, the weld zone of alternately immersed specimens suffered severe degradation by pitting and intergranular corrosion, which may be associated with galvanic coupling of filler metal and

Development and Testing of Dispersion-Strengthened Tungsten Alloys via Spark Plasma Sinterin

Science.gov (United States)

Lang, Eric; Madden, Nathan; Smith, Charles; Krogstad, Jessica; Allain, Jean Paul

2017-10-01

Tungsten (W) is a common plasma-facing component (PFC) material in the divertor region of tokamak fusion devices due to its high melting point and high sputter threshold. However, W is intrinsically brittle and is further embrittled under neutron irradiation, and the low recrystallization temperature pose complications in fusion environments. More ductile W alloys, such as dispersion-strengthened tungsten are being developed. In this work, W samples are processed via spark plasma sintering (SPS) with TiC, ZrC, and TaC dispersoids alloyed from 0.5 to 10 weight %. SPS is a powder compaction technique that provides high pressure and heating rates via electrical current, allowing for a lower final temperature and hold time for compaction. Initial testing of material properties, smicrostructure, and composition of specimens will be presented. Deuterium and helium irradiations have been performed in IGNIS, a multi-functional, in-situ irradiation and characterization facility at the University of Illinois. High-flux, low-energy exposures at the Magnum-PSI facility at DIFFER exposed samples to a D fluence of 1×1026 cm-2 and He fluence of 1x1025-1x1026 cm-2 at temperatures of 300-1000 C. In-situ chemistry changes via XPS and ex-situ morphology changes via SEM will be studied. Work supported by US DOE Contract DE-SC0014267.

Experimental and FE simulation validation of sheet thickness optimization in superplastic forming of Al alloy

Energy Technology Data Exchange (ETDEWEB)

Kumaresan, G.; Jothilingam, A. [Anna University, Chennai (India)

2016-07-15

Superplasticity is the ability of a polycrystalline materials to exhibit very large elongations without necking prior to failure. In this paper, the superplastic forming potential of fine grained 7075 aluminium alloy was studied. The process parameters like pressure, forming time and initial sheet thickness were selected, using the design of experiments technique. The same condition of formation process was attempted in the finite element simulation using ABAQUS software. The deviation of the thickness distribution between the simulation and experiment was made and the variation lies within 8%.

Radiation-induced strengthening and absorption of dislocation loops in ferritic Fe–Cr alloys: the role of Cr segregation

International Nuclear Information System (INIS)

Terentyev, D; Bakaev, A

2013-01-01

The understanding of radiation-induced strengthening in ferritic FeCr-based steels remains an essential issue in the assessment of materials for fusion and fission reactors. Both early and recent experimental works on Fe–Cr alloys reveal Cr segregation on radiation-induced nanostructural features (mainly dislocation loops), whose impact on the modification of the mechanical response of the material might be key for explaining quantitatively the radiation-induced strengthening in these alloys. In this work, we use molecular dynamics to study systematically the interaction of dislocations with 1/2〈111〉 and 〈100〉 loops in all possible orientations, both enriched by Cr atoms and undecorated, for different temperatures, loop sizes and dislocation velocities. The configurations of the enriched loops have been obtained using a non-rigid lattice Monte Carlo method. The study reveals that Cr segregation influences the interaction mechanisms with both 1/2〈111〉 and 〈100〉 loops. The overall effect of Cr enrichment is to penalize the mobility of intrinsically glissile 1/2〈111〉 loops, modifying the reaction mechanisms as a result. The following three most important effects associated with Cr enrichment have been revealed: (i) absence of dynamic drag; (ii) suppression of complete absorption; (iii) enhanced strength of small dislocation loops (2 nm and smaller). Overall the effect of the Cr enrichment is therefore to increase the unpinning stress, so experimentally ‘invisible’ nanostructural features may also contribute to radiation-induced strengthening. The reasons for the modification of the mechanisms are explained and the impact of the loading conditions is discussed. (paper)

Microstructure evolution of the oxide dispersion strengthened CLAM steel during mechanical alloying process

Energy Technology Data Exchange (ETDEWEB)

Song, Liangliang [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230031 (China); Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China); Mao, Xiaodong [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China)

2016-11-15

Highlights: • A nano-sized oxides dispersed ODS-CLAM steel was obtained by MA and HIP. • A minimum saturated grain size of down to 30 nm was achieved by varying the milling time from 0 to 100 h. • Solution of W in the MA powder could be significantly improved by increasing MA rotation speed. - Abstracts: Oxide dispersion strengthened Ferritic/Martensitic steel is considered as one of the most potential structural material for future fusion reactor, owing to its high mechanical properties and good irradiation resistance. The oxide dispersion strengthened China Low Activation Martensitic (ODS-CLAM) steel was fabricated by mechanical alloying (MA) and hot isostatic pressing (HIP). The microstructural evolutions during the process of ball milling and subsequent consolidation were investigated by SEM, XRD and TEM. The results showed that increasing the milling time during the first 36 h milling could effectively decrease the grain size to a value of around 30 nm, over which grain sized remained nearly constant. Increasing the rotation speed promoted the solution of tungsten (W) element obviously and decreased the grain size to a certain degree. Observation on the consolidated and further heat-treated ODS-CLAM steel samples indicated that a martensite microstructure with a high density of nano-particles was achieved.

MICROSTRUCTURE AND MECHANICAL STRENGTH OF SURFACE ODS TREATED ZIRCALOY-4 SHEET USING LASER BEAM SCANNING

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HYUN-GIL KIM

2014-08-01

Full Text Available The surface modification of engineering materials by laser beam scanning (LBS allows the improvement of properties in terms of reduced wear, increased corrosion resistance, and better strength. In this study, the laser beam scan method was applied to produce an oxide dispersion strengthened (ODS structure on a zirconium metal surface. A recrystallized Zircaloy-4 alloy sheet with a thickness of 2 mm, and Y2O3 particles of 10 μm were selected for ODS treatment using LBS. Through the LBS method, the Y2O3 particles were dispersed in the Zircaloy-4 sheet surface at a thickness of 0.4 mm, which was about 20% when compared to the initial sheet thickness. The mean size of the dispersive particles was 20 nm, and the yield strength of the ODS treated plate at 500°C was increased more than 65 % when compared to the initial state. This strength increase was caused by dispersive Y2O3 particles in the matrix and the martensite transformation of Zircaloy-4 matrix by the LBS.

Instantaneous strain measurements during high-temperature stress cycling of a dispersion-strengthened niobium alloy

International Nuclear Information System (INIS)

Farkas, D.M.; Mishra, R.S.; Mukherjee, A.K.

1995-01-01

Experimental results obtained from stress cycling tests performed during high-temperature creep of a dispersion strengthened niobium alloy indicate that the instantaneous strain following the stress change decreases with accumulated strain. The true work-hardening rate was shown to be a small fraction of the elastic modulus which remained fairly constant throughout the strain history. The instantaneous strain change from a stress addition was typically greater than the strain from the corresponding stress reduction. This effect is quite pronounced for small stress changes and diminishes as the magnitude of the stress change increases. This implies that the mobility of dislocations is impeded in the reverse direction unless the magnitude of stress reduction exceeds the value of the internal stress

Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

International Nuclear Information System (INIS)

Castro, V. de; Marquis, E.A.; Lozano-Perez, S.; Pareja, R.; Jenkins, M.L.

2011-01-01

Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y 2 O 3 alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

Energy Technology Data Exchange (ETDEWEB)

Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Marquis, E.A.; Lozano-Perez, S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes, Madrid (Spain); Jenkins, M.L. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom)

2011-06-15

Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y{sub 2}O{sub 3} alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

Effect of Hydraulic Pressure on Warm Hydro Mechanical Deep Drawing of Magnesium Alloy Sheet

Science.gov (United States)

Liu, Wei; Wu, Linzhi; Yuan, Shijian

The uniaxial tensile test and hydraulic bulging test of AZ31 magnesium alloy sheets were applied to study the influence of temperature on the material properties and obtain the forming limit curves at different temperatures. Numerical simulations of warm hydro mechanical deep drawing were carried out to investigate the effect of hydraulic pressure on the formability of a cylindrical cup, and the simplified hydraulic pressure profiles were used to simulate the loading procedure of hydraulic pressure. The optimal hydraulic pressure at different temperatures were given and verified by experimental studies at temperature 100°C and 170V.

An Improvement of the Anisotropy and Formability Predictions of Aluminum Alloy Sheets

Science.gov (United States)

Banabic, D.; Comsa, D. S.; Jurco, P.; Wagner, S.; Vos, M.

2004-06-01

The paper presents an yield criterion for orthotropic sheet metals and its implementation in a theoretical model in order to calculate the Forming Limit Curves. The proposed yield criterion has been validated for two aluminum alloys: AA3103-0 and AA5182-0, respectively. The biaxial tensile test of cross specimens has been used for the determination of the experimental yield locus. The new yield criterion has been implemented in the Marciniak-Kuczynski model for the calculus of limit strains. The calculated Forming Limit Curves have been compared with the experimental ones, determined by frictionless test: bulge test, plane strain test and uniaxial tensile test. The predicted Forming Limit Curves using the new yield criterion are in good agreement with the experimental ones.

Strengthening of defected beam–column joints using CFRP

Directory of Open Access Journals (Sweden)

Mohamed H. Mahmoud

2014-01-01

Full Text Available This paper presents an experimental study for the structural performance of reinforced concrete (RC exterior beam–column joints rehabilitated using carbon-fiber-reinforced polymer (CFRP. The present experimental program consists of testing 10 half-scale specimens divided into three groups covering three possible defects in addition to an adequately detailed control specimen. The considered defects include the absence of the transverse reinforcement within the joint core, insufficient bond length for the beam main reinforcement and inadequate spliced implanted column on the joint. Three different strengthening schemes were used to rehabilitate the defected beam–column joints including externally bonded CFRP strips and sheets in addition to near surface mounted (NSM CFRP strips. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and the developed ultimate strain in the reinforcing steel and CFRP were considered and compared for each group for the control and the CFRP-strengthened specimens. The test results showed that the proposed CFRP strengthening configurations represented the best choice for strengthening the first two defects from the viewpoint of the studied failure criteria. On the other hand, the results of the third group showed that strengthening the joint using NSM strip technique enabled the specimen to outperform the structural performance of the control specimen while strengthening the joints using externally bonded CFRP strips and sheets failed to restore the strengthened joints capacity.

Strengthening of defected beam-column joints using CFRP.

Science.gov (United States)

Mahmoud, Mohamed H; Afefy, Hamdy M; Kassem, Nesreen M; Fawzy, Tarek M

2014-01-01

This paper presents an experimental study for the structural performance of reinforced concrete (RC) exterior beam-column joints rehabilitated using carbon-fiber-reinforced polymer (CFRP). The present experimental program consists of testing 10 half-scale specimens divided into three groups covering three possible defects in addition to an adequately detailed control specimen. The considered defects include the absence of the transverse reinforcement within the joint core, insufficient bond length for the beam main reinforcement and inadequate spliced implanted column on the joint. Three different strengthening schemes were used to rehabilitate the defected beam-column joints including externally bonded CFRP strips and sheets in addition to near surface mounted (NSM) CFRP strips. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and the developed ultimate strain in the reinforcing steel and CFRP were considered and compared for each group for the control and the CFRP-strengthened specimens. The test results showed that the proposed CFRP strengthening configurations represented the best choice for strengthening the first two defects from the viewpoint of the studied failure criteria. On the other hand, the results of the third group showed that strengthening the joint using NSM strip technique enabled the specimen to outperform the structural performance of the control specimen while strengthening the joints using externally bonded CFRP strips and sheets failed to restore the strengthened joints capacity.

Liquid Film Migration in Warm Formed Aluminum Brazing Sheet

Science.gov (United States)

Benoit, M. J.; Whitney, M. A.; Wells, M. A.; Jin, H.; Winkler, S.

2017-10-01

Warm forming has previously proven to be a promising manufacturing route to improve formability of Al brazing sheets used in automotive heat exchanger production; however, the impact of warm forming on subsequent brazing has not previously been studied. In particular, the interaction between liquid clad and solid core alloys during brazing through the process of liquid film migration (LFM) requires further understanding. Al brazing sheet comprised of an AA3003 core and AA4045 clad alloy, supplied in O and H24 tempers, was stretched between 0 and 12 pct strain, at room temperature and 523K (250 °C), to simulate warm forming. Brazeability was predicted through thermal and microstructure analysis. The rate of solid-liquid interactions was quantified using thermal analysis, while microstructure analysis was used to investigate the opposing processes of LFM and core alloy recrystallization during brazing. In general, liquid clad was consumed relatively rapidly and LFM occurred in forming conditions where the core alloy did not recrystallize during brazing. The results showed that warm forming could potentially impair brazeability of O temper sheet by extending the regime over which LFM occurs during brazing. No change in microstructure or thermal data was found for H24 sheet when the forming temperature was increased, and thus warm forming was not predicted to adversely affect the brazing performance of H24 sheet.

Thermomechanical treatment of titanium alloys

International Nuclear Information System (INIS)

Khorev, A.K.

1979-01-01

The problems of the theory and practical application of thermomechanical treatment of titanium alloys are presented. On the basis of the systematic investigations developed are the methods of thermomechanical treatment of titanium alloys, established are the optimum procedures and produced are the bases of their industrial application with an account of alloy technological peculiarities and the procedure efficiency. It is found that those strengthening methods are more efficient at which the contribution of dispersion hardening prevails over the strengthening by phase hardening

Fabrication technological development of the oxide dispersion strengthened alloy MA957 for fast reactor applications

Energy Technology Data Exchange (ETDEWEB)

ML Hamilton; DS Gelles; RJ Lobsinger; GD Johnson; WF Brown; MM Paxton; RJ Puigh; CR Eiholzer; C Martinez; MA Blotter

2000-03-27

A significant amount of effort has been devoted to determining the properties and understanding the behavior of the alloy MA957 to define its potential usefulness as a cladding material, in the fast breeder reactor program. The numerous characterization and fabrication studies that were conducted are documented in this report. The alloy is a ferritic stainless steel developed by International Nickel Company specifically for structural reactor applications. It is strengthened by a very fine, uniformly distributed yttria dispersoid. Its fabrication involves a mechanical alloying process and subsequent extrusion, which ultimately results in a highly elongated grain structure. While the presence of the dispersoid produces a material with excellent strength, the body centered cubic structure inherent to the material coupled with the high aspect ratio that results from processing operations produces some difficulties with ductility. The alloy is very sensitive to variations in a number of processing parameters, and if the high strength is once lost during fabrication, it cannot be recovered. The microstructural evolution of the alloy under irradiation falls into two regimes. Below about 550 C, dislocation development, {alpha}{prime} precipitation and void evolution in the matrix are observed, while above about 550 C damage appears to be restricted to cavity formation within oxide particles. The thermal expansion of the alloy is very similar to that of HT9 up to the temperature where HT9 undergoes a phase transition to austenitic. Pulse magnetic welding of end caps onto MA957 tubing can be accomplished in a manner similar to that in which it is performed on HT9, although the welding parameters appear to be very sensitive to variations in the tubing that result from small changes in fabrication conditions. The tensile and stress rupture behavior of the alloy are acceptable in the unirradiated condition, being comparable to HT9 below about 700 C and exceeding those of HT9

Tensile and fracture characteristics of oxide dispersion strengthened Fe–12Cr produced by hot isostatic pressing

Energy Technology Data Exchange (ETDEWEB)

Castro, Vanessa de, E-mail: vanessa.decastro@uc3m.es [Departamento de Física, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid (Spain); Garces-Usan, Jose Maria; Leguey, Teresa; Pareja, Ramiro [Departamento de Física, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid (Spain)

2013-11-15

The mechanical characteristics of a model oxide dispersion strengthened (ODS) alloy with nominal composition Fe–12 wt%Cr–0.4 wt%Y{sub 2}O{sub 3} were investigated by means of microhardness measurements, tensile tests up to fracture in the temperature range of 298–973 K, and fracture surface analyses. A non-ODS Fe–12 wt%Cr alloy was also studied to assess the real capacity of the oxide dispersion for strengthening the alloy. The materials were produced by mechanical alloying followed by hot isostatic pressing consolidation and heat treatment at 1023 K. The strengthening effect of the oxide nanodispersion was effective at all temperatures studied, although the tensile strength converges towards the one obtained for the reference alloy at higher temperatures. Moreover, the ODS alloys failed prematurely at T < 673 K due to the presence of Y-rich inclusions, as seen in the fracture surface of these alloys.

Tensile and fracture characteristics of oxide dispersion strengthened Fe–12Cr produced by hot isostatic pressing

International Nuclear Information System (INIS)

Castro, Vanessa de; Garces-Usan, Jose Maria; Leguey, Teresa; Pareja, Ramiro

2013-01-01

The mechanical characteristics of a model oxide dispersion strengthened (ODS) alloy with nominal composition Fe–12 wt%Cr–0.4 wt%Y 2 O 3 were investigated by means of microhardness measurements, tensile tests up to fracture in the temperature range of 298–973 K, and fracture surface analyses. A non-ODS Fe–12 wt%Cr alloy was also studied to assess the real capacity of the oxide dispersion for strengthening the alloy. The materials were produced by mechanical alloying followed by hot isostatic pressing consolidation and heat treatment at 1023 K. The strengthening effect of the oxide nanodispersion was effective at all temperatures studied, although the tensile strength converges towards the one obtained for the reference alloy at higher temperatures. Moreover, the ODS alloys failed prematurely at T < 673 K due to the presence of Y-rich inclusions, as seen in the fracture surface of these alloys

Processing and microstructure of Nb-1 percent Zr-0.1 percent C alloy sheet

Science.gov (United States)

Uz, Mehmet; Titran, Robert H.

1992-01-01

A systematic study was carried out to evaluate the effects of processing on the microstructure of Nb-1 wt. pct. Zr-0.1 wt. pct. C alloy sheet. The samples were fabricated by cold rolling different sheet bars that were single-, double- or triple-extruded at 1900 K. Heat treatment consisted on one- or two-step annealing of different samples at temperatures ranging from 1350 to 1850 K. The assessment of the effects of processing on microstructure involved characterization of the precipitates including the type, crystal structure, chemistry and distribution within the material as well as an examination of the grain structure. A combination of various analytical and metallographic techniques were used on both the sheet samples and the residue extracted from them. The results show that the relatively coarse orthorhombic Nb2C carbides in the as-rolled samples transformed to rather fine cubic monocarbides of Nb and Zr with varying Zr/Nb ratios upon subsequent heat treatment. The relative amount of the cubic carbides and the Zr/Nb ratio increased with increasing number of extrusions prior to cold rolling. Furthermore, the size and the aspect ratio of the grains appear to be strong functions of the processing history of the material. These and other results obtained will be presented with the emphasis on a possible relationship between processing and microstructure.

Mechanical Properties of Titanium and Aluminum Alloys at Cryogenic Temperatures

Science.gov (United States)

1962-03-01

aluminum alloys. Table I is a tabulation of the chemical composition of the tita - nium alloys. The bar was 5/8 inch in diameter and the sheet 0.060 inch...Ti-6AI-4V Tensile azid yield strength data for both bar and sheet of this tita - nium alloy are shown in Figure A-3. Bar and sheet data show approxi...not recommended for low temperature applications. The remainder of the tita - nium alloys were tested from room temperature to -452 F. In general, Ti

Catalogue of X-Ray Texture Data for Al-Cu-Li Alloy 1460, 2090, 2096 and 2195 Near-Net-Shape Extrusions, Sheet and Plate

Science.gov (United States)

Hales, Stephen J.; Hafley, Robert A.; Alexa, Joel A.

1998-01-01

The effect of crystallographic texture on the mechanical properties of near-net-shape extrusions is of major interest ff these products are to find application in launch vehicle or aircraft structures. The objective of this research was to produce a catalogue containing quantitative texture information for extruded product, sheet and plate. The material characterized was extracted from wide, integrally stiffened panels fabricated from the Al-Cu-Li alloys 1460, 2090, 2096 and 2195. The textural characteristics of sheet and plate products of the same alloys were determined for comparison purposes. The approach involved using X-ray diffraction to generate pole figures in combination with orientation distribution function analysis. The data were compiled as a function of location in the extruded cross-sections and the variation in the major deformation- and recrystallization-related texture components was identified.

A new ultrahigh-strength stainless steel strengthened by various coexisting nanoprecipitates

Energy Technology Data Exchange (ETDEWEB)

Xu, W., E-mail: w.xu@m2i.nl [Materials Innovation Institute M2i, Kluyverweg 1, 2629 HS, Delft (Netherlands)] [Novel Aerospace Materials (NovAM) Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Rivera-Diaz-del-Castillo, P.E.J. [Novel Aerospace Materials (NovAM) Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Yan, W.; Yang, K. [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); San Martin, D. [Materalia Group, Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas (CENIM-CSIC), Av. Gregorio del Amo 8, 28040 Madrid (Spain); Kestens, L.A.I. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, 9052 Gent (Belgium); Zwaag, S. van der [Novel Aerospace Materials (NovAM) Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands)

2010-06-15

A general computational alloy design approach based on thermodynamic and physical metallurgical principles and coupled with a genetic optimization scheme is presented. The model is applied to develop a new ultrahigh-strength maraging stainless steel. The alloy composition and heat treatment parameters are integrally optimized so as to achieve microstructures of fully lath martensite matrix strengthened by multiple precipitates of MC carbides, Cu particles and Ni{sub 3}Ti intermetallics. The combined mechanical properties, corrosion resistance and identification of actual strengthening precipitates in the experimental prototype produced on the basic of the model predictions provide a strong justification for the alloy design approach.

A new ultrahigh-strength stainless steel strengthened by various coexisting nanoprecipitates

International Nuclear Information System (INIS)

Xu, W.; Rivera-Diaz-del-Castillo, P.E.J.; Yan, W.; Yang, K.; San Martin, D.; Kestens, L.A.I.; Zwaag, S. van der

2010-01-01

A general computational alloy design approach based on thermodynamic and physical metallurgical principles and coupled with a genetic optimization scheme is presented. The model is applied to develop a new ultrahigh-strength maraging stainless steel. The alloy composition and heat treatment parameters are integrally optimized so as to achieve microstructures of fully lath martensite matrix strengthened by multiple precipitates of MC carbides, Cu particles and Ni 3 Ti intermetallics. The combined mechanical properties, corrosion resistance and identification of actual strengthening precipitates in the experimental prototype produced on the basic of the model predictions provide a strong justification for the alloy design approach.

Microstructural comparison of effects of hafnium and titanium additions in spark-plasma-sintered Fe-based oxide-dispersion strengthened alloys

Energy Technology Data Exchange (ETDEWEB)

Huang, Yina, E-mail: huangyina1981@hotmail.com [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); School of Electronic Science & Applied Physics, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang, Hongtao [Department of Materials, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Auger, Maria A.; Hong, Zuliang [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Ning, Huanpo [School of Engineering of Materials Science, Queen Mary University of London, London, E1 4NS (United Kingdom); Nanoforce Technology Ltd, London, E1 4NS (United Kingdom); Gorley, Michael J. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom); Grant, Patrick S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Reece, Michael J.; Yan, Haixue [School of Engineering of Materials Science, Queen Mary University of London, London, E1 4NS (United Kingdom); Nanoforce Technology Ltd, London, E1 4NS (United Kingdom); Roberts, Steve G. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom)

2017-04-15

Two oxide dispersion strengthened alloys: 14Cr-0.25Y{sub 2}O{sub 3}-0.22Hf (wt.%) and Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.4Ti (wt.%) were fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). Electron backscatter diffraction showed grain sizes in the range 0.5–15 μm in both alloys. Transmission electron microscopy and scanning transmission electron microscopy showed a homogeneous distribution of nano-oxides precipitated during SPS. Using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography, several different oxide phases were found in both alloys, but the majority of dispersoids were Y-Hf-O type in Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.22Hf and Y-Ti-O type in Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.4Ti. There were a variety of orientation relationships between the different dispersoids and the ferritic matrix. Both alloys had dispersoid densities of ∼10{sup 23}/m{sup 3}, with average diameters of 4.3 nm and 3.5 nm in the 0.22Hf and 0.4Ti containing alloys, respectively. Per atom added, Hf (0.07 at.%) is suggested to be more potent than Ti (0.46 at.%) in refining the nano-oxides.

Ab initio identified design principles of solid-solution strengthening in Al

International Nuclear Information System (INIS)

Ma Duancheng; Friák, Martin; Pezold, Johann von; Raabe, Dierk; Neugebauer, Jörg

2013-01-01

Solid-solution strengthening in six Al–X binary systems is investigated using first-principle methods. The volumetric mismatch parameter and the solubility enthalpy per solute were calculated. We derive three rules for designing solid-solution strengthened alloys: (i) the solubility enthalpy per solute is related to the volumetric mismatch by a power law; (ii) for each annealing temperature, there exists an optimal solute–volume mismatch to achieve maximum strength; and (iii) the strengthening potential of high volumetric mismatch solutes is severely limited by their low solubility. Our results thus show that the thermodynamic properties of the system (here Al–X alloys) set clear upper bounds to the achievable strengthening effects owing to the reduced solubility with increasing volume mismatch. (paper)

New deformation model of grain boundary strengthening in polycrystalline metals

International Nuclear Information System (INIS)

Trefilov, V.I.; Moiseev, V.F.; Pechkovskij, Eh.P.

