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Sample records for temperature intermetallic alloys

  1. Ultrahigh temperature intermetallic alloys

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    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  2. High-temperature ordered intermetallic alloys V

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    Baker, I. (ed.) (Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering); Darolia, R. (ed.) (GE Aircraft Engines, Cincinnati, OH (United States)); Whittenberger, J.D. (ed.) (NASA, Cleveland, OH (United States). Lewis Research Center); Yoo, M.H. (ed.) (Oak Ridge National Lab., TN (United States))

    1993-01-01

    These proceedings represent the written record of the High-Temperature Ordered Intermetallic Alloys 5 Symposium which was held in conjunction with the 1992 Fall Materials Research Society meeting in Boston, Massachusetts. This symposium, which was the fifth in the series originated by C.C Koch, C.T. Liu and N.S. Stoloff in 1984, was very successful with 86 oral presentations over four days, and approximately 140 posters given during two lively evening sessions. Such a response, in view of the increasing number of conferences being held on intermetallics each year, reveals the continued high regard for this series of symposia. Individual papers have been processed separately for inclusion in the appropriate data bases.

  3. Advances in nanoscale alloys and intermetallics: low temperature solution chemistry synthesis and application in catalysis.

    Science.gov (United States)

    Jana, Subhra

    2015-11-21

    Based on the bottom-up chemistry techniques, the size, shape, and composition controlled synthesis of nanoparticles can now be achieved uniformly, which is of great importance to the nanoscience community as well as in modern catalysis research. The low-temperature solution-phase synthesis approach represents one of the most attractive strategies and has been utilized to synthesize nanoscale metals, alloys and intermetallics, including a number of new metastable phases. This perspective will highlight the solution-based nanoparticle synthesis techniques, a low-temperature platform, for the synthesis of size and shape-tunable nanoscale transition metals, alloys, and intermetallics from the literature, keeping a focus on the utility of these nanomaterials in understanding the catalysis. For each solution-based nanoparticle synthesis technique, a comprehensive overview has been given for the reported nanoscale metals, alloys, and intermetallics, followed by critical comments. Finally, their enhanced catalytic activity and durability as novel catalysts have been discussed towards several hydrogenation/dehydrogenation reactions and also for different inorganic to organic reactions. Hence, the captivating advantages of this controllable low-temperature solution chemistry approach have several important implications and together with them this approach provides a promising route to the development of next-generation nanostructured metals, alloys, and intermetallics since they possess fascinating properties as well as outstanding catalytic activity.

  4. High temperature corrosion performance of FeAl intermetallic alloys in molten salts

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    Amaya, M.; Espinosa-Medina, M.A.; Porcayo-Calderon, J.; Martinez, L.; Gonzalez-Rodriguez, J.G

    2003-05-25

    The corrosion performance of FeAl base intermetallic alloys fabricated by spray-atomization and deposition during their immersion in molten sodium metavanadate (NaVO{sub 3}), 80% (wt.%) sodium pentoxide (V{sub 2}O{sub 5}) +20% sodium sulfate (Na{sub 2}SO{sub 4}) and pure Na{sub 2}SO{sub 4} in the temperature range of 600-1000 deg. C during 200 h was investigated. The experiments were realized by the weight loss method in the intermetallic alloys of composition FeAl40(at.%), FeAl40+0.1B and FeAl40+0.1B+10Al{sub 2}O{sub 3}. In all cases, the FeAl40+0.1B+10Al{sub 2}O{sub 3} alloy showed the best corrosion resistance in the temperatures interval studied here. This behavior was discussed in terms of the formation of a protective Al{sub 2}O{sub 3} layer and its dissolution by vanadate phases and internal sulfidation in the case of experiments carried out in pure Na{sub 2}SO{sub 4}. The morphology of the external layers and the corrosion products formed during the tests revealed that the corrosion rate of this type alloy depends on the corrosion compounds that are formed and the development of protective alumina scales.

  5. Advanced ordered intermetallic alloy deployment

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    Liu, C.T.; Maziasz, P.J.; Easton, D.S. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  6. Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

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    Vijay Vasudevan

    2008-03-31

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. In the first part of this project, the compression creep behavior of a Mo-8.9Si-7.71B (in at.%) alloy, at 1100 and 1200 C was studied, whereas in the second part of the project, the constant strain rate compression behavior at 1200, 1300 and 1400 C of a nominally Mo-20Si-10B (in at.%) alloy, processed such as to yield five different {alpha}-Mo volume fractions ranging from 5 to 46%, was studied. In order to determine the deformation and damage mechanisms and rationalize the creep/high temperature deformation data and parameters, the microstructure of both undeformed and deformed samples was characterized in detail using x-ray diffraction, scanning electron microscopy (SEM) with back scattered electron imaging (BSE) and energy dispersive x-ray spectroscopy (EDS), electron back scattered diffraction (EBSD)/orientation electron microscopy in the SEM and transmission electron microscopy (TEM). The microstructure of both alloys was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The values of stress exponents and activation energies, and their dependence on microstructure were determined. The data suggested the operation of both dislocation as well as diffusional mechanisms, depending on alloy, test temperature, stress level and microstructure. Microstructural observations of post-crept/deformed samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. TEM observations revealed the presence of recrystallized {alpha}-Mo grains and sub-grain boundaries composed of dislocation arrays within the grains (in Mo-8.9Si-7.71B) or fine sub-grains with a high density of b = 1/2<111> dislocations (in Mo-20Si-10B), which

  7. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    Science.gov (United States)

    Liu, K.; Chen, X.-G.

    2016-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  8. Titanium aluminide intermetallic alloys with improved wear resistance

    Science.gov (United States)

    Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

    2014-07-08

    The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

  9. Thermal stability and elevated temperature mechanical properties of electroslag remelted Fe-16wt.%Al-(0.14-0.5)wt.%C intermetallic alloys

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    Baligidad, R.G. [Defence Metallurgical Research Lab., Hyderabad (India); Prakash, U. [Defence Metallurgical Research Lab., Hyderabad (India); Radha Krishna, A. [Defence Metallurgical Research Lab., Hyderabad (India)

    1997-07-01

    Addition of carbon in the range of 0.14-0.5 wt.% to the Fe{sub 3}Al-based intermetallic Fe-16wt.%Al (Fe-28at.%Al) alloy results in the formation of a thermally stable dispersion of Fe{sub 3}AlC carbide phase. The volume fraction of these precipitates increases with increase in carbon content. Processing of these alloys through a combination of air induction melting and electroslag remelting leads to enhanced elevated temperature mechanical properties compared to those reported for the low (<0.01 wt.%) carbon alloys with similar Al contents. Enhancement of up to 30% in elevated temperature yield strength was observed at the test temperatures (600, 700 and 800 C) used. The improvement in mechanical properties may be attributed to the presence of strengthening Fe{sub 3}AlC phase as well as the interstitial carbon present in the alloy matrix. The addition of carbon also leads to improved room temperature mechanical properties in contrast with other alloying additions (such as Mo, Ti and Si) used for enhancing elevated temperature properties of Fe{sub 3}Al-based intermetallic alloys. It is suggested that carbon may be an important alloying addition to these alloys. (orig.)

  10. High temperature tensile and creep properties of a cast AIM and ESR intermetallic alloy based on Fe{sub 3}Al

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    Baligidad, R.G. [Defence Metallurgical Research Lab., Hyderabad (India); Prakash, U. [Defence Metallurgical Research Lab., Hyderabad (India); Radhakrishna, A. [Defence Metallurgical Research Lab., Hyderabad (India)

    1997-07-15

    A high carbon intermetallic Fe-16 wt.% A1-1.1 wt.% C alloy based on Fe{sub 3}Al was melted under a flux cover by air induction melting (AIM). The AIM ingots exhibited excellent elevated temperature tensile properties in the temperature range (600-800 C) studied, in contrast to poor properties expected in ingots melted without a flux cover. Subsequent processing of the AIM ingots through electroslag remelting (ESR) resulted in improvement in ductility. However, the AIM ingots exhibited better creep properties because of their coarser gain structure. The presence of large (1.1 wt.%) amount of carbon in the alloy resulted in significant improvement in elevated temperature tensile as well as creep properties over those reported for Fe{sub 3}Al based intermetallic alloys with lower carbon contents. These improvements in mechanical properties are attributed to the extensive precipitation of Fe{sub 3}AlC phase and to the formation of a duplex Fe{sub 3}Al-Fe{sub 3}AlC structure at such high levels of carbon. It is suggested that carbon may be an important alloying addition to Fe{sub 3}Al-based intermetallic alloys. (orig.)

  11. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF Mo-Si-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

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    Vijay K. Vasudevan

    2005-12-21

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy at 1100 and 1200 C were studied and related to the deformation mechanisms through electron microscopy observations of microstructural changes and deformation structures. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. Results of compressive creep tests at 1200 and 1100 C showed that the creep rates were quite high at stress levels between 250 and 500 MPa, Two minima in the creep strain rate versus strain data were noted, one at small strain values and the second at much larger strains. A stress exponent of 4.26 was obtained upon plotting the strain rate corresponding to the first minima versus stress, which suggests that dislocation climb and glide dominate the creep process in the early stages. On the other hand, the large strain, minimum creep rate versus stress data gave a stress exponent of {approx}1.18, which indicates diffusional mechanisms and recrystallization dominate the later stages of the creep process. At 1100 C, a stress exponent of 2.26 was obtained, which suggests that both diffusional and dislocation mechanisms contribute to the creep strain. Based on the minimum creep rate data at 1100 C and 1200 C, the activation energy for creep was determined to be 525 kJ/mole, which is somewhat higher than that reported for self diffusion in {alpha}-Mo. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. In addition, TEM observations revealed the presence of recrystallized grains and sub-grain boundaries composed of dislocation arrays

  12. Wear deformation of ordered Fe-Al intermetallic alloys

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    Maupin, H.E. (US Bureau of Mines, Albany Research Center, OR (United States)); Wilson, R.D. (US Bureau of Mines, Albany Research Center, OR (United States)); Hawk, J.A. (US Bureau of Mines, Albany Research Center, OR (United States))

    1993-04-13

    The Bureau of Mines conducted abrasive wear research on DO[sub 3] ordered and disordered Fe[sub 3]Al intermetallics. The effect of abrasion on these alloys was studied through mixroscopy, X-ray diffraction and hardness measurements. The region near the wear surface undergoes dynamic recrystallization, i.e. the original microstructural morphology of micron-size grains is replaced by one with nanosize grains. Abrasion of the Fe[sub 3]Al alloys also results in a loss of the DO[sub 3] ordering in the wear surface region. The bulk temperature rise of the specimen during abrasion was approximately 28 C which is insufficient to cause recrystallization in these alloys. Therefore, the flash temperature due to interface frictional heating is considered more important than the bulk temperature when considering dynamic recrystallization as the transformation mechanism in the near wear surface region. (orig.)

  13. ON DEVELOPMENT OF OPTIMAL METALLURGICAL PROCESS FOR PREPARATION OF A NEW GENERATION OF INTERMETALLIC ALLOYS

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    Viliam Hrnčiar

    2009-06-01

    Full Text Available Intermetallic TiAl based alloys are used in extreme conditions, e.g. high temperature, aggressive atmosphere and combined high temperature mechanical loading. The contribution deals with development and optimization of plasma melting metallurgical process in new developed crystallizer with rotational and axial movement of melt, for preparation of new intermetallic alloys based on Ti-(45-48Al-(1-10Ta (at.%. The melting process parameters and their influence to final microstructure and properties of alloys are discussed. The aim of this work is to produce alloys with lower number of technological steps necessary to achieve chemical composition, homogeneity and purity as well.

  14. Corrosion of Mechanically Alloyed Nanostructured FeAl Intermetallic Powders

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    A. Torres-Islas

    2012-01-01

    Full Text Available The corrosion behavior of the Fe40Al60 nanostructured intermetallic composition was studied using electrochemical impedance spectroscopy (EIS and linear polarization resistance (LPR techniques with an innovative electrochemical cell arrangement. The Fe40Al60 (% at intermetallic composition was obtained by mechanical alloying using elemental powders of Fe (99.99% and Al (99.99%. All electrochemical testing was carried out in Fe40Al60 particles that were in water with different pH values. Temperature and test time were also varied. The experimental data was analyzed as an indicator of the monitoring of the particle corrosion current density icorr. Different oxide types that were formed at surface particle were found. These oxides promote two types of surface corrosion mechanisms: (i diffusion and (ii charge transfer mechanisms, which are a function of icorr behavior of the solution, pH, temperature, and test time. The intermetallic was characterized before and after each test by transmission electron microscopy. Furthermore, the results show that at the surface particles uniform corrosion takes place. These results confirm that it is possible to sense the nanoparticle corrosion behavior by EIS and LPR conventional electrochemical techniques.

  15. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    Science.gov (United States)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  16. Magnetic hysteresis in the Cu-Al-Mn intermetallic alloy: experiments and modeling

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    Obrado, Eduard; Vives, Eduard; Planes, Antoni

    1999-01-01

    We study isothermal magnetization processes in the Cu-Al-Mn intermetallic alloy. Hysteresis is observed at temperatures below the spin-freezing of the system. The characteristics of the hysteresis cycles as a function of temperature and Mn content (magnetic element) are obtained. At low temperature (5 K) a change from smooth to sharp cycles is observed with increasing Mn content, which is related to the decrease of configurational disorder. We also study a zero-temperature site-diluted Ising ...

  17. Tribological properties of the Fe-Al intermetallic alloys after annealing

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    K. Garbala

    2011-04-01

    Full Text Available In paper researching results of tribological proprieties Fe3Al intermetallic alloys after annealing are presented. Studies were conducted in the following environments: a water; an air and oil. For investigation purposes the tribotester pin-on-disk type with the contrsample made of steel 40H quenched and tempered was used. Tests were carried out with the following process parameters: pressure p = 2MPa and linear velocity (circuital V = 0.46m/s. It was noted, that intermetallic samples with the small distinction in chemical compositions, annealed at different temperatures showed a large difference in the quantity of material loss in the all tested environments. Appropriately selected parameters of the intermetallic alloys annealing, provide their greater resistance to abrasion in the air and oil environments than in the case of steel.

  18. Microstructure and high temperature oxidation resistance of in-situ synthesized TiN/Ti{sub 3}Al intermetallic composite coatings on Ti6Al4V alloy by laser cladding process

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    Liu, Hongxi, E-mail: piiiliuhx@sina.com; Zhang, Xiaowei; Jiang, Yehua; Zhou, Rong

    2016-06-15

    High temperature anti-oxidation TiN/Ti{sub 3}Al intermetallic composite coatings were fabricated with the powder and AlN powder on Ti6Al4V titanium alloy surface by 6 kW transverse-flow CO{sub 2} laser apparatus. The chemical composition, morphology and microstructure of the TiN/Ti{sub 3}Al composite coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high temperature oxidation resistance of TiN/Ti{sub 3}Al coating, the isothermal oxidation test was performed in a high temperature resistance furnace at 600 °C and 800 °C, respectively. The result shows that the composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like or dendrites), with an even distribution in Ti{sub 3}Al matrix. It indicates that a physical and chemical reaction between Ti powder and AlN powder has completely occurred under the laser irradiation condition. In addition, the microhardness of the TiN/Ti3Al intermetallic composite coating is 3.4 times higher than that of the Ti6Al4V alloy substrate and reaches 844 HV{sub 0.2}. The high temperature oxidation behavior test reveals that the high temperature oxidation resistance of TiN/Ti{sub 3}Al composite coating is much better than that of titanium alloy substrate. The excellent high temperature oxidation resistance of TiN/Ti{sub 3}Al intermetallic composite coating is attributed to the formation of reinforced phases TiN, Al{sub 2}O{sub 3} and TiO{sub 2}. The laser cladding TiN/Ti{sub 3}Al intermetallic composite coating is anticipated to be a promising high temperature oxidation resistance coating for Ti6Al4V alloy. - Highlights: • In-situ TiN/Ti{sub 3}Al composite coating was synthesized on Ti6Al4V alloy by laser cladding. • The influence of Ti and AlN molar ratio on the microstructure of the coating was studied. • The TiN/Ti{sub 3}Al intermetallic

  19. Phase transformations in intermetallic phases in zirconium alloys

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    Filippov, V. P., E-mail: vpfilippov@mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Kirichenko, V. G. [Kharkiv National Karazin University (Ukraine); Salomasov, V. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Khasanov, A. M. [University of North Carolina – Asheville, Chemistry Department (United States)

    2017-11-15

    Phase change was analyzed in intermetallic compounds of zirconium alloys (Zr – 1.03 at.% Fe; Zr – 0.51 at.% Fe; Zr – 0.51 at.% Fe – M(M = Nb, Sn). Mössbauer spectroscopy on {sup 57}Fe nuclei in backscattering geometry with the registration of the internal conversion electrons and XRD were used. Four types of iron bearing intermetallic compounds with Nb were detected. A relationship was found between the growth process of intermetallic inclusions and segregation of these phases. The growth kinetics of inclusions possibly is not controlled by bulk diffusion, and a lower value of the iron atom’s activation energy of migration can be attributed to the existence of enhanced diffusion paths and interface boundaries.

  20. Phase transformations in intermetallic phases in zirconium alloys

    Science.gov (United States)

    Filippov, V. P.; Kirichenko, V. G.; Salomasov, V. A.; Khasanov, A. M.

    2017-11-01

    Phase change was analyzed in intermetallic compounds of zirconium alloys (Zr - 1.03 at.% Fe; Zr - 0.51 at.% Fe; Zr - 0.51 at.% Fe - M(M = Nb, Sn). Mössbauer spectroscopy on 57Fe nuclei in backscattering geometry with the registration of the internal conversion electrons and XRD were used. Four types of iron bearing intermetallic compounds with Nb were detected. A relationship was found between the growth process of intermetallic inclusions and segregation of these phases. The growth kinetics of inclusions possibly is not controlled by bulk diffusion, and a lower value of the iron atom's activation energy of migration can be attributed to the existence of enhanced diffusion paths and interface boundaries.

  1. Microstructure and Tribological Properties of Mo–40Ni–13Si Multiphase Intermetallic Alloy

    Science.gov (United States)

    Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong

    2016-01-01

    Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo–40Ni–13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo–Ni–Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy—including wear resistance, friction coefficient, and metallic tribological compatibility—were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear. PMID:28774106

  2. Determination of Charge Component Composition in Self-Propagating High-Temperature Synthesis of Intermetallic Compounds

    Science.gov (United States)

    Evtushenko, A. T.; Lebedeva, O. A.; Torbunov, S. S.

    2005-05-01

    A method for determining the component composition of the charge for the self-propagating high-temperature synthesis of intermetallic compounds from the maximum value of the emitted heat in the combustion of thermit, which is required for melting the alloying components, is suggested. The mass composition of the alloying components is determined by solving a closed system of algebraic equations represented by regression equations derived from the results of physical experiment for obtaining specific properties of the intermetallic compound. Theoretical computations are partially confirmed by experimental results.

  3. Directional Solidification of AlSi Alloys with Fe Intermetallic Phases

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    Mikołajczak P.

    2014-03-01

    Full Text Available Directional solidification technique is an important research instrument to study solidification of metals and alloys. In the paper the model [6,7,8] of directional solidification in special Artemis-3 facility was presented. The current work aimed to propose the ease and efficient way in calibrating the facility. The introduced M coefficient allowed effective calibration and implementation of defined thermal conditions. The specimens of AlSi alloys with Fe-rich intermetallics and especially deleterious β-Al5FeSi were processed by controlled solidification velocity, temperature gradient and cooling rate.

  4. Iron Intermetallic Phases in the Alloy Based on Al-Si-Mg by Applying Manganese

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    Podprocká R.

    2017-09-01

    Full Text Available Manganese is an effective element used for the modification of needle intermetallic phases in Al-Si alloy. These particles seriously degrade mechanical characteristics of the alloy and promote the formation of porosity. By adding manganese the particles are being excluded in more compact shape of “Chinese script” or skeletal form, which are less initiative to cracks as Al5FeSi phase. In the present article, AlSi7Mg0.3 aluminium foundry alloy with several manganese content were studied. The alloy was controlled pollution for achieve higher iron content (about 0.7 wt. % Fe. The manganese were added in amount of 0.2 wt. %, 0.6 wt. %, 1.0 wt. % and 1.4 wt. %. The influence of the alloying element on the process of crystallization of intermetallic phases were compared to microstructural observations. The results indicate that increasing manganese content (> 0.2 wt. % Mn lead to increase the temperature of solidification iron rich phase (TAl5FeSi and reduction this particles. The temperature of nucleation Al-Si eutectic increase with higher manganese content also. At adding 1.4 wt. % Mn grain refinement and skeleton particles were observed.

  5. The role of ALCHEMI in understanding the properties of ordered intermetallic alloys

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    Anderson, I.M.

    1998-11-01

    After one and one-half decades of development, ALCHEMI is approaching the status of an established analytical technique. Many of the problems that have plagued ALCHEMI, especially for the analysis of ordered intermetallic alloys, are now well understood, and accurate site-distributions can be extracted from a variety of intermetallic alloys. This paper begins with an overview of the factors that can lead to large systematic errors or gross misinterpretations of ALCHEMI data, with illustrations from a variety of ordered intermetallic alloys. The paper concludes with a discussion of ALCHEMI in the broader context of understanding the properties of ordered intermetallic alloys. The results of systematic studies are used to illustrate the role of ALCHEMI in determining the competing effects of thermodynamic and kinetic factors during alloy processing and the correlation of alloy properties with the atomic site distributions on which the properties ultimately depend.

  6. Mechanical Behavior and Fracture Properties of NiAl Intermetallic Alloy with Different Copper Contents

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    Tao-Hsing Chen

    2016-03-01

    Full Text Available The deformation behavior and fracture characteristics of NiAl intermetallic alloy containing 5~7 at% Cu are investigated at room temperature under strain rates ranging from 1 × 10−3 to 5 × 103 s−1. It is shown that the copper contents and strain rate both have a significant effect on the mechanical behavior of the NiAl alloy. Specifically, the flow stress increases with an increasing copper content and strain rate. Moreover, the ductility also improves as the copper content increases. The change in the mechanical response and fracture behavior of the NiAl alloy given a higher copper content is thought to be the result of the precipitation of β-phase (Ni,CuAl and γ'-phase (Ni,Cu3Al in the NiAl matrix.

  7. Application of feal intermetallic phase matrix based alloys in the turbine components of a turbocharger

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    J. Cebulski

    2015-01-01

    Full Text Available This paper presents a possible application of the state-of-the-art alloys based on the FeAl intermetallic phases as materials for the manufacture of heat-proof turbine components in an automobile turbocharger. The research was aimed at determining the resistance to corrosion of Fe40Al5CrTiB alloy in a gaseous environment containing 9 % O2 + 0,2 % HCl + 0,08 % SO2 + N2. First the kinetics of corrosion processes for the considered alloy were determined at the temperatures of 900 °C, 1 000 °C and 1 100 °C, which was followed by validation under operating conditions. To do so, the tests were carried out over a distance of 20 000 km. The last stage involved examination of the surfaces after the test drive. The obtained results are the basis for further research in this field.

  8. 3D study of intermetallics and their effect on the corrosion morphology of rheocast aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Mingo, B. [Departamento de Ciencia de Materiales, Facultad de Ciencias Químicas, Universidad Complutense, 28040, Madrid (Spain); Arrabal, R., E-mail: rarrabal@ucm.es [Departamento de Ciencia de Materiales, Facultad de Ciencias Químicas, Universidad Complutense, 28040, Madrid (Spain); Pardo, A.; Matykina, E. [Departamento de Ciencia de Materiales, Facultad de Ciencias Químicas, Universidad Complutense, 28040, Madrid (Spain); Skeldon, P. [Corrosion and Protection Group, School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2016-02-15

    In the present study, the effect of heat treatment T6.1 on the microstructure and corrosion behaviour of rheocast aluminium alloy A356 is investigated on the basis of 2D/3D characterization techniques and electrochemical and SKPFM measurements. Heat treatment strengthens the α-Al matrix, modifies the intermetallic particles and spheroidizes eutectic Si. These changes do not modify significantly the corrosion behaviour of the alloy. 3D SEM-Tomography clearly shows that the corrosion advances in the shape of narrow paths between closely spaced intermetallics without a major influence of eutectic Si. - Highlights: • T6.1 spheroidizes Si, strengthens the matrix and modifies the intermetallics. • Electrochemical behaviour of untreated and heat-treated alloys is similar. • 3D SEM-Tomography provides additional information on the corrosion morphology. • Corrosion advances as paths between intermetallics with little influence of Si.

  9. Intermetallic particles-induced pitting corrosion in 6061-T651 aluminium alloy

    CSIR Research Space (South Africa)

    Mutombo, K

    2011-07-01

    Full Text Available -Induced Pitting Corrosion in 6061-T651 Aluminium Alloy Kalenda Mutombo Council for Scientific and Industrial Research (CSIR), South Africa kmutombo@csir.co.za Keywords: pitting corrosion, 6061-T651 aluminium alloy, intermetallic particles, 3.5% Na... extrudability, reasonable weldability and good corrosion resistance. This alloy finds widespread application in ship building and in the fabrication of tank containers for transporting various liquids. 6061-T651 aluminium alloy is, however, prone to pitting...

  10. Intermetallic Nickel-Titanium Alloys for Oil-Lubricated Bearing Applications

    Science.gov (United States)

    DellaCorte, C.; Pepper, S. V.; Noebe, R.; Hull, D. R.; Glennon, G.

    2009-01-01

    An intermetallic nickel-titanium alloy, NITINOL 60 (60NiTi), containing 60 wt% nickel and 40 wt% titanium, is shown to be a promising candidate material for oil-lubricated rolling and sliding contact applications such as bearings and gears. NiTi alloys are well known and normally exploited for their shape memory behavior. When properly processed, however, NITINOL 60 exhibits excellent dimensional stability and useful structural properties. Processed via high temperature, high-pressure powder metallurgy techniques or other means, NITINOL 60 offers a broad combination of physical properties that make it unique among bearing materials. NITINOL 60 is hard, electrically conductive, highly corrosion resistant, less dense than steel, readily machined prior to final heat treatment, nongalling and nonmagnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Further, NITINOL 60 has shown remarkable tribological performance when compared to other aerospace bearing alloys under oil-lubricated conditions. Spiral orbit tribometer (SOT) tests were conducted in vacuum using NITINOL 60 balls loaded between rotating 440C stainless steel disks, lubricated with synthetic hydrocarbon oil. Under conditions considered representative of precision bearings, the performance (life and friction) equaled or exceeded that observed with silicon nitride or titanium carbide coated 440C bearing balls. Based upon this preliminary data, it appears that NITINOL 60, despite its high titanium content, is a promising candidate alloy for advanced mechanical systems requiring superior and intrinsic corrosion resistance, electrical conductivity and nonmagnetic behavior under lubricated contacting conditions.

  11. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    scatter observed in life at low strain ranges (figure 1). It has been suggested that strict control over cleanliness of the powder needs to be exercised in order to improve the fatigue life in alloys processed by the HP route. Comparative evaluation of fatigue life of NiAl and the lives of various turbine disk and blade alloys at ...

  12. Synthesis, shape control, and methanol electro-oxidation properties of Pt-Zn alloy and Pt3Zn intermetallic nanocrystals.

    Science.gov (United States)

    Kang, Yijin; Pyo, Jun Beom; Ye, Xingchen; Gordon, Thomas R; Murray, Christopher B

    2012-06-26

    We report the first synthesis of highly monodisperse Pt(3)Zn nanocrystals (NCs). Shape-controlled synthesis generates cubic and spherical Pt-Zn NCs. Reaction temperature is the key to incorporate Zn into Pt, even in the absence of a strong reducing agent. The Pt-Zn NCs are active toward methanol oxidation, with the spherical NCs exhibiting higher activity than the cubic NCs. The Pt-Zn alloy phase can be transformed into the Pt(3)Zn intermetallic phase, upon annealing. The intermetallic Pt(3)Zn shows better performance than the alloy phase Pt-Zn. Besides the activity toward methanol oxidation, Pt-Zn NCs show excellent poisoning tolerance. With activities comparable to the commercial Pt catalyst, enhanced poisoning tolerance and lower cost, Pt-Zn and Pt(3)Zn NCs are a promising new family of catalysts for direct methanol fuel cells.