1988-01-01

A new model explaining grain boundary strengthening in polycrystalline metals and alloys by strain hardening due to localization of plastic deformation in narrow bands near grain boundaries is suggested. Occurrence of localized deformation is caused by different flow stresses in grains of different orientation. A new model takes into account the active role of stress concentrator, independence of the strengthening coefficient on deformation, influence of segregations. Successful use of the model suggested for explanation of rhenium effect in molybdenum and tungsten is alloys pointed out

The influence of surface topography on the forming friction of automotive aluminum sheet

Energy Technology Data Exchange (ETDEWEB)

Kramer, Pamela Ann [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

1998-05-01

Interest in utilizing aluminum alloys in automobiles has increased in recent years as a result of the desire to lower automobile weight and, consequently, increase fuel economy. While aluminum alloy use in cast parts has increased, outer body panel applications are still being investigated. The industry is interested in improving the formability of these sheet alloys by a combination of alloy design and processing. A different avenue of improving the formability of these alloys may be through patterning of the sheet surface. Surface patterns hold the lubricant during the forming process, with a resulting decrease in the sheet-die surface contact. While it has been speculated that an optimum surface pattern would consist of discrete cavities, detailed investigation into the reduction of forming friction by utilizing discrete patterns is lacking. A series of discrete patterns were investigated to determine the dependence of the forming friction of automotive aluminum alloys on pattern lubricant carrying capacity and on material strength. Automotive aluminum alloys used in outer body panel applications were rolled on experimental rolls that had been prepared with a variety of discrete patterns. All patterns for each alloy were characterized before and after testing both optically and, to determine pattern lubricant capacity, using three dimensional laser profilometry. A draw bead simulation (DBS) friction tester was designed and fabricated to determine the forming friction of the patterned sheets. Tensile testing and frictionless DBS testing were performed to ascertain the material properties of each sheet. The most striking result of this work was the inversely linear dependence of forming friction on the lubricant carrying capacity of the discrete patterns.

Nanocavity formation and hardness increase by dual ion beam irradiation of oxide dispersion strengthened FeCrAl alloy

Energy Technology Data Exchange (ETDEWEB)

Koegler, R., E-mail: r.koegler@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstrasse 400, 01328 Dresden (Germany); Anwand, W. [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstrasse 400, 01328 Dresden (Germany); Richter, A. [Department of Engineering, Technical University of Applied Sciences Wildau, Bahnhofstrasse 1, 15745 Wildau (Germany); Butterling, M.; Ou, Xin; Wagner, A. [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstrasse 400, 01328 Dresden (Germany); Chen, C.-L. [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China)

2012-08-15

Open volume defects generated by ion implantation into oxide dispersion strengthened (ODS) alloy and the related hardness were investigated by positron annihilation spectroscopy and nanoindentation measurements, respectively. Synchronized dual beam implantation of Fe and He ions was performed at room temperature and at moderately enhanced temperature of 300 Degree-Sign C. For room temperature implantation a significant hardness increase after irradiation is observed which is more distinctive in heat treated than in as-received ODS alloy. There is also a difference between the simultaneous and sequential implantation mode as the hardening effect for the simultaneously implanted ODS alloy is stronger than for sequential implantation. The comparison of hardness profiles and of the corresponding open volume profiles shows a qualitative agreement between the open volume defects generated on the nanoscopic scale and the macroscopic hardness characteristics. Open volume defects are drastically reduced for performing the simultaneous dual beam irradiation at 300 Degree-Sign C which is a more realistic temperature under application aspects. Few remaining defects are clusters of 3-4 vacancies in connection with Y oxide nanoparticles. These defects completely disappear in a shallow layer at the surface. The results are in agreement with hardness measurements showing little hardness increase after irradiation at 300 Degree-Sign C. Suitable characteristics of ODS alloy for nuclear applications and the close correlation between He-related open volume defects and the hardness characteristics are verified.

Microstructure and Mechanical Properties of Nano-Size Zirconium Carbide Dispersion Strengthened Tungsten Alloys Fabricated by Spark Plasma Sintering Method

International Nuclear Information System (INIS)

Xie Zhuoming; Liu Rui; Fang Qianfeng; Zhang Tao; Jiang Yan; Wang Xianping; Liu Changsong

2015-01-01

W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature, higher tensile strength at high temperature, and a lower ductile to brittle transition temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C–600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening. (paper)

Microstructure, plastic deformation and strengthening mechanisms of an Al–Mg–Si alloy with a bimodal grain structure

International Nuclear Information System (INIS)

Shakoori Oskooie, M.; Asgharzadeh, H.; Kim, H.S.

2015-01-01

Highlights: • Al6063 with bimodal grain structures was fabricated by a powder metallurgy route. • The bimodal alloys showed a reasonable ductility together with a high strength. • Grain boundary strengthening was reduced at higher fraction of coarse grains. • The enhanced tensile ductility was attributed to crack blunting and delamination. - Abstract: Al6063 alloys with bimodal grain size distributions comprised of ultrafine-grained (UFG) and coarse-grained (CG) regions were produced via mechanical milling followed by hot extrusion. High-energy planetary ball milling for 22.5 h with a rotational speed of 350 rpm was employed for the synthesis of nanocrystalline Al6063 powders. The as-milled Al6063 powders were mixed with 15, 30, and 45 vol.% of the unmilled powders and then the powder mixtures were consolidated via extrusion at 450 °C with an extrusion ratio of 9:1. The microstructure of the bimodal extrudates was investigated using optical microscope, transmission electron microscope (TEM) and field emission scanning electron microscope equipped with an electron backscattered diffraction (EBSD) detector. The deformation behavior was investigated by means of uniaxial tensile tests. The bimodal Al6063 exhibited balanced mechanical properties, including high yield stress and ultimate tensile strength resulting from the UFG regions together with reasonable ductility attained from the CG areas. The fracture surfaces demonstrated a ductile fracture mode, in which the dimple size was correlated with the grain structure. The strengthening mechanisms are discussed based on the dislocation models and the functions of the CGs in the deformation behavior and ductility enhancement of bimodal Al6063 are explored

Processing and properties of Nb-Ti-based alloys

International Nuclear Information System (INIS)

Sikka, V.K.; Viswanathan, S.

1992-01-01

The processing characteristics, tensile properties, and oxidation response of two Nb-Ti-Al-Cr alloys were investigated. One creep test at 650 C and 172 MPa was conducted on the base alloy which contained 40Nb-40Ti-10Al-10Cr. A second alloy was modified with 0.11 at. % carbon and 0.07 at. % yttrium. Alloys were arc melted in a chamber backfilled with argon, drop cast into a water-cooled copper mold, and cold rolled to obtain a 0.8-mm sheet. The sheet was annealed at 1,100 C for 0.5 h. Longitudinal tensile specimens and oxidation specimens were obtained for both the base alloy and the modified alloy. Tensile properties were obtained for the base alloy at room temperature, 400, 600, 700, 800, 900, and 1,000 C, and for the modified alloy at room temperature, 400, 600, 700, and 800 C. Oxidation tests on the base alloy and modified alloy, as measured by weight change, were carried out at 600, 700, 800, and 900 C. Both the base alloy and the modified alloy were extremely ductile and were cold rolled to the final sheet thickness of 0.8 mm without an intermediate anneal. The modified alloy exhibited some edge cracking during cold during cold rolling. Both alloys recrystallized at the end of a 0.5-h annealing treatment. The alloys exhibited moderate strength and oxidation resistance below 600 C, similar to the results of alloys reported in the literature

Joining of Aluminium Alloy Sheets by Rectangular Mechanical Clinching

International Nuclear Information System (INIS)

Abe, Y.; Mori, K.; Kato, T.

2011-01-01

A mechanical clinching has the advantage of low running costs. However, the joint strength is not high. To improve the maximum load of the joined sheets by a mechanical clinching, square and rectangular mechanical clinching were introduced. In the mechanical clinching, the two sheets are mechanically joined by forming an interlock between the lower and upper sheets by the punch and die. The joined length with the interlock was increased by the rectangular punch and die. The deforming behaviours of the sheets in the mechanical clinching were investigated, and then the interlock in the sheets had distribution in the circumference of the projection. Although the interlocks were formed in both projection side and diagonal, the interlock in the diagonal was smaller because of the long contact length between the lower sheet and the die cavity surface. The maximum load of the joined sheets by the rectangular mechanical clinching was two times larger than the load by the round mechanical clinching.

Modeling and optimization of kerf taper and surface roughness in laser cutting of titanium alloy sheet

Energy Technology Data Exchange (ETDEWEB)

Pandey, Arun Kumar; Dubey, Avanish Kumar [Motilal Nehru National Institute of Technology Allahabad, Uttar Pradesh (India)

2013-07-15

Laser cutting of titanium and its alloys is difficult due to it's poor thermal conductivity and chemical reactivity at elevated temperatures. But demand of these materials in different advanced industries such as aircraft, automobile and space research, require accurate geometry with high surface quality. The present research investigates the laser cutting process behavior of titanium alloy sheet (Ti-6Al-4V) with the aim to improve geometrical accuracy and surface quality by minimizing the kerf taper and surface roughness. The data obtained from L{sub 27} orthogonal array experiments have been used for developing neural network (NN) based models of kerf taper and surface roughness. A hybrid approach of neural network and genetic algorithm has been proposed and applied for the optimization of different quality characteristics. The optimization results show considerable improvements in both the quality characteristics. The results predicted by NN models are well in agreement with the experimental data.

Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Rieken, Joel [Iowa State Univ., Ames, IA (United States)

2011-12-13

Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O₂) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

STUDY THE EFFECTS OF PRESTRAINS IN UNIAXIAL TENSION ON THE FORMING LIMIT DIAGRAM OF ALUMINUM ALLOY SHEETS(2024 T3

Directory of Open Access Journals (Sweden)

Waleed J. Ali

2015-02-01

Full Text Available           The strain path for sheet metal may be changed during forming , this may be affect the forming limit curve (FLC . In this work the FLC before and after prestraining was determined for aluminum alloy (2024 T3 to study the effect of this type of prestraining and in different values on the FLC. This alloy was chosen because it is used widely , specially in aircraft structures .It was shown that the using of uniaxial tension prestrain affects the FLC . The major strain in right side is increased with the increasing in the prestrain , while in the left side the effect is small .

The role of TiB2 in strengthening TiB2 reinforced aluminium casting composites

International Nuclear Information System (INIS)

Chen, Z; Kang, H; Zhao, Y; Zheng, Y; Wang, T

2016-01-01

With an aim of developing high quality in situ TiB 2 reinforced aluminium foundry alloy based composites, the conventional direct synthesis method was modified into a two-step route. In step one we optimized the halide salt route to fabricate in situ TiB 2 particulate reinforced aluminium matrix composites and in step two we investigated the effects of the Al-5wt.% TiB 2 composite, as a “master composite”, on strengthening the practical foundry alloys. The in situ formed TiB 2 particles play two roles while strengthening the composites: (1) The grain refinement effect that improves the quality of the alloy matrix; and (2) The interactions between the hard particulates and the matrix add extra increment to the material strength. In different alloy systems, TiB 2 may play distinct roles in these two aspects (figure 1). Further analysis of the strengthening mechanisms shows that particle agglomeration behaviour during solidification is responsible for the latter one. The present work details the role of TiB 2 in strengthening TiB 2 reinforced aluminium casting composites. (paper)

Nano-scale clusters formed in the early stage of phase decomposition of Al-Mg-Si alloys

Energy Technology Data Exchange (ETDEWEB)

Hirosawa, S.; Sato, T. [Dept. of Metallurgy and Ceramics Science, Tokyo Inst. of Tech. (Japan)

2005-07-01

The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the strengthening {beta}'' phase significantly influences two-step aging behavior of Al-Mg-Si alloys. In this work, the existence of two kinds of nanoclusters has been verified in the early stage of phase decomposition by differential scanning calorimetry (DSC) and three-dimensional atom probe (3DAP). Pre-aging treatment at 373 K before natural aging was also found to form preferentially one of the two nanoclusters, resulting in the remarkable restoration of age-hardenability at paint-bake temperatures. Such microstructural control by means of optimized heat-treatments; i.e. nanocluster assist processing (NCAP), possesses great potential for enabling Al-Mg-Si alloys to be used more widely as a body-sheet material of automobiles. (orig.)

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...

Pseudo-creep in Shape Memory Alloy Wires and Sheets

Science.gov (United States)

Russalian, V. R.; Bhattacharyya, A.

2017-10-01

Interruption of loading during reorientation and isothermal pseudoelasticity in shape memory alloys with a strain arrest ( i.e., holding strain constant) results in a time-dependent evolution in stress or with a stress arrest ( i.e., holding stress constant) results in a time-dependent evolution in strain. This phenomenon, which we term as pseudo-creep, is similar to what was reported in the literature three decades ago for some traditional metallic materials undergoing plastic deformation. In a previous communication, we reported strain arrest of isothermal pseudoelastic loading, isothermal pseudoelastic unloading, and reorientation in NiTi wires as well as a rate-independent phase diagram. In this paper, we provide experimental results of the pseudo-creep phenomenon during stress arrest of isothermal pseudoelasticity and reorientation in NiTi wires as well as strain arrest of isothermal pseudoelasticity and reorientation in NiTi sheets. Stress arrest in NiTi wires accompanied by strain accumulation or recovery is studied using the technique of multi-video extensometry. The experimental results were used to estimate the amount of mechanical energy needed to evolve the wire from one microstructural state to another during isothermal pseudoelastic deformation and the difference in energies between the initial and the final rest state between which the aforementioned evolution has occurred.

Vacuum hot-pressed beryllium and TiC dispersion strengthened tungsten alloy developments for ITER and future fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiang, E-mail: xliu@swip.ac.cn [Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, Sichuan (China); Chen, Jiming; Lian, Youyun; Wu, Jihong; Xu, Zengyu; Zhang, Nianman; Wang, Quanming; Duan, Xuro [Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, Sichuan (China); Wang, Zhanhong; Zhong, Jinming [Northwest Rare Metal Material Research Institute, CNMC, Ningxia Orient Group Co. Ltd.,No.119 Yejin Road, Shizuishan City, Ningxia,753000 (China)

2013-11-15

Beryllium and tungsten have been selected as the plasma facing materials of the ITER first wall (FW) and divertor chamber, respectively. China, as a participant in ITER, will share the manufacturing tasks of ITER first-wall mockups with the European Union and Russia. Therefore ITER-grade beryllium has been developed in China and a kind of vacuum hot-pressed (VHP) beryllium, CN-G01, was characterized for both physical, and thermo-mechanical properties and high heat flux performance, which indicated an equivalent performance to U.S. grade S-65C beryllium, a reference grade beryllium of ITER. Consequently CN-G01 beryllium has been accepted as the armor material of ITER-FW blankets. In addition, a modification of tungsten by TiC dispersion strengthening was investigated and a W–TiC alloy with TiC content of 0.1 wt.% has been developed. Both surface hardness and recrystallization measurements indicate its re-crystallization temperature approximately at 1773 K. Deuterium retention and thermal desorption behaviors of pure tungsten and the TiC alloy were also measured by deuterium ion irradiation of 1.7 keV energy to the fluence of 0.5–5 × 10{sup 18} D/cm{sup 2}; a main desorption peak at around 573 K was found and no significant difference was observed between pure tungsten and the tungsten alloy. Further characterization of the tungsten alloy is in progress.

The physical metallurgy of mechanically-alloyed, dispersion-strengthened Al-Li-Mg and Al-Li-Cu alloys

Science.gov (United States)

Gilman, P. S.

1984-01-01

Powder processing of Al-Li-Mg and Al-Li-Cu alloys by mechanical alloying (MA) is described, with a discussion of physical and mechanical properties of early experimental alloys of these compositions. The experimental samples were mechanically alloyed in a Szegvari attritor, extruded at 343 and 427 C, and some were solution-treated at 520 and 566 C and naturally, as well as artificially, aged at 170, 190, and 210 C for times of up to 1000 hours. All alloys exhibited maximum hardness after being aged at 170 C; lower hardness corresponds to the solution treatment at 566 C than to that at 520 C. A comparison with ingot metallurgy alloys of the same composition shows the MA material to be stronger and more ductile. It is also noted that properly aged MA alloys can develop a better combination of yield strength and notched toughness at lower alloying levels.

Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet

Science.gov (United States)

Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo

A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests

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

Effects of aging and sheet thickness on the room temperature deformation behavior and in-plane anisotropy of cold rolled and solution treated Nimonic C-263 alloy sheet

Energy Technology Data Exchange (ETDEWEB)

Ankamma, Kandula; Chandra Mohan Reddy, Gangireddy [Mahatma Ghandi Institute of Technology, Hyderabad (India). Mechanical Engineering Dept.; Singh, Ashok Kumar; Prasad, Konduri Satya [Defence Research and Development Organisation (DRDO), Hyderabad (India). Defence Metallurgical Research Lab.; Komaraiah, Methuku [Malla Reddy College of Engineering and Technology, Secunderabad (India); Eswara Prasad, Namburi [Regional Centre for Military Airworthiness (Materials), Hyderabad (India)

2011-10-15

The deformation behavior under uni-axial tensile loading is investigated and reported in the case of cold rolled Nimonic C-263 alloy sheet products of different thicknesses (0.5 mm and 1 mm) in the solution treated and aged conditions. The studies conducted include (i) Microstructure, (ii) X-ray diffraction, (iii) Texture and (iv) Tensile properties and inplane anisotropy in the yield behavior (both tensile yield strength and ultimate tensile strength as well as ductility). The results of the present study showed that despite the presence of weak crystallographic texture in this crystal symmetric material, the degrees of in-plane anisotropy in strength as well as plastic deformation properties are found to be significant in both solution treated and aged conditions, thus having significant technological relevance for both further processing and design purposes. Further, the influence of aging and sheet thickness on the tensile deformation behaviour is also found to be considerable. A brief discussion on the technological implications of these results is also included. (orig.)

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

Intermetallic Strengthened Alumina-Forming Austenitic Steels for Energy Applications

Energy Technology Data Exchange (ETDEWEB)

Hu, Bin [Dartmouth College, Hanover, NH (United States); Baker, Ian [Dartmouth College, Hanover, NH (United States)

2016-03-31

In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, the materials required must be strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and L1₂ precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe₂Nb + L1₂-Ni₃Al precipitates) without harmful effects on oxidation resistance. Microstructural and microchemical analyses of the recently developed alumina-forming austenitic (AFA) steels (Fe-14Cr-32Ni-3Nb-3Al-2Ti-based) indicated they are strengthened by Ni₃Al(Ti) L1₂, NiAl B₂, Fe₂Nb Laves phase and MC carbide precipitates. Different thermomechanical treatments (TMTs) were performed on these stainless steels in an attempt to further improve their mechanical properties. The thermo-mechanical processing produced nanocrystalline grains in AFA alloys and dramatically increased their yield strength at room temperature. Unfortunately, the TMTs didn’t increase the yield strengths of AFA alloys at ≥700ºC. At these temperatures, dislocation climb is the dominant mechanism for deformation of TMT alloys according to strain rate jump tests. After the characterization of aged AFA alloys, we found that the largest strengthening effect from L1₂ precipitates can be obtained by aging for less than 24 h. The coarsening behavior of the L1₂ precipitates was not influenced by carbon and boron additions. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these AFA steels after creep tests. Though the Laves and B2-NiAl phase precipitated along the boundaries can improve the creep properties, cracks were

Large scale model experimental analysis of concrete containment of nuclear power plant strengthened with externally wrapped carbon fiber sheets

International Nuclear Information System (INIS)

Yang Tao; Chen Xiaobing; Yue Qingrui

2005-01-01

Concrete containment of Nuclear Power Station is the last shield structure in case of nuclear leakage during an accident. The experiment model in this paper is a 1/10 large-scale model of a real-sized prestressed reinforced concrete containment. The model containment was loaded by hydraulic pressure which simulated the design pressure during the accident. Hundreds of sensors and advanced data-collect systems were used in the test. The containment was first loaded to the damage pressure then strengthened with externally wrapping Carbon fiber sheet around the outer surface of containment structure. Experimental results indicate that CFRP system can greatly increase the capacity of concrete containment to endure the inner pressure. CFRP system can also effectively confine the deformation and the cracks caused by loading. (authors)

A new 12% chromium steel strengthened by Z-phase precipitates

DEFF Research Database (Denmark)

Liu, Fang; Rashidi, Masoud; Johansson, Lennart

2016-01-01

In order to increase the corrosion resistance and simultaneously maintain the creep resistance of 9-12% Cr steels at 650 degrees C, a new alloy design concept was proposed, using thermodynamically stable Z-phase (CrTaN) precipitates to strengthen the steel. A new trial Z-phase strengthened 12% Cr...

Influence on SME and microstructure in FeMnSiCrNi SMA for strengthening of austenite matrix

International Nuclear Information System (INIS)

Gu, N.; Lin, C.; Song, X.; Peng, H.; Yin, F.

2000-01-01

Influences of solution- and deformation-strengthening on SME and the microstructures of FeMnSiCrNi SMA were researched. SME and the training effect were both obviously improved when 0.3%C added into the alloy. It was observed that some thermo-induced martensites, distributing disorderly in the matrix, formed in the alloy without carbon, while in the alloy with carbon, more stress-induced martensites, distributing orderly in the matrix, were found, thus resulting in the better SME. As far as the treatment methods were concerned, one time deformation-strengthening could be better than training many times. The ε-martensites in the strengthened alloy appeared larger in amount, short plate in shape and distributed with nearly the same orientation, which is closely related to the better SME. (orig.)

Effect of Heating Rate on Grain Structure and Superplasticity of 7B04 Aluminum Alloy Sheets

Directory of Open Access Journals (Sweden)

CHEN Min

2017-03-01

Full Text Available Fine-grained 7B04 aluminum alloy sheets were manufactured through thermo-mechanical treatment. The effects of anneal heating rate on grain structure and superplasticity were investigated using electron back scattering diffraction(EBSD and high temperature tensile test. The results show that at the heating rate of 5.0×10-3K/s, the average grain sizes along the rolling direction(RD and normal direction(ND are 28.2μm and 13.9μm respectively, the nucleation rate is 1/1000. With the increase of heating rate, the average grain size decreases, and the nucleation rate increases. When the heating rate increases to 30.0K/s, the average grain sizes along the RD and ND decrease respectively to 9.9μm and 5.1μm, and the nucleation rate increases to 1/80. Besides, with the increase of heating rate, the elongation of sheets also increases. The elongation of the specimens increases from 100% to 730% under the deforming condition of 773K/8×10-4s-1.

Strengthening from Nb-rich clusters in a Nb-microalloyed steel

International Nuclear Information System (INIS)

Xie, Kelvin Y.; Zheng, Tianxiao; Cairney, Julie M.; Kaul, Harold; Williams, James G.; Barbaro, Frank J.; Killmore, Chris R.; Ringer, Simon P.

2012-01-01

We demonstrate that a Nb-microalloyed ultra-thin cast strip steel can be strengthened substantially without compromising ductility by performing a simple heat treatment at 700 °C for 4 min. The strengthening was attributed to a fine dispersion of Nb-rich solute atom clusters. These clusters had an average size of ∼60 atoms at peak hardness and resembled Guinier–Preston zones in Al–Cu alloys. The application of the Ashby–Orowan equation indicates that these clusters are potent strengthening agents when compared to conventional Nb(C,N) precipitation strengthening.

Transitions in creep mechanisms and creep anisotropy in Zr-1Nb-1Sn-0.2Fe sheet

International Nuclear Information System (INIS)

Murty, K.L.; Ravi, J.; Wiratmo

1995-01-01

The creep characteristics of a Zr-1Nb-1Sn-0.2Fe alloy sheet were investigated at temperatures from 773 to 923K and at stresses ranging from 9 to 150MPa along both the rolling and transverse directions. Transitions in creep mechansims are noted, with diffusional viscous creep at low stresses, viscous-glide-controlled microcreep in the intermediate stress regime and the climb of edge dislocations at high stresses. The creep anisotropy decreases with a decrease in the stress exponent and the creep rates differ by only 30% in the viscous creep regime, while an order-of-magnitude difference is noted at high stresses. The solute-strengthening effect of Nb addition is evident in the stress regime where appropriate data are available. These transitions in creep mechansims clearly reveal the dangers in blind extrapolation of short-term high stress data to low stresses and long times relevant to in-reactor conditions. The creep behavior of these materials is similar to that noted in Class I alloys, while the transitions in deformation mechanisms in Zircaloy-4 resemble those found in pure metals or Class II alloys with no viscous glide mechanism. ((orig.))

Integrated Computational Materials Engineering Development of Alternative Cu-Be Alloys

Science.gov (United States)

2012-08-01

metastable FCC state @ Room temp.  Alloying to suppress martensitic transformation  Significant work-hardening associated with the phase... transformation  Existing CoCr alloy rely upon cold- or warm- work to achieve high strength (size dependent!) ● No equivalent to L12- strengthened Ni... strengthened Copper and Cobalt alloy VIM/VAR melting Homogen- ization Hot working >4” dia. Solution treatment Machining Tempering Processing

Polycrystalline strengthening

DEFF Research Database (Denmark)

Hansen, Niels

1985-01-01

for the understanding of polycrystalline strengthening is obtained mainly from surface relief patterns and from bulk structures observed by transmission electron microscopy of thin foils. The results obtained by these methods are discussed and correlations are proposed. A number of features characterizing the deformed...... structure are summarized and the behavior of a number of metals and alloys is reviewed with emphasis on the structural changes in the interior of the grains and in the vicinity of the grain boundaries. The models for strain accommodation during deformation are discussed on the basis of the microstructures...

Oxide dispersion strengthened ferritic alloys. 14/20% chromium: effects of processing on deformation texture, recrystallization and tensile properties

International Nuclear Information System (INIS)

Regle, H.

1994-01-01

The ferritic oxide dispersion strengthened alloys are promising candidates for high temperature application materials, in particular for long life core components of advanced nuclear reactors. The aim of this work is to control the microstructure, in order to optimise the mechanical properties. The two ferritic alloys examined here, MA956 and MA957, are obtained by Mechanical Alloying techniques. They are characterised by quite anisotropic microstructure and mechanical properties. We have investigated the influence of hot and cold working processes (hot extrusion, swaging and cold-drawing) and recrystallization heat treatments on deformation textures, microstructures and tensile properties. The aim was to control the size of the grains and their anisotropic shape, using recrystallization heat treatments. After consolidation and hot extrusion, as-received materials present a extremely fine microstructure with elongated grains and a very strong (110) deformation texture with single-crystal character. At that stage of processing, recrystallization temperature are very high (1450 degrees C for MA957 alloy and 1350 degrees C for MA956 alloy) and materials develop millimetric recrystallized grains. Additional hot extrusion induce a fibre texture. Cold-drawing maintains a fibre texture, but the intensity decreases with increasing cold-work level. For both materials, the decrease of texture intensities correspond to a decrease of the recrystallization temperatures (from 1350 degrees C for a low cold-work level to 750 degrees C for 60 % cold-deformation, case of MA956 alloy) and a refinement of the grain size (from a millimetric size to less than an hundred of micrometer). Swaging develop a cyclic component where the intensity increases with increasing deformation in this case, the recrystallization temperature remains always very high and the millimetric grain size is slightly modified, even though cold-work level increases. Technologically, cold-drawing is the only way

Mechanical and corrosion properties of AA8011 sheets and foils:

OpenAIRE

Asanović, Vanja; Dalijić, Kemal; Radonjić, Dragan

2006-01-01

The mechanical and corrosion properties of a twin-roll cast Al-Fe-Si aluminum alloy with 0.74 % Fe and 0.52 % Si (AA8011) were investigated. The influence of the thermo-mehanical processing route on the mechanical behavior of AA8011 sheets was determined. Comparisons were made with AA3003 and A199.5 sheets. The restoration of the mechanical properties was used in the analysis of the recrystallization behavior of the twin-roll cast AA8011 alloy deformed under cold-working conditions and subseq...

Superplastic Forming/Adhesive Bonding of Aluminum (SPF/AB) Multi-Sheet Structures

Science.gov (United States)

Wagner, John A. (Technical Monitor); Will, Jeff D.; Cotton, James D.

2003-01-01

A significant fraction of airframe structure consists of stiffened panels that are costly and difficult to fabricate. This program explored a potentially lower-cost processing route for producing such panels. The alternative process sought to apply concurrent superplastic forming and adhesive bonding of aluminum alloy sheets. Processing conditions were chosen to balance adequate superplasticity of the alloy with thermal stability of the adhesive. As a first objective, an air-quenchable, superplastic aluminum-lithium alloy and a low-volatile content, low-viscosity adhesive with compatible forming/curing cycles were identified. A four-sheet forming pack was assembled which consisted of a welded two-sheet core separated from the face sheets by a layer of adhesive. Despite some preliminary success, of over 30 forming trials none was completely successful. The main problem was inadequate superplasticity in the heat-affected zones of the rib welds, which generally fractured prior to completion of the forming cycle. The welds are a necessary component in producing internal ribs by the 'four-sheet' process. Other challenges, such as surface preparation and adhesive bonding, were adequately solved. But without the larger issue of tearing at the weld locations, complex panel fabrication by SPF/AB does not appear viable.

Strengthening by ordered precipitates in a Ni--Ni4Mo system

International Nuclear Information System (INIS)

Goodrum, J.W.; LeFevre, B.G.

1977-01-01

The strength characteristics and microstructures of aged Ni-Mo alloys containing ordered (Ni 4 Mo) precipitates were studied as a function of aging time and temperature. It was found that 17 at. percent Mo alloy aged at 750 0 C produced a uniform dispersion of cuboidal β precipitates which coarsened with time producing a gradual increase in flow stress. The flow stress increment was found to vary in qualitative agreement with both order strengthening and coherency strain models. Both these models give over-estimates of the strengthening increment. A negative dependence of flow stress on temperature is attributed to coherency strain contributions

Creep characteristics of precipitation hardened carbon free martensitic alloys

International Nuclear Information System (INIS)

Muneki, S.; Igarashi, M.; Abe, F.

2000-01-01

A new attempt has been demonstrated using carbon free Fe-Ni-Co martensitic alloys strengthened by Laves phase such as Fe 2 W or Fe 2 Mo to achieve homogeneous creep deformation at high temperatures under low stress levels. Creep behavior of the alloys is found to be completely different from that of the conventional high-Cr ferritic steels. The alloys exhibit gradual change in the creep rate with strain both in the transient and acceleration creep regions, and give a larger strain for the minimum creep rate. In these alloys the creep deformation takes place very homogeneously and no heterogeneous creep deformation is enhanced even at low stress levels. The minimum creep rates of the Fe-Ni-Co alloys at 700 C are found to be much lower than that of the conventional steel, which is due to fine dispersion strengthening useful even at 700 C in these alloys. It is thus concluded that the Fe-Ni-Co martensite strengthened by Laves phase is very useful to increase the creep resistance at elevated temperatures over 650 C. (orig.)

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.

Effects of nanometric inclusions on the microstructural characteristics and strengthening of a friction-stir processed aluminum–magnesium alloy

Energy Technology Data Exchange (ETDEWEB)

Khodabakhshi, F., E-mail: farzadkhodabakhshi83@gmail.com [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Boulevard, Shiraz (Iran, Islamic Republic of); Simchi, A., E-mail: simchi@sharif.edu [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Kokabi, A.H. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Švec, P. [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava (Slovakia); Simančík, F. [Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Racianska 75, Bratislava (Slovakia); Gerlich, A.P. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON (Canada)

2015-08-26

An aluminum–magnesium alloy was friction-stir processed in the presence of TiO{sub 2} nanoparticles which were pre-placed in a groove on the surface to produce a composite. Field emission-scanning and transmission electron microscopy studies show that solid state chemical reactions occur between the Al–Mg matrix and the ceramic particles upon the severe plastic deformation process. The microstructure of the aluminum alloy consists of a coarse grain structure, large complex (Fe,Mn,Cr){sub 3}SiAl{sub 12} particles, and small Mg{sub 2}Si precipitates. After friction stir processing, a deformed grain structure containing rod-like Al–Fe–Mn–Si precipitates is attained, along with cuboidal (~100 nm) Cr{sub 2} precipitates and spherical (~100 and 5 nm) Mg{sub 2}Si particles. In the presence of TiO{sub 2} nanoparticles, magnesium oxide (MgO) and titanium aluminide (Al{sub 3}Ti) nanophases are formed. It is shown that these microstructural modifications lead to a significant enhancement in the hardness and tensile strength of the aluminum alloy. The relationship between the microstructural evolution and mechanical properties and the role of hard inclusions are presented and discussed. An analysis based on strengthening models indicates that the yield strength of the nanocomposite is mainly controlled by dislocations and grain boundaries rather than the nano-scale inclusions.

Thermomechanical processing of plasma sprayed intermetallic sheets

Science.gov (United States)

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Alloy development for cladding and duct applications

International Nuclear Information System (INIS)

Straalsund, J.L.; Johnson, G.D.

1981-01-01

Three general classes of materials under development for cladding and ducts are listed. Solid solution strengthened, or austenitic, alloys are Type 316 stainless steel and D9. Precipitation hardened (also austenitic) alloys consist of D21, D66 and D68. These alloys are similar to such commercial alloys as M-813, Inconel 706, Inconel 718 and Nimonic PE-16. The third general class of alloys is composed of ferritic alloys, with current emphasis being placed on HT-9, a tempered martensitic alloy, and D67, a delta-ferritic steel. The program is comprised of three parallel paths. The current reference, or first generation alloy, is 20% cold worked Type 316 stainless steel. Second generation alloys for near-term applications include D9 and HT-9. Third generation materials consist of the precipitation strengthened steels and ferritic alloys, and are being considered for implementation at a later time than the first and second generation alloys. The development of second and third generation materials was initiated in 1974 with the selection of 35 alloys. This program has proceeded to today where there are six advanced alloys being evaluated. These alloys are the developmental alloys D9, D21, D57, D66 and D68, together with the commerical alloy, HT-9. The status of development of these alloys is summarized

Geometry task & drill sheets : grades 6-8

CERN Document Server

Rosenberg, Mary

2011-01-01

For grades 6-8, our Common Core State Standards-based combined resource meets the geometry concepts addressed by the NCTM standards and encourages the students to review the concepts in unique ways. The task sheets introduce the mathematical concepts to the students around a central problem taken from real-life experiences, while the drill sheets provide warm-up and timed practice questions for the students to strengthen their procedural proficiency skills.

The Properties of 7xxx Series Alloys Formed by Alloying Additions

Directory of Open Access Journals (Sweden)

Kwak Z.

2015-06-01

Full Text Available Currently there is a constant development in the field of aluminium alloys engineering. This results from, i.a., better understanding of the mechanisms that direct strengthening of these alloys and the role of microalloying. Now it is microalloying in aluminum alloys that is receiving a lot of attention. It affects substantially the macro- and microstructure and kinetics of phase transformation influencing the properties during production and its exploitation. 7xxx series aluminum alloys, based on the Al-Zn-Mg-Cu system, are high-strength alloys, moreover, the presence of Zr and Sr further increases their strength and improves resistance to cracking.

TEM in situ micropillar compression tests of ion irradiated oxide dispersion strengthened alloy

Energy Technology Data Exchange (ETDEWEB)

Yano, K.H., E-mail: kaylayano@u.boisestate.edu [Boise State University, 1910 University Drive, Boise, ID, 83725 (United States); Swenson, M.J. [Boise State University, 1910 University Drive, Boise, ID, 83725 (United States); Wu, Y. [Boise State University, 1910 University Drive, Boise, ID, 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID, 83401 (United States); Wharry, J.P. [Boise State University, 1910 University Drive, Boise, ID, 83725 (United States); Purdue University, 400 Central Drive, West Lafayette, IN 47907 (United States)

2017-01-15

The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near-surface irradiation damage layers just a few micrometers thick. In situ transmission electron microscopic (TEM) mechanical testing is one such promising method. In this work, microcompression pillars are fabricated from a Fe{sup 2+} ion irradiated bulk specimen of a model Fe-9%Cr oxide dispersion strengthened (ODS) alloy. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated microstructure. Measured elastic modulus values, once adjusted for the amount of deformation and deflection in the base material, are also within the expected range. A pillar size effect is only observed in samples with minimum dimension ≤100 nm due to the low inter-obstacle spacing in the as received and irradiated material. TEM in situ micropillar compression tests hold great promise for quantitatively determining mechanical properties of shallow ion-irradiated layers.

Microstructure evolution of a dissimilar junction interface between an Al sheet and a Ni-coated Cu sheet joined by magnetic pulse welding

Energy Technology Data Exchange (ETDEWEB)

Itoi, Takaomi, E-mail: itoi@faculty.chiba-u.jp [Department of Mechanical Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Mohamad, Azizan Bin; Suzuki, Ryo [Department of Mechanical Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Okagawa, Keigo [Department of Electrical and Electronics Engineering, Tokyo Metropolitan College of Industrial Technology, 1-10-40 Higashi ohi, Shinagawa-ku, Tokyo 140-0011 (Japan)

2016-08-15

An Al sheet and a Ni-coated Cu sheet were lap joined by using magnetic pulse welding (MPW). Tensile tests were performed on the joined sheets, and a good lap joint was achieved at a discharge energy of > 0.9 kJ. The weld interface exhibited a wavy morphology and an intermediate layer along the weld interface. Microstructure observations of the intermediate layer revealed that the Ni coating region consisted of a Ni–Al binary amorphous alloy and that the Al sheet region contained very fine Al nanograins. Ni fragments indicative of unmelted residual Ni from the coating were also observed in parts of the intermediate layer. Formation of these features can be attributed to localize melting and a subsequent high rate cooling of molten Al and Ni confined to the interface during the MPW process. In the absence of an oxide film, atomic-scale bonding was also achieved between the intermediate layer and the sheet surfaces after the collision. MPW utilises impact energy, which affects the sheet surfaces. From the obtained results, good lap joint is attributed to an increased contact area, the anchor effect, work hardening, the absence of an oxide film, and suppressed formation of intermetallic compounds at the interface. - Highlights: •Good lap joint of an Al sheet and a Ni-coated Cu sheet was achieved by using magnetic pulse welding. •A Ni–Al binary amorphous alloy was formed as an intermediate layer at weld interface. •Atomic-scale bonding was achieved between the intermediate layer and the sheet surfaces.

Improvement in ductility of high strength polycrystalline Ni-rich Ni{sub 3}Al alloy produced by EB-PVD

Energy Technology Data Exchange (ETDEWEB)

Sun, J.Y.; Pei, Y.L.; Li, S.S.; Zhang, H.; Gong, S.K., E-mail: gongsk@buaa.edu.cn

2014-11-25

Highlights: • High strength and high ductility of polycrystalline Ni-rich Ni{sub 3}Al alloy sheets were produced. • The elongation could be enhanced from ∼0.5% to ∼14.6% by microstructural control. • The fracture strength (∼820 MPa) was enhanced by the precipitation strengthening. • This work provides a general processing for repairing the worn single crystal blades. - Abstract: A 300 μm Ni-rich Ni{sub 3}Al sheet was produced by electron beam physical vapor deposition (EB-PVD) and followed by different heat treatments to obtain fine γ′/γ two-phase structures with large elongation. Tensile testing was performed at room-temperature, and the corresponding mechanisms were investigated in detail. Results indicated that the as-deposited Ni{sub 3}Al alloy exhibited non-equilibrium directional columnar crystal, and transited to equiaxed crystal with uniformly distributed tough γ phase after heat treatment. Meanwhile, the fracture mechanism transited from brittleness to a mixture of ductility and brittleness modes. With an appropriate heat treatment, high strength (ultimate tensile strength obtained 828 MPa) and high ductility (elongation obtained 14.6%) Ni{sub 3}Al alloy has been achieved, which was due to the mesh network microstructure. A series of transmission electron microscope (TEM) characterizations confirmed that the increasing flow stress of Ni{sub 3}Al alloy was attributed to the cubical secondary γ′ phase precipitates (25–50 nm) within the γ phase. This work provides a potential strategy for repairing the worn tip of single crystal engine blades using Ni-rich Ni{sub 3}Al alloy by EB-PVD.

Powder Metallurgy Processing of a WxTaTiVCr High-Entropy Alloy and Its Derivative Alloys for Fusion Material Applications.

Science.gov (United States)

Waseem, Owais Ahmed; Ryu, Ho Jin

2017-05-16

The W x TaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.

Synergetic effects of Sc and Zr microalloying and heat treatment on mechanical properties and exfoliation corrosion behavior of Al-Mg-Mn alloys

International Nuclear Information System (INIS)

Peng, Yongyi; Li, Shu; Deng, Ying; Zhou, Hua; Xu, Guofu; Yin, Zhimin

2016-01-01

Mechanical properties, exfoliation corrosion behavior and microstructure of Al-5.98Mg-0.47Mn and Al-6.01Mg-0.45Mn-0.25Sc-0.10Zr (wt%) alloy sheets under various homogenizing and annealing processes were investigated comparatively by tensile tests, electrochemical measurements, X-ray diffraction technique and microscopy methods. The as-cast alloys mainly consist of Fe and Mn enriched impurity phases, Mg and Mn enriched non-equilibrium aluminides and Mg 3 Al 2 phases. During homogenization treatment, solvable intermetallics firstly precipitate and then dissolve into matrix. The optimized homogenization processes for removing micro-segregation and obtaining maximum precipitation strengthening of secondary Al 3 (Sc, Zr) particles are 440 °C×8 h and 300 °C×8 h, respectively. Sc and Zr additions can make the yield strength of Al-Mg-Mn alloy increase by 21 MPa (6.9%), 120 MPa (61.2%) and 127 MPa (68.3%), when annealed at 270 °C, 300 °C and 330 °C, respectively, indicating that Orowan precipitation strengthening caused by secondary Al 3 (Sc, Zr) nano-particles is much greater than grain boundary strengthening from primary Al 3 (Sc, Zr) micro-particles. Increasing homogenization and annealing degrees and adding Sc and Zr all can decrease corrosion current density and improve exfoliation corrosion resistance. The exfoliation corrosion behavior is dominant by anodic dissolution occurring at the interface between intermetallics and α(Al) matrix. After homogenizing at 440 °C for 8 h and annealing at 300 °C for 1 h, yield strength, ultimate strength, elongation to failure and exfoliation corrosion rank are 196 MPa, 360 MPa, 20.2% and PA (slight pitting corrosion) in Al-Mg-Mn alloy, and reach to 316 MPa, 440 MPa, 17.0% and PA in Al-Mg-Mn-Sc-Zr alloy, respectively, revealing that high strength, high ductility and admirable corrosion resistance of Al-Mg-Mn alloys can be achieved by the synergetic effects of Sc and Zr microalloying and heat treatment.

Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

Science.gov (United States)

Aravind, N.; Samanta, Amiya K.; Roy, Dilip Kr. Singha; Thanikal, Joseph V.

2015-01-01

Strengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

Microstructure and Strengthening Mechanisms of Carbon Nanotube Reinforced Magnesium Matrix Composites Fabricated by Accumulative Roll Bonding

International Nuclear Information System (INIS)

Yoo, Seong Jin; Kim, Woo Jin

2014-01-01

A combination of accumulative roll bonding (ARB) and high-energy ball milling was used to fabricate carbon nano tube (CNT)-reinforced Mg composites in sheet form. CNT-Al composite powders synthesized using the high-energy ball-milling process, were coated on the surface of Mg sheets using either spraying or dipping methods. The coated sheets were stacked and then subjected to ARB. Formation of CNT-intermetallic compounds through inter-diffusion between Al and Mg, fragmentation of the CNTintermetallic compounds, and their dispersion into the matrix by plastic flow; as well as dissolution of the intermetallic compound particles into the matrix while leaving CNTs in the matrix, occurred in sequence during the ARB process. This eventually resulted in the uniform distribution of nano-sized CNT particles in the Mg matrix. As the thickness of the Mg sheet and of the coating layer of Al-CNT powder on the surface of the Mg sheet were similar, the dispersion of CNTs into the Mg matrix occurred more uniformly and the strengthening effect of adding CNTs was greater. The strengthening gained by adding CNTs was attributed to Orowan strengthening and dislocation-density increase due to a thermal mismatch between the matrix and the CNTs.

Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates

Science.gov (United States)

Yamamoto, Y.; Brady, M. P.; Lu, Z. P.; Liu, C. T.; Takeyama, M.; Maziasz, P. J.; Pint, B. A.

2007-11-01

Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.

Development of precipitation strengthened brass with Ti and Sn alloying elements additives by using water atomized powder via powder metallurgy route

Energy Technology Data Exchange (ETDEWEB)

Li, Shufeng, E-mail: shufengli@hotmail.com [Joining and Welding Research Institute, Osaka University, Osaka (Japan); Imai, Hisashi; Kondoh, Katsuyoshi [Joining and Welding Research Institute, Osaka University, Osaka (Japan); Kojima, Akimichi; Kosaka, Yoshiharu [San-Etsu Metals Co. LTD., 1892 OHTA, Tonami, Toyama (Japan); Yamamoto, Koji; Takahashi, Motoi [Nippon Atomized Metal Powders Corporation, 87-16, Nishi-Sangao, Noda, Chiba (Japan)

2012-08-15

Effect of Ti and Sn alloying elements on microstructure and mechanical properties of 60/40 brass has been studied via the powder metallurgy (P/M) route. The water-atomized BS40-0.6Sn1.0Ti (Cu40wt%Zn-0.6wt%Sn1.0wt%Ti) pre-alloyed powder was consolidated at various temperatures within range of 400-600 Degree-Sign C using spark plasma sintering (SPS) and hot extrusion was carried out at 500 Degree-Sign C. Effects of extrusion temperature on microstructure and tensile strength were investigated by employing SEM-EDS/EBSD, TEM, XRD and tensile test. Results indicated that super-saturated solid solution Ti and Sn elements created high chemical potential for a precipitate reaction in rapidly solidified brass powder, which showed significant strengthening effects on the extruded sample consolidated at lower temperature. Solid solubility of Ti in brass matrix decreased with increasing of sintering temperature, thus resulted in degradation of mechanical properties. Consequently, lower hot processing temperature is necessary to obtain excellent mechanical properties for BS40-0.6Sn1.0Ti during sintering and extrusion. An yield strength of 398 MPa and ultimate tensile strength of 615 MPa were achieved, they respectively showed 31.3% and 22.9% higher values than those of extruded Cu40Zn brass. -- Graphical abstract: The Ti and Sn alloying elements additions showed significant grain refinement on Cu40Zn-0.6Sn1.0Ti brass (b) as comparing with that of the conventional Cu40Zn brass (a), detected by electron backscatter diffraction (EBSD) technique. The grain boundaries maps of (a) BS40 (b) BS40-0.6Sn1.0Ti SPS compact sintered at 400 Degree-Sign C reveals by electron backscatter diffraction (EBSD) technique. Highlights: Black-Right-Pointing-Pointer Alloying elements Ti and Sn are proposed as additives in 60/40 brass. Black-Right-Pointing-Pointer Super-saturated Ti in powder creates high chemical potential for precipitation. Black-Right-Pointing-Pointer CuSn{sub 3}Ti{sub 5

Dispersoid reinforced alloy powder and method of making

Energy Technology Data Exchange (ETDEWEB)

Anderson, Iver E.; Terpstra, Robert L.

2017-12-05

A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

Dispersoid reinforced alloy powder and method of making

Energy Technology Data Exchange (ETDEWEB)

Anderson, Iver E.; Terpstra, Robert L.

2017-10-10

A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

Titanium Alloys Thin Sheet Welding with the Use of Concentrated Solar Energy

Science.gov (United States)

Pantelis, D. I.; Kazasidis, M.; Karakizis, P. N.

2017-12-01

The present study deals with the welding of titanium alloys thin sheets 1.3 mm thick, with the use of concentrated solar energy. The experimental part of the work took place at a medium size solar furnace at the installation of the Centre National de la Recherche Scientifique, at Odeillo, in Southern France, where similar and dissimilar defect-free welds of titanium Grades 4 and 6 were achieved, in the butt joint configuration. After the determination of the appropriate welding conditions, the optimum welded structures were examined and characterized microstructurally, by means of light optical microscopy, scanning electron microscopy, and microhardness testing. In addition, test pieces extracted from the weldments were tested under uniaxial tensile loading aiming to the estimation of the strength and the ductility of the joint. The analysis of the experimental results and the recorded data led to the basic concluding remarks which demonstrate increased hardness distribution inside the fusion area and severe loss of ductility, but adequate yield and tensile strength of the welds.

Creep of titanium--silicon alloys

International Nuclear Information System (INIS)

Paton, N.E.; Mahoney, M.W.

1976-01-01

Operative creep mechanisms in laboratory melts of Ti-5Zr-0.5Si and Ti-5Zr-0.5Si have been investigated as a function of microstructure, creep stress, and temperature. From creep rate data and transmission electron microscopy results, it has been shown that an important creep strengthening mechanism at 811 0 K in Si-bearing Ti alloys is clustering of solute atoms on dislocations. All of the alloys investigated showed anomalously high apparent activation energies and areas for creep and a high exponent (n) in the Dorn equation. In addition, the effect of heat treatment was investigated and it is shown that the highest creep strength was obtained by using a heat treatment which retained the maximum amount of silicon in solution. This is consistent with the proposed creep strengthening mechanism. An investigation of the creep behavior of several other Si containing alloys including two commercial alloys, Ti-11 and IMI-685 indicated similar results. 12 fig., 6 tables

On the Possibility of using Alluminium-Magnesium Alloys with Improved Mechanical Characteristics for Body Elements of Zenit-2S Launch Vehicle Propellant Tanks

Science.gov (United States)

Sitalo, V.; Lytvyshko, T.