  13. Solidification processing of intermetallic Nb-Al alloys

    Science.gov (United States)

    Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

    1992-01-01

    Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

  14. Effects of iron on intermetallic compound formation in scandium modified Al–Si–Mg Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Patakham, Ussadawut [National Metal and Materials Technology Center, National Science and Technology Development Agency, 114 Thailand Science Park, Klong Nueng, Klong Luang, Pathumthani 12120 (Thailand); Limmaneevichitr, Chaowalit, E-mail: chaowalit.lim@mail.kmutt.ac.th [Production Engineering Department, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, 126 Pracha-Utid Rd., Bangmod, Tungkhru, Bangkok 10140 (Thailand)

    2014-12-15

    Highlights: • Iron reduces the modification effects of scandium in Al–Si–Mg alloys. • Morphologies of Sc-rich intermetallic phases vary with Fe and Sc contents and the cooling rates. • Sc neutralizes effects of Fe by changing Fe-rich intermetallic phases from platelets to more cubic. - Abstract: In general, iron has a strong tendency to dissolve in molten aluminum. Iron has very low solid solubility in aluminum–silicon casting alloys, so it will form intermetallic compounds that cause detrimental effects on mechanical properties. In this work, the effects of iron on intermetallic compound formations in scandium modified Al–Si–Mg alloys were studied. There were two levels of iron addition (0.2 and 0.4 wt.%) and two levels of scandium addition (0.2 and 0.4 wt.%). We found that the effects of scandium modification decreased with increasing iron addition. The morphologies of the complex intermetallic compounds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques. It was found that scandium changes the morphology of Fe-rich intermetallic compounds from β-phase (plate-like) to α-phase, which reduces the harmful effects of β-phase.

  15. The Effect of Aluminum Content on the Microstructure and Cavitation Wear of Feal Intermetallic Alloys

    Directory of Open Access Journals (Sweden)

    Jasionowski Robert

    2014-03-01

    Full Text Available Intermetallic-based alloys (so called intermetallics of the Fe-Al binary system are modern construction materials, which in recent decades have found application in many branches of the power, chemical and automotive industries. High resistance of FeAl based alloys to cavitational erosion results first of all from their high hardness in the as-cast state, large compressive stresses in the material, as well as homogeneous structure. In the present paper, the effect of aluminum content on the microstructure, texture and strain implemented upon cavitation wear of FeAl intermetallic alloys, have been analyzed by field emission gun scanning electron microscopy (FEG SEM and electron backscatter diffraction (EBSD analysis. Obtained results of structural characterization indicates that with increasing aluminium content effects of orientation randomization (weakening of //ND casting texture, grain refinement and rising of mechanical strenght (and so cavitational resistance take place.

  16. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    Science.gov (United States)

    Raj, S. V.

    2015-03-01

    Thermal expansion measurements were conducted on hot-pressed CrSi2, TiSi2, WSi2 and a two-phase Cr-Mo-Si intermetallic alloy between 303 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (Δ L/ L 0)thermal, varied with the absolute temperature, T, as where, A, B, C, and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from first heat-up cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  17. Investigations of intermetallic alloy hydriding mechanisms. Annual progress report, May 1 1979-April 30, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Livesay, B.R.; Larsen, J.W.

    1980-05-01

    Investigations are being conducted on mechanisms involved with the hydrogen-metal interactions which control the absorption and desorption processes in intermetallic compounds. The status of the following investigations is reported: modeling of hydride formation; microbalance investigations; microstructure investigations; flexure experiments; resistivity experiments; and nuclear backscattering measurements. These investigations concern fundamental hydrogen interaction mechanisms involved in storage alloys.

  18. Low-temperature solution synthesis of the non-equilibrium ordered intermetallic compounds Au3Fe, Au3Co, and Au3Ni as nanocrystals.

    Science.gov (United States)

    Vasquez, Yolanda; Luo, Zhiping; Schaak, Raymond E

    2008-09-10

    Alloys and intermetallic compounds of Au with the 3d transition metals Fe, Co, and Ni are nonequilibrium phases that have many useful potential applications as catalytic, magnetic, optic, and multifunctional magneto-optic materials. However, the atomically ordered Au-M (M = Fe, Co, Ni) intermetallics are particularly elusive from a synthetic standpoint. Here we report the low-temperature solution synthesis of the L12 (Cu3Au-type) intermetallic compounds Au3Fe, Au3Co, and Au3Ni using n-butyllithium as a reducing agent. Reaction pathway studies for the Au3Co system indicate that Au nucleates first, followed by Co incorporation to form the intermetallic. The nonequilibrium intermetallic nanocrystals have been characterized by powder XRD, TEM, EDS, selected area electron diffraction, and nanobeam electron diffraction, which collectively confirm the compositions and superlattice structures.

  19. High temperature fatigue behaviour of intermetallics

    Indian Academy of Sciences (India)

    There would be considerable benefits in developing new structural materials where high use temperatures and strength coupled with low density are minimum capabilities. Nickel and titanium aluminides exhibit considerable potential for near-term application in various branches of modern industry due to the number of ...

  20. (Nano-)mechanical properties of intermetallic phases in the Fe-Mo system at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Schroeders, Sebastian; Korte-Kerzel, Sandra [Institut fuer Metallkunde und Metallphysik, RWTH Aachen University (Germany)

    2015-07-01

    Topologically close packed (TCP) intermetallic phases which precipitate in nickel-base superalloys are suspected to cause a deterioration of the mechanical properties of the γ - γ* matrix. Although the existing intermetallics, namely Laves-, R-, sigma- and mue-phases are well understood in terms of their structure, their mechanical properties have still not been investigated in detail due to their size and pronounced brittleness. In order to investigate the plastic deformation behavior of these phases, but exclude the effect of complex phase composition in the first instance, the Fe-Mo system was chosen as a model system, where all phases are available as binary alloys. Using nanomechanical testing methods like nanoindentation and micropillar-compression, the experimental challenges of high brittleness and anisotropy encountered in conventional testing can be disregarded and plastic deformation can be achieved due to the confining pressure in nanoindentation and the reduction in specimen size in microcompression. This work aims to examine the mechanical properties such as elastic modulus, yield and flow stress of intermetallic Fe-Mo phases over a range of temperatures. To this end, tests were performed in vacuum. Based on this type of study it is envisaged to form a better understanding of the way hard TCP precipitates influence the performance of superalloys.

  1. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts

    Directory of Open Access Journals (Sweden)

    Rodiansono Rodiansono

    2015-07-01

    Full Text Available A bulk structure of inexpensive intermetallic nickel-tin (Ni-Sn alloys catalysts demonstrated highly selective in the hydrogenation of levulinic acid in water into g-valerolactone. The intermetallic Ni-Sn catalysts were synthesized via a very simple thermochemical method from non-organometallic precursor at low temperature followed by hydrogen treatment at 673 K for 90 min. The molar ratio of nickel salt and tin salt was varied to obtain the corresponding Ni/Sn ratio of 4.0, 3.0, 2.0, 1.5, and 0.75. The formation of Ni-Sn alloy species was mainly depended on the composition and temperature of H2 treatment. Intermetallics Ni-Sn that contain Ni3Sn, Ni3Sn2, and Ni3Sn4 alloy phases are known to be effective heterogeneous catalysts for levulinic acid hydrogenation giving very excellence g-valerolactone yield of >99% at 433 K, initial H2 pressure of 4.0 MPa within 6 h. The effective hydrogenation was obtained in H2O without the formation of by-product. Intermetallic Ni-Sn(1.5 that contains Ni3Sn2 alloy species demonstrated very stable and reusable catalyst without any significant loss of its selectivity. © 2015 BCREC UNDIP. All rights reserved. Received: 26th February 2015; Revised: 16th April 2015; Accepted: 22nd April 2015  How to Cite: Rodiansono, R., Astuti, M.D., Ghofur, A., Sembiring, K.C. (2015. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (2: 192-200. (doi:10.9767/bcrec.10.2.8284.192-200Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.8284.192-200  

  2. Primary Crystals of AlfeMnSi Intermetallics in the Cast AlSi Alloys

    Directory of Open Access Journals (Sweden)

    Warmuzek M.

    2017-09-01

    Full Text Available In this paper the results of the microscopic observations of the intermetallic AlFeMnSi phases crystals formed in the liquid hypo- and eutectic AlSi alloys containing transition metals 3.0 wt.% Fe and 0.1, 0.5 and 2.0 wt.% Mn were presented. The crystals morphology has been revealed on both polished and deep etched microsections. The different stages of the primary AlFeMnSi phases particles formation in the solidifying alloy and their final morphology were shown as influenced by cooling rate and alloy chemical composition.

  3. The chemical phenol extraction of intermetallic particles from casting AlSi5Cu1Mg alloy.

    Science.gov (United States)

    Mrówka-Nowotnik, G; Sieniawski, J; Nowotnik, A

    2010-03-01

    This paper presents a chemical extraction technique for determination of intermetallic phases formed in the casting AlSi5Cu1Mg aluminium alloy. Commercial aluminium alloys contain a wide range of intermetallic particles that are formed during casting, homogenization and thermomechanical processing. During solidification, particles of intermetallics are dispersed in interdendritic spaces as fine primary phases. Coarse intermetallic compounds that are formed in this aluminium alloy are characterized by unique atomic arrangement (crystallographic structure), morphology, stability, physical and mechanical properties. The volume fraction, chemistry and morphology of the intermetallics significantly affect properties and material behaviour during thermomechanical processing. Therefore, accurate determination of intermetallics is essential to understand and control microstructural evolution in Al alloys. Thus, in this paper it is shown that chemical phenol extraction method can be applied for precise qualitative evaluation. The results of optical light microscopy LOM, scanning electron microscopy SEM and X-ray diffraction XRD analysis reveal that as-cast AlSi5Cu1Mg alloy contains a wide range of intermetallic phases such as Al(4)Fe, gamma- Al(3)FeSi, alpha-Al(8)Fe(2)Si, beta-Al(5)FeSi, Al(12)FeMnSi.

  4. Chemical Frustration. A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Fredrickson, Daniel C [Univ. of Wisconsin, Madison, WI (United States)

    2015-06-23

    Final technical report for "Chemical Frustration: A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases" funded by the Office of Science through the Materials Chemistry Program of the Office of Basic Energy Sciences.

  5. CaO insulator and Be intermetallic coatings on V-base alloys for liquid-lithium fusion blanket applications

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.H.; Kassner, T.F. [Argonne National Laboratory, Chicago, IL (United States)

    1996-04-01

    The objective of this study is to develop (a) stable CaO insulator coatings at the Liquid-Li/structural-material interface, with emphasis on electrically insulating coating that prevent adverse MHD-generated currents from passing through the V-alloy wall, and (b) stable Be-V intermetallic coating for first-wall components that face the plasma. Electrically insulating and corrosion-resistant coatings are required at the liquid-Li/structural interface in fusion first-wall/blanket application. The electrical resistance of CaO coatings produced on oxygen-enriched surface layers of V-5%Cr-5%Ti by exposing the alloy to liquid Li that contained 0.5-85 wt% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Crack-free Be{sub 2}V intermetallic coatings were also produced by exposing V-alloys to liquid Li that contained Be as a solute. These techniques can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coatings are formed by liquid-phase reactions.

  6. The role of intermetallic phases in the corrosion of magnesium-rare earth alloys

    Energy Technology Data Exchange (ETDEWEB)

    Silva Campos, Maria del Rosario

    2016-07-25

    A new concept to develop a RE based Mg alloy with improved corrosion resistance was followed in the current work. Based on subsequent characterisation steps to eliminate less suitable RE elements the best microstructure for improved corrosion resistance was identified. At first, the corrosion properties of selected RE elements were determined. Based on these results RE elements that have a potential to enhance the corrosion resistance of Mg-RE alloys were selected. Two aspects of RE elements were important for the selection: the electrochemical properties and the solid solubility in Mg. If the solubility limit of RE elements in the Mg matrix is exceeded, they form intermetallic phases with Mg. By performing galvanic coupling measurements the compatibility between Mg matrix and intermetallic phases were estimated. At that point three binary Mg-RE alloys systems remained (Mg-Ce, Mg-La, and Mg-Gd). To evaluate the influence of composition (amount of intermetallic phases) on the corrosion behaviour, four concentrations were cast with 1, 5, 10 and 15 wt. % of RE. Ce and La have a lower solid solubility in Mg matrix generating higher volume fraction of the secondary phases, thus higher dissolution rates in the binary Mg-RE alloys. While Gd with higher solid solubility shows a different behaviour. Additions of up to 10 wt. % Gd resulted in similar behaviour compared to 1 wt. % Gd addition. The most promising results were obtained for the Mg-Gd system with 10 wt. % Gd. Thus, the microstructure of this alloy was further modified by heat treatments to understand the influence of microstructural changes on corrosion behaviour. A ternary element was used to attempt further optimisation of the corrosion performance. Additions of Al, Zn, Ga and Y did not show any improvement in the corrosion resistance of Mg10Gd. This is due to increasing volume fractions of critical more noble phases and the microstructure dominated by eutectic phase formation. Thus galvanic effects became much

  7. The intermetallic bonding between a ring carrier and aluminum piston alloy

    Energy Technology Data Exchange (ETDEWEB)

    Manasijevie, S.; Dolie, N.; Djurdjevic, M.; Misic, N.; Davitkov, N.