2002-01-01

Yuzhnoye SDO developed several generations of launch vehicles and spacecraft that are characterized by weight perfection, optimal cost, accuracy of output geometrical characteristics, stable strength characteristics, high tightness. The main structural material of launch vehicles are thermally welded non-strengthened aluminium- magnesium alloys. The aluminium-magnesium alloys in the annealed state have insufficiently high strength characteristics. Considerable increase of yield strength of sheets and plates can be reached by cold working but in this case, plasticity reduces. An effective way to improve strength of aluminium-magnesium alloys is their alloying with scandium. The alloying with scandium leads to modification of the structure of ingots (size reduction of cast grain) and formation of supersaturated solid solutions of scandium and aluminium during crystallization. During subsequent heatings (annealing of the ingots, heating for deformation) the solid solution disintegrates with the formation of disperse particles of Al3Sc type, that cause great strengthening of the alloy. High degree of dispersion and density of distribution in the matrix of secondary Al3Sc particles contribute to the considerable increase of the temperature of recrystallization of deformed intermediate products and to the formation of stable non-recrystallized structure. The alloying of alluminium-magnesium alloys with scandium increases their strength and operational characteristics, preserves their technological and corrosion properties, improves weldability. The alloys can be used within the temperature limits ­196-/+150 0C. The experimental structures of propellant tanks made of alluminium-magnesium alloys with scandium have been manufactured and tested. It was ascertained that the propellant tanks have higher margin of safety during loading with internal pressure and higher stability factor of the shrouds during loading with axial compression force which is caused by higher value

Collected Engineering Data Sheets (Air Force Data Sheet Program)

Science.gov (United States)

1978-12-01

I12 HP 9-4-25 The HP 9-4-25 alloy is a nickel-cobalt quenched and tempered martensitic steel possessing excellent toughness at yield strength levels up...temperatures ranging from subzero to 1100 F. Below a tempering temperature of 900 F, the primary strengthening mechanism depends on precipitation reactions...properties at elevated temper - atures, and good creep properties and corrosion resistance . Because of the current interest in titanium castings, the material

Microstructural, mechanical and weldability assessments of the dissimilar welds between γ′- and γ″-strengthened nickel-base superalloys

Energy Technology Data Exchange (ETDEWEB)

Naffakh Moosavy, Homam, E-mail: homam_naffakh@iust.ac.ir [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114 (Iran, Islamic Republic of); Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114 (Iran, Islamic Republic of); Mapelli, Carlo [Dipartimento di Meccanica, Politecnico di Milano, Via La Massa 34, Milan 20156 (Italy)

2013-08-15

Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys has been investigated to identify the relationship between the microstructure of the welds and the resultant mechanical and weldability characteristics. γ′-Strengthened nickel-base Alloy 500 and γ″-strengthened nickel-base Alloy 718 were used for dissimilar welding. Gas tungsten arc welding operations were utilized for performing the autogenous dissimilar welding. Alloy 500 and Alloy 718 base metals showed various types of phases, carbides, intermetallics and eutectics in their microstructure. The results for Alloy 500 weld metal showed severe segregation of titanium to the interdendritic regions. The Alloy 718 weld metal compositional analysis confirmed the substantial role of Nb in the formation of low-melting eutectic-type morphologies which can reduce the weldability. The microstructure of dissimilar weld metal with dilution level of 65% wt.% displayed semi-developed dendritic structure. The less segregation and less formation of low-melting eutectic structures caused to less susceptibility of the dissimilar weld metal to the solidification cracking. This result was confirmed by analytic modeling achievements. Dissolution of γ″-Ni{sub 3}Nb precipitations took place in the Alloy 718 heat-affected zone leading to sharp decline of the microhardness in this region. Remelted and resolidified regions were observed in the partially-melted zone of Alloy 500 and Alloy 718. Nevertheless, no solidification and liquation cracking happened in the dissimilar welds. Finally, this was concluded that dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys can successfully be performed. - Highlights: • Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys is studied. • Microstructural, mechanical and weldability aspects of the welds are assessed. • Microstructure of welds, bases and heat-affected zones is characterized in detail. • The type

Depositing laser-generated nanoparticles on powders for additive manufacturing of oxide dispersed strengthened alloy parts via laser metal deposition

Science.gov (United States)

Streubel, René; Wilms, Markus B.; Doñate-Buendía, Carlos; Weisheit, Andreas; Barcikowski, Stephan; Henrich Schleifenbaum, Johannes; Gökce, Bilal

2018-04-01

We present a novel route for the adsorption of pulsed laser-dispersed nanoparticles onto metal powders in aqueous solution without using any binders or surfactants. By electrostatic interaction, we deposit Y2O3 nanoparticles onto iron-chromium based powders and obtain a high dispersion of nano-sized particles on the metallic powders. Within the additively manufactured component, we show that the particle spacing of the oxide inclusion can be adjusted by the initial mass fraction of the adsorbed Y2O3 particles on the micropowder. Thus, our procedure constitutes a robust route for additive manufacturing of oxide dispersion-strengthened alloys via oxide nanoparticles supported on steel micropowders.

Lubricant Test Methods for Sheet Metal Forming

DEFF Research Database (Denmark)

Bay, Niels; Olsson, David Dam; Andreasen, Jan Lasson

2008-01-01

appearing in different sheet forming operations such as stretch forming, deep drawing, ironing and punching. The laboratory tests have been especially designed to model the conditions in industrial production. Application of the tests for evaluating new lubricants before introducing them in production has......Sheet metal forming of tribologically difficult materials such as stainless steel, Al-alloys and Ti-alloys or forming in tribologically difficult operations like ironing, punching or deep drawing of thick plate requires often use of environmentally hazardous lubricants such as chlorinated paraffin...... oils in order to avoid galling. The present paper describes a systematic research in the development of new, environmentally harmless lubricants focusing on the lubricant testing aspects. A system of laboratory tests has been developed to study the lubricant performance under the very varied conditions...

Stress analysis and deformation prediction of sheet metal workpieces based on finite element simulation

OpenAIRE

Ren Penghao; Wang Aimin; Wang Xiaolong; Zhang Yanlin

2017-01-01

After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation ...

Microstructural evolution in friction stir welding of nanostructured ODS alloys

International Nuclear Information System (INIS)

Chen, C.-L.; Tatlock, G.J.; Jones, A.R.

2010-01-01

Nanostructured oxide dispersion strengthened (ODS) Fe-based alloys manufactured by mechanical alloying (MA) are generally considered to be promising candidate materials for high-temperature applications up to at least 1100 o C because of their excellent creep strength and good oxidation resistance. However, a key issue with these alloys is the difficulty in using fusion welding techniques to join components due to oxide particle agglomeration and loss in the weld zone and the disruption and discontinuity in the grain structure introduced at the bond. In this study, the evolution of microstructure has been comprehensively studied in friction stir welds in a ferritic ODS alloy. Initially, electron backscattering diffraction (EBSD) was used to analyze the grain orientation, the grain boundary geometries and recrystallization behaviour. It suggested that deformation heterogeneities were introduced during the friction stirring process which facilitated the onset of recrystallization. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were used to observe the effects of the friction stir welding (FSW) process on the grain structure and the distribution of Y 2 O 3 and other particles in the metal substrates in the FSW and adjacent regions, after the alloys had been recrystallized at temperatures up to 1380 o C for 1 h in air. The results show that fine-equiaxed grains and a uniform distribution of oxide particles were present in the friction stirred region but that the grain boundaries in the parent metal were pinned by particles. Friction stirring appeared to release these boundaries and allowed secondary recrystallization to occur after further heat treatment. The FSW process appears to be a promising technique for joining ferritic ODS alloys in the form of sheet and tube.

Two main and a new type rare earth elements in Mg alloys: A review

Science.gov (United States)

Kong, Linghang

2017-09-01

Magnesium (Mg) alloys stand for the lightest structure engineering materials. Moreover, the strengthening of Mg alloys in ductility, toughness and corrosion predominates their wide applications. With adding rare earth elements in Mg, the mechanical properties will be improved remarkably, especially their plasticity and strength. A brief overview of the addition of rare earth elements for Mg alloys is shown. The basic mechanisms of strengthening Mg alloys with rare earth elements are reviewed, including the solid solution strengthening, grain refinement and long period stacking ordered (LPSO) phase. Furthermore, the available rare earth elements are summarized by type, chemical or physical effects and other unique properties. Finally, some challenge problems that the research is facing and future expectations of ra-re-earth Mg alloys are stated and discussed.

Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

Directory of Open Access Journals (Sweden)

Wang Dan

2014-08-01

Full Text Available The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods (chromium plating, TiAlN coating, surface polishing and nitriding treatment were applied to the H13 surfaces. Taking the coefficient of friction (CoF and the wear degree as evaluation indicators, the high-temperature tribological behavior of the surface modified H13 steel was experimentally investigated under different tribological conditions. The results of this study indicate that the tribological properties of the TiAlN coating under dry friction condition are better than the others for a wide range of temperature (from room temperature to 500 °C, while there is little difference of tribological properties between different surface modifications under graphite lubricated condition, and the variation law of CoF with temperature under graphite lubricated is opposite to that under the dry friction.

Effects in Mg-Zn-based alloys strengthened by quasicrystalline phase

International Nuclear Information System (INIS)

Vlček, M; Čížek, J; Lukáč, F; Melikhova, O; Hruška, P; Procházka, I; Vlach, M; Stulíková, I; Smola, B; Jäger, A

2016-01-01

Magnesium Mg-based alloys are promising lightweight structural materials for automotive, aerospace and biomedical applications. Recently Mg-Zn-Y system attracted a great attention due to a stable icosahedral phase (I-phase) with quasicrystalline structure which is formed in these alloys. Positron lifetime spectroscopy and in situ synchrotron X-ray diffraction were used to study thermal stability of I-phase and precipitation effects in Mg-Zn-Y and Mg- Zn-Al alloys. All alloys containing quasicrystalline I-phase exhibit misfit defects characterized by positron lifetime of ∼ 300 ps. These defects are associated with the interfaces between I- phase particles and Mg matrix. The quasicrystalline I-phase particles were found to be stable up to temperatures as high as ∼ 370°C. The W-phase is more stable and melts at ∼ 420°C. Concentration of defects associated with I-phase decreases after annealing at temperatures above ∼ 300°C. (paper)

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.

Final Technical Report - High-Performance, Oxide-Dispersion-Strengthened Tubes for Production of Ethylene adn Other Industrial Chemicals

Energy Technology Data Exchange (ETDEWEB)

McKimpson, Marvin G.

2006-04-06

This project was undertaken by Michigan Technological University and Special Metals Corporation to develop creep-resistant, coking-resistant oxide-dispersion-strengthened (ODS) tubes for use in industrial-scale ethylene pyrolysis and steam methane reforming operations. Ethylene pyrolysis tubes are exposed to some of the most severe service conditions for metallic materials found anywhere in the chemical process industries, including elevated temperatures, oxidizing atmospheres and high carbon potentials. During service, hard deposits of carbon (coke) build up on the inner wall of the tube, reducing heat transfer and restricting the flow of the hydrocarbon feedstocks. About every 20 to 60 days, the reactor must be taken off-line and decoked by burning out the accumulated carbon. This decoking costs on the order of $9 million per year per ethylene plant, accelerates tube degradation, and requires that tubes be replaced about every 5 years. The technology developed under this program seeks to reduce the energy and economic cost of coking by creating novel bimetallic tubes offering a combination of improved coking resistance, creep resistance and fabricability not available in current single-alloy tubes. The inner core of this tube consists of Incoloy(R) MA956, a commercial ferritic Fe-Cr-Al alloy offering a 50% reduction in coke buildup combined with improved carburization resistance. The outer sheath consists of a new material - oxide dispersion strengthened (ODS) Alloy 803(R) developed under the program. This new alloy retains the good fireside environmental resistance of Alloy 803, a commercial wrought alloy currently used for ethylene production, and provides an austenitic casing to alleviate the inherently-limited fabricability of the ferritic Incoloy(R) MA956 core. To provide mechanical compatibility between the two alloys and maximize creep resistance of the bimetallic tube, both the inner Incoloy(R) MA956 and the outer ODS Alloy 803 are oxide dispersion

Hot forging of roll-cast high aluminum content magnesium alloys

Science.gov (United States)

Kishi, Tomohiro; Watari, Hisaki; Suzuki, Mayumi; Haga, Toshio

2017-10-01

This paper reports on hot forging of high aluminum content magnesium alloy sheets manufactured using horizontal twin-roll casting. AZ111 and AZ131 were applied for twin-roll casting, and a hot-forging test was performed to manufacture high-strength magnesium alloy components economically. For twin-roll casting, the casting conditions of a thick sheet for hot forging were investigated. It was found that twin-roll casting of a 10mm-thick magnesium alloy sheet was possible at a roll speed of 2.5m/min. The grain size of the cast strip was 50 to 70µm. In the hot-forging test, blank material was obtained from as-cast strip. A servo press machine with a servo die cushion was used to investigate appropriate forging conditions (e.g., temperature, forging load, and back pressure) for twin-roll casts (TRCs) AZ111 and AZ131. It was determined that high aluminum content magnesium alloy sheets manufactured using twin-roll casting could be forged with a forging load of 150t and a back pressure of 3t at 420 to 430°C. Applying back pressure during hot forging effectively forged a pin-shaped product.

Contact Behavior of Composite CrTiSiN Coated Dies in Compressing of Mg Alloy Sheets under High Pressure

Directory of Open Access Journals (Sweden)

T.S. Yang

2018-01-01

Full Text Available Hard coatings have been adopted in cutting and forming applications for nearly two decades. The major purpose of using hard coatings is to reduce the friction coefficient between contact surfaces, to increase strength, toughness and anti-wear performance of working tools and molds, and then to obtain a smooth work surface and an increase in service life of tools and molds. In this report, we deposited a composite CrTiSiN hard coating, and a traditional single-layered TiAlN coating as a reference. Then, the coatings were comparatively studied by a series of tests. A field emission SEM was used to characterize the microstructure. Hardness was measured using a nano-indentation tester. Adhesion of coatings was evaluated using a Rockwell C hardness indentation tester. A pin-on-disk wear tester with WC balls as sliding counterparts was used to determine the wear properties. A self-designed compression and friction tester, by combining a Universal Testing Machine and a wear tester, was used to evaluate the contact behavior of composite CrTiSiN coated dies in compressing of Mg alloy sheets under high pressure. The results indicated that the hardness of composite CrTiSiN coating was lower than that of the TiAlN coating. However, the CrTiSiN coating showed better anti-wear performance. The CrTiSiN coated dies achieved smooth surfaces on the Mg alloy sheet in the compressing test and lower friction coefficient in the friction test, as compared with the TiAlN coating.

Contact Behavior of Composite CrTiSiN Coated Dies in Compressing of Mg Alloy Sheets under High Pressure.

Science.gov (United States)

Yang, T S; Yao, S H; Chang, Y Y; Deng, J H

2018-01-08

Hard coatings have been adopted in cutting and forming applications for nearly two decades. The major purpose of using hard coatings is to reduce the friction coefficient between contact surfaces, to increase strength, toughness and anti-wear performance of working tools and molds, and then to obtain a smooth work surface and an increase in service life of tools and molds. In this report, we deposited a composite CrTiSiN hard coating, and a traditional single-layered TiAlN coating as a reference. Then, the coatings were comparatively studied by a series of tests. A field emission SEM was used to characterize the microstructure. Hardness was measured using a nano-indentation tester. Adhesion of coatings was evaluated using a Rockwell C hardness indentation tester. A pin-on-disk wear tester with WC balls as sliding counterparts was used to determine the wear properties. A self-designed compression and friction tester, by combining a Universal Testing Machine and a wear tester, was used to evaluate the contact behavior of composite CrTiSiN coated dies in compressing of Mg alloy sheets under high pressure. The results indicated that the hardness of composite CrTiSiN coating was lower than that of the TiAlN coating. However, the CrTiSiN coating showed better anti-wear performance. The CrTiSiN coated dies achieved smooth surfaces on the Mg alloy sheet in the compressing test and lower friction coefficient in the friction test, as compared with the TiAlN coating.

The effects of Ti and Sn alloying elements on precipitation strengthened Cu40Zn brass using powder metallurgy and hot extrusion

International Nuclear Information System (INIS)

Li Shufeng; Imai, Hisashi; Atsumi, Haruhiko; Kondoh, Katsuyoshi; Kojima, Akimichi; Kosaka, Yoshiharu; Yamamoto, Koji; Takahashi, Motoi

2012-01-01

Highlights: ► Alloying elements Ti and Sn are proposed as additives in 60/40 brass. ► Super-saturated Ti in powder creates high chemical potential for precipitation. ► Ti is readily segregated in primary particle boundaries in BS40–1.0Ti. ► Sn was proposed as an additive to inhibit segregation of Ti in BS40–1.0Ti. ► The introduction of Sn to BS40–1.0Ti brass effectively impedes Ti segregation. - Abstract: The effects of Ti and Sn alloying elements on the microstructural and mechanical properties of 60/40 brass were studied by powder metallurgy processing. The super-saturated solid solution of Ti creates a high precipitation reaction chemical potential in water-atomized BS40-1.0Ti brass powder. Consequently, BS40–1.0Ti brass was remarkably strengthened by the addition of Ti. However, Ti readily segregated in the primary particle boundaries at elevated temperatures, which detrimentally affected the mechanical properties of BS40–1.0Ti brass. Accordingly, Sn was proposed as an additive to BS40–0.6Sn1.0Ti to inhibit the segregation of Ti. Consequently, the Ti precipitate was retained in the form of CuSn 3 Ti 5 in the interior of grains and grain boundaries rather than in the primary particle boundaries. This result demonstrates that the addition of Sn can effectively hinder Ti segregation in the primary particle boundaries. Sn addition produced significant grain refinement and mechanical strengthening effects in BS40–0.6Sn1.0Ti brass. As a result, outstanding strengthening effects were observed for BS40–0.6Sn1.0Ti sintered at 600 °C, which exhibited a yield strength of 315 MPa, an ultimate tensile strength of 598 MPa, and a Vickers micro-hardness of 216 Hv. These values represent increases of 27.5%, 20.1% and 45.6%, over those of extruded BS40–1.0Ti brass.

The effects of Ti and Sn alloying elements on precipitation strengthened Cu40Zn brass using powder metallurgy and hot extrusion

Energy Technology Data Exchange (ETDEWEB)

Li Shufeng, E-mail: shufenglimail@gmail.com [Joining and Welding Research Institute, Osaka University (Japan); Imai, Hisashi; Atsumi, Haruhiko; Kondoh, Katsuyoshi [Joining and Welding Research Institute, Osaka University (Japan); Kojima, Akimichi; Kosaka, Yoshiharu [San-Etsu metals Co. Ltd., 1892, OHTA, Tonami, Toyama (Japan); Yamamoto, Koji; Takahashi, Motoi [Nippon Atomized Metal Powders Corporation, 87-16, Nishi-Sangao, Noda, Chiba (Japan)

2012-02-15

Highlights: Black-Right-Pointing-Pointer Alloying elements Ti and Sn are proposed as additives in 60/40 brass. Black-Right-Pointing-Pointer Super-saturated Ti in powder creates high chemical potential for precipitation. Black-Right-Pointing-Pointer Ti is readily segregated in primary particle boundaries in BS40-1.0Ti. Black-Right-Pointing-Pointer Sn was proposed as an additive to inhibit segregation of Ti in BS40-1.0Ti. Black-Right-Pointing-Pointer The introduction of Sn to BS40-1.0Ti brass effectively impedes Ti segregation. - Abstract: The effects of Ti and Sn alloying elements on the microstructural and mechanical properties of 60/40 brass were studied by powder metallurgy processing. The super-saturated solid solution of Ti creates a high precipitation reaction chemical potential in water-atomized BS40-1.0Ti brass powder. Consequently, BS40-1.0Ti brass was remarkably strengthened by the addition of Ti. However, Ti readily segregated in the primary particle boundaries at elevated temperatures, which detrimentally affected the mechanical properties of BS40-1.0Ti brass. Accordingly, Sn was proposed as an additive to BS40-0.6Sn1.0Ti to inhibit the segregation of Ti. Consequently, the Ti precipitate was retained in the form of CuSn{sub 3}Ti{sub 5} in the interior of grains and grain boundaries rather than in the primary particle boundaries. This result demonstrates that the addition of Sn can effectively hinder Ti segregation in the primary particle boundaries. Sn addition produced significant grain refinement and mechanical strengthening effects in BS40-0.6Sn1.0Ti brass. As a result, outstanding strengthening effects were observed for BS40-0.6Sn1.0Ti sintered at 600 Degree-Sign C, which exhibited a yield strength of 315 MPa, an ultimate tensile strength of 598 MPa, and a Vickers micro-hardness of 216 Hv. These values represent increases of 27.5%, 20.1% and 45.6%, over those of extruded BS40-1.0Ti brass.

Evaluation of the microstructure of Al-Cu-Li-Ag-Mg Weldalite (tm) alloys, part 4

Science.gov (United States)

Pickens, Joseph R.; Kumar, K. S.; Brown, S. A.; Gayle, Frank W.

1991-01-01

Weldalite (trademark) 049 is an Al-Cu-Li-Ag-Mg alloy designed to have ultrahigh strength and to serve in aerospace applications. The alloy displays significantly higher strength than competitive alloys in both naturally aged and artificially aged tempers. The strengthening phases in such tempers have been identified to, in part, explain the mechanical properties attained. In general, the alloy is strengthened by delta prime Al3Li and Guinier-Preston (GP) zones in the naturally aged tempers. In artificially aged tempers in slightly underaged conditions, strengthening is provided by several phases including GP zones, theta prime Al2Cu, S prime Al2CuMg, T(sub 1) Al2CuLi, and possibly a new phase. In the peak strength artificially aged tempers, T(sub 1) is the predominant strengthening phase.

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

Influence of thermo- and hydrodynamic phenomena on microstructure and mechanical properties of laser welded Al-Li-Cu-Zr alloy sheets

International Nuclear Information System (INIS)

Czujko, T.; Przetakiewicz, W.

1998-01-01

The influence of Marongoni type forces on the microstructure of laser welded Al-Li-Cu-Zr alloy sheets was discussed. On the base of mass transport phenomenon analysis and heat diffusion analysis the model explaining the appearing of the double front of crystallization and the axis of weld symmetry was proposed. Moreover, the influence of 'laser effect' connected with the rapid weld solidification on the Al m Fe phase precipitation was deliberated. The influence above mentioned phenomena on the Cu segregation causing formation of near eutectic microregions along grain boundaries was defined as well. (author)

Number & operations task & drill sheets : grades 3-5

CERN Document Server

Reed, Nat

2011-01-01

For grades 3-5, our Common Core State Standards-based combined resource meets the number & operations concepts addressed by the NCTM standards and encourages the students to review the concepts in unique ways. The task sheets introduce the mathematical concepts to the students around a central problem taken from real-life experiences, while the drill sheets provide warm-up and timed practice questions for the students to strengthen their procedural proficiency skills.

Irradiation-assisted stress corrosion cracking of HTH Alloy X-750 and Alloy 625

International Nuclear Information System (INIS)

Bajaj, R.; Mills, W.J.; Lebo, M.R.; Hyatt, B.Z.; Burke, M.G.

1995-01-01

In-reactor testing of bolt-loaded compact tension specimens was performed in 360 C water. New data confirms previous results that high irradiation levels reduce SCC resistance in Alloy X-750. Low boron heats show improved IASCC (irradiation-assisted stress corrosion cracking). Alloy 625 is resistant to IASCC. Microstructural, microchemical, and deformation studies were carried out. Irradiation of X-750 caused significant strengthening and ductility loss associated with formation of cavities and dislocation loops. High irradiation did not cause segregation in X-750. Irradiation of 625 resulted in formation of small dislocation loops and a fine body-centered-orthorhombic phase. The strengthening due to loops and precipitates was apparently offset in 625 by partial dissolution of γ precipitates. Transmutation of boron to helium at grain boundaries, coupled with matrix strengthening, is believed to be responsible for IASCC in X-750, and the absence of these two effects results in superior IASCC resistance in 625

Fracture toughness of copper-base alloys for ITER applications: A preliminary report

Energy Technology Data Exchange (ETDEWEB)

Alexander, D.J.; Zinkle, S.J.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States)

1997-04-01

Oxide-dispersion strengthened copper alloys and a precipitation-hardened copper-nickel-beryllium alloy showed a significant reduction in toughness at elevated temperature (250{degrees}C). This decrease in toughness was much larger than would be expected from the relatively modest changes in the tensile properties over the same temperature range. However, a copper-chromium-zirconium alloy strengthened by precipitation showed only a small decrease in toughness at the higher temperatures. The embrittled alloys showed a transition in fracture mode, from transgranular microvoid coalescence at room temperature to intergranular with localized ductility at high temperatures. The Cu-Cr-Zr alloy maintained the ductile microvoid coalescence failure mode at all test temperatures.

Warm Deep Drawing of Aluminium Sheet

NARCIS (Netherlands)

Bolt, P.J.; Werkhoven, R.J.; van den Boogaard, Antonius H.

2003-01-01

Aluminium sheet drawing processes can be improved by manipulating local flow behaviour by means of elevated temperatures and temperature gradients in the tooling. Forming tests showed that a substantial improvement is possible not only for 5xxx but also for 6xxx series alloys. Finite element method

HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

Directory of Open Access Journals (Sweden)

Fahrmann Michael G.

2014-01-01

Full Text Available HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability as they pertain to the intended use in rings and seals of advanced gas turbines.

The quantitative inspection of iron aluminide green sheet using transient thermography

International Nuclear Information System (INIS)

Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

1999-01-01

The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet

Development oxide dispersion strengthened ferritic steels for fusion

Energy Technology Data Exchange (ETDEWEB)

Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)

1997-04-01

Uniaxial tension creep response is reported for an oxide dispersion strengthened (ODS) steel, Fe-13.5Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) manufactured using the mechanical alloying process. Acceptable creep response is obtained at 900{degrees}C.

Electrochemical profiling of multi-clad aluminium sheets used in automotive heat exchangers

DEFF Research Database (Denmark)

Bordo, Kirill; Ambat, Rajan; Peguet, Lionel

2014-01-01

The objective of the present study is to understand the mechanisms of corrosion propagation across the multi-clad structure of Al alloys sheets as a function of local alloy composition and microstructure, with and without brazing treatment. Electro-chemical behaviour at different depths was profi...

Oxide dispersion strengthened CoCrFeNiMn high-entropy alloy

Czech Academy of Sciences Publication Activity Database

Hadraba, Hynek; Chlup, Zdeněk; Dlouhý, Antonín; Dobeš, Ferdinand; Roupcová, Pavla; Vilémová, Monika; Matějíček, Jiří

2017-01-01

Roč. 689, MAR (2017), s. 252-256 ISSN 0921-5093 R&D Projects: GA ČR(CZ) GA14-25246S; GA ČR(CZ) GA14-22834S Institutional support: RVO:68081723 ; RVO:61389021 Keywords : Creep * High-entropy alloy (HEA) * Mechanical alloying * Oxide dispersion strength ened (ODS) alloy * Powder metallurgy * Spark plasma sintering Subject RIV: JG - Metallurgy; JG - Metallurgy (UFP-V) OBOR OECD: Materials engineering; Materials engineering (UFM-A); Materials engineering (UFP-V) Impact factor: 3.094, year: 2016

Progress in development of iron base alloys

International Nuclear Information System (INIS)

Zackay, V.V.; Parker, E.R.

1980-01-01

The ways of development of new iron base high-strength alloys are considered. Perspectiveness of ferritic steel strengthening with intermetallides (TaFe 2 , for instance) is shown. Favourable combination of plasticity, strength and fracture toughness in nickel-free iron-manganese alloys (16-20%) is also pointed out. A strength level of alloyed maraging steels can be achieved by changes in chemical composition and by proper heat treatments of low- and medium-alloyed steels

Joining of Dissimilar alloy Sheets (Al 6063&AISI 304 during Resistance Spot Welding Process: A Feasibility Study for Automotive industry

Directory of Open Access Journals (Sweden)

Reddy Sreenivasulu

2014-12-01

Full Text Available Present design trends in automotive manufacture have shifted emphasis to alternative lightweight materials in order to achieve higher fuel efficiency and to bring down vehicle emission. Although some other joining techniques are more and more being used, spot welding still remains the primary joining method in automobile manufacturing so far. Spot welds for automotive applications should have a sufficiently large diameter, so that nugget pullout mode is the dominant failure mode. Interfacial mode is unacceptable due to its low load carrying and energy absorption capability. Strength tests with different static loading were performed in, to reveal the failure mechanisms for the lap-shear geometry and the cross-tension geometry. Based on the literature survey performed, venture into this work was amply motivated by the fact that a little research work has been conducted to joining of dissimilar materials like non ferrous to ferrous. Most of the research works concentrated on joining of different materials like steel to steel or aluminium alloy to aluminium alloy by resistance spot welding. In this work, an experimental study on the resistance spot weldability of aluminium alloy (Al 6063 and austenitic stainless steel (AISI304 sheets, which are lap joined by using a pedestal type resistance spot welding machine. Welding was conducted using a 45-deg truncated cone copper electrode with 10-mm face diameter. The weld nugget diameter, force estimation under lap shear test and T – peel test were investigated using digital type tensometer attached with capacitive displacement transducer (Mikrotech, Bangalore, Model: METM2000ER1. The results shows that joining of Al 6063 and AISI 304 thin sheets by RSW method are feasible for automotive structural joints where the loads are below 1000N act on them, it is observed that by increasing the spots per unit length, then the joint with standing strength to oppose failure is also increased linearly incase of

Forming properties and springback evaluation of copper beryllium sheets

International Nuclear Information System (INIS)

Tseng, A.A.; Jen, K.P.; Chen, T.C.; Kondetimmamhalli, R.

1995-01-01

Copper beryllium (CuBe) alloys possess excellent strength and conductivity. They have become the most important materials used for producing high reliability connectors and interconnections for electrical and electronic applications. As demand for high connection density in electrical and electronic products grows, springback behaviors become increasingly critical in fabricating these miniaturized contact components from sheet base materials. In the present article, a study of the springback behavior of CuBe sheets under different heat treatments is presented, with the goal of providing reliable information needed for fabricating more intricate connection parts. Both experimental and analytical techniques were adopted. The tensile tester was first used to study the springback related tensile properties. The governing tensile parameters on springback were identified, and their variations for sheets with different heat treatments were studied. It was found that a bilinear constitutive relationship can be characterize the stress strain behavior of the CuBe alloy. A closed form solution based on this bilinear relationship was formulated to predict the springback for the CuBe sheets at bending conditions. A V-shaped bend tester having an interchangeable punch to accommodate multiple radii was designed and built to evaluate the springback properties of CuBe sheets. A good correlation was found between the analytical predictions and experimental data. A parametric study, as an example, was also performed to provide the springback information needed for designing complicated connectors

Improved Mechanical and Tribological Properties of Metal-Matrix Composites Dispersion-Strengthened by Nanoparticles

Directory of Open Access Journals (Sweden)

Evgenii Levashov

2009-12-01

Full Text Available Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix composites (MMCs and alloys reinforced with nanoparticles is a promising way to resolve this problem. In this work, we have investigated the effect of nano-sized WC, ZrO2, Al2O3, and Si3N4 additives on the properties of sintered dispersion-strengthened Co- and Fe-based MMCs. The results show an increase in the hardness (up to 10 HRB, bending strength (up to 50%, wear resistance (by a factor of 2–10 and a decrease in the friction coefficient (up to 4-fold of the dispersion-strengthened materials. The use of designed alloys as a binder of cutting diamond tools gave a 4-fold increment in the service life, without reduction in their cutting speed.

Electron-microscopic investigations of dispersion-strengthened superalloys

International Nuclear Information System (INIS)

Schroeder, J.H.; Arzt, E.

1988-01-01

Oxide dispersion strengthened (ODS) superalloys possess a high creep strength up to temperatures above 1000 0 C. This is due to a fine dispersion of incoherent Y 2 O 3 particles in connection with a highly elongated grain structure. To investigate the production and properties of ODS alloys, the grain structure was studied and the shape and distribution of dispersoids were characterized after each of the various production steps. Because the interactions between lattice dislocations and dispersoids control the deformation behaviour at high temperatures, the dislocation-dispersoid configurations in crept specimens have been studied by a TEM stereo technique and under weak-beam conditions. It was possible to detect strain fields around the dispersoids using TEM. The results lead to an improved understanding of dispersion strengthening at high temperatures and provide guidelines for the optimum use of this strengthening mechanism. (orig.) [de

Production and fabrication of vanadium alloys for the radiative divertor program of DIII-D

International Nuclear Information System (INIS)

Johnson, W.R.; Smith, J.P.

1997-01-01

V-4Cr-4Ti alloy has been selected for use in the manufacture of a portion of the DIII-D Radiative Divertor upgrade. The production of a 1200-kg ingot of V-4Cr-4Ti alloy, and processing into final sheet and rod product forms suitable for components of the DIII-D Radiative Divertor Program (RDP), has been completed by Wah Chang (formerly Teledyne Wah Chang) of Albany, Oregon (WCA). CVN impact tests on sheet material indicate that the material has properties comparable to other previously-processed V-4Cr-4Ti and V-5Cr-5Ti alloys. Joining of V-4Cr-4Ti alloy has been identified as the most critical fabrication issue for its use in the RDP, and research into several joining methods for fabrication of the RDP components, including resistance seam, friction, and electron beam welding, and explosive bonding is being pursued. Preliminary trials have been successful in the joining of V-alloy to itself by resistance, friction, and electron beam welding processes, and to Inconel 625 by friction welding. In addition, an effort to investigate the explosive bonding of V-4Cr-4Ti alloy to Inconel 625, in both tube-to-bar and sheet-to-sheet configurations, has been initiated, and results have been encouraging

Production and fabrication of vanadium alloys for the radiative divertor program of DIII-D

Energy Technology Data Exchange (ETDEWEB)

Johnson, W.R.; Smith, J.P.

1997-08-01

V-4Cr-4Ti alloy has been selected for use in the manufacture of a portion of the DIII-D Radiative Divertor upgrade. The production of a 1200-kg ingot of V-4Cr-4Ti alloy, and processing into final sheet and rod product forms suitable for components of the DIII-D Radiative Divertor Program (RDP), has been completed by Wah Chang (formerly Teledyne Wah Chang) of Albany, Oregon (WCA). CVN impact tests on sheet material indicate that the material has properties comparable to other previously-processed V-4Cr-4Ti and V-5Cr-5Ti alloys. Joining of V-4Cr-4Ti alloy has been identified as the most critical fabrication issue for its use in the RDP, and research into several joining methods for fabrication of the RDP components, including resistance seam, friction, and electron beam welding, and explosive bonding is being pursued. Preliminary trials have been successful in the joining of V-alloy to itself by resistance, friction, and electron beam welding processes, and to Inconel 625 by friction welding. In addition, an effort to investigate the explosive bonding of V-4Cr-4Ti alloy to Inconel 625, in both tube-to-bar and sheet-to-sheet configurations, has been initiated, and results have been encouraging.

A System of Test Methods for Sheet Metal Forming Tribology

DEFF Research Database (Denmark)

Bay, Niels; Olsson, David Dam; Andreasen, Jan Lasson

2007-01-01

Sheet metal forming of tribologically difficult materials such as stainless steel, Al-alloys and Ti-alloys or forming in tribologically difficult operations like ironing, punching or deep drawing of thick plate requires often use of environmentally hazardous lubricants such as chlorinated paraffin...... oils in order to avoid galling. The present paper describes a systematic research in the development of new, environmentally harmless lubricants focusing on the lubricant testing aspects. A system of laboratory tests has been developed to study the lubricant performance under the very varied conditions...... appearing in different sheet forming operations such as stamping, deep drawing, ironing and punching. The laboratory tests have been especially designed to model the conditions in industrial production....

Study on microstructure and strengthening mechanism of AZ91-Y magnesium alloy

Science.gov (United States)

Cai, Huisheng; Guo, Feng; Su, Juan; Liu, Liang; Chen, Baodong

2018-03-01

AZ91-Y magnesium alloy with different thicknesses were prepared by die casting process. The main existence forms of Y in alloy and the effects of Y on microstructure and mechanical properties of alloy were studied, the main reason for the change of mechanical properties and fracture mechanism were analyzed. The results show that, yttrium exists mainly in the forms of Al2Y phase and trace solid solution in α-Mg. Yttrium can refine the grain of α-Mg, reduce the amount of eutectic β-Mg17Al12 phase and promote its discrete distribution. The room temperature tensile strength and elongation of alloy increased first and then decreased with the increase of Y content. The designed alloys containing 0.6% Y (measured containing 0.63% Y) have better mechanical properties. The change of mechanical properties of alloy is a comprehensive reflection of the effect of solid solution, grain refinement and second phase. The cracking of Al2Y phase and β-Mg17Al12 phase and crack propagation through Al2Y phase and β-Mg17Al12 phase are the main fracture mechanism of magnesium alloy containing yttrium. The cooling rate does not change the trend of the influence of Y, but affects the degree of influence of Y.

Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

Science.gov (United States)

Herbell, T. P.

1976-01-01

Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

Experimental and analytical investigation of reinforced high strength concrete continuous beams strengthened with fiber reinforced polymer

International Nuclear Information System (INIS)

Akbarzadeh, H.; Maghsoudi, A.A.

2010-01-01

Carbon and glass fiber reinforced polymer (CFRP and GFRP) are two materials suitable for strengthening the reinforced concrete (RC) beams. Although many in situ RC beams are of continuous constructions, there has been very limited research on the behavior of such beams with externally applied FRP laminate. In addition, most design guidelines were developed for simply supported beams with external FRP laminates. This paper presents an experimental program conducted to study the flexural behavior and redistribution in moment of reinforced high strength concrete (RHSC) continuous beams strengthened with CFRP and GFRP sheets. Test results showed that with increasing the number of CFRP sheet layers, the ultimate strength increases, while the ductility, moment redistribution, and ultimate strain of CFRP sheet decrease. Also, by using the GFRP sheet in strengthening the continuous beam reduced loss in ductility and moment redistribution but it did not significantly increase ultimate strength of beam. The moment enhancement ratio of the strengthened continuous beams was significantly higher than the ultimate load enhancement ratio in the same beam. An analytical model for moment-curvature and load capacity are developed and used for the tested continuous beams in current and other similar studies. The stress-strain curves of concrete, steel and FRP were considered as integrity model. Stress-strain model of concrete is extended from Oztekin et al.'s model by modifying the ultimate strain. Also, new parameters of equivalent stress block are obtained for flexural calculation of RHSC beams. Good agreement between experiment and prediction values is achieved.

Manufacturing Experience for Oxide Dispersion Strengthened Alloys

Energy Technology Data Exchange (ETDEWEB)

Bennett, Wendy D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Doherty, Ann L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Montgomery, Robert O. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Omberg, Ronald P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Mark T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Webster, Ryan A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-09-22

This report documents the results of the development and the manufacturing experience gained at the Pacific Northwest National Laboratories (PNNL) while working with the oxide dispersion strengthened (ODS) materials MA 956, 14YWT, and 9YWT. The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. ODS materials have the potential to provide improved performance for the U-Mo concept.

Study on the improvement of the properties of Zr alloys

International Nuclear Information System (INIS)

Kim, Young Suk; Han, Jung Ho; Jeong, Yong Hwan; Lee, Duk Hyun; Park, Gi Sung; Hong, Jun Hwa; Park, Ji Yun; No, Gae Ho

1992-01-01

1) The objective of this study is to develop the corrosion resistant zirconium base alloys. In order to achieve this goal, this year's activities have focused on the guidelines for the corrosion resistant zirconium alloy design, the manufacturing of the sheets of zirconium base alloys and finally the characterization of the NAZAs (New Alternate Zirconium alloys). The main results from this study can be summarized as follows: 2) Based on the evaluation of the role of alloying elements, i.e., Nb, Sn, Fe, Cr, and etc, as many as 23 different kinds of the NAZAs were preliminarily designed. 3) The 3 kinds of the NAZAs-Lot 15, 22 and 23 manufactured into a sheet though a series of manufacturing procedures. 4) The microstructures, hardness and the corrosion performances of 3 kinds of NAZAs were investigated. (Author)

A Computational Investigation of Precipitates in Mg-RE Alloys With Applications To Mg-X Systems

Science.gov (United States)

Issa, Ahmed

Increasing fuel efficiency in transportation vehicles is a major policy goal for both government and auto and aerospace manufacturers. Lightweight structural materials, such as magnesium alloys, hold great promise in enabling such fuel efficiency gains. Understanding the controlling factors in Mg alloy strengthening is crucial for the rational design of structurally strong and inexpensive Mg alloys. In this work, we seek to understand the energetic underpinnings giving rise to a class of remarkably strong Mg alloys: Mg-RE systems. We use first-principles methods to efficiently explore seventeen Mg-RE systems, drawing out broad patterns and distilling our knowledge into simple design rules for Mg alloys. We begin by investigating the controlling factors for the Mg-strengthening prismatic plate precipitates in Mg-RE systems, discovering the critical role of strain in such systems. We then proceed to investigate the surprising role of interfacial energies in determining the course of the Mg-RE precipitation reactions. Using strain and interfacial energies, we construct a phase-field model which accurately depicts the precipitate morphology as a function of time and size in a Mg-Nd system. Finally, we combine our gained insights to implement a computational alloy design scheme on a large portion of the periodic table where we seek Mg-strengthening solutes. Our work advances the understanding of strengthening in Mg alloys and lays the groundwork for full scale computational alloy design.

Effect of Temperature and Sheet Temper on Isothermal Solidification Kinetics in Clad Aluminum Brazing Sheet

Science.gov (United States)

Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

2016-09-01

Isothermal solidification (IS) is a phenomenon observed in clad aluminum brazing sheets, wherein the amount of liquid clad metal is reduced by penetration of the liquid clad into the core. The objective of the current investigation is to quantify the rate of IS through the use of a previously derived parameter, the Interface Rate Constant (IRC). The effect of peak temperature and initial sheet temper on IS kinetics were investigated. The results demonstrated that IS is due to the diffusion of silicon (Si) from the liquid clad layer into the solid core. Reduced amounts of liquid clad at long liquid duration times, a roughened sheet surface, and differences in resolidified clad layer morphology between sheet tempers were observed. Increased IS kinetics were predicted at higher temperatures by an IRC model as well as by experimentally determined IRC values; however, the magnitudes of these values are not in good agreement due to deficiencies in the model when applied to alloys. IS kinetics were found to be higher for sheets in the fully annealed condition when compared with work-hardened sheets, due to the influence of core grain boundaries providing high diffusivity pathways for Si diffusion, resulting in more rapid liquid clad penetration.

Shear Strengthening of Concrete Structures with the use of mineral based composites

DEFF Research Database (Denmark)

Blanksvärd, Thomas; Täljsten, Björn; Carolin, Anders

2009-01-01

concrete (RC) beams strengthened in shear with the use of cementitious bonding agents and carbon fiber grids, denoted mineral based composites (MBC). In this study it is shown that the MBC system has a strengthening effect corresponding to that of strengthening systems using epoxy bonding agents and carbon...... for rehabilitation. In addition, more traffic and heavier loads lead to the need for upgrading. Existing externally bonded strengthening systems using FRP (fiber reinforced polymers) and epoxy as bonding agents have been proven to be a good approach to repair and strengthen concrete structures. However, the use...... fiber sheets. Different designs and material properties of the MBC system have been tested. An extensive monitoring set-up has been carried out using traditional strain gauges and photometric strain measurements to obtain strains in steel reinforcement, in FRP and strain fields on the strengthened...

Comparison of Corrosion Behavior of Electrochemically Deposited Nano-Cobalt-Coated Ni Sheet

Directory of Open Access Journals (Sweden)

Nasser Al-Aqeeli

2013-01-01

Full Text Available Corrosion behavior of nano-coblat-coated Ni sheet was compared with pure Ni and 20% Fe-Ni alloy sheet using potentiodynamic polarization and linear polarization technique in 0.1 M NaCl solution at room temperature. Results showed that corrosion resistance properties of nano-Co-coated Ni sheet were almost same as that of pure Ni sheet, however corrosion resistance of 20% Fe-Ni sheet was decreased significantly. Pitting potential of 20% Fe-Ni sheet was subsequently decreased as compared to pure Ni sheet as well as nano-cobalt-coated Ni sheet. SEM/EDS analysis of the corroded surfaces showed that both pure Ni and nano-coblat-coated Ni sheet did not show any appreciable corrosion however significant corrosion was observed in the case of 20% Fe-Ni sheet.

Surface characteristics of the galvannealed coating in Interstitial-free high strengthen steels containing Si and Mn

International Nuclear Information System (INIS)

Jeon, Sun Ho; Chin, Kwang Geun; Kim, Dai Ryong

2008-01-01

Surface-void defects observed on the Galvannealed (GA) steel sheets in Interstitial-free high-strengthened steels containing Si and Mn have been investigated using the combination of the FIB(Focused Ion Beam) and FE-TEM(Field Emission-Transmission Electron Microscope) techniques. The scanning ion micrographs of cross-section microstructure of defects showed that these defects were identified as craters which were formed on the projecting part of the substrate surface. Also, those craters were formed on the Si or Mn-Si oxides film through the whole interface between galvannealed coating and steel substrate. Interface enrichments and oxidations of the active alloying elements such as Si and Mn during reduction annealing process for galvanizing were found to interrupt Zn and Fe interdiffusion during galvannealing process. During galvannealing, Zn and Fe interdiffusion is preferentially started on the clean substrate surface which have no oxide layer on. And then, during galvannealing, crater is developed with consumption of molten zinc on the oxide layer

Surface characteristics of the galvannealed coating in Interstitial-free high strengthen steels containing Si and Mn

Energy Technology Data Exchange (ETDEWEB)

Jeon, Sun Ho; Chin, Kwang Geun [Pohang Iron and Steel Co. Technical Research Laboratories, Gwangyang (Korea, Republic of); Kim, Dai Ryong [Kyungpook National University, Daegu (Korea, Republic of)

2008-02-15

Surface-void defects observed on the Galvannealed (GA) steel sheets in Interstitial-free high-strengthened steels containing Si and Mn have been investigated using the combination of the FIB(Focused Ion Beam) and FE-TEM(Field Emission-Transmission Electron Microscope) techniques. The scanning ion micrographs of cross-section microstructure of defects showed that these defects were identified as craters which were formed on the projecting part of the substrate surface. Also, those craters were formed on the Si or Mn-Si oxides film through the whole interface between galvannealed coating and steel substrate. Interface enrichments and oxidations of the active alloying elements such as Si and Mn during reduction annealing process for galvanizing were found to interrupt Zn and Fe interdiffusion during galvannealing process. During galvannealing, Zn and Fe interdiffusion is preferentially started on the clean substrate surface which have no oxide layer on. And then, during galvannealing, crater is developed with consumption of molten zinc on the oxide layer.

Influence of Mn on the tensile properties of SSM-HPDC Al-Cu-Mg-Ag alloy A201

CSIR Research Space (South Africa)

Müller, H

2011-03-01

Full Text Available A201 aluminium alloy is a high strength casting alloy with a nominal composition of Al-4.6Cu-0.3Mg-0.6Ag. It is strengthened by the O(Al2Cu) phase and the ’(Al2Cu) phase during heat treatment. Further strengthening of this alloy system can...

Design of powder metallurgy titanium alloys and composites

International Nuclear Information System (INIS)

Liu, Y.; Chen, L.F.; Tang, H.P.; Liu, C.T.; Liu, B.; Huang, B.Y.

2006-01-01

Low cost and good performance are two major factors virtually important for Ti alloy development. In this paper, we have studied the effects of alloying elements, thermo-mechanical treatment and particle reinforcement on microstructures and mechanical properties of powder metallurgy (PM) Ti alloys and their composites. Our results indicate that low cost PM Ti alloys and their composites with attractive properties can be fabricated through a single compaction-sintering process, although secondary treatments are required for high performance applications. Three new PM Ti alloys and one TiC/Ti composite of high performance are developed, and new design principles are also proposed. For design of PM Ti alloys, addition of alloying elements has the beneficial effect of enhanced sintering and/or improved mechanical properties. For example, Fe element accelerates the sintering process, Mo and Al are good candidates for solution strengthening, and rare earth elements effectively increase the material ductility by scavenging oxygen from the Ti matrix. For the design of Ti-based composites, in situ formation of strengthening particles and solid solution hardening of the matrix both should be considered simultaneously for alloy development. Cr 3 C 2 is found to be a very suitable additive for processing particle reinforced Ti composites

A highly ductile magnesium alloy system

International Nuclear Information System (INIS)

Gao, W; Liu, H

2009-01-01

Magnesium (Mg) alloys are finding increasing applications in industry mainly due to their high strength-to-weight ratio. However, they have intrinsically poor plastic deformation ability at room temperature. Therefore, the vast majority of Mg alloys are used only in cast state, severely limiting the development of their applications. We have recently discovered a new Mg alloy system that possesses exceptionally high ductility as well as good mechanical strength. The superior plasticity allows this alloy system to be mechanically deformed at room temperature, directly from an as-cast alloy plate, sheet or ingot into working parts. This type of cold mechanical forming properties has never been reported with any other Mg alloy systems.

Cost and Ductility Effectiveness of Concrete Columns Strengthened with CFRP and SFRP Sheets

Directory of Open Access Journals (Sweden)

Khaled Abdelrahman

2014-05-01

Full Text Available Recently, steel fibre reinforced polymers (SFRP sheets have been introduced for the repair and rehabilitation of concrete structures. Few researchers studied the behaviour of the concrete columns wrapped with SFRP sheets; however, several critical parameters such as the cost and ductility effectiveness of the SFRP wrapped concrete columns have been lightly addressed. Thus, the main objective of this paper is to study the cost and ductility effectiveness of SFRP wrapped concrete columns and compare the results with the conventionally used carbon FRP (CFRP wrapped concrete columns. In addition, an analytical procedure to predict the cost effectiveness of SFRP wrapped concrete columns is also suggested, from which, a parametric study was conducted. The parametric study investigated the effect of the concrete strength, the number of SFRP layers, and the size and slenderness effects on the cost effectiveness of the concrete columns wrapped with SFRP sheets. The results from the cost and ductility effectiveness study indicated that the SFRP wrapped concrete columns showed enhanced performance over the CFRP wrapped concrete columns. The suggested analytical procedure proved to be a reliable and accurate method to predict the cost effectiveness parameter of SFRP wrapped concrete columns. The parametric study showed the significant impact of the investigated parameters on the cost effectiveness of concrete columns wrapped with SFRP sheets.

Neutronographic Texture Analysis of Zirconium Based Alloys

International Nuclear Information System (INIS)

Kruz'elová, M; Vratislav, S; Kalvoda, L; Dlouhá, M

2012-01-01

Neutron diffraction is a very powerful tool in texture analysis of zirconium based alloys used in nuclear technique. Textures of five samples (two rolled sheets and three tubes) were investigated by using basal pole figures, inversion pole figures, and ODF distribution function. The texture measurement was performed at diffractometer KSN2 on the Laboratory of Neutron Diffraction, Department of Solid State Engineering, Faculty of Nuclear Sciences and Physical Engineering, CTU in Prague. Procedures for studying textures with thermal neutrons and procedures for obtaining texture parameters (direct and inverse pole figures, three dimensional orientation distribution function) are also described. Observed data were processed by software packages HEXAL and GSAS. Our results can be summarized as follows: i) All samples of zirconium alloys show the distribution of middle area into two maxima in basal pole figures. This is caused by alloying elements. A characteristic split of the basal pole maxima tilted from the normal direction toward the transverse direction can be observed for all samples, ii) Sheet samples prefer orientation of planes (100) and (110) perpendicular to rolling direction and orientation of planes (002) perpendicular to normal direction, iii) Basal planes of tubes are oriented parallel to tube axis, meanwhile (100) planes are oriented perpendicular to tube axis. Level of resulting texture and maxima position is different for tubes and for sheets. The obtained results are characteristic for zirconium based alloys.

Improved Mo-Re VPS Alloys for High-Temperature Uses

Science.gov (United States)

Hickman, Robert; Martin, James; McKechnie, Timothy; O'Dell, John Scott

2011-01-01

Dispersion-strengthened molybdenum- rhenium alloys for vacuum plasma spraying (VPS) fabrication of high-temperature-resistant components are undergoing development. In comparison with otherwise equivalent non-dispersion-strengthened Mo-Re alloys, these alloys have improved high-temperature properties. Examples of VPS-fabricated high-temperature-resistant components for which these alloys are expected to be suitable include parts of aircraft and spacecraft engines, furnaces, and nuclear power plants; wear coatings; sputtering targets; x-ray targets; heat pipes in which liquid metals are used as working fluids; and heat exchangers in general. These alloys could also be useful as coating materials in some biomedical applications. The alloys consist of 60 weight percent Mo with 40 weight percent Re made from (1) blends of elemental Mo and Re powders or (2) Re-coated Mo particles that have been subjected to a proprietary powder-alloying-and-spheroidization process. For most of the dispersion- strengthening experiments performed thus far in this development effort, 0.4 volume percent of transition-metal ceramic dispersoids were mixed into the feedstock powders. For one experiment, the proportion of dispersoid was 1 volume percent. In each case, the dispersoid consisted of either ZrN particles having sizes <45 m, ZrO2 particles having sizes of about 1 m, HfO2 particles having sizes <45 m, or HfN particles having sizes <1 m. These materials were chosen for evaluation on the basis of previously published thermodynamic stability data. For comparison, Mo-Re feedstock powders without dispersoids were also prepared.