    2015-07-01

    This paper presents the results of investigating the formation of intermetallic bond between a ring carrier and aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) in order to increase the wear resistance of the first ring groove and applied in highly loaded diesel engines. Metallographic examination of the quality of al fin bond was done. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that can be made successfully as well as the formation of metal connection (alfin bond) between the ring carrier and aluminum piston alloy. (Author)

  8. The intermetallic bonding between a ring carrier and aluminum piston alloy

    OpenAIRE

    Manasijevic, Srećko; Dolić, Natalija; Djurdjevic, Mile; Mišić, Nataša; Davitkov, Novica

    2015-01-01

    This paper presents the results of investigating the formation of intermetallic bond between a ring carrier and aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) in order to increase the wear resistance of the first ring groove and applied in highly loaded diesel engines. Metallographic examination of the quality of alfin bond was done. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the in...

  9. Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Bruce S. Kang

    2005-10-10

    The objective of this project was to understand and improve high-temperature structural properties of metal-silicide intermetallic alloys. Through research collaboration between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical tests, and metallurgical studies. In this study, molybdenum-based alloys were ductilized by dispersing MgAl2O4 or MgO spinel particles. The addition of spinel particles is hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with the result of ductility improvement. The introduction of fine dispersions has also been postulated to improve ductility by acting as a dislocation source or reducing dislocation pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local notches or crack initiation sites, which is detrimental to the alloy mechanical properties. Optimization of material processing condition is important to develop the desirable molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were conducted to further understand the mechanism of ductility improvement of the molybdenum alloys and the results showed that trace amount of residual oxygen may be responsible for the brittle behavior of the as-cast Mo alloys. For the alloys studied, uniaxial tensile tests were conducted at different loading rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical properties was also studied. Tensile tests for specimens subjected to either ten or twenty thermal cycles were conducted. For each test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time. Thermal expansion tests were carried out using thermo

  10. Thermal Stability of Platinum-Cobalt Bimetallic Nanoparticles: Chemically Disordered Alloys, Ordered Intermetallics, and Core-Shell Structures.

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Zhang, Yang; Wen, Yu-Hua

    2017-04-12

    Pt-Co bimetallic nanoparticles are promising candidates for Pt-based nanocatalysts and magnetic-storage materials. By using molecular dynamics simulations, we here present a detailed examination on the thermal stabilities of Pt-Co bimetallic nanoparticles with three configurations including chemically disordered alloy, ordered intermetallics, and core-shell structures. It has been revealed that ordered intermetallic nanoparticles possess better structural and thermal stability than disordered alloyed ones for both Pt3Co and PtCo systems, and Pt3Co-Pt core-shell nanoparticles exhibit the highest melting points and the best thermal stability among Pt-Co bimetallic nanoparticles, although their meltings all initiate at the surface and evolve inward with increasing temperatures. In contrast, Co-Pt core-shell nanoparticles display the worst thermal stability compared with the aforementioned nanoparticles. Furthermore, their melting initiates in the core and extends outward surface, showing a typical two-stage melting mode. The solid-solid phase transition is discovered in Co core before its melting. This work demonstrates the importance of composition distribution to tuning the properties of binary nanoparticles.

  11. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al-5Mg-Mn Alloys Solidified Under Near-Rapid Cooling.

    Science.gov (United States)

    Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

    2016-01-29

    Mn was an important alloying element used in Al-Mg-Mn alloys. However, it had to be limited to a low level (alloy with low Fe content (alloys (0.5 wt % Fe), intermetallic Al₆(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al₆(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al₆(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al₆(Fe,Mn) to become the primary phase at a lower Mn content.

  12. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling

    Science.gov (United States)

    Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

    2016-01-01

    Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (alloy with low Fe content (alloys (0.5 wt % Fe), intermetallic Al6(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn) to become the primary phase at a lower Mn content. PMID:28787888

  13. An Analysis of Intermetallic Bonding between a Ring Carrier and an Aluminum Piston Alloy

    Science.gov (United States)

    Manasijević, Srećko; Dolić, Natalija; Zovko Brodarac, Zdenka; Djurdjević, Mile; Radiša, Radomir

    2014-09-01

    This paper presents the results of an analysis of the formation of an intermetallic bond between a ring carrier and an aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) to increase the wear resistance of the first ring groove and is applied in highly loaded diesel engines. The most important thing is that the Ni-Resist (ferrous) must be bonded with a non-ferrous piston material during the casting of the piston. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that if the proper conditions are met, then the preparation of the ring carrier can be made successfully, as can the formation of the metal connection between the two materials of different qualities.

  14. A New Thermodynamic Parameter to Predict Formation of Solid Solution or Intermetallic Phases in High Entropy Alloys (Postprint)

    Science.gov (United States)

    2015-11-02

    AFRL-RX-WP-JA-2016-0345 A NEW THERMODYNAMIC PARAMETER TO PREDICT FORMATION OF SOLID SOLUTION OR INTERMETALLIC PHASES IN HIGH ENTROPY...Interim 22 September 2014 – 21 September 2015 4. TITLE AND SUBTITLE A NEW THERMODYNAMIC PARAMETER TO PREDICT FORMATION OF SOLID SOLUTION OR...simple thermodynamic criterion is proposed to predict the presence or absence of equilibrium intermetallic phases in a high entropy alloy at a given

  15. Deformation Behavior of the Percolating Eutectic Intermetallic in HPDC and Squeeze-Cast Mg Alloys

    Science.gov (United States)

    Zhang, Bao; Yang, Kun V.; Nagasekhar, Anumalasetty V.; Cáceres, Carlos H.; Easton, Mark

    2014-10-01

    The structural compliance of the spatially interconnected intermetallic network in a squeeze-cast MRI230D alloy was determined using focused ion beam (FIB) data and finite element (FE) modeling, and compared with data for a high-pressure die-cast AZ91D and three binary Mg-RE alloys from the existing literature. The respective elastic responses were sorted out into two characteristic behaviors: for eutectic volume fractions less than ~22% the behavior was akin to that of highly compliant, bending-dominated structures, whereas for larger fractions, it reproduced that of structurally efficient, stretch-dominated microtruss structures. In all cases, the contribution from the interconnected network added to the total strength of the alloy an amount comparable with the strengthening expected from a similar volume fraction of dispersed particles. Being more compliant, the bending-dominated structures appeared less prone to developing damage by cracking at low strains than the stretch dominated ones.

  16. Characteristic of intermetallic phases in cast dental CoCrMo alloy

    Directory of Open Access Journals (Sweden)

    M. Podrez-Radziszewska

    2010-07-01

    Full Text Available Apart from chromium and molybdenum, casting alloys of cobalt usually contain also up to 0.35 % of carbon. With significant content ofcarbon, presence of carbide-forming alloying elements results in creating carbide phases. These alloys are characterised by dendriticstructure of solid solution of chromium and molybdenum in cobalt with interdendritically precipitated carbides. Because of high chromiumcontent, dominating are M23C6-type carbides, but chromium-rich carbides can be also of M7C3 and M3C2-types. The other elements inthe alloy result in creating M6C and MC-type carbides. In the case of low carbon content, creating carbides and forming intermetallicphases based on the alloying elements and cobalt become limited.The presented research was aimed at characterising structure of the cobalt-based dental alloy containing trace quantity of carbon.Characterised were intermetallic phases hardening the alloy. Microscopic examinations using light microscopy, SEM and TEM werecarried out. Chemical microanalysis of the precipitates using X-ray analyser EDS was performed, as well as phase analysis using selectedarea electron diffraction.

  17. Intermetallic Alloys as CO Electroreduction Catalysts-Role of Isolated Active Sites

    DEFF Research Database (Denmark)

    Karamad, Mohammadreza; Tripkovic, Vladimir; Rossmeisl, Jan

    2014-01-01

    , we studied intermetallic compounds consisting of transition metal (TM) elements that can reduce CO (Ru, Co, Rh, Ir, Ni, Pd, Pt, and Cu) separated by TM and post transition metal elements (Ag, Au, Cd, Zn, Hg, In, Sn, Pb, Sb, and Bi) that are very poor HER catalysts. In total, 34 different stable...... binary bulk alloys forming from these elements have been investigated using density functional theory calculations. The electronic and geometric properties of the catalyst surface can be tuned by varying the size of the active centers and the elements forming them. We have identified six different...

  18. Hot-working behavior of an advanced intermetallic multi-phase γ-TiAl based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Schwaighofer, Emanuel, E-mail: emanuel.schwaighofer@unileoben.ac.at [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Roseggerstr. 12, A-8700 Leoben (Austria); Clemens, Helmut [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Roseggerstr. 12, A-8700 Leoben (Austria); Lindemann, Janny [Chair of Physical Metallurgy and Materials Technology, Brandenburg University of Technology, Konrad-Wachsmann-Allee 17, D-03046 Cottbus (Germany); GfE Fremat GmbH, Lessingstr. 41, D-09599 Freiberg (Germany); Stark, Andreas [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, D-21502 Geesthacht (Germany); Mayer, Svea [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Roseggerstr. 12, A-8700 Leoben (Austria)

    2014-09-22

    New high-performance engine concepts for aerospace and automotive application enforce the development of lightweight intermetallic γ-TiAl based alloys with increased high-temperature capability above 750 °C. Besides an increased creep resistance, the alloy system must exhibit sufficient hot-workability. However, the majority of current high-creep resistant γ-TiAl based alloys suffer from poor workability, whereby grain refinement and microstructure control during hot-working are key factors to ensure a final microstructure with sufficient ductility and tolerance against brittle failure below the brittle-to-ductile transition temperature. Therefore, a new and advanced β-solidifying γ-TiAl based alloy, a so-called TNM alloy with a composition of Ti–43Al–4Nb–1Mo–0.1B (at%) and minor additions of C and Si, is investigated by means of uniaxial compressive hot-deformation tests performed with a Gleeble 3500 simulator within a temperature range of 1150–1300 °C and a strain rate regime of 0.005–0.5 s{sup −1} up to a true deformation of 0.9. The occurring mechanisms during hot-working were decoded by ensuing constitutive modeling of the flow curves by a novel phase field region-specific surface fitting approach via a hyperbolic-sine law as well as by evaluation through processing maps combined with microstructural post-analysis to determine a safe hot-working window of the refined TNM alloy. Complementary, in situ high energy X-ray diffraction experiments in combination with an adapted quenching and deformation dilatometer were conducted for a deeper insight about the deformation behavior of the alloy, i.e. phase fractions and texture evolution as well as temperature uncertainties arising during isothermal and non-isothermal compression. It was found that the presence of β-phase and the contribution of particle stimulated nucleation of ζ-Ti{sub 5}Si{sub 3} silicides and h-type carbides Ti{sub 2}AlC enhance the dynamic recrystallization behavior during

  19. Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

    Science.gov (United States)

    Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

    2016-12-01

    Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu6Sn5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 K (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu6Sn5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu6Sn5 observed, while in the melt spun alloy, Cu6Sn5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu6Sn5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. The reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu6Sn5 was maintained for both alloys.

  20. Ceramic-intermetallic composites produced by mechanical alloying and spark plasma sintering

    CERN Document Server

    Cabanas-Moreno, J G; Martínez-Sanchez, R; Delgado-Gutierrez, O; Palacios-Gomez, J; Umemoto, M

    1998-01-01

    Nano-and microcomposites of intermetallic (Co/sub 3/Ti, AlCo/sub 2 /Ti) and ceramic (TiN, Ti(C, N), Al/sub 2/O/sub 3/) phases have been produced by spark plasma sintering (SPS) of powders resulting from mechanical alloying of Al-Co-Ti elemental powder mixtures. The mechanically alloyed powders consisted of mixtures of nanocrystalline and amorphous phases which, on sintering, transformed into complex microstructures of the intermetallic and ceramic phases. For Al contents lower than about 30 at% in the original powder mixtures, the use of SPS led to porosities of 1-2% in the sintered compacts and hardness values as high as ~1700 kg/mm/sup 2/; in these cases, the composite matrix was TiN and Ti(C, N), with the Al/sub 2/O/sub 3/ phase found as finely dispersed particles in the matrix and the Co /sub 3/Ti and AlCo/sub 2/Ti phases as interdispersed grains. (19 refs).

  1. THREE DIMENSIONAL COMPLEX SHAPES ANALYSIS FROM 3D LOCAL CURVATURE MEASUREMENTS. APPLICATION TO INTERMETALLIC PARTICLES IN ALUMINIUM ALLOY 5XXX

    Directory of Open Access Journals (Sweden)

    Estelle Parra-Denis

    2011-05-01

    Full Text Available The studied material is a 5xxx aluminium alloys containing 2 types of intermetallic particles : Alx(Fe;Mn and Mg2Si. It is usually used in car industry as reinforcement pieces or in packaging industry, such as bottle liquid box lid. Scanning electronic microscope coupled with EDX analysis shows complex shapes of intermetallic particles. The particle shape is obtained during the solidification of alloys. Particles fill vacant spaces between aluminium grains. Therefore final sheet properties depend on intermetallic particles shapes and notably on the matrix-particle interface properties. The goal of the present study is to classify intermetallic particles versus their shapes using local curvature information. The aluminium alloys sample is observed by X ray micro tomography performed at the ESRF. Three dimensional images are segmented, and intermetallic particles are identified in a data base. Each particle is stored as a set of voxels. The surface of each particle is meshed by a marching cubes triangular meshing with the software Amira©. A simplification of the surface is performed by an algorithm contracting the edges. Finally, principal curvatures: kmin and kmax are estimated by Amira© on each facet centre of the mesh. From the full intermetallic population, the bivariate distribution of kmin and kmax is estimated. The obtained graph kmin ¡kmax shows geometrical properties of interface portions of the surface of particles. A factorial correspondence analysis is performed to summarize the information on all intermetallic particles. In the obtained subspace, particles are classified into five shape families, in relation with their interface geometrical properties.

  2. Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

    Science.gov (United States)

    Shen, P. Z.; Gao, H. Y.; Song, M.; He, Y. H.

    2013-12-01

    Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.