Mechanical properties and microstructure of copper alloys and copper alloy-stainless steel laminates for fusion reactor high heat flux applications

Science.gov (United States)

Leedy, Kevin Daniel

A select group of copper alloys and bonded copper alloy-stainless steel panels are under consideration for heat sink applications in first wall and divertor structures of a planned thermonuclear fusion reactor. Because these materials must retain high strengths and withstand high heat fluxes, their material properties and microstructures must be well understood. Candidate copper alloys include precipitate strengthened CuNiBe and CuCrZr and dispersion strengthened Cu-Alsb2Osb3 (CuAl25). In this study, uniaxial mechanical fatigue tests were conducted on bulk copper alloy materials at temperatures up to 500sp°C in air and vacuum environments. Based on standardized mechanical properties measurement techniques, a series of tests were also implemented to characterize copper alloy-316L stainless steel joints produced by hot isostatic pressing or by explosive bonding. The correlation between mechanical properties and the microstructure of fatigued copper alloys and the interface of copper alloy-stainless steel laminates was examined. Commercial grades of these alloys were used to maintain a degree of standardization in the materials testing. The commercial alloys used were OMG Americas Glidcop CuAl25 and CuAl15; Brush Wellman Hycon 3HP and Trefimetaux CuNiBe; and Kabelmetal Elbrodur and Trefimetaux CuCrZr. CuAl25 and CuNiBe alloys possessed the best combination of fatigue resistance and microstructural stability. The CuAl25 alloy showed only minimal microstructural changes following fatigue while the CuNiBe alloy consistently exhibited the highest fatigue strength. Transmission electron microscopy observations revealed that small matrix grain sizes and high densities of submicron strengthening phases promoted homogeneous slip deformation in the copper alloys. Thus, highly organized fatigue dislocation structure formation, as commonly found in oxygen-free high conductivity Cu, was inhibited. A solid plate of CuAl25 alloy hot isostatically pressed to a 316L stainless steel

The oxidation and corrosion of ODS alloys

Science.gov (United States)

Lowell, Carl E.; Barrett, Charles A.

1990-01-01

The oxidation and hot corrosion of high temperature oxide dispersion strengthened (ODS) alloys are reviewed. The environmental resistance of such alloys are classified by oxide growth rate, oxide volatility, oxide spalling, and hot corrosion limitations. Also discussed are environmentally resistant coatings for ODS materials. It is concluded that ODS NiCrAl and FeCrAl alloys are highly oxidation and corrosion resistant and can probably be used uncoated.

Oxidation And Hot Corrosion Of ODS Alloy

Science.gov (United States)

Lowell, Carl E.; Barrett, Charles A.

1993-01-01

Report reviews oxidation and hot corrosion of oxide-dispersion-strengthened (ODS) alloys, intended for use at high temperatures. Classifies environmental resistances of such alloys by rates of growth of oxides, volatilities of oxides, spalling of oxides, and limitations imposed by hot corrosion. Also discusses environmentally resistant coatings for ODS materials. Concludes ODS NICrAl and FeCrAl alloys highly resistant to oxidation and corrosion and can be used uncoated.

Acoustic emission monitoring of concrete columns and beams strengthened with fiber reinforced polymer sheets

Science.gov (United States)

Ma, Gao; Li, Hui; Zhou, Wensong; Xian, Guijun

2012-04-01

Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering. During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of concrete crack patterns during the loading process was revealed.

Prediction of formability of aluminum alloy 5454 sheet

International Nuclear Information System (INIS)

Kim, Chan Il; Yang, Seung Han; Kim, Young Suk

2012-01-01

In the automobile industry, reducing the weight is the most important objective for reducing air pollution and improving the fuel efficiency. For this reason, the application of aluminum sheets is increasing. When the sheets are applied to the automobile, using inappropriate variables for the material, product design, and press processing can generate tearing, wrinkling, and spring back problems, which are the main types of failure in the manufacturing process. Therefore, it is necessary to reduce these failures by harmonizing the many variables and strictly managing the processes. In this research, we study the theoretical plasticity instability of Al5454 and obtain the forming limit diagram (FLD) using MATLAB. Moreover, we compare the theoretical FLD with an experimental FLD obtained from a stretching test

Sintering and microstructure evolution of columnar nickel-based superalloy sheets prepared by EB-PVD

International Nuclear Information System (INIS)

Chen, S.; Qu, S.J.; Liang, J.; Han, J.C.

2010-01-01

Research highlights: → EB-PVD technology is commonly used to deposit thermal barrier coatings (TBCs) and columnar structure is commonly seen in EB-PVD condensates. The unique columnar structure can provide outstanding resistance against thermal shock and mechanical strains for TBCs. However, a number of researchers have found that the columnar structure can affect the mechanical properties of EB-PVD alloy thin sheet significantly. As yet, works on how to reduce this kind of effects are seldom done. In the present article, we tried to reveal the sintering effects on microstructure evolution and mechanical properties of columnar Ni-based superalloy sheet. The results suggests that after sintering, the columnar structure degrades. Degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering. - Abstract: A ∼0.15 mm-thick columnar nickel-based superalloy sheet was obtained by electron beam physical vapor deposition (EB-PVD). The as-deposited alloy sheet was sintered at different conditions. The microstructure of the specimens before and after sintering was characterized by using scanning electron microscopy. An X'Pert texture facility was used to determine the crystallographic orientation of the as-deposited alloy sheet. The phase transformation was investigated by X-ray diffraction. Tensile tests were conducted at room temperature on as-deposited and sintered specimens. The results show that the as-deposited sheet is composed of typical columnar structures. After sintering, however, the columnar structure degrades. The degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering.

Axial Fatigue Tests at Zero Mean Stress of 24S-T Aluminum-alloy Sheet with and Without a Circular Hole

Science.gov (United States)

Brueggeman, W C; Mayer, M JR; Smith, W H

1944-01-01

Axial fatigue tests were made on 189 coupon specimens of 0.032-inch 24S-T aluminum-alloy sheet and a few supplementary specimens of 0.004-inch sheet. The mean load was zero. The specimens were restrained against lateral buckling by lubricated solid guides described in a previous report on this project. About two-thirds of the 0.032-inch specimens were plain coupons nominally free from stress raisers. The remainder contained a 0.1285-inch drilled hole at the center where the reduced section was 0.5 inch wide. S-N diagrams were obtained for cycles to failure between about 1000 and 10 to the 7th power cycles for the plain specimens and 17 and 10 to the 7th power cycles for the drilled specimens. The fatigue stress concentration factor increased from about 1.08 for a stress amplitude causing failure at 0.25 cycles (static) to a maximum of 1.83 at 15,000 cycles and then decreased gradually. The graph for the drilled specimens showed less scatter than that for the plain specimens.

Production and processing of Cu-Cr-Nb alloys

International Nuclear Information System (INIS)

Ellis, D.L.; Michal, G.M.; Orth, N.W.

1990-01-01

A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling

Production and processing of Cu-Cr-Nb alloys

Science.gov (United States)

Ellis, David L.; Michal, Gary M.; Orth, Norman W.

1990-01-01

A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling.

A study of creep behavior in refractory alloys for thermionic emitter applications

International Nuclear Information System (INIS)

Gao Hong; Zee, Ralph

1997-01-01

The creep behavior of HfC strengthened tungsten alloys was studied. An ultrahigh vacuum high precision creep test system was constructed for this purpose so that the samples could be heated up to 3000 K for heat treatment and creep strain could be measured from the creep sample inside the vacuum chamber. Creep tests were conducted in tungsten strengthened with 0.37 percent of HfC at temperatures between 2000 K to 2500 K for durations up to 8 weeks. To explain the creep behavior observed in this dispersion strengthened alloy, a creep model was proposed which accounted for the presence of HfC particles in the form of a back stress generated by these particles. This model was verified by the creep test data of a W-0.37HfC alloy tested under both extruded and recrystallized microstructural conditions. According to this model, the steady state creep of this type alloys was expected to increase with time due to the HfC particle coarsening and recrystallization under high temperatures. In contrast, conventional simple power law creep only predicts a constant steady state creep for these materials, which does not represent the microstructural evolution of the materials. In this study, the experimental study was designed to verify the semi-mechanistic phenomenological creep model developed for carbide particle strengthened tungsten alloys

Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates.

Science.gov (United States)

Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N; Huang, Shenyan; Teng, Zhenke; Liu, Chain T; Asta, Mark D; Gao, Yanfei; Dunand, David C; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E; Liaw, Peter K

2015-11-09

There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures.

Condition assessment and strengthening of residential units

Directory of Open Access Journals (Sweden)

Tatheer Zahra

2014-01-01

Full Text Available About 40, ground plus one (G+1 residential units were designed using a hybrid structural framing system (RC frame and load bearing walls. A few months after the completion of the ground floor of the residential units, cracks appeared at several locations in the structure. Field and Laboratory testing was conducted to ascertain the in situ strength of concrete and steel reinforcement. The results of the experimental work were used in the analytical ETABS model for the structural stability calculations. The results indicated that residential units were marginally safe in the existing condition (completed ground floor, but the anticipated construction of the floor above the ground floor (G+1 could not be carried out as the strength of the structural system was inadequate. To increase the safety of existing ground floor and to provide the option of the construction of one floor above, rehabilitation and strengthening design was performed. The proposed strengthening design made use of welded wire fabric (WWF and carbon fibre reinforced polymer (CFRP laminates/sheets for the strengthening of walls, columns and slabs. The residential units will be strengthened in the near future.

Copper alloys for high heat flux structure applications

International Nuclear Information System (INIS)

Zinkle, S.J.; Fabritsiev, S.A.

1994-01-01

The mechanical and physical properties of copper alloys are reviewed and compared with the requirements for high heat flux structural applications in fusion reactors. High heat flux structural materials must possess a combination of high thermal conductivity and high mechanical strength. The three most promising copper alloys at the present time are oxide dispersion-strengthened copper (Cu-Al 2 O 3 ) and two precipitation-hardened copper alloys (Cu-Cr-Zr and Cu-Ni-Be). These three alloys are capable of room temperature yield strengths >400 MPa and thermal conductivities up to 350 W/m-K. All of these alloys require extensive cold working to achieve their optimum strength. Precipitation-hardened copper alloys such Cu-Cr-Zr are susceptible to softening due to precipitate overaging and recrystallization during brazing, whereas the dislocation structure in Cu-Al 2 O 3 remains stabilized during typical high temperature brazing cycles. All three alloys exhibit good resistance to irradiation-induced softening and void swelling at temperatures below 300 degrees C. The precipitation-strengthened allows typically soften during neutron irradiation at temperatures above about 300 degrees C and therefore should only be considered for applications operating at temperatures 2 O 3 ) is considered to be the best candidate for high heat flux structural applications

Research and Application of New Type of High Performance Titanium Alloy

Directory of Open Access Journals (Sweden)

ZHU Zhishou

2016-06-01

Full Text Available With the continuous extension of the application quantity and range for titanium alloy in the fields of national aviation, space, weaponry, marine and chemical industry, etc., even more critical requirements to the comprehensive mechanical properties, low cost and process technological properties of titanium alloy have been raised. Through the alloying based on the microstructure parameters design, and the comprehensive strengthening and toughening technologies of fine grain strengthening, phase transformation and process control of high toughening, the new type of high performance titanium alloy which has good comprehensive properties of high strength and toughness, anti-fatigue, failure resistance and anti-impact has been researched and manufactured. The new titanium alloy has extended the application quantity and application level in the high end field, realized the industrial upgrading and reforming, and met the application requirements of next generation equipment.

Mechanical Properties of Magnesium-Rare Earth Alloy Systems: A Review

Directory of Open Access Journals (Sweden)

Sravya Tekumalla

2014-12-01

Full Text Available Magnesium-rare earth based alloys are increasingly being investigated due to the formation of highly stable strengthening phases, activation of additional deformation modes and improvement in mechanical properties. Several investigations have been done to study the effect of rare earths when they are alloyed to pure magnesium and other Mg alloys. In this review, the mechanical properties of the previously investigated different magnesium-rare earth based binary alloys, ternary alloys and other higher alloys with more than three alloying elements are presented.

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

Energy Technology Data Exchange (ETDEWEB)

Chen, Haiyan [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China); Fu, Li, E-mail: fuli@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China); Liang, Pei; Liu, Fenjun [Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China)

2017-03-15

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

International Nuclear Information System (INIS)

Chen, Haiyan; Fu, Li; Liang, Pei; Liu, Fenjun

2017-01-01

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.

Recent research and developments on wrought magnesium alloys

Directory of Open Access Journals (Sweden)

Sihang You

2017-09-01

Full Text Available Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys. In this contribution, recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design, focusing on Mg-Al, Mg-Zn and Mg-rare earth (RE systems. The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms, e.g. grain refinement, precipitation and texture hardening effect. Finally, the new alloy design and also the future research of wrought magnesium alloys to improve their mechanical properties are discussed.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

Science.gov (United States)

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2000-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr.ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix

Science.gov (United States)

Zhang, Zhenbo; Pantleon, Wolfgang

2017-07-01

Oxide nanoparticles are quintessential for ensuring the extraordinary properties of oxide dispersion strengthened (ODS) steels. In this study, the crystallographic structure of oxide nanoparticles, and their interface with the ferritic steel matrix in an Al-alloyed ODS steel, i.e. PM2000, were systematically investigated by high-resolution transmission electron microscopy. The majority of oxide nanoparticles were identified to be orthorhombic YAlO3. During hot consolidation and extrusion, they develop a coherent interface and a near cuboid-on-cube orientation relationship with the ferrite matrix in the material. After annealing at 1200 °C for 1 h, however, the orientation relationship between the oxide nanoparticles and the matrix becomes arbitrary, and their interface mostly incoherent. Annealing at 1300 °C leads to considerable coarsening of oxide nanoparticles, and a new orientation relationship of pseudo-cube-on-cube between oxide nanoparticles and ferrite matrix develops. The reason for the developing interfaces and orientation relationships between oxide nanoparticles and ferrite matrix under different conditions is discussed.

Development of Rolling Schedules for AZ31 Magnesium Alloy Sheets

Science.gov (United States)

2015-06-01

Materials 2 2.2 Hot Rolling 3 2.2 Sample Characterization: Microstructure and Tensile Properties 3 3. Rolling Experiments 5 3.1 High-Temperature...material systems for protective and structural applications, especially in ground vehicles. Magnesium (Mg), due to its low density (~25% that of steel ...applications, wrought Mg is difficult to produce in thin sheets because of its inherently low ductility . As a result, Mg sheet is often produced at

Experimental investigation of the degree of weakening in structural notch area of 7075-T6 aluminum alloy sheet welded with the RFSSW method

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Kubit Andrzej

2017-01-01

Full Text Available The paper presents the methodology of the research determining the degree of weakening of the welded sheet obtained by the refill friction stir spot welding (RFSSW method. The considered weakness is the effect of a structural notch resulting from penetration by the tool. RFSSW technology is a relatively new method of joining metals, which can successfully provide an alternative to resistance welding or riveting - traditionally used methods of joining thin-walled structures in the aerospace and automotive industries. The study presented in the paper focuses on the overlapping of sheet metal with 7075-T6 aluminum alloy combined in the configuration: 1.6 mm top sheet and 0.8 mm bottom sheet. Joints were assembled following the following process parameters: Welding time 1.5 s, the tool plunge depth in the range of 1.5 ÷ 1.9 mm, and the spindle speed of 2600 rpm. The analysis of the microstructure of joints revealed that along the edge of the tool path a structural notch is formed, the size and shape of which depend on the parameters applied. The paper describes the study consisting in punching the welded area along the formed notch in the upper sheet. The punching process was performed on a universal testing machine and the punching force was measured during the test. Based on the force value, the degree of sheet weakening in the notched area was determined. The smallest weakening was observed in joints made with the smallest tool depth, i.e. 1.5 mm, whereas the biggest weakening was obtained for tool depth of 1.9 mm. The load applied to the joints was equal to 5290N and 7585N respectively.

Swelling in several commercial alloys irradiated to very high neutron fluence

International Nuclear Information System (INIS)

Gelles, D.S.; Pintler, J.S.

1984-01-01

Swelling values have been obtained from a set of commercial alloys irradiated in EBR-II to a peak fluence of 2.5 x 10 23 n/cm 2 (E > 0.1 MeV) or approx. 125 dpa covering the range 400 to 650 0 C. The alloys can be ranked for swelling resistance from highest to lowest as follows: the martensitic and ferritic alloys, the niobium based alloys, the precipitation strengthened iron and nickel based alloys, the molybdenum alloys and the austenitic alloys

Improved creep strength of nickel-base superalloys by optimized γ/γ′ partitioning behavior of solid solution strengthening elements

International Nuclear Information System (INIS)

Pröbstle, M.; Neumeier, S.; Feldner, P.; Rettig, R.; Helmer, H.E.; Singer, R.F.; Göken, M.

2016-01-01

Solid solution strengthening of the γ matrix is one key factor for improving the creep strength of single crystal nickel-base superalloys at high temperatures. Therefore a strong partitioning of solid solution hardening elements to the matrix is beneficial for high temperature creep strength. Different Rhenium-free alloys which are derived from CMSX-4 are investigated. The alloys have been characterized regarding microstructure, phase compositions as well as creep strength. It is found that increasing the Titanium (Ti) as well as the Tungsten (W) content causes a stronger partitioning of the solid solution strengtheners, in particular W, to the γ phase. As a result the creep resistance is significantly improved. Based on these ideas, a Rhenium-free alloy with an optimized chemistry regarding the partitioning behavior of W is developed and validated in the present study. It shows comparable creep strength to the Rhenium containing second generation alloy CMSX-4 in the high temperature / low stress creep regime and is less prone to the formation of deleterious topologically close packed (TCP) phases. This more effective usage of solid solution strengtheners can enhance the creep properties of nickel-base superalloys while reducing the content of strategic elements like Rhenium.

Creep and creep rupture properties of unalloyed vanadium and solid-solution-strengthened vanadium-base alloys

International Nuclear Information System (INIS)

Kainuma, T.; Iwao, N.; Suzuki, T.; Watanabe, R.

1982-01-01

The creep and creep rupture properties of vanadium and vanadium-base alloys were studied at 700 and 1000 0 C. The alloys were vanadium-base binary alloys containing about 5 - 21 at.% Al, Ti, Nb, Ta, Cr, Mo or Fe, three V-20wt.%Nb-base ternary alloys containing 5 or 10 wt.% Al, Cr or Mo, V-10wt.%Ta-10wt.%Al and V-25wt.%Cr-0.8wt.%Zr. The creep rupture stress of the binary alloys, except the V-Al and V-Ti alloys, increased linearly with increasing concentration of the alloying elements. The V-Nb alloy had the best properties with respect to the rupture stress and creep rate at 700 0 C and the rupture stress at 1000 0 C, but the V-Mo alloy appeared likely to have better creep properties at longer times and higher temperatures. Of the five ternary alloys, V-20wt.%Nb-5wt.%Cr and V-20wt.%Nb-10wt.%Mo showed the best creep properties. The creep properties of these two alloys were compared with those of other vanadium alloys and of type 316 stainless steel. (Auth.)

The evolution of texture in aluminum alloy sheet during asymmetric rolling

International Nuclear Information System (INIS)

Kim, K-H.; Lee, D.N.

2000-01-01

Asymmetric rolling, in which the upper and lower roll radii are different, imposes shear deformation on sheets through the thickness, which in turn gives rise to shear deformation textures in the sheets through the thickness. A component of ND// in the shear deformation textures can improve the plastic strain ratios of aluminum sheets. In order to understand the evolution of ND// , the strain histories and distributions in the sheets during the asymmetric rolling are calculated by the finite element method. The strain history and distribution are used to calculate crystallographic orientations and stable orientations based on the Taylor-Bishop-Hill theory and the Renouward-Wintenberger theory. The shear deformation texture can vary with the ratio of shear to normal strain increments. As the ratio increases from zero to infinity, the texture moves from the plane strain compression texture (β fiber) to the ideal shear deformation texture consisting of {001} , {111} , and {111} . The ratio increases with rolling reduction per pass in asymmetric rolling. However, it is practically difficult to the rolling reduction per pass high enough to obtain the ideal shear deformation texture. Imposing the positive and negative shear deformations on the sheet by reversing the shearing direction can give rise to the ideal shear deformation texture. This has been discussed. (author)

A Study on Load Carrying Capacity of Fly Ash Based Polymer Concrete Columns Strengthened Using Double Layer GFRP Wrapping

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S. Nagan

2014-01-01

Full Text Available This paper investigates the suitability of glass fiber reinforced polymer (GFRP sheets in strengthening of fly ash based polymer members under compression. Experimental results revealed that load carrying capacity of the confined columns increases with GFRP sheets wrapping. Altogether 18 specimens of M30 and G30 grade short columns were fabricated. The G30 specimens were prepared separately in 8 molarity and 12 molarity of sodium hydroxide concentration. Twelve specimens for low calcium fly ash based reinforced polymer concrete and six specimens of ordinary Portland cement reinforced concrete were cast. Three specimens from each molarity fly ash based reinforced polymer concrete and ordinary Portland cement reinforced concrete were wrapped with double layer of GFRP sheets. The load carrying capacity of fly ash based polymer concrete was tested and compared with control specimens. The results show increase in load carrying capacity and ductility index for all strengthened elements. The maximum increase in load carrying capacity was 68.53% and is observed in strengthened G30 specimens.

Rapidly cast crystalline thin sheet materials

International Nuclear Information System (INIS)

Warlimont, H.; Emmerich, K.

1986-01-01

The current state and progress of casting thin sheet and ribbons directly from the melt are reviewed. First, the solidification phenomena pertinent to the process are outlined. Subsequently, Fe-Si,l Fe-Si-Al, Fe-Nd-B, Ag-Cu-Ti, alloy steels, Ni superalloys and Si are treated as examples. Finally, the information available on process development is critically assessed

Salt fog corrosion behavior in a powder-processed icosahedral-phase-strengthened aluminum alloy

International Nuclear Information System (INIS)

Watson, T.J.; Gordillo, M.A.; Ernst, A.T.; Bedard, B.A.; Aindow, M.

2017-01-01

Highlights: • Pitting corrosion resistance has been evaluated for an Al-Cr-Mn-Co-Zr alloy. • Pit densities and depths are far lower than for other high-strength Al alloys. • Corrosion proceeds by selective oxidation of the Al matrix around the other phases. - Abstract: The pitting corrosion resistance has been evaluated for a powder-processed Al-Cr-Mn-Co-Zr alloy which contains ≈35% by volume of an icosahedral quasi-crystalline phase and a little Al 9 Co 2 in an Al matrix. ASTM standard salt fog exposure tests show that the alloy exhibits far lower corrosion pit densities and depths than commercial high-strength aerospace Al alloys under the same conditions. Electron microscopy data show that the salt fog exposure leads to the selective oxidation of the face-centered cubic Al matrix around the other phases, and to the development of a porous outer oxide scale.

Friction stir spot welding of dissimilar aluminium alloys

International Nuclear Information System (INIS)

Bozkurt, Yahya

2016-01-01

Friction stir spot welding (FSSW) has been proposed as an effective technology to spot weld the so-called “difficult to be welded” metal alloys such as thin sheets aluminum alloys and dissimilar materials. FSSW is derived from friction stir welding technology, its principle benefit being low cost joining, lower welding temperature and shorter welding time than conventional welding methods. In this study, dissimilar AlMg 3 and AlCu 4 Mg 1 aluminium alloy plates were FSSWed by offsetting the low strength sheet on upper side of the weld. The effects of tool rotation speed on the microstructure, lap shear fracture load (LSFL), microhardness and fracture features of the weld are investigated by constant welding parameters. The maximum LSFL was obtained by increasing the tool rotational speed. However, the joints exhibited pull-out nugget fracture mode under lap shear tensile testing conditions. The largest completely bonded zone was observed as 5.86 mm which was narrower at the opposite position of the joint. Key words: friction stir spot welding, aluminium alloys, mechanical properties, dissimilar joint, welding parameters

Electron-beam welding of thorium-doped iridium alloy sheets

International Nuclear Information System (INIS)

David, S.A.; Liu, C.T.; Hudson, J.D.

1979-04-01

Modified iridium alloys containing 100 ppM Th were found to be very susceptible to hot-cracking during gas tungsten-arc and electron-beam welding. However, the electron-beam welding process showed greater promise of success in welding these alloys, in particular Ir--0.3% W doped with 200 ppM Th and 50 ppM Al. The weldability of this particular alloy was extremely sensitive to the welding parameters, such as beam focus condition and welding speed, and the resulting fusion zone structure. At low speed successful electron-beam welds were made over a narrow range of beam focus conditions. However, at high speeds successful welds can be made over an extended range of focus conditions. The fusion zone grain structure is a strong function of welding speed and focus condition, as well. In the welds that showed hot-cracking, a region of positive segregation of thorium was identified at the fusion boundary. This highly thorium-segregated region seems to act as a potential source for the nucleation of a liquation crack, which later grows as a centerline crack

Positron annihilation study of the vacancy clusters in ODS Fe-14Cr alloys

Science.gov (United States)

Domínguez-Reyes, R.; Auger, M. A.; Monge, M. A.; Pareja, R.

2017-04-01

Oxide dispersion strengthened Fe14Cr and Fe14CrWTi alloys produced by mechanical alloying and hot isostatic pressing were subjected to isochronal annealing up to 1400 °C, and the evolution and thermal stability of the vacancy-type defects were investigated by positron annihilation spectroscopy (PAS). The results were compared to those from a non-oxide dispersion strengthened Fe14Cr alloy produced by following the same powder metallurgy route. The long lifetime component of the PAS revealed the existence of tridimensional vacancy clusters, or nanovoids, in all these alloys. Two recovery stages are found in the oxide dispersion strengthened alloys irrespective of the starting conditions of the samples. The first one starting at T > 750 °C is attributed to thermal shrinkage of large vacancy clusters, or voids. A strong increase in the intensity of the long lifetime after annealing at temperatures in the 800-1050 °C range indicates the development of new vacancy clusters. These defects appear to be unstable above 1050 °C, but some of them remain at temperatures as high as 1400 °C, at least for 90 min.

Microstructure and strengthening mechanisms in an FCC structured single-phase nanocrystalline Co25Ni25Fe25Al7.5Cu17.5 high-entropy alloy

International Nuclear Information System (INIS)

Fu, Zhiqiang; Chen, Weiping; Wen, Haiming; Zhang, Dalong; Chen, Zhen; Zheng, Baolong; Zhou, Yizhang; Lavernia, Enrique J.

2016-01-01

We report on a study of the design, phase formation, microstructure, mechanical behavior and strengthening mechanisms of a novel single-phase Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 (at.%) high-entropy alloy (HEA). In this investigation, a bulk nanocrystalline (nc) Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEA with the face-centered cubic (FCC) crystal structure was fabricated by mechanical alloying (MA) followed by consolidation via spark plasma sintering (SPS). The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that a single FCC solid-solution phase with an average grain diameter of 24 nm was produced following MA. Following SPS, bulk samples exhibiting a bimodal microstructure with both nanoscale grains and ultra-fine grains (UFGs) and with an average grain diameter of 95 nm were obtained, possessing a single FCC solid-solution phase identical to that in the milled powders. The single-phase feature of the Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEA principally resulted from remarkably high mutual solubility in most binary atom-pairs of the constituent elements, which appears to correspond to a high entropy of mixing. Approximately 5 vol.% of nanoscale twins were observed in the bulk nc samples. The bulk nc Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEA exhibits a compressive yield strength of 1795 MPa with a hardness of 454 Hv, which is dramatically higher than the yield strength of most previously reported FCC structured HEAs (∼130–700 MPa). Compared to those of the bulk coarse-grained (CG) Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEA fabricated by arc-melting, the yield strength and Vickers hardness values of the bulk nc samples increased by 834.9% and 251.9%, respectively. Quantitative calculations of the respective contributions from each strengthening mechanism demonstrate that grain boundary strengthening and dislocation strengthening are principally responsible for the measured ultra-high strength of the bulk nc Co 25 Ni 25 Fe 25 Al 7.5 Cu 17.5 HEA.

Effect on strength of ternary alloying additions in L12 intermetallics

International Nuclear Information System (INIS)

Wu Yuanpang.

1991-01-01

The thermodynamic properties of {111} antiphase boundaries (APBs) as well as the site preference of ternary additions in an A 3 B intermetallic with L1 2 structure are studied, using a thermodynamic model. A survey of the results from a variety of ternary alloying additions to Ni 3 Al has shown that there is a conflict in the actual role which solid solution strengthening plays in the athermal increment of yield strength. For instance, a good quantitative agreement with linear concentration law is observed only in alloys with stoichiometric compositions but not in the general case of non-stoichiometric alloys. In the light of the possibility that micro-segregation could explain the experimental discrepancy, the author extends the binary solid solution strengthening theory to the ternary system in an L1 2 structure for the four real systems of Ni-Al-Si, Ni-Al-Ti, Ni-Al-Hf, and Ni-Al-V. It is found that ternary site preference plays an important role in the ternary solid solution strengthening theory with L1 2 structure. Good quantitative agreement was found between the calculated and experimentally measured strength for both stoichiometric and nonstoichiometric alloys

Texture and microstructure development during hot deformation of ME20 magnesium alloy: Experiments and simulations

International Nuclear Information System (INIS)

Li, X.; Al-Samman, T.; Mu, S.; Gottstein, G.

2011-01-01

Highlights: → Second phase precipitates in ME20 hindered activation of tensile twinning at 300 deg. C. → New off-basal sheet texture during c-axis compression at low Z conditions. → Ce amplifies the role of pyramidal -slip over prismatic slip at 0.3T m . → Prismatic slip becomes equally important to deformation at 0.6T m . → Accurate texture predictions using a cluster-type Taylor model with grain interaction. - Abstract: The influence of deformation conditions and starting texture on the microstructure and texture evolution during hot deformation of a commercial rare earth (RE)-containing magnesium alloy sheet ME20 was investigated and compared with a conventional Mg sheet alloy AZ31. For all the investigated conditions, the two alloys revealed obvious distinctions in the flow behavior and the development of texture and microstructure, which was primarily attributed to the different chemistry of the two alloys. The presence of precipitates in the fine microstructure of the ME20 sheet considerably increased the recrystallization temperature and suppressed tensile twinning. This gave rise to an uncommon Mg texture development during deformation. Texture simulation using an advanced cluster-type Taylor approach with consideration of grain interaction was employed to correlate the unique texture development in the ME20 alloy with the activation scenarios of different deformation modes.

Effects of Al-Mn-Ti-P-Cu master alloy on microstructure and properties of Al-25Si alloy

Directory of Open Access Journals (Sweden)

Xu Chunxiang

2013-09-01

Full Text Available To obtain a higher microstructural refining efficiency, and improve the properties and processing ability of hypereutectic Al-25Si alloy, a new environmentally friendly Al-20.6Mn-12Ti-0.9P-6.1Cu (by wt.% master alloy was fabricated; and its modification and strengthening mechanisms on the Al-25Si alloy were studied. The mechanical properties of the unmodified, modified and heat treated alloys were investigated. Results show that the optimal addition amount of the Al-20.6Mn-12Ti-0.9P-6.1Cu master alloy is 4wt.%. In this case, primary Si and eutectic Si as well as メ-Al phase were clearly refined, and this refining effect shows an excellent long residual action as it can be heat-retained for at least 5 h. After being T6 heat treated, the morphology of primary and eutectic Si in the Al-25Si alloys with the addition of 4wt.% Al-20.6Mn-12Ti-0.9P-6.1Cu alloy changes into particles and short rods. The average grain size of the primary and eutectic Si decreases from 250 レm (unmodified to 13.83 レm and 35 レm (unmodified to 7 レm; the メ-Al becomes obviously finer and the distribution of Si phases tends to be uniform and dispersed. Meanwhile, the tensile properties are improved obviously; the tensile strengths at room temperature and 300 ìC reach 241 MPa and 127 MPa, increased by 153.7% and 67.1%, respectively. In addition, the tensile fracture mechanism changes from brittle fracture for the alloy without modification to ductile fracture after modification. Modifying the morphology of Si phase and strengthening the matrix can effectively block the initiation and propagation of cracks, thus improving the strength of the hypereutectic Al-25Si alloy.

Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Hsu, T.Y.

2000-01-01

Characteristics of martensitic transformation fcc(γ)→hcp(ε) in Fe-Mn-Si based alloys are briefly reviewed. By analyzing the influences of constituents and treatments on shape memory effect (SME) in Fe-Mn-Si, the main factors controlling SME are summarized as austenite strengthening, stacking fault energy (probability) and antiferromagnetic temperature. Contribution of thermomechanical training to SME is introduced. The Fe-Mn-Si-RE (rare earth elements) and Fe-Mn-Si-Cr-N alloys are recommended as two novel shape memory alloys with superior SME. (orig.)

Development of new ferritic alloys reinforced by nano titanium nitrides

International Nuclear Information System (INIS)

Mathon, M.H.; Perrut, M.; Poirier, L.; Ratti, M.; Hervé, N.; Carlan, Y. de

2015-01-01

Nano-reinforced steels are considered for future nuclear reactors or for application at high temperature like the heat exchangers tubes or plates. Oxide Dispersion Strengthened (ODS) alloys are the most known of the nano-reinforced alloys. They exhibit high creep strength as well as high resistance to radiation damage. This article deals with the development of new nano reinforced alloys called Nitride Dispersed Strengthened (NDS). Those are also considered for nuclear applications and could exhibit higher ductility with a simplest fabrication way. Two main fabrication routes were studied: the co-milling of Fe–18Cr1W0.008N and TiH 2 powders and the plasma nitration at low temperature of a Fe–18Cr1W0.8Ti powder. The materials were studied mainly by Small Angle Neutron Scattering. The feasibility of the reinforcement by nano-nitride particles is demonstrated. The final size of the nitrides can be similar (few nanometers) to the nano-oxides observed in ODS alloys. The mechanical properties of the new NDS show an amazing ductility at high temperature for a nano-reinforced alloy

Development of new ferritic alloys reinforced by nano titanium nitrides

Energy Technology Data Exchange (ETDEWEB)

Mathon, M.H., E-mail: marie-helene.mathon@cea.fr [Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif-sur-Yvette (France); Perrut, M., E-mail: mikael.perrut@onera.fr [Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif-sur-Yvette (France); Poirier, L., E-mail: poirier@nitruvid.com [Bodycote France and Belgium, 9 r Jean Poulmarch, 95100 Argenteuil (France); Ratti, M., E-mail: mathieu.ratti@snecma.fr [CEA, DEN, Service de Recherches Métallurgiques Appliquées, F91191 Gif-sur-Yvette (France); Hervé, N., E-mail: nicolas.herve@cea.fr [CEA, DRT, LITEN, F38054 Grenoble (France); Carlan, Y. de, E-mail: yann.decarlan@cea.fr [CEA, DEN, Service de Recherches Métallurgiques Appliquées, F91191 Gif-sur-Yvette (France)

2015-01-15

Nano-reinforced steels are considered for future nuclear reactors or for application at high temperature like the heat exchangers tubes or plates. Oxide Dispersion Strengthened (ODS) alloys are the most known of the nano-reinforced alloys. They exhibit high creep strength as well as high resistance to radiation damage. This article deals with the development of new nano reinforced alloys called Nitride Dispersed Strengthened (NDS). Those are also considered for nuclear applications and could exhibit higher ductility with a simplest fabrication way. Two main fabrication routes were studied: the co-milling of Fe–18Cr1W0.008N and TiH{sub 2} powders and the plasma nitration at low temperature of a Fe–18Cr1W0.8Ti powder. The materials were studied mainly by Small Angle Neutron Scattering. The feasibility of the reinforcement by nano-nitride particles is demonstrated. The final size of the nitrides can be similar (few nanometers) to the nano-oxides observed in ODS alloys. The mechanical properties of the new NDS show an amazing ductility at high temperature for a nano-reinforced alloy.

Microstructural characterization of dispersion-strengthened Cu-Ti-Al alloys obtained by reaction milling

International Nuclear Information System (INIS)

Espinoza, Rodrigo A.; Palma, Rodrigo H.; Sepulveda, Aquiles O.; Fuenzalida, Victor; Solorzano, Guillermo; Craievich, Aldo; Smith, David J.; Fujita, Takeshi; Lopez, Marta

2007-01-01

The microstructure, electrical conductivity and hot softening resistance of two alloys (G-10 and H-20), projected to attain Cu-2.5 vol.% TiC-2.5 vol.% Al 2 O 3 nominal composition, and prepared by reaction milling and hot extrusion, were studied. The alloys were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and several chemical analysis techniques. The first alloy, G-10, showed the formation of Al 2 O 3 nanodispersoids and the presence of particles from non-reacted raw materials (graphite, Ti and Al). A second alloy, H-20, was prepared employing different fabrication conditions. This alloy exhibited a homogeneous distribution of Al 2 O 3 and Ti-Al-Fe nanoparticles, with the microstructure being stable after annealing and hot compression tests. These nanoparticles acted as effective pinning sites for dislocation slip and grain growth. The room-temperature hardness of the H-20 consolidated material (330 HV) was approximately maintained after annealing for 1 h at 1173 K; the electrical conductivity was 60% IACS (International Annealing Copper Standard)

Strengthening Interprofessional Requirements Engineering Through Action Sheets: A Pilot Study.

Science.gov (United States)

Kunz, Aline; Pohlmann, Sabrina; Heinze, Oliver; Brandner, Antje; Reiß, Christina; Kamradt, Martina; Szecsenyi, Joachim; Ose, Dominik

2016-10-18

The importance of information and communication technology for healthcare is steadily growing. Newly developed tools are addressing different user groups: physicians, other health care professionals, social workers, patients, and family members. Since often many different actors with different expertise and perspectives are involved in the development process it can be a challenge to integrate the user-reported requirements of those heterogeneous user groups. Nevertheless, the understanding and consideration of user requirements is the prerequisite of building a feasible technical solution. In the course of the presented project it proved to be difficult to gain clear action steps and priorities for the development process out of the primary requirements compilation. Even if a regular exchange between involved teams took place there was a lack of a common language. The objective of this paper is to show how the already existing requirements catalog was subdivided into specific, prioritized, and coherent working packages and the cooperation of multiple interprofessional teams within one development project was reorganized at the same time. In the case presented, the manner of cooperation was reorganized and a new instrument called an Action Sheet was implemented. This paper introduces the newly developed methodology which was meant to smooth the development of a user-centered software product and to restructure interprofessional cooperation. There were 10 focus groups in which views of patients with colorectal cancer, physicians, and other health care professionals were collected in order to create a requirements catalog for developing a personal electronic health record. Data were audio- and videotaped, transcribed verbatim, and thematically analyzed. Afterwards, the requirements catalog was reorganized in the form of Action Sheets which supported the interprofessional cooperation referring to the development process of a personal electronic health record for the

Effect of Heat Treatments on Microstructures and Tensile Properties of Cu-3 wt%Ag-0.5 wt%Zr Alloy

Science.gov (United States)

Chen, Gang; Wang, ChuanJie; Zhang, Ying; Yi, Cen; Zhang, Peng

2018-03-01

The microstructures and tensile properties of Cu-3 wt%Ag-0.5 wt%Zr alloy sheets under different aging treatments are investigated in this research. As one kind of precipitate, Ag nanoparticles with coherent orientation relationship with matrix precipitate. However, after the peak-age point, most of Ag nanoparticles grow into short rod shape with the interface translating to semi-coherent, which leads to the lower strength of over-aging sample. The yield strength is estimated by considering solid solute, grain boundary and precipitation strengthening mechanisms. The result shows that the Ag precipitates provide the main strengthening role. Then a constitutive equation representing the evolution of dislocation density with plastic strain is built by considering work-hardening behavior coming from shearable and non-shearable precipitates which is mainly the particles containing Zr. The flow stress contributed by shearable particle hardening is higher than that of non-shearable one. Due to the coarsening of grain boundary precipitates and low rate of damage accumulation of these non-shearable particles, the micro-cracks nucleate easily at grain boundary which leads to intergranular fracture.

Formation of metastable phases and nanocomposite structures in rapidly solidified Al-Fe alloys

International Nuclear Information System (INIS)

Nayak, S.S.; Chang, H.J.; Kim, D.H.; Pabi, S.K.; Murty, B.S.

2011-01-01

Highlights: → Structures of nanocomposites in rapidly solidified Al-Fe alloys were investigated. → Nanoquasicrystalline, amorphous and intermetallics phases coexist with α-Al. → Nanoquasicrystalline phase was observed for the first time in the dilute Al alloys. → Thermodynamic driving force plays dominant role in precipitation of Fe-rich phases. → High hardness (3.57 GPa) was observed for nanocomposite of Al-10Fe alloy. - Abstract: In the present work the structure and morphology of the phases of nanocomposites formed in rapidly solidified Al-Fe alloys were investigated in details using analytical transmission electron microscopy and X-ray diffraction. Nanoquasicrystalline phases, amorphous phase and intermetallics like Al 5 Fe 2 , Al 13 F 4 coexisted with α-Al in nanocomposites of the melt spun alloys. It was seen that the Fe supersaturation in α-Al diminished with the increase in Fe content and wheel speed indicating the dominant role of the thermodynamic driving force in the precipitation of Fe-rich phases. Nanoquasicrystalline phases were observed for the first time in the dilute Al alloys like Al-2.5Fe and Al-5Fe as confirmed by high resolution TEM. High hardness (3.57 GPa) was measured in nanocomposite of Al-10Fe alloy, which was attributed to synergistic effect of solid solution strengthening due to high solute content (9.17 at.% Fe), dispersion strengthening by high volume fraction of nanoquasicrystalline phase; and Hall-Petch strengthening from finer cell size (20-30 nm) of α-Al matrix.

Comparative Evaluation of Cast Aluminum Alloys for Automotive Cylinder Heads: Part II—Mechanical and Thermal Properties

Science.gov (United States)

Roy, Shibayan; Allard, Lawrence F.; Rodriguez, Andres; Porter, Wallace D.; Shyam, Amit

2017-05-01

The first part of this study documented the as-aged microstructure of five cast aluminum alloys namely, 206, 319, 356, A356, and A356+0.5Cu, that are used for manufacturing automotive cylinder heads (Roy et al. in Metall Mater Trans A, 2016). In the present part, we report the mechanical response of these alloys after they have been subjected to various levels of thermal exposure. In addition, the thermophysical properties of these alloys are also reported over a wide temperature range. The hardness variation due to extended thermal exposure is related to the evolution of the nano-scale strengthening precipitates for different alloy systems (Al-Cu, Al-Si-Cu, and Al-Si). The effect of strengthening precipitates (size and number density) on the mechanical response is most obvious in the as-aged condition, which is quantitatively demonstrated by implementing a strength model. Significant coarsening of precipitates from long-term heat treatment removes the strengthening efficiency of the nano-scale precipitates for all these alloys systems. Thermal conductivity of the alloys evolve in an inverse manner with precipitate coarsening compared to the strength, and the implications of the same for the durability of cylinder heads are noted.

Effect of boron and carbon addition on microstructure and mechanical properties of Ti-15-3 alloy

International Nuclear Information System (INIS)

Sarkar, R.; Ghosal, P.; Muraleedharan, K.; Nandy, T.K.; Ray, K.K.

2011-01-01

Highlights: → Development of β Ti alloys with B and C addition for improved mechanical properties. → Detailed characterization of microstructural constituents using electron microscopy. → Microstructure-mechanical property correlation in this new class of alloys. → Strengthening mechanism in β Ti alloy in the presence of hard and non-deformable phases. - Abstract: A detailed microstructure-mechanical property correlation was carried out in beta titanium alloys (Ti-15V-3Al-3Sn-3Cr) with boron and carbon additions. The alloys were prepared by non-consumable vacuum arc melting followed by hot rolling. Microstructural characterization was carried out using an optical microscope, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a high resolution TEM (HRTEM). Addition of boron and carbon resulted in the precipitation of TiB and TiC, respectively, and these phases acted as reinforcements. Evaluation of mechanical properties in solution treated and solution treated plus aged condition showed strengthening in the boron and carbon containing alloy with respect to the base. Strengthening in solution treated condition was attributed to a synergistic effect of grain refinement and load transfer in the presence of non-deformable phases. On the other hand, higher strength in boron and carbon containing alloys on aging was ascribed to the presence of finer aged microstructures.

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.

TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

International Nuclear Information System (INIS)

Dou, Peng; Kimura, Akihiko; Kasada, Ryuta; Okuda, Takanari; Inoue, Masaki; Ukai, Shigeharu; Ohnuki, Somei; Fujisawa, Toshiharu; Abe, Fujio; Jiang, Shan; Yang, Zhigang

2017-01-01

The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y 2 O 3 ), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y 2 O 3 ), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y 2 Hf 2 O 7 oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y 2 Hf 2 O 7 oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

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

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

International Nuclear Information System (INIS)

Lee, Kee Ahn; Kim, Yong Chan; Kim, Jung Han; Lee, Chong Soo; Namkung, Jung; Kim, Moon Chul

2007-01-01

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

Energy Technology Data Exchange (ETDEWEB)

Lee, Kee Ahn [School of Advanced Materials Engineering, Andong National University, Andong 760-749 (Korea, Republic of)]. E-mail: keeahn@andong.ac.kr; Kim, Yong Chan [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Jung Han [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Lee, Chong Soo [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Namkung, Jung [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Moon Chul [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of)

2007-03-25

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys.

Interaction of ice sheets and climate on geological time scales

NARCIS (Netherlands)

Stap, L.B.

2017-01-01

Since the inception of the Antarctic ice sheet at the Eocene-Oligocene Transition (~34 Myr ago), land ice plays a crucial role in Earth’s climate. Through the ice-albedo and surface-height-temperature feedbacks, land ice variability strengthens atmospheric temperature changes induced by orbital and

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

Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

Energy Technology Data Exchange (ETDEWEB)

Hareesh, K., E-mail: appi.2907@gmail.com [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Joshi, R.P. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Sunitha, D.V. [School of Physics, Reva University, Bangalore 560064 (India); Bhoraskar, V.N. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

2016-12-15

Highlights: • Ag-Au-rGO nanocomposite was synthesized by gamma radiation assisted method. • Ag-Au nanoparticles of size (5–19) nm were decorated on rGO. • Ag-Au-rGO showed enhanced catalytic activity for reduction of 4-Nitrophenol. - Abstract: One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV–vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5–19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp{sup 2} domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

Optimization of resistance spot welding on the assembly of refractory alloy 50Mo-50Re thin sheet

Energy Technology Data Exchange (ETDEWEB)

Xu, Jianhui [Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY 40506 (United States); Jiang, Xiuping [Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY 40506 (United States); Zeng, Qiang [Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY 40506 (United States); Zhai, Tongguang [Department of Chemical and Materials Engineering, University of Kentucky, 177 Anderson Hall, Lexington, KY 40506 (United States)]. E-mail: tzhai0@engr.uky.edu; Leonhardt, Todd [Rhenium Alloys Inc., Elyria, OH 44036 (United States); Farrell, John [Semicon Associates, 695 Laco Drive, Lexington, KY 40510 (United States); Umstead, Williams [Semicon Associates, 695 Laco Drive, Lexington, KY 40510 (United States); Effgen, Michael P. [Semicon Associates, 695 Laco Drive, Lexington, KY 40510 (United States)

2007-07-01

Resistance spot welding (RSW) was employed to pre-join refractory alloy 50Mo-50Re (wt%) sheet with a 0.127 mm gage. Five important welding parameters (hold time, electrode, ramp time, weld current and electrode force) were adjusted in an attempt to optimize the welding quality. It was found that increasing the hold time from 50 ms to 999 ms improved the weld strength. Use of rod-shaped electrodes produced symmetric nugget and enhanced the weld strength. Use of a ramp time of 8 ms minimized electrode sticking and molten metal expulsion. The weld strength continuously increased with increasing the weld current up to 1100 A, but the probabilities of occurrence of electrode sticking and molten metal expulsion were also increased. Electrode force was increased from 4.44 N to 17.8 N, in order to reduce the inconsistency of the welding quality. Welding defects including porosities, columnar grains and composition segregation were also studied.

Compressive pre-stress effects on magnetostrictive behaviors of highly textured Galfenol and Alfenol thin sheets

Directory of Open Access Journals (Sweden)

Julia R. Downing

2017-05-01

Full Text Available Fe-Ga (Galfenol and Fe-Al (Alfenol are rare-earth-free magnetostrictive alloys with mechanical robustness and strong magnetoelastic coupling. Since highly textured Galfenol and Alfenol thin sheets along orientations have been developed with magnetostrictive performances of ∼270 ppm and ∼160 ppm, respectively, they have been of great interest in sensor and energy harvesting applications. In this work, we investigate stress-dependent magnetostrictive behaviors in highly textured rolled sheets of NbC-added Fe80Al20 and Fe81Ga19 alloys with a single (011 grain coverage of ∼90%. A compact fixture was designed and used to introduce a uniform compressive pre-stress to those thin sheet samples along a [100] direction. As compressive pre-stress was increased to above 100 MPa, the maximum observed magnetostriction increased 42% in parallel magnetostriction along the stress direction, λ//, in highly textured (011 Fe81Ga19 thin sheets for a compressive pre-stress of 60 MPa. The same phenomena were observed for (011 Fe80Al20 (maximum increase of 88% with a 49 MPa compressive stress. This trend is shown to be consistent with published results on the effect of pre-stress on magnetostriction in rods of single crystal and textured polycrystalline Fe-Ga alloy of similar compositions, and single crystal data gathered using our experimental set up. Interestingly, the saturating field (Hs does not vary with pre-stresses, while the saturating field in rod-shaped samples of Fe-Ga increases with an increase of pre-stress. This suggests that for a range of compressive pre-stresses, thin sheet samples have larger values of d33 transduction coefficients and susceptibility than rod-shaped samples of similar alloy compositions, and hence they should provide performance benefits when used in sensor and actuator device applications. Thus, we discuss potential reasons for the unexpected trends in Hs with pre-stress, and present preliminary results from tests conducted

Microstructural evolution and mechanical properties of Ti–Zr beta titanium alloy after laser surface remelting

International Nuclear Information System (INIS)

Yao, Y.; Li, X.; Wang, Y.Y.; Zhao, W.; Li, G.; Liu, R.P.

2014-01-01

Highlights: • The surface mechanical properties of the alloy have been greatly improved. • Its grain size was decreased from 100 μm to 10 μm. • The metastable ω with the size of 20–50 nm was observed in the alloy after LSR. • The strengthening effect is mainly due to fine microstructure and strengthened phase. -- Abstract: The effects of laser surface remelting (LSR) on the microstructural evolution and surface mechanical properties of Ti–Zr beta titanium alloy were investigated. The surfaces of the Ti–Zr alloy was re-melted using a CO 2 laser. X-ray diffraction, Scanning electron microscope, Transmission electron microscope, nanoindentation, and microhardness analyses were performed to evaluate the microstructural and mechanical properties of the alloy. The results showed that the alloy microstructure in the remelting region was greatly refined and homogeneous compared with that in the base material because of the rapid remelting and resolidifying. Meanwhile, the metastable hexagonal ω phases with the size of 20–50 nm was found and uniformly distributed throughout the β matrix after LSR. Phase transformation and microstructural refinement were the major microstructural changes in the alloys after LSR. The microhardness and elastic modulus in the remelted region clearly increased by 92.9% and 21.78%, respectively, compared with those in the region without laser processing. The strengthening effect of LSR on the mechanical properties of the Ti–Zr alloy was also addressed. Our results indicated that LSR was an effective method of improving the surface mechanical properties of alloys

Iron-nickel-chromium alloys

International Nuclear Information System (INIS)

Karenko, M.K.