  3. Synthesis and Characterization of Nanocrystalline Ni50Al50-xMox (X=0-5 Intermetallic Compound During Mechanical Alloying Process

    Directory of Open Access Journals (Sweden)

    A. Khajesarvi

    2015-07-01

    Full Text Available In the present study, nanocrystalline Ni50Al50-xMox (X = 0, 0.5, 1, 2.5, 5 intermetallic compound was produced through mechanical alloying of nickel, aluminum, and molybdenum powders. AlNi compounds with good and attractive properties such as high melting point, high strength to weight ratio and high corrosion resistance especially at high temperatures have attracted the attention of many researchers. Powders produced from milling were analyzed using scanning electron microscopy (SEM and X-ray diffractometry (XRD. The results showed that intermetallic compound of NiAl formed at different stage of milling operation. It was concluded that at first disordered solid solution of (Ni,Al was formed then it converted into ordered intermetallic compound of NiAl. With increasing the atomic percent of molybdenum, average grain size decreased from 3 to 0.5 μm. Parameter lattice and lattice strain increased with increasing the atomic percent of molybdenum, while the crystal structure became finer up to 10 nm. Also, maximum microhardness was obtained for NiAl49Mo1 alloy.

  4. Effect of Intermetallic Compound Formation in Friction Welded Al Alloy Rods.

    Science.gov (United States)

    Im, Yong-Deok; Park, Kwang-Suk; Song, Kuk-Hyun

    2018-03-01

    This study was carried out to evaluate the development of microstructures and mechanical properties on friction welded dissimilar materials with a light weight. For this work, Al6063 and Duralumin alloys with a shape of rod were selected as experimental materials, and friction welding was performed under conditions with a rotation speed of 2,000 RPM, a friction load of 12 kgf/cm2 and an upset force of 25 kgf/cm2, respectively. After welding, the microstructural analysis such as the grain boundary characteristic distributions and the formation of intermetallic compounds was analyzed by electron back-scattering diffraction method and transmission electron microscopy, respectively. In addition, the evaluation of mechanical properties on welded materials was conducted by Vickers microhardness and tensile test. As a result, applying the friction welding led to the significant grain refinement from 50 μm in base material to 2 μm in welded zone, respectively. In case of mechanical properties, Vickers micro-hardness and tensile strength of the welded material occupied 81% and 96% in fraction relative to the base material, respectively, which was attributable to the formation and growth of intermetallic compounds during the welding.

  5. Free energy of melts and intermetallic compounds of binary alloys determined by a molecular dynamics approach.

    Science.gov (United States)

    Guerdane, M

    2014-02-01

    We present an atomistic approach aimed at determining the free energy g(liq) of binary alloy liquids, a quantity which governs the thermodynamics of phase transformations and whose evaluation has long been a challenge to modeling methods. Our approach, illustrated here for a metallic system model NiZr, combines two methods: the quasiharmonic approximation, applied for some existing (real or hypothetical) intermetallic compounds, and the liquid-solid coexistence conditions. The underlying equations for g(liq) are solved by means of a subregular-solution approximation. We demonstrate the high reliability of our calculated free energies in determining the phase diagram of a binary system and describing quantitatively the growth kinetics. The latter issue is illustrated by linking molecular dynamics simulations to phase-field modeling with regard to directional solidification and melting in a two-phase system [Ni(x)Zr(1-x)](liq)-Zr(cryst) out of chemical equilibrium.

  6. The intermetallic bonding between a ring carrier and aluminum piston alloy

    Directory of Open Access Journals (Sweden)

    Manasijevic, Srećko

    2015-09-01

    Full Text Available This paper presents the results of investigating the formation of intermetallic bond between a ring carrier and aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist in order to increase the wear resistance of the first ring groove and applied in highly loaded diesel engines. Metallographic examination of the quality of alfin bond was done. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that can be made successfully as well as the formation of metal connection (alfin bond between the ring carrier and aluminum piston alloy.El artículo presenta los resultados de la investigación sobre la formación de una unión intermetálica entre el portasegmento y la aleación de aluminio del pistón. El portasegmento es una fundición de hierro austenítico (Ni-Resist con el fin de aumentar la resistencia al desgaste de la unión Al-fin del primer segmento y se utiliza en motores diésel altamente cargados. Se realizó un examen metalográfico de la unión intermetálica, mediante un microscopio óptico en combinación con SEM/EDS. Los satisfactorios resultados obtenidos muestran la formación de contacto metálico (unión Al-fin del primer segmento entre el portasegmento y la aleación de aluminio del pistón.

  7. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling

    Directory of Open Access Journals (Sweden)

    Yulin Liu

    2016-01-01

    Full Text Available Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt % to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al–5Mg–Mn alloy with low Fe content (<0.1 wt %, intermetallic Al6(Fe,Mn was small in size and amount. With increasing Mn content, intermetallic Al6(Fe,Mn increased, but in limited amount. In high-Fe-containing Al–5Mg–Mn alloys (0.5 wt % Fe, intermetallic Al6(Fe,Mn became the dominant phase, even in the alloy with low Mn content (0.39 wt %. Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn to become the primary phase at a lower Mn content.

  8. BFS Method for Alloys Optimized and Verified for the Study of Ordered Intermetallic Material

    Science.gov (United States)

    1997-01-01

    The aerospace industry has a need for new metallic alloys that are lightweight and have high strength at elevated temperatures. The BFS (Bozzolo, Ferrante, and Smith) method is a new, computationally efficient and physically sound quantum semi-perturbative approach for describing metals and their defects. Based on a simple interpretation of the alloy formation process that identifies strain and chemical contributions to the energy of the alloy, the method provides an atom-by-atom description of an alloy. Its implementation requires little more than algebra and the solution of transcendental equations. At the NASA Lewis Research Center, we have demonstrated that BFS can investigate the properties of a large number of alloys with a minimum computational effort on low-level computers. This screening allows the selection of the best alloy candidates for a particular application and, therefore, promises large cost savings over current approaches.

  9. Heat resistance of Fe-Al intermetallics in the context of selected heat-resistant and hihg-temperature creep resistant steels

    Directory of Open Access Journals (Sweden)

    P. Baranowski

    2009-04-01

    Full Text Available Results are hereby presented of heat-resistance tests of two Fe3Al and FeAl intermetallic phase-based alloys in the context of St41k-typeboiler steel and 50H21G9N4 high-temperature creep resistant steel. It has been ascertained that heat resistance of the 50H21G9N4 steeland of the Fe3Al and FeAl intermetallic phase-based alloys significantly exceeds that of the boiler steel tested in the air atmosphere and the atmosphere of a flue gas with CO, CO2, SiO2 content alike. Improvement of these properties depends of exposure conditions. The largest differences have been observed when the tests were carried out in temperature 1023 K and in the flue gas atmosphere. The differences have been more and more noticeable as the exposition duration extended. A tendency has been also recorded of smaller mass decrements of the Fe3Al and FeAl intermetallic phase-based alloys as compared to the 50H21G9N4 steel.

  10. Combined effects of ultrasonic vibration and manganese on Fe-containing inter-metallic compounds and mechanical properties of Al-17Si alloy with 3wt.%Fe

    Directory of Open Access Journals (Sweden)

    Lin Chong

    2013-05-01

    Full Text Available The research studied the combined effects of ultrasonic vibration (USV and manganese on the Fe-containing inter-metallic compounds and mechanical properties of Al-17Si-3Fe-2Cu-1Ni (wt.% alloys. The results showed that, without USV, the alloys with 0.4wt.% Mn or 0.8wt.% Mn both contain a large amount of coarse plate-like δ-Al4(Fe,MnSi2 phase and long needle-like β-Al5(Fe,MnSi phase. When the Mn content changes from 0.4wt.% to 0.8wt.% in the alloys, the amount and the length of needle-like β-Al5(Fe,MnSi phase decrease and the plate-like δ-Al4(Fe,MnSi2 phase becomes much coarser. After USV treatment, the Fe-containing compounds in the alloys are refined and exist mainly as δ-Al4(Fe,MnSi2 particles with an average grain size of about 20 μm, and only a small amount of β-Al5(Fe,MnSi phase remains. With USV treatment, the ultimate tensile strengths (UTS of the alloys containing 0.4wt.%Mn and 0.8wt.%Mn at room temperature are 253 MPa and 262 MPa, respectively, and the ultimate tensile strengths at 350 °C are 129 MPa and 135 MPa, respectively. It is considered that the modified morphology and uniform distribution of the Fe-containing inter-metallic compounds, which are caused by the USV process, are the main reasons for the increase in the tensile strength of these two alloys.

  11. Effect of Specific Energy Input on Microstructure and Mechanical Properties of Nickel-Base Intermetallic Alloy Deposited by Laser Cladding

    Science.gov (United States)

    Awasthi, Reena; Kumar, Santosh; Chandra, Kamlesh; Vishwanadh, B.; Kishore, R.; Viswanadham, C. S.; Srivastava, D.; Dey, G. K.

    2012-12-01

    This article describes the microstructural features and mechanical properties of nickel-base intermetallic alloy laser-clad layers on stainless steel-316 L substrate, with specific attention on the effect of laser-specific energy input (defined as the energy required per unit of the clad mass, kJ/g) on the microstructure and properties of the clad layer, keeping the other laser-cladding parameters same. Defect-free clad layers were observed, in which various solidified zones could be distinguished: planar crystallization near the substrate/clad interface, followed by cellular and dendritic morphology towards the surface of the clad layer. The clad layers were characterized by the presence of a hard molybdenum-rich hexagonal close-packed (hcp) intermetallic Laves phase dispersed in a relatively softer face-centered cubic (fcc) gamma solid solution or a fine lamellar eutectic phase mixture of an intermetallic Laves phase and gamma solid solution. The microstructure and properties of the clad layers showed a strong correlation with the laser-specific energy input. As the specific energy input increased, the dilution of the clad layer increased and the microstructure changed from a hypereutectic structure (with a compact dispersion of characteristic primary hard intermetallic Laves phase in eutectic phase mixture) to near eutectic or hypoeutectic structure (with reduced fraction of primary hard intermetallic Laves phase) with a corresponding decrease in the clad layer hardness.

  12. Two-phase chromium-niobium alloys exhibiting improved mechanical properties at high temperatures

    Science.gov (United States)

    Liu, Chain T.; Takeyama, Masao

    1994-01-01

    The specification discloses chromium-niobium alloys which exhibit improved mechanical properties at high temperatures in the range of 1250.degree. C. and improved room temperature ductility. The alloys contain a Cr.sub.2 Nb-rich intermetallic phase and a Cr-rich phase with an overall niobium concentration in the range of from about 5 to about 18 at. %. The high temperature strength is substantially greater than that of state of the art nickel-based superalloys for enhanced high temperature service. Further improvements in the properties of the compositions are obtained by alloying with rhenium and aluminum; and additional rare-earth and other elements.

  13. Study of Fatigue and Fracture Behavior of Cr-Based Alloys and Intermetallic Materials

    Energy Technology Data Exchange (ETDEWEB)

    He, YH

    2001-01-31

    The microhardness, and tensile and fracture-toughness properties of drop-cast and directionally-solidified Cr-9.25 at.% (atomic percent) Ta alloys have been investigated. Directional solidification was found to soften the alloy, which could be related to the development of equilibrium and aligned microstructures. It was observed that the tensile properties of the Cr-Ta alloys at room and elevated temperatures could be improved by obtaining aligned microstructures. The directionally-solidified alloy also showed increased fracture toughness at room temperature. This trend is mainly associated with crack deflection and the formation of shear ribs in the samples with aligned microstructures. The sample with better-aligned lamellar exhibits greater fracture toughness.

  14. Direct separation of arsenic and antimony oxides by high-temperature filtration with porous FeAl intermetallic.

    Science.gov (United States)

    Zhang, Huibin; Liu, Xinli; Jiang, Yao; Gao, Lin; Yu, Linping; Lin, Nan; He, Yuehui; Liu, C T

    2017-09-15

    A temperature-controlled selective filtration technology for synchronous removal of arsenic and recovery of antimony from the fume produced from reduction smelting process of lead anode slimes was proposed. The chromium (Cr) alloyed FeAl intermetallic with an asymmetric pore structure was developed as the high-temperature filter material after evaluating its corrosive resistance, structural stability and mechanical properties. The results showed that porous FeAl alloyed with 20wt.% Cr had a long term stability in a high-temperature sulfide-bearing environment. The separation of arsenic and antimony trioxides was realized principally based on their disparate saturated vapor pressures at specific temperature ranges and the asymmetric membrane of FeAl filter elements with a mean pore size of 1.8μm. Pilot-scale filtration tests showed that the direct separation of arsenic and antimony can be achieved by a one-step or two-step filtration process. A higher removal percentage of arsenic can reach 92.24% at the expense of 6∼7% loss of antimony in the two-step filtration process at 500∼550°C and 300∼400°C. The FeAl filters had still good permeable and mechanical properties with 1041h of uninterrupted service, which indicates the feasibility of this high-temperature filtration technology. Copyright © 2017. Published by Elsevier B.V.

  15. Effect of intensive melt shearing on the formation of Fe-containing intermetallics in LM24 Al-alloy

    Science.gov (United States)

    Li, H. T.; Ji, S.; Wang, Y.; Xia, M.; Fan, Z.

    2012-01-01

    Fe is one of the inevitable and detrimental impurities in aluminium alloys that degrade the mechanical performance of castings. In the present work, intensive melt shearing has been demonstrated to modify the morphology of Fe-containing intermetallic compounds by promoting the formation of compact α-Al(Fe,Mn)Si at the expense of needle-shaped β-AlFeSi, leading to an improved mechanical properties of LM24 alloy processed by MC-HPDC process. The promotion of the formation of α -Al(Fe, Mn)Si phase is resulted from the enhanced nucleation on the well dispersed MgAl2O4 particles in the melt. The Fe tolerance of LM24 alloy can be effectively improved by combining Mn alloying and intensive melt shearing.

  16. The effect of casting porosities on cavitational erosion of intermetallic alloy FeAl36

    Directory of Open Access Journals (Sweden)

    R. Jasionowski

    2010-07-01

    Full Text Available The machinery and equipment elements operating in a turbulent fluid flow, are exposed to destruction as a result of the impact of thecavitation, corrosion and abrasion processes, among which are hardest to minimize the imploding cavitation bubbles. Repeated cavitationimplosions of bubbles give rise to cracks, material loss, resulting in increased flow resistance and reduction of the efficiency of the device, or even its destruction. In order to prevent or mitigate the cavitation phenomenon and its harmful effects, two basic methods are applied. The first of these is the selection of geometrical parameters and hydraulic machinery and the relevant elements of the streamlined shape and flow channels. The second solution is the selection of engineering plastics with greater resistance to cavitation. In case of materials manufactured with the casting method, a very important role is being played by the quality of manufactured casting having the smallest number of casting defects. The aim of the present study was to examine the effect of casting porosities of an intermetallic alloy FeAl36 on cavitational erosion.

  17. An investigation of the fatigue and fracture behavior of a Nb-12Al-44Ti-1.5Mo intermetallic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Soboyejo, W.O.; Dipasquale, J.; Ye, F.; Mercer, C. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Srivatsan, T.S. [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering; Konitzer, D.G. [General Electric Aircraft Engines, Cincinnati, OH (United States)

    1999-04-01

    This article presents the results of a study of the fatigue and fracture behavior of a damage-tolerant Nb-12Al-44Ti-1.5Mo alloy. This partially ordered B2 + orthorhombic intermetallic alloy is shown to have attractive combinations of room-temperature ductility (11 to 14 pct), fracture toughness (60 to 92 MPa{radical}m), and comparable fatigue crack growth resistance to IN718, Ti-6Al-4V, and pure Nb at room temperature. The studies show that tensile deformation in the Nb-12Al-44Ti-1.5Mo alloy involves localized plastic deformation (microplasticity via slip-band formation) which initiates at stress levels that are significantly below the uniaxial yield stress ({approximately}9.6 pct of the 0.2 pct offset yield strength (YS)). The onset of bulk yielding is shown to correspond to the spread of microplasticity completely across the gage sections of the tensile specimen. Fatigue crack initiation is also postulated to occur by the accumulation of microplasticity (coarsening of slip bands). Subsequent fatigue crack growth then occurs by the unzipping of cracks along slip bands that form ahead of the dominant crack tip. The proposed mechanism of fatigue crack growth is analogous to the unzipping crack growth mechanism that was suggested originally by Neumann for crack growth in single-crystal copper. Slower near-threshold fatigue crack growth rates at 750 C are attributed to the shielding effects of oxide-induced crack closure. The fatigue and fracture behavior are also compared to those of pure Nb and emerging high-temperature niobium-based intermetallics.

  18. Intermetallic nanoparticles

    Science.gov (United States)

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules

    2015-07-14

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  19. The intermetallic formation and growth kinetics at the interface of near eutectic tin-silver-copper solder alloys and gold/nickel metallization

    Science.gov (United States)

    Gao, Mao

    The formation of a one micron thick layer of an intermetallic compound between a solder alloy and a metallic substrate generally constitutes a good solder joint in an electronic device. However, if the compound grows too thick, and/or if multiple intermetallic compounds form, poor solder joint reliability may result. Thus significant interest has been focused on intermetallic compound phase selection and growth kinetics at such solder/metal interfaces. The present study focuses on one such specific problem, the formation and growth of intermetallic compounds at near eutectic Sn-Ag-Cu solder alloy/Ni interfaces. Sn-3.0Ag-0.5Cu solder was reflowed on Au/Ni substrates, resulting in the initial formation and growth of (CuNi)6Sn 5 at Sn-3.0Ag-0.5Cu /Ni interfaces. (NiCu)3Sn4 formed between the (CuNi)6Sn5 and the Ni substrate when the concentration of Cu in the liquid SnAgCu solder decreased to a critical value which depended upon temperature: 0.37, 0.31 and 0.3(wt.%) at reflow temperatures of 260°C, 245°C and 230°C respectively. The growth rate of (CuNi)6Sn5 was found to be consistent with extrapolations of a diffusion limited growth model formulated for lower temperature, solid state diffusion couples. The long range diffusion of Cu did not limit growth rates. The spalling of (CuNiAu)6Sn5 from (NiCu)3 Sn4 surfaces during reflow was also examined. When the Cu concentration in the solder decreased to approximately 0.28wt.%, the (Cu,Ni,Au) 6Sn5 was observed to spall. Compressive stress in (CuNiAu) 6Sn5 and weak adhesion between (CuNiAu)6Sn 5 and (NiCu)3Sn4 was found to cause this effect.

  20. In Situ Characterization Techniques Based on Synchrotron Radiation and Neutrons Applied for the Development of an Engineering Intermetallic Titanium Aluminide Alloy

    Directory of Open Access Journals (Sweden)

    Petra Erdely

    2016-01-01

    Full Text Available Challenging issues concerning energy efficiency and environmental politics require novel approaches to materials design. A recent example with regard to structural materials is the emergence of lightweight intermetallic TiAl alloys. Their excellent high-temperature mechanical properties, low density and high stiffness constitute a profile perfectly suitable for their application as advanced aero-engine turbine blades or as turbocharger turbine wheels in next-generation automotive engines. As the properties of TiAl alloys during processing as well as during service are dependent on the phases occurring, detailed knowledge of their volume fractions and distribution within the microstructure is of paramount importance. Furthermore, the behavior of the individual phases during hot deformation and subsequent heat treatments is of interest to define reliable and cost-effective industrial production processes. In situ high-energy X-ray diffraction methods allow tracing the evolution of phase fractions over a large temperature range. Neutron diffraction unveils information on order-disorder transformations in TiAl alloys. Small-angle scattering experiments offer insights into the materials’ precipitation behavior. This review attempts to shine a light on selected in situ diffraction and scattering techniques and the ways in which they promoted the development of an advanced engineering TiAl alloy.

  1. High temperature intermetallic compounds Ni{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Kursa, M. [Vysoka Skola Banska, Ostrava (Czech Republic); Hypeska, L. [Vysoka Skola Banska, Ostrava (Czech Republic); Drapala, J. [Vysoka Skola Banska, Ostrava (Czech Republic); Karnik, T. [Vysoka Skola Banska, Ostrava (Czech Republic); Losertova, M. [Vysoka Skola Banska, Ostrava (Czech Republic)

    1995-11-01

    The paper describes the preparation of Ni3Al intermetallic compounds, and investigations of their structures in the as-cast, remelted, and annealed states. The materials were produced by three techniques : in a high frequency vacuum furnace, by zonal remelting in an electron beam furnace, and by remelting with unidirectional solidification. Those melted in an h. f. vacuum furnace and poured into graphite moulds had well developed dendritic structures, a Ni3Al ({gamma}`) phase, with interdendritic spaces formed by Ni5Al3 + {gamma}`. Many specimens contained shrinkage cavities. Unidirectional solidification allowed casting defects to be eliminated and the grain size to be controlled in dependence on the solidification rate. Rates from 650 to 60 mm per hour were tried to examine their effects on the grain size, homogeneity, and structure. The authors further investigated the influence of B and Zr additions on the solidification process and formation of the structure of Ni3Al. Annealing, in an argon atmosphere at 1100 C for various durations, was tried out for homogenizing the as-cast structures. (orig.).

  2. Nd-induced honeycomb structure of intermetallic phase enhances the corrosion resistance of Mg alloys for bone implants.

    Science.gov (United States)

    Shuai, Cijun; Yang, Youwen; Peng, Shuping; Gao, Chengde; Feng, Pei; Chen, Jian; Liu, Yong; Lin, Xin; Yang, Sheng; Yuan, Fulai

    2017-09-01

    Mg-5.6Zn-0.5Zr alloy (ZK60) tends to degrade too rapid for orthopedic application, in spite of its natural degradation, suitable strength and good biocompatibility. In this study, Nd was alloyed with ZK60 via laser melting method to enhance its corrosion resistance. The microstructure features, mechanical properties and corrosion behaviors of ZK60-xNd (x = 0, 1.8, 3.6, 5.4 wt.%) were investigated. Results showed that laser melted ZK60-xNd were composed of fine ɑ-Mg grains and intermetallic phases along grain boundaries. And the precipitated intermetallic phases experienced successive changes: divorced island-like MgZn phase → honeycomb-like T phase → coarsened and agglomerated W phase with Nd increasing. It was worth noting that ZK60-3.6Nd with honeycomb-like T phase exhibited an optimal corrosion behavior with a corrosion rate of 1.56 mm year-1. The improved corrosion behavior was ascribed to: (I) dense surface film caused by the formation of Nd2O3 hindered the invasion of immersion solution; (II) the three-dimensional honeycomb structure of intermetallic phases formed a tight barrier to restrain the propagation of corrosion. Moreover, ZK60-3.6Nd exhibited good biocompatibility. It was suggested that ZK60-3.6Nd was a preferable candidate for biodegradable bone implant.

  3. Study of the structure and development of the set of reference materials of composition and structure of heat resisting nickel and intermetallic alloys

    Directory of Open Access Journals (Sweden)

    E. B. Chabina

    2016-01-01

    Full Text Available Relevance of research: There are two sizes (several microns and nanodimensional of strengthening j'-phase in single-crystal heat resisting nickel and intermetallic alloys, used for making blades of modern gas turbine engines (GTD. For in-depth study of structural and phase condition of such alloys not only qualitative description of created structure is necessary, but quantitative analysis of alloy components geometrical characteristics. Purpose of the work: Development of reference material sets of heat resisting nickel and intermetallic alloy composition and structure. Research methods: To address the measurement problem of control of structural and geometrical characteristics of single-crystal heat resisting and intermetallic alloys by analytical microscopy and X-ray diffraction analysis the research was carried out using certified measurement techniques on facilities, entered in the Register of Measurement Means of the Russian Federation. The research was carried out on microsections, foils and plates, cut in the plane {100}. Results: It is established that key parameters, defining the properties of these alloys are particle size of strengthening j' -phase, the layer thickness of j-phase between them and parameters of phases lattice. Metrological requirements for reference materials of composition and structure of heat resisting nickel and intermetallic alloys are formulated. The necessary and sufficient reference material set providing the possibility to determine the composition and structure parameters of single-crystal heat resisting nickel and intermetallic alloys is defined. The developed RM sets are certified as in-plant reference materials. Conclusion: The reference materials can be used for graduation of spectral equipment when conducting element analysis of specified class alloys; for calibration of means of measuring alloy structure parameters; for measurement of alloys phases lattice parameters; for structure reference pictures

  4. Effect of ultrasonic treatment on formation of iron-containing intermetallic compounds in Al-Si alloys

    Directory of Open Access Journals (Sweden)

    Yu-bo Zhang

    2016-09-01

    Full Text Available Iron is generally regarded as an unavoidable impurity in Al-Si casting alloys. The acicular Al3Fe and β-Al5FeSi (or Al9Si2Fe2 are common iron-containing intermetallic compounds (IMCs in conventional structure which have a detrimental impact on the mechanical properties. In this paper, ultrasonic field (USF was applied to modify acicular iron phases in Al-12%Si-2%Fe and Al-2%Fe alloys. The results show that the USF applied to Al-Fe alloys caused the morphological transformation of both primary and eutectic Al3Fe from acicular to blocky and granular without changes in their composition. In the case of Al-Si-Fe alloys, ultrasonic treatment led to both morphological and compositional conversion of the ternary iron IMCs. When the USF was applied, the acicular β-Al9Si2Fe2 was substituted by star-like α-Al12Si2Fe3. The modification rate of both binary and ternary iron IMCs relates to the USF treatment duration. The undercooling induced by the ultrasonic vibration contributes to the nucleation of intermetallics and can explain the transformation effect.

  5. Mechanical behavior of Al-Mg-Si alloys reinforced with ceramic and intermetallic particles

    Energy Technology Data Exchange (ETDEWEB)

    Costa, C.E. da [Dept. de Ingenieria Mecanica y de Materiales, Univ. Politecnica de Valencia (Spain); Martinez, N.; Amigo, V.; Salvador, M.D. [Univ. do Estado de Santa Catarina, Centro de Ciencias Tecnologicas, Dept. Ingenieria Mecanica, Joinville (Brazil)

    2003-07-01

    Aluminum matrix composites (AMCs) reinforced with ceramic and Ti-Al intermetallic particles were prepared in the laboratory by following a powder metallurgy route. Hot extrusion was used as consolidation processes. Different studies were carried out in the composites developed. The influence of production process was also estimated. To evaluate interfaces and possible reaction products between the matrix and reinforcement, heat treatments regarding time were carried out. Tests were developed in fabricated AMCs and in unreinforced aluminum matrix, to evaluate influence of reinforcement type. In this study, optical and scanning electron microscopy with X-ray microanalysis, were used to determine the possible reaction products in the matrix/reinforcement interface and its composition. Ultimate strength and strain to failure were studied. There were performed tests at room temperature and at high temperature of the material in different precipitation state. The type of damage was analyzed by scanning electron microscopy. Ultimate strength trends to grow with reinforcement addition in both T1 and T6 conditions for low temperature. Strain to failure remains the lowest on T6 state. The effect of reinforcement addition decrease for high temperature testing and matrix influence was demonstrated. (orig.)

  6. Thermodynamic properties and solidification kinetics of intermetallic Ni{sub 7}Zr{sub 2} alloy investigated by electrostatic levitation technique and theoretical calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, L. H.; Hu, L.; Yang, S. J.; Wang, W. L.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2016-01-21

    The thermodynamic properties, including the density, volume expansion coefficient, ratio of specific heat to emissivity of intermetallic Ni{sub 7}Zr{sub 2} alloy, have been measured using the non-contact electrostatic levitation technique. These properties vary linearly with temperature at solid and liquid states, even down to the obtained maximum undercooling of 317 K. The enthalpy, glass transition, diffusion coefficient, shear viscosity, and surface tension were obtained by using molecular dynamics simulations. Ni{sub 7}Zr{sub 2} has a relatively poor glass forming ability, and the glass transition temperature is determined as 1026 K. The inter-diffusivity of Ni{sub 7}Zr{sub 2} alloy fitted by Vogel–Fulcher–Tammann law yields a fragility parameter of 8.49, which indicates the fragile nature of this alloy. Due to the competition of increased thermodynamic driving force and decreased atomic diffusion, the dendrite growth velocity of Ni{sub 7}Zr{sub 2} compound exhibits double-exponential relationship to the undercooling. The maximum growth velocity is predicted to be 0.45 m s{sup −1} at the undercooling of 335 K. Theoretical analysis reveals that the dendrite growth is a diffusion-controlled process and the atomic diffusion speed is only 2.0 m s{sup −1}.