1981-01-01

A specification is given for iron-nickel-chromium age-hardenable alloys suitable for use in fast breeder reactor ducts and cladding, which utilize the gamma-double prime strengthening phase and are characterized in having a delta or eta phase distributed at or near grain boundaries. A range of compositions is given. (author)

Use of a high temperature hydrostatic extrusion technique for powders strengthening

International Nuclear Information System (INIS)

Decours, J.; Gavinet, J.; Weisz, M.

1975-01-01

A conventional 575 tonnes extrusion press has been modified by a device permitting the extrusion process by hydrostatic pression through a leakless mechanical set (13,000 bars maximum), from room temperature to 1,200 deg C. This new device allows: the high temperature hydrostatic extrusion for strengthening of powders, the isostatic compression of powders. Examples of realisations obtained by this process are described, including the influence of different parameters: pressure, temperature, extrusion ratio and for different materials: pure metals (iron, nickel, niobium, etc...) and alloys (stainless steel, molybdenum, niobium nickel alloys, etc...). Then, the advantages of the process are emphasized [fr

Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

Directory of Open Access Journals (Sweden)

Feng Lili

2011-01-01

Full Text Available Abstract In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future.

Effect of CFRP and TRM Strengthening of RC Slabs on Punching Shear Strength

Directory of Open Access Journals (Sweden)

Husain Abbas

Full Text Available Abstract The paper presents experiments involving punching of RC slabs strengthened using externally bonded carbon fiber reinforced polymer (CFRP sheet and textile reinforced mortar (TRM. Twelve RC slab specimens of two concrete grades (39.9 and 63.2 MPa and employing two strengthening schemes (CFRP and TRM were tested. Specimens were supported on two opposite edges. Experimental load-displacement variations show two peak loads in strengthened slabs and one peak followed by a plateau in control. Second peak or the plateau corresponds to the combined action of aggregate interlock and the dowel action of back face rebars and strengthening layers. The dowel action of back face rebars and strengthening layers had no role in ultimate punching load (i.e. first peak. Strengthened slabs showed 9-18% increase in ultimate punching load (i.e. first peak whereas there was significant increase in the second peak load (190-276% for CFRP; 55-136% for TRM and energy absorption (~66% for CFRP and 22-56% for TRM. An analytical model was also developed for predicting the punching shear strength (first and second peaks of strengthened slabs showing good comparison with experiments.

Investigation of a hot-pressed Nb–Ti–Al alloy: Mechanical alloying, microstructure and mechanical property

Energy Technology Data Exchange (ETDEWEB)

Shi, Zhiwu; Wei, Hua; Zhang, Hongyu; Jin, Tao; Sun, Xiaofeng; Zheng, Qi, E-mail: qzheng@imr.ac.cn

2016-01-10

The Nb–23Ti–15Al (at%) alloy was prepared by mechanical alloying (MA) and hot-pressing (HPing). The microstructure evolution of powder particles during MA and its influence on the microstructure and mechanical properties of the hot-pressed (HPed) alloy have been investigated. The powder and HPed alloy were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that particle size increases in the first stage and then decreases in the second stage during MA; as milling speed increases, mechanically alloyed (MAed) powder with convoluted elemental lamellae, homogeneous Nb solid-solution and an amorphous phase could be obtained respectively in 24 h. Higher homogeneity in microstructure and composition of the MAed powder particles promotes the precipitation of the δ phase and refines the β and Ti(O,C) phases in the HPed alloy. Moreover, due to the phase equilibrium changes caused by Fe and Cr in the amorphous powder, σ phase appears in the alloy as a stable phase instead of the δ phase. Properly MAed powder contributes to higher hardness of the HPed alloy, for reasons of microstructure refinement and sufficient precipitating of strengthening phases.

Investigation of a hot-pressed Nb–Ti–Al alloy: Mechanical alloying, microstructure and mechanical property

International Nuclear Information System (INIS)

Shi, Zhiwu; Wei, Hua; Zhang, Hongyu; Jin, Tao; Sun, Xiaofeng; Zheng, Qi

2016-01-01

The Nb–23Ti–15Al (at%) alloy was prepared by mechanical alloying (MA) and hot-pressing (HPing). The microstructure evolution of powder particles during MA and its influence on the microstructure and mechanical properties of the hot-pressed (HPed) alloy have been investigated. The powder and HPed alloy were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that particle size increases in the first stage and then decreases in the second stage during MA; as milling speed increases, mechanically alloyed (MAed) powder with convoluted elemental lamellae, homogeneous Nb solid-solution and an amorphous phase could be obtained respectively in 24 h. Higher homogeneity in microstructure and composition of the MAed powder particles promotes the precipitation of the δ phase and refines the β and Ti(O,C) phases in the HPed alloy. Moreover, due to the phase equilibrium changes caused by Fe and Cr in the amorphous powder, σ phase appears in the alloy as a stable phase instead of the δ phase. Properly MAed powder contributes to higher hardness of the HPed alloy, for reasons of microstructure refinement and sufficient precipitating of strengthening phases.

Influence of heat treatment on fatigue performances for self-piercing riveting similar and dissimilar titanium, aluminium and copper alloys

OpenAIRE

Zhang, Xianlian; He, Xiaocong; Xing, Baoying; Zhao, Lun; Lu, Yi; Gu, Fengshou; Ball, Andrew

2016-01-01

The fatigue performances of self-piercing riveting (SPR) joints connecting similar and dissimilar sheets of TA1 titanium alloy (TA1), Al5052 aluminium alloy (Al5052) and H62 copper alloy (H62) were studied in this paper. The specimens of similar TA1 sheets treated with stress relief annealing were prepared to investigate the influence of relief annealing on the mechanical properties of SPR joints. Fatigue tests were conducted to characterize the fatigue lives and failure modes of the joints. ...

Simulation of Concurrent Precipitation of Two Strengthening Phases in Magnesium Alloys

Science.gov (United States)

Sun, Weihua; Zhang, Chuan; Klarner, Andrew D.; Cao, Weisheng; Luo, Alan A.

The precipitation kinetics and microtructure in Mg-Sn binary and Mg-Al-Sn ternary alloys are simulated using PanPrecipitation coupled with Mg thermodynamic database and a newly established mobility database of the Mg-Al-Sn ternary system. Both Mg2Sn and Mg17Al12 precipitates are considered in this work. The obtained kinetic parameters for these two precipitates can be used in the simulation of both individual and concurrent precipitations of Mg17Al12 and Mg2Sn in Mg-Al-Sn alloys. The simulated microstructure evolution, such as the particle size and number density, are in agreement with experimental data.

Microstructure of oxide dispersion strengthened Eurofer and iron-chromium alloys investigated by means of small-angle neutron scattering and transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Heintze, C. [Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Bergner, F., E-mail: f.bergner@fzd.de [Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Ulbricht, A. [Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Hernandez-Mayoral, M. [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Keiderling, U. [Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Lindau, R. [Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Weissgaerber, T. [Fraunhofer Institute IFAM-Dresden, Winterbergstr. 28, 01277 Dresden (Germany)

2011-09-01

Oxide dispersion strengthening of ferritic/martensitic chromium steels is a promising route for the extension of the range of operation temperatures for nuclear applications. The investigation of dedicated model alloys is an important means in order to separate individual effects contributing to the mechanical behaviour under irradiation and to improve mechanistic understanding. A powder metallurgy route based on spark plasma sintering was applied to fabricate oxide dispersion strengthened (ODS) Fe9Cr model materials. These materials along with Eurofer97 and ODS-Eurofer were investigated by means of small-angle neutron scattering (SANS) and TEM. For Fe9Cr-0.6 wt.%Y{sub 2}O{sub 3}, TEM results indicate a peak radius of the size distribution of Y{sub 2}O{sub 3} particles of 4.2 nm with radii ranging up to 15 nm, and a volume fraction of 0.7%, whereas SANS indicates a peak radius of 3.8 nm and a volume fraction of 0.6%. It was found that the non-ODS Fe9Cr and Eurofer97 are suitable reference materials for ODS-Fe9Cr and ODS-Eurofer, respectively, and that the ODS-Fe9Cr variants are suitable model materials for the separated investigation of irradiation-Y{sub 2}O{sub 3} particle interaction effects.

Corrosion behavior of friction stir welded AZ31B Mg alloy - Al6063 alloy joint

Directory of Open Access Journals (Sweden)

B. Ratna Sunil

2016-12-01

Full Text Available In the present work, AZ31B Mg alloy and Al6063 alloy-rolled sheets were successfully joined by friction stir welding. Microstructural studies revealed a sound joint with good mechanical mixing of both the alloys at the nugget zone. Corrosion performance of the joint was assessed by immersing in 3.5% NaCl solution for different intervals of time and the corrosion rate was calculated. The joint has undergone severe corrosion attack compared with both the base materials (AZ31B and Al6063 alloys. The predominant corrosion mechanism behind the high corrosion rate of the joint was found to be high galvanic corrosion. From the results, it can be suggested that the severe corrosion of dissimilar Mg–Al joints must be considered as a valid input while designing structures intended to work in corroding environment.

Weldability of molybdenum and its alloy sheet, 1

International Nuclear Information System (INIS)

Matsuda, Fukuhisa; Ushio, Masao; Nakata, Kazuhiro; Edo, Yoshiaki

1979-01-01

Basic weldability of electron-beam melted pure molybdenum has been examined in electron-beam welding in high vacuum and GTA welding in pure and air mixed argon atmospheres by paying attention to weld defects such as hot cracking and porosity in weld metal and also mechanical properties of welded joint in comparison with conventional TZM alloys. The main conclusions obtained were as follows; (1) The weld metals of electron-beam melted pure molybdenum with electron-beam and GTA weldings in pure and air mixed argon atmosphere up to about 1% were almost porosity free. However, large amount of oxygen content of 200 ppm in powder-metallurgy TZM alloy made very porous weld bead in electron-beam welding in high vacuum. Therefore, oxygen content in base metal should be lowered to the minimum, that is, less than 10 ppm, especially in electron-beam welding in high vacuum. (2) Hot cracking occurred in the weld metal of GTA welding when air content in argon atmosphere exceeded about 0.6% for electron-beam melted pure molybdenum and powder metallurgy TZM alloy. In less than 0.26% air, no hot cracking were observed in this experiment. Moreover, in electron-beam welding, no hot cracking was observed in weld metals for both materials. In order to prevent the formation of hot cracking, the purity of welding atmosphere should be kept as high as possible. (3) Joint efficiency of the welded joint of electron-beam melted pure molybdenum with electron-beam welding was 50 to 60% to base metal at room temperature and 500 0 C and almost 100% at 1000 0 C. Those of GTA welds in pure and 0.13% air mixed argon atmospheres were fairly lower than those in electron-beam welding for each testing temperature. (author)

Development of Oxide Dispersion Strengthened (ODS) Ferritic Steel Through Powder Forging

Science.gov (United States)

Kumar, Deepak; Prakash, Ujjwal; Dabhade, Vikram V.; Laha, K.; Sakthivel, T.

2017-04-01

Oxide dispersion strengthened (ODS) ferritic steels are candidates for cladding tubes in fast breeder nuclear reactors. In this study, an 18%Cr ODS ferritic steel was prepared through powder forging route. Elemental powders with a nominal composition of Fe-18Cr-2 W-0.2Ti (composition in wt.%) with 0 and 0.35% yttria were prepared by mechanical alloying in a Simoloyer attritor under argon atmosphere. The alloyed powders were heated in a mild steel can to 1473 K under flowing hydrogen atmosphere. The can was then hot forged. Steps of sealing, degassing and evacuation are eliminated by using powder forging. Heating ODS powder in hydrogen atmosphere ensures good bonding between alloy powders. A dense ODS alloy with an attractive combination of strength and ductility was obtained after re-forging. On testing at 973 K, a loss in ductility was observed in yttria-containing alloy. The strength and ductility increased with increase in strain rate at 973 K. Reasons for this are discussed. The ODS alloy exhibited a recrystallized microstructure which is difficult to achieve by extrusion. No prior particle boundaries were observed after forging. The forged compacts exhibited isotropic mechanical properties. It is suggested that powder forging may offer several advantages over the traditional extrusion/HIP routes for fabrication of ODS alloys.

Heated Hydro-Mechanical Deep Drawing of Magnesium Sheet Metal

Science.gov (United States)

Kurz, Gerrit

In order to reduce fuel consumption efforts have been made to decrease the weight of automobile constructions by increasing the use of lightweight materials. In this field of application magnesium alloys are important because of their low density. A promising alternative to large surfaced and thin die casting parts has been found in construction parts that are manufactured by sheet metal forming of magnesium. Magnesium alloys show a limited formability at room temperature. A considerable improvement of formability can be achieved by heating the material. Formability increases above a temperature of approximately T = 225 °C.

Study on shear strengthening of RC continuous T-beams using different layers of CFRP strips

Energy Technology Data Exchange (ETDEWEB)

Alferjani, M. B. S.; Samad, A. A. Abdul; Mohamad, Noridah [Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, Batu Pahat (Malaysia); Elrawaff, Blkasem S.; Elzaroug, Omer [Faculty of Civil Engineering Omar Al Mukhtar University, Bayda, Libya, Africa (Libya)

2015-05-15

Carbon fiber reinforced polymer (CFRP) laminates are externally bonded to reinforced concrete (RC) members to provide additional strength such as flexural, shear, etc. However, this paper presents the results of an experimental investigation for enhancing the shear capacity of reinforced concrete (RC) continuous T- beams using different layers of CFRP wrapping schemes. A total of three concrete beams were tested and various sheet configurations and layouts were studied to determine their effects on ultimate shear strength and shear capacity of the beams. One beam was kept as control beams, while other beams were strengthened with externally bonded CFRP strips with three side bonding and one or two layers of CFRP strips. From the test results, it was found that all schemes were found to be effective in enhancing the shear strength of RC beams. It was observed that the strength increases with the number of sheet layers provided the most effective strengthening for RC continuous T- beam. Beam strengthened using this scheme showed 23.21% increase in shear capacity as compared to the control beam. Two prediction models available in literature were used for computing the contribution of CFRP strips and compared with the experimental results.

Fracture toughness of oxide-dispersion strengthened copper

Energy Technology Data Exchange (ETDEWEB)

Alexander, D.J. [Oak Ridge National Lab., TN (United States)

1996-10-01

The fracture toughness of an oxide-dispersion strengthened copper alloy AL-15 has been examined at room temperature and 250{degrees}C, in air and in vacuum (< 10{sup {minus}6} torr). Increasing test temperature causes a significant decrease in the fracture toughness of this material, in either air or vacuum environments. In addition, specimens oriented in the T-L orientation (crack growth parallel to the extrusion direction) show significantly lower toughness than those in the L-T orientation (crack growth perpendicular to the extrusion direction).

Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si

Science.gov (United States)

Kennedy, J. R.; Gilman, P. S.; Zedalis, M. S.; Skinner, D. J.; Peltier, J. M.

1991-01-01

The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

A review of chromium, molybdenum, and tungsten alloys

International Nuclear Information System (INIS)

Klopp, W.D.

1975-01-01

The mechanical properties of chromium, molybdenum, and tungsten alloys are reviewed, with particular emphasis on high-temperature strength and low-temperature ductility. Precipitate strengthening is highly effective at 0.4-0.8 Tsub(m) in these metals, with HfC being most effective in tungsten and molybdenum, and Ta(B,C) most effective in chromium. Low-temperature ductility can be improved by alloying to promote rhenium ductilizing or solution softening. The low-temperature mechanical properties of these alloys appear related to electronic interactions rather than to the usual metallurgical considerations. (Auth.)

Design of Novel Precipitate-Strengthened Al-Co-Cr-Fe-Nb-Ni High-Entropy Superalloys

Science.gov (United States)

Antonov, Stoichko; Detrois, Martin; Tin, Sammy

2018-01-01

A series of non-equiatomic Al-Co-Cr-Fe-Nb-Ni high-entropy alloys, with varying levels of Co, Nb and Fe, were investigated in an effort to obtain microstructures similar to conventional Ni-based superalloys. Elevated levels of Co were observed to significantly decrease the solvus temperature of the γ' precipitates. Both Nb and Co in excessive concentrations promoted the formation of Laves and NiAl phases that formed either during solidification and remained undissolved during homogenization or upon high-temperature aging. Lowering the content of Nb, Co, or Fe prevented the formation of the eutectic type Laves. In addition, lowering the Co content resulted in a higher number density and volume fraction of the γ' precipitates, while increasing the Fe content led to the destabilization of the γ' precipitates. Various aging treatments were performed which led to different size distributions of the strengthening phase. Results from the microstructural characterization and hardness property assessments of these high-entropy alloys were compared to a commercial, high-strength Ni-based superalloy RR1000. Potentially, precipitation-strengthened high-entropy alloys could find applications replacing Ni-based superalloys as structural materials in power generation applications.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets

Directory of Open Access Journals (Sweden)

Tobias Gabriel

2017-03-01

Full Text Available Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co–28Cr–9W–1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM and scanning electron microscopy (SEM, combined with electron backscatter diffraction (EBSD and energy dispersive X-ray spectroscopy (EDX. Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

Science.gov (United States)

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-03-10

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

Energy Technology Data Exchange (ETDEWEB)

Dou, Peng, E-mail: doup@tsinghua.edu.cn [School of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko, E-mail: kimura@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kasada, Ryuta, E-mail: r-kasada@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Okuda, Takanari, E-mail: okuda.takanari@kki.kobelco.com [Kobelco Research Institute, 1-5-5 Takatsukadai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan); Inoue, Masaki, E-mail: inoue.masaki@jaea.go.jp [Advanced Nuclear System R& D Directorate, Japan Atomic Energy Agency, 4002 Narita, O-arai, Ibaraki 311-1393 (Japan); Ukai, Shigeharu, E-mail: s-ukai@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Ohnuki, Somei, E-mail: ohnuki@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Fujisawa, Toshiharu, E-mail: fujisawa@esi.nagoya-u.ac.jp [EcoTopia Science Institute, Nagoya University, Furo, Chikusa-ku, Nagoya 464-8603 (Japan); Abe, Fujio, E-mail: ABE.Fujio@nims.go.jp [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Jiang, Shan, E-mail: js93518@gmail.com [School of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Yang, Zhigang, E-mail: zgyang@tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Sciences and Engineering, Tsinghua University, Beijing 100084 (China)

2017-03-15

The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y{sub 2}O{sub 3}), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y{sub 2}O{sub 3}), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y{sub 2}Hf{sub 2}O{sub 7} oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y{sub 2}Hf{sub 2}O{sub 7} oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

Durability of reinforced concrete beams strengthened with fiber reinforced polymers under varying environmental conditions

International Nuclear Information System (INIS)

El-Sadani, R.A.M.G

2008-01-01

Fiber reinforced polymers (FRP) materials were adopted by the aerospace and marine industries, not only for their lightweight and high strength characteristics but also due to their tough and durable nature . As the engineering community has become more familiar with the performance advantages of these materials, new applications have been investigated and implemented. Researches and design guidelines concluded that externally bonded FRP to concrete elements could efficiently increase the capacity of RC elements. Long-term exposure to harsh environments deteriorates concrete and the need for repair and rehabilitation is evident. In order to accept these FRP materials, they must be evaluated for durability in harsh environments. An experimental program was conducted at the materials laboratory- faculty of engineering-Ain Shams university to study the durability of RC beams strengthened with FRP sheets and to compare them with un strengthened beams.The effect of gamma rays on FRP materials and concrete specimens bonded to FRP sheets were also investigated.

Porosity in fiber laser formation of 5A06 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Yu, Yang Chun; Wang, Chun Ming; Hu, Xi Yuan; Wang, Jun; Yu, Sheng Fu [HUST, Wuhan (China)

2010-05-15

The mechanism of porosity formation and its suppression methods in laser formation of aluminum alloy have been studied using a 4kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It was found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in the laser welding aluminum alloy. The filling wire increased the instability of the keyhole and weld pool, thus further increasing the amount of gas cavities in the joint. Prefabrication of a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken, and even completely eliminate the disturbance of the filling wire on the formation of keyhole. The gap can also provide a passage for the escape of the bubble. Thus, this method can greatly decrease the sheet's susceptibility to porosity. Moreover, for a thin sheet, if the power of the laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without porosity can also be obtained because closing the keyhole is almost impossible

Porosity in fiber laser formation of 5A06 aluminum alloy

International Nuclear Information System (INIS)

Yu, Yang Chun; Wang, Chun Ming; Hu, Xi Yuan; Wang, Jun; Yu, Sheng Fu

2010-01-01

The mechanism of porosity formation and its suppression methods in laser formation of aluminum alloy have been studied using a 4kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It was found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in the laser welding aluminum alloy. The filling wire increased the instability of the keyhole and weld pool, thus further increasing the amount of gas cavities in the joint. Prefabrication of a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken, and even completely eliminate the disturbance of the filling wire on the formation of keyhole. The gap can also provide a passage for the escape of the bubble. Thus, this method can greatly decrease the sheet's susceptibility to porosity. Moreover, for a thin sheet, if the power of the laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without porosity can also be obtained because closing the keyhole is almost impossible

Temperature-dependent transformation from whisker- to nanoparticle-strengthened composite interface in the Al2O3/Ag-based alloy system and mechanical properties of the joints

International Nuclear Information System (INIS)

Wang, Yifeng; Cao, Jian; Wang, Zhijie; Chen, Zhe; Song, Xiaoguo; Feng, Jicai

2015-01-01

Al 4 B 2 O 9 -whisker-coated Al 2 O 3 ceramics were bonded by AgCu–4.5 wt.%Ti alloy in vacuum. The microstructure of the whisker-coated Al 2 O 3 joints was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A continuous (Cu,Al) 3 Ti 3 O layer formed against the alloy at lower bonding temperatures, and a complex transition zone bordering the whiskers was observed, which consisted of Ag nanoparticles, titanium oxides, TiB 2 , (Cu,Al) 3 Ti 3 O nanoparticles and possible Ag 3 Al. As the bonding temperature increased, the Al 2 O 3 /AgCuTi interface was found to transform from whisker- to nanoparticle-strengthened composite region. Bend test results revealed that both the whiskers grown on Al 2 O 3 and the dispersive nanoscale products in the alloy played positive roles in improving the joint properties. The maximum bend strength of the whisker-coated Al 2 O 3 joints was 313 MPa at the bonding temperature of 820 °C. - Highlights: • Al 4 B 2 O 9 -whisker-coated Al 2 O 3 ceramics were bonded by AgCu–4.5 wt.%Ti alloy in vacuum. • Microstructures of whisker-coated Al 2 O 3 joints were investigated in detail. • Both whiskers and the dispersive nanoscale products can improve the joint properties. • The maximum bend strength of the whisker-coated Al 2 O 3 joints was 313 MPa.

Multi-Axial Deformation Setup for Microscopic Testing of Sheet Metal to Fracture

NARCIS (Netherlands)

Tasan, C.C.; Hoefnagels, J.P.M.; Dekkers, E.C.A.; Geers, M.G.D.

2012-01-01

While the industrial interest in sheet metal with improved specific-properties led to the design of new alloys with complex microstructures, predicting their safe forming limits and understanding their microstructural deformation mechanisms remain as significant challenges largely due to the

Mechanical properties and grindability of experimental Ti-Au alloys.

Science.gov (United States)

Takahashi, Masatoshi; Kikuchi, Masafumi; Okuno, Osamu

2004-06-01

Experimental Ti-Au alloys (5, 10, 20 and 40 mass% Au) were made. Mechanical properties and grindability of the castings of the Ti-Au alloys were examined. As the concentration of gold increased to 20%, the yield strength and the tensile strength of the Ti-Au alloys became higher without markedly deteriorating their ductility. This higher strength can be explained by the solid-solution strengthening of the a titanium. The Ti-40%Au alloy became brittle because the intermetallic compound Ti3Au precipitated intensively near the grain boundaries. There was no significant difference in the grinding rate and grinding ratio among all the Ti-Au alloys and the pure titanium at any speed.

Comparison of the Effects of Tool Geometry for Friction Stir Welding Thin Sheet Aluminum Alloys for Aerospace Applications

Science.gov (United States)

Merry, Josh; Takeshita, Jennifer; Tweedy, Bryan; Burford, Dwight

2006-01-01

In this presentation, the results of a recent study on the effect of pin tool design for friction stir welding thin sheets (0.040") of aluminum alloys 2024 and 7075 are provided. The objective of this study was to investigate and document the effect of tool shoulder and pin diameter, as well as the presence of pin flutes, on the resultant microstructure and mechanical properties at both room temperature and cryogenic temperature. Specifically, the comparison between three tools will include: FSW process load analysis (tool forces required to fabricate the welds), Static Mechanical Properties (ultimate tensile strength, yield strength, and elongation), and Process window documenting the range of parameters that can be used with the three pin tools investigated. All samples were naturally aged for a period greater than 10 days. Prior research has shown 7075 may require post weld heat treatment. Therefore, an additional pair of room temperature and cryogenic temperature samples was post-weld aged to the 7075-T7 condition prior to mechanical testing.

Genetic design and characterization of novel ultra-high-strength stainless steels strengthened by Ni3Ti intermetallic nanoprecipitates

International Nuclear Information System (INIS)

Xu, W.; Rivera-Diaz-del-Castillo, P.E.J.; Wang, W.; Yang, K.; Bliznuk, V.; Kestens, L.A.I.; Zwaag, S. van der

2010-01-01

A general computational alloy design approach based on thermodynamic and physical metallurgical principles, and coupled with a genetic optimization scheme, is presented. The method is applied to the design of new ultra-high-strength maraging stainless steels strengthened by Ni 3 Ti intermetallics. In the first design round, the alloy composition is optimized on the basis of precipitate formation at a fixed ageing temperature without considering other steps in the heat treatment. In the second round, the alloy is redesigned, applying an integrated model which allows for the simultaneous optimization of alloy composition and the ageing temperature as well as the prior austenitization temperature. The experimental characterizations of prototype alloys clearly demonstrate that alloys designed by the proposed approach achieve the desired microstructures.