  7. Selective aluminum dissolution as a means to observe the microstructure of nanocrystalline intermetallic phases from Al-Fe-Cr-Ti-Ce rapidly solidified alloy.

    Science.gov (United States)

    Michalcová, Alena; Vojtěch, Dalibor; Novák, Pavel

    2013-02-01

    Rapidly solidified aluminum alloys are promising materials with very fine microstructure. The microscopy observation of these materials is complicated due to overlay of fcc-Al matrix and different intermetallic phases. A possible way to solve this problem is to dissolve the Al matrix. By this process powder formed by single intermetallic phase particles is obtained. In this paper a new aqueous based dissolving agent for Al-based alloy is presented. The influence of oxidation agent (FeCl(3)) concentration on quality of extraction process was studied. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

    Science.gov (United States)

    Silvayeh, Zahra; Vallant, Rudolf; Sommitsch, Christof; Götzinger, Bruno; Karner, Werner; Hartmann, Matthias

    2017-11-01

    Hybrid components made of aluminum alloys and high-strength steels are typically used in automotive lightweight applications. Dissimilar joining of these materials is quite challenging; however, it is mandatory in order to produce multimaterial car body structures. Since especially welding of tailored blanks is of utmost interest, single-sided Cold Metal Transfer butt welding of thin sheets of aluminum alloy EN AW 6014 T4 and galvanized dual-phase steel HCT 450 X + ZE 75/75 was experimentally investigated in this study. The influence of different filler alloy compositions and welding process parameters on the thickness of the intermetallic layer, which forms between the weld seam and the steel sheet, was studied. The microstructures of the weld seam and of the intermetallic layer were characterized using conventional optical light microscopy and scanning electron microscopy. The results reveal that increasing the heat input and decreasing the cooling intensity tend to increase the layer thickness. The silicon content of the filler alloy has the strongest influence on the thickness of the intermetallic layer, whereas the magnesium and scandium contents of the filler alloy influence the cracking tendency. The layer thickness is not uniform and shows spatial variations along the bonding interface. The thinnest intermetallic layer (mean thickness < 4 µm) is obtained using the silicon-rich filler Al-3Si-1Mn, but the layer is more than twice as thick when different low-silicon fillers are used.

  9. The solidification and structure of Al-17wt.%Si alloy modified with intermetallic phases containing Ti and Fe

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2011-10-01

    Full Text Available The article describes the process of casting and solidification of Al-17wt.%Si alloy that have been modified with composite powdercontaining the intermetallic phases of Ti and Fe. The chemical and phase composition of the applied modifier was described with thefollowingformula:FeAlx–TiAlx–Al2O3. Applying the method of thermal analysis ATD, the characteristic parameters of the solidificationprocess were determined, and exo-and endothermic effects of the modifying powder on the run of the silumin solidification curves wereobserved. By the methods of light, scanning, and X-ray microscopy, the structure of alloy and the chemical composition of the dispersionhardening precipitates were examined. A change in the morphology of Al-Si eutectic from the lamellar to fibrous type was reportedtogether with changes in the form of complex eutectics of an Al-Si-Ti and Al-Si-Fe type and size reduction of primary silicon crystals.

  10. Nucleation and Growth of Intermetallic Compounds Formed in Boron Steel Hot-Dipped in Al–Ni alloy

    Directory of Open Access Journals (Sweden)

    Jae-Hyeong Lee

    2017-11-01

    Full Text Available The formation mechanism of intermetallic compounds formed in boron steel hot-dipped in Al–7Ni (wt % at 690 °С for 10–120 s was studied by identifying the intermetallic phases and investigating the growth process. Initially, a Fe3O4 oxide layer formed on the steel. The oxide layer separated into multiple layers sporadically; following this, the Al–Ni molten alloy permeated into the region of the oxide layer breakdown and formed the Al9FeNi (T, monoclinic, space group: P21/c phase on the steel surfaces. The Al9FeNi (T phase formed from the reaction between the Al–Ni molten alloy and Fe eluted from the steel; this phase not only acts as an Al interdiffusion channel, but also as a barrier for Fe; and facilitates only grain growth without a significant change in thickness. Inside the steel, the Fe2Al5 (η, orthorhombic, space group: Cmcm phase grows along the c-axis in the [001] direction; and has a long columnar structure. The Fe3AlC (κ, Cubic, space group: Pm3m phase is formed owing to a reduction in the Al concentration and the simultaneous diffusion and discharge of C toward the steel interface, as C cannot dissolve in the Fe2Al5 (η phase.

  11. Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, A.; Uwakweh, O.N.C. [Univ. of Cincinnati, OH (United States); Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect the structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.

  12. Influence of Intermetallic Compounds on RF Resistance of Joints Soldered with Lead Free Alloys

    Directory of Open Access Journals (Sweden)

    J. Podzemsky

    2012-06-01

    Full Text Available During soldering process intermetallic compounds as a reaction between solder and substrate are created. Physical properties of those compounds are different to properties of solder and substrate. The influence of intermetallic compounds (IMC on radio frequency resistance of soldered joint has been identified. Tested solders were lead free Sn-1Cu, Sn-4Ag and Sn-3.8Ag-0.7Cu and lead containing Sn-37Pb (all in weight percent. Samples were annealed up to 3000 hours at 150 °C to accelerated growing of IMC. Radio frequency measuring method has been developed and is described. Influence of IMC on resistance of joint is growing with growing frequency because IMC with slightly different resistivity to base solder is creating barrier to current. Resistance of joints has been measured up to 3 GHz.

  13. Dynamic nanomechanical properties of novel Si-rich intermetallic coatings growth on a medical 316 LVM steel by hot dipping in a hypereutectic Al-25Si alloy.

    Science.gov (United States)

    Frutos, E; González-Carrasco, J L

    2015-06-01

    This aim of this study is to determine the elastoplastic properties of Ni-free Al3FeSi2 intermetallic coatings grown on medical stainless steel under different experimental conditions. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus. Special emphasis is devoted to correlate the PI with the wear resistance under sliding contact, determined by scratch testing, and fracture toughness, determined by using a novel method based on successive impacts with small loads. With regard to the substrate, the developed coatings are harder and exhibit a lower Young's reduced modulus, irrespective of the experimental conditions. It has been shown that preheating of the samples prior to hot dipping and immersion influences the type and volume fraction of precipitates, which in turn also affect the nanomechanical properties. The higher the preheating temperature is, the greater the Young's reduced modulus is. For a given preheating condition, an increase of the immersion time yields a decrease in hardness. Although apparent friction coefficients of coated specimens are smaller than those obtained on AISI 316 LVM, they increase when using preheating or higher immersion times during processing, which correlates with the PI. The presence of precipitates produces an increase in fracture toughness, with values greater than those presented by samples processed on melted AlSi alloys with lower Si content (12 wt%). Therefore, these intermetallic coatings could be considered "hard but tough", suitable to enhance the wear resistance, especially when using short periods of immersion. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Tribaloy intermetallic alloy compositions: new materials or additives for wear resistant applications

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, C.B.; Hoffman, R.A.; Poskitt, R.W.

    1975-01-01

    Properties and uses of TRIBALOY alloys in powder metallurgy fabrication are discussed. Powders of TRIBALOY can be blended with essentially any powder processed by powder metallurgy. Green strength of the blended powder parts is reduced as the amount of TRIBALOY is increased. The concentration of TRIBALOY, however, is usually 15 to 20 volume percent, a compromise between green strength and effectiveness as a wear resistant part. Blended powders are sintered at the temperature normally used for the base metal with special consideration given to a low dew point in the atmosphere. The sintered parts can be coined, carburized, machined, or impregnated in any of the well-known ways. TRIBALOY as a powder blending agent has extended the useful life of P/M parts by factors of 5 and more. A variety of industries are presently using P/M parts at higher temperatures, heavier loads, in poorer or non-lubricated conditions or at higher speeds because of the addition of TRIBALOY. More important, however, is that TRIBALOY can be incorporated in parts to be made by powder metallurgy which until now had not been feasible. The overall effect has been considerable savings for the customer by switching to the powder metal method of manufacturing and increased activity for the fabricator.

  15. Synthesis of hydrides by interaction of intermetallic compounds with ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, Boris P., E-mail: tarasov@icp.ac.ru [Institute of Problems of Chemical Physics of the Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Fokin, Valentin N.; Fokina, Evelina E. [Institute of Problems of Chemical Physics of the Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Yartys, Volodymyr A., E-mail: volodymyr.yartys@ife.no [Institute for Energy Technology, Kjeller NO 2027 (Norway); Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim NO 7491 (Norway)

    2015-10-05

    Highlights: • Interaction of the intermetallics A{sub 2}B, AB, AB{sub 2}, AB{sub 5} and A{sub 2}B{sub 17} with NH{sub 3} was studied. • The mechanism of interaction of the alloys with ammonia is temperature-dependent. • Hydrides, hydridonitrides, disproportionation products or metal–N–H compounds are formed. • NH{sub 4}Cl was used as an activator of the reaction between ammonia and intermetallics. • Interaction with ammonia results in the synthesis of the nanopowders. - Abstract: Interaction of intermetallic compounds with ammonia was studied as a processing route to synthesize hydrides and hydridonitrides of intermetallic compounds having various stoichiometries and types of crystal structures, including A{sub 2}B, AB, AB{sub 2}, AB{sub 5} and A{sub 2}B{sub 17} (A = Mg, Ti, Zr, Sc, Nd, Sm; B = transition metals, including Fe, Co, Ni, Ti and nontransition elements, Al and B). In presence of NH{sub 4}Cl used as an activator of the reaction between ammonia and intermetallic alloys, their interaction proceeds at rather mild P–T conditions, at temperatures 100–200 °C and at pressures of 0.6–0.8 MPa. The mechanism of interaction of the alloys with ammonia appears to be temperature-dependent and, following a rise of the interaction temperature, it leads to the formation of interstitial hydrides; interstitial hydridonitrides; disproportionation products (binary hydride; new intermetallic hydrides and binary nitrides) or new metal–nitrogen–hydrogen compounds like magnesium amide Mg(NH{sub 2}){sub 2}. The interaction results in the synthesis of the nanopowders where hydrogen and nitrogen atoms become incorporated into the crystal lattices of the intermetallic alloys. The nitrogenated materials have the smallest particle size, down to 40 nm, and a specific surface area close to 20 m{sup 2}/g.

  16. Vacuum brazing of TiAl48Cr2Nb2 casting alloys based on TiAl (γ intermetallic compound

    Directory of Open Access Journals (Sweden)

    Z. Mirski

    2010-01-01

    Full Text Available A growing interest in modern engineering materials characterised by increasingly better operational parameters combined with a necessity to obtain joints of such materials representing good operation properties create important research and technological problems of today. These issues include also titanium joints or joints of titanium alloys based on intermetallic compounds. Brazing is one of the basic and sometimes even the only available welding method used for joining the aforesaid materials in production of various systems, heat exchangers and, in case of titanium alloys based on intermetallic compounds, turbine elements and space shuttle plating etc. This article presents the basic physical and chemical properties as well as the brazability of alloys based on intermetallic compounds. The work also describes the principle and mechanisms of diffusion-brazed joint formation as well as reveals the results of metallographic and strength tests involving diffusion-welded joints of TiAl48Cr3Nb2 casting alloy based on TiAl (γ phase with the use of sandwich-type layers of silver-based parent metal (grade B- Ag72Cu-780 (AG 401 and copper (grade CF032A. Structural examination was performed by means of light microscopy, scanning electron microscope (SEM and energy dispersion spectrometer (EDS. Furthermore, the article reveals the results of shear strength tests involving the aforementioned joints.

  17. INFLUENCE OF THE HOMOGENIZATION TEMPERATURE ON THE MICROSTRUCTURE AND PROPERTIES OF AlSi10CuNiMgMn ALLOY

    Directory of Open Access Journals (Sweden)

    Jaromir Cais

    2017-03-01

    Full Text Available The article examines the impact of changes in homogenization temperature in the hardening process on the microstructure of aluminum alloys. Samples where the research was conducted were cast from AlSi10CuNiMn alloy produced by gravity casting technology in metal mold. Subsequently, the castings were subjected to a heat treatment. In an experiment with changing temperature and staying time in the process of homogenization. The microstructure of the alloy was investigated by methods of light and electron microscopy. Examination of the microstructure has focused on changing the morphology of separated particles of eutectic silicon and intermetallic phases. Analysis of intermetallic phases was supplemented by an analysis of the chemical composition - EDS analysis. Effect of heat treatment on the properties investigated alloy was further complemented by Vickers microhardness. Investigated alloy is the result of longtime research conducted at Faculty of Production Technology and Management.

  18. Electronic structure and magnetic properties of selected lanthanide and actinide intermetallic Laves-phase alloys

    DEFF Research Database (Denmark)

    Eriksson, Olle; Johansson, Börje; Brooks, M. S. S.

    1989-01-01

    The electronic structure and magnetic properties of some yttrium and uranium Laves-phase pseudobinary alloys with 3d elements have been calculated. The calculations were done by simulating the electronic structure of the alloy by that of an ordered compound with the same stoichiometry. In general...

  19. Oxide composite prepared from intermetallic and amorphous Zr67Fe30M3- (M=Au, Pt) alloys and their catalytic activity for CO oxidation

    Science.gov (United States)

    Huang, Yung-Han; Wang, Sea-Fue; Kameoka, Satoshi; Miyamoto, Kanji; Tsai, An-Pang

    2017-01-01

    In this study, Zr67Fe30M3 (M=Au, Pt) intermetallic compounds and amorphous alloys were prepared and used as precursors for the synthesis of oxides. Oxidation treatment of the intermetallic compounds at 500 °C followed by X-ray diffraction (XRD) analysis indicated that zirconium and iron were oxidized to ZrO2 and Fe2O3, respectively. In the case of Zr67Fe30M3 amorphous alloys, cubic Zr6Fe3O was observed on the surface of the ribbons after heat treatment at 500 °C in vacuum. Addition of 3% of gold or platinum to the alloy resulted in an increase in the lattice constants of the Zr6Fe3O phase. Grounding the treated ribbons into powders followed by an oxidation treatment at 500 °C in air produced Fe2O3 and ZrO2 supports, where Au and Pt are dissolved in the oxides as confirmed by X-ray photoelectron spectroscopy (XPS). No matter precursors are intermetallics or amorphous phases, the resultant oxides are the same. Although Pt and Au dissolved in the oxides, catalytic activities for CO oxidation were significant improved.

  20. The Effect of Increasing Sn Content on High-Temperature Mechanical Deformation of an Mg-3%Cu-1%Ca Alloy

    Directory of Open Access Journals (Sweden)

    Georgios S.E. Antipas

    2013-11-01

    Full Text Available Chill casting of magnesium alloy samples with secondary alloying elements of Cu, Ca and Sn at % w.t. concentrations in the range 1–5, 0.1–5 and 0.1–3 respectively, gave rise to appreciably enhanced resistance to high-temperature creep, while maintaining good heat conductivity. The latter was considered to be driven by Cu and Mg-Cu intermetallics while it was clear that Sn mediated the high-temperature performance, mainly via networks of Mg2Sn and MgCaSn precipitates along the Mg matrix grain boundaries. It was postulated that Sn formed intermetallics by preferential substitution of Ca atoms and, thus, did not degrade the heat conductivity by retaining Cu. The % w.t. stoichiometry with the optimum combination of heat conductivity and resistance to high-temperature creep was found to be Mg-3Cu-1Ca-0.1Sn.

  1. Mechanical properties of high carbon Fe{sub 3}Al-based intermetallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baligidad, R.G.; Radhakrishna, A.; Prakash, U. [Defence Metallurgical Research Lab., Hyderabad (India)

    1998-12-15

    Fe-16 wt% Al alloys containing 0.074 to 1.1 wt% carbon were prepared by a combination of air induction melting and electroslag remelting (ESR). The cast ESR ingots exhibited a two-phase structure consisting of Fe{sub 3}AlC{sub 0.5} precipitate in an Fe{sub 3}Al-based matrix. The precipitate volume fraction increased with increasing carbon content of the ingot. Most of the carbon was found to be present as the Fe{sub 3}AlC{sub 0.5} phase. The bulk hardness of these alloys increases linearly with increasing volume fraction of the precipitates. However, the Young`s modulus of these alloys was measured to be around 175 GPa and does not change significantly with change in volume fraction of the phases present. This is explained by arguing that both the matrix as well as precipitate exhibit the same modulus values for the alloys studied in the present work. Both the bulk hardness and Young`s modulus follow the rule of mixture for two phase alloys. However, the same may not be true for structure sensitive properties such as yield strength, ductility and creep resistance. (orig.) 18 refs.

  2. Volume expansion contribution to the magnetism of atomically disordered intermetallic alloys

    Science.gov (United States)

    Nogués, J.; Apiñaniz, E.; Sort, J.; Amboage, M.; D'Astuto, M.; Mathon, O.; Puzniak, R.; Fita, I.; Garitaonandia, J. S.; Suriñach, S.; Muñoz, J. S.; Baró, M. D.; Plazaola, F.; Baudelet, F.

    2006-07-01

    The origin of magnetism in atomically disordered transition-metal-nonmagnetic (i.e., FeAl) alloys has been investigated by dichroism and diffraction measurements at high pressure and by band structure calculations. The results show that, in contrast to earlier studies, besides the effects of the local environment of the magnetic ions, disorder-induced lattice changes play a key role in the magnetic properties of these systems. We demonstrate experimentally and theoretically that about 35-45% of the magnetic moment of Fe60Al40 alloys arises from lattice expansion effects induced during the disordering process. Such large effects in Fe60Al40 could actually be related to the moment-volume instability observed in these alloys.

  3. Mechanical properties of cast composites on Al-Si alloy matrix with intermetallic phases reinforcement

    Directory of Open Access Journals (Sweden)

    M. Cholewa

    2010-10-01

    Full Text Available In paper is presented research results of microstructure and selected mechanical properties of composite on EN AC-AlSi11 alloy matrix with reinforcement in form of particle of Cr-Fe-C alloy (composite ex situ and carbonitrides Ti, Zr, V (composite in situ. Metallographic studies were made with use of light microscopy and with scanning electron microscope with EDS. In range of studies of usable properties were made measurements of hardness, abrasive wear resistance of type metal-mineral, impact resistance, tensile strength, yield point and elongation.

  4. Spark plasma-sintered Sn-based intermetallic alloys and their Li-storage studies

    CSIR Research Space (South Africa)

    Nithyadharseni, P

    2016-06-01

    Full Text Available In the present study, SnSb, SnSb/Fe, SnSb/Co, and SnSb/Ni alloy powders processed by co-precipitation were subjected to spark plasma-sintering (SPS) at 400 °C for 5 min. The compacts were structurally and morphologically characterized by X...

  5. Amino Acids Aided Sintering for the Formation of Highly Porous FeAl Intermetallic Alloys.

    Science.gov (United States)

    Karczewski, Krzysztof; Stepniowski, Wojciech J; Salerno, Marco

    2017-07-04

    Fabrication of metallic foams by sintering metal powders mixed with thermally degradable compounds is of interest for numerous applications. Compounds releasing gaseous nitrogen, minimizing interactions between the formed gases and metallic foam by diluting other combustion products, were applied. Cysteine and phenylalanine, were used as gas releasing agents during the sintering of elemental Fe and Al powders in order to obtain metallic foams. Characterization was carried out by optical microscopy with image analysis, scanning electron microscopy with energy dispersive spectroscopy, and gas permeability tests. Porosity of the foams was up to 42 ± 3% and 46 ± 2% for sintering conducted with 5 wt % cysteine and phenylalanine, respectively. Chemical analyses of the formed foams revealed that the oxygen content was below 0.14 wt % and the carbon content was below 0.3 wt %. Therefore, no brittle phases could be formed that would spoil the mechanical stability of the FeAl intermetallic foams. The gas permeability tests revealed that only the foams formed in the presence of cysteine have enough interconnections between the pores, thanks to the improved air flow through the porous materials. The foams formed with cysteine can be applied as filters and industrial catalysts.

  6. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    Science.gov (United States)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  7. Copper Alloy For High-Temperature Uses

    Science.gov (United States)

    Dreshfield, Robert L.; Ellis, David L.; Michal, Gary

    1994-01-01

    Alloy of Cu/8Cr/4Nb (numbers indicate parts by atom percent) improved over older high-temperature copper-based alloys in that it offers enhanced high temperature strength, resistance to creep, and ductility while retaining most of thermal conductivity of pure copper; in addition, alloy does not become embrittled upon exposure to hydrogen at temperatures as high as 705 degrees C. Designed for use in presence of high heat fluxes and active cooling; for example, in heat exchangers in advanced aircraft and spacecraft engines, and other high-temperature applications in which there is need for such material. High conductivity and hardness of alloy exploited in welding electrodes and in high-voltage and high-current switches and other applications in which wear poses design problem.

  8. Room temperature creep in metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deibler, Lisa Anne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Materials Characterization and Performance

    2014-09-01

    Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 Tm for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

  9. Effects of Alloying Elements on Room and High Temperature Tensile Properties of Al-Si Cu-Mg Base Alloys =

    Science.gov (United States)

    Alyaldin, Loay

    In recent years, aluminum and aluminum alloys have been widely used in automotive and aerospace industries. Among the most commonly used cast aluminum alloys are those belonging to the Al-Si system. Due to their mechanical properties, light weight, excellent castability and corrosion resistance, these alloys are primarily used in engineering and in automotive applications. The more aluminum is used in the production of a vehicle, the less the weight of the vehicle, and the less fuel it consumes, thereby reducing the amount of harmful emissions into the atmosphere. The principal alloying elements in Al-Si alloys, in addition to silicon, are magnesium and copper which, through the formation of Al2Cu and Mg2Si precipitates, improve the alloy strength via precipitation hardening following heat treatment. However, most Al-Si alloys are not suitable for high temperature applications because their tensile and fatigue strengths are not as high as desired in the temperature range 230-350°C, which are the temperatures that are often attained in automotive engine components under actual service conditions. The main challenge lies in the fact that the strength of heat-treatable cast aluminum alloys decreases at temperatures above 200°C. The strength of alloys under high temperature conditions is improved by obtaining a microstructure containing thermally stable and coarsening-resistant intermetallics, which may be achieved with the addition of Ni. Zr and Sc. Nickel leads to the formation of nickel aluminide Al3Ni and Al 9FeNi in the presence of iron, while zirconium forms Al3Zr. These intermetallics improve the high temperature strength of Al-Si alloys. Some interesting improvements have been achieved by modifying the composition of the base alloy with additions of Mn, resulting in an increase in strength and ductility at both room and high temperatures. Al-Si-Cu-Mg alloys such as the 354 (Al-9wt%Si-1.8wt%Cu-0.5wt%Mg) alloys show a greater response to heat treatment as a

  10. Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al-12.6%Si alloy.

    Science.gov (United States)

    Arenas, M A; Frutos, E; Saldaña, L; Conde, A; Labajos-Broncano, L; González-Martín, M L; González-Carrasco, J L; Vilaboa, N

    2011-04-01

    Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al-12.6%Si alloy for 120 s. The coating consists of the Al(12)(Fe,Cr)(3)Si(2) intermetallic. In vitro corrosion behaviour has been evaluated in the Ringer's solution by means of potentiodynamic curves and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised corrosion with respect to the substrate. XPS analysis suggests that the ennoblement of the pitting potential is due to the formation of a chromium oxyhydroxide containing passive layer. The intermetallic coating shows a good biocompatibility, as demonstrated by culturing human mesenchymal stem cells isolated from bone marrow which attached, grew and differentiated to the osteoblastic lineage to a similar extent on coated and bare steels. In summary, this study proposes a method that generates Ni-free coatings of the stainless steel with useful properties for biomedical applications.

  11. Intermetallic {gamma}-titanium aluminide based alloys from a metallographic point of view. A continuation; Intermetallische {gamma}-Titanaluminid-Basislegierungen aus metallographischer Sicht. Eine Fortsetzung

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Helmut; Mayer, Svea [Montanuniversitaet Leoben (Austria). Inst. fuer Metallkunde und Werkstoffpruefung

    2011-02-15

    This article is a continuation of the article ''Intermetallic {gamma}-Titanium Aluminide Based Alloys from a Metallographic Point of View'' by H. Clemens and F. Jeglitsch published in Practical Metallography, 37 (2000) 194-217. In addition to the motivation behind the development of these types of materials, this second part also contains details regarding their properties and possible applications. The composition of such modern multiphase alloys is described and their processing routes discussed. In this respect, the development strategy of the current {gamma}-TiAl based alloys is presented. The micro- and nano-structures present after processing and multiple heat treatments are also described. Each of these points is illustrated with examples taken from metallographic investigations interpreted with reference to both physical metallurgy and materials physics. (orig.)

  12. Vapor phase lubrication of high temperature alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hanyaloglu, B.F.; Graham, E.E.; Oreskovic, T.; Hajj, C.G. [Cleveland State Univ., OH (United States)

    1995-06-01

    In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would exhibit similar behavior. It was found that under static conditions, all three alloys formed a lubricious nodular coating when exposed to a vapor of aryl phosphate. Under dynamic sliding conditions at 500{degrees}C, these alloys were successfully lubricated with a coefficient of friction of 0.1 and no detectable wear. In order to explain these results, a direct correlation between successful vapor phase lubrication and the composition of the alloys containing aluminum has been proposed. If the ratio of copper/aluminum or iron/aluminum is greater that 100 vapor phase, lubrication will be successful. If the ratio is less than 10, a passive aluminum oxide layer will prevent vapor phase lubrication. By selecting alloys with a high iron or copper content, vapor phase lubrication can provide excellent lubrication at high temperatures. 14 refs., 11 figs., 1 tab.

  13. Nanophase intermetallic FeAl obtained by sintering after mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    D' Angelo, L., E-mail: luisa.dangelo@gmail.co [Departamento de Mecanica, UNEXPO, Luis Caballero Mejias, Charallave (Venezuela, Bolivarian Republic of); D' Onofrio, L. [Facultad de Ciencias, Dpto. Fisica, Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of); Gonzalez, G., E-mail: gemagonz@ivic.v [Laboratorio de Materiales, Centro Tecnologico, Instituto Venezolano de Investigaciones Cientificas, Apdo. 21827, Caracas 1020A (Venezuela, Bolivarian Republic of)

    2009-08-26

    The preparation of bulk nanophase materials from nanocrystalline powders has been carried out by the application of sintering at high pressure. Fe-50 at.%Al system has been prepared by mechanical alloying for different milling periods from 1 to 50 h, using vials and balls of stainless steel and a ball-to-powder weight ratio (BPR) of 8:1 in a SPEX 8000 mill. Sintering of the 5 and 50 h milled powders was performed under high uniaxial pressure at 700 deg. C. The characterization of powders from each interval of milling was performed by X-ray diffraction, Moessbauer spectroscopy, scanning and transmission electron microscopy. After 5 h of milling formation of a nanocrystalline alpha-Fe(Al) solid solution that remains stable up to 50 h occurs. The grain size decreases to 7 nm after 50 h of milling. The sintering of the milled powders resulted in a nanophase-ordered FeAl alloys with a grain size of 16 nm. Grain growth during sintering was very small due to the effect of the high pressure applied.

  14. Intermetallic Formation and Fluidity in Sn-Rich Sn-Cu-Ni Alloys

    Science.gov (United States)

    Gourlay, C. M.; Nogita, K.; Read, J.; Dahle, A. K.

    2010-01-01

    This paper investigates the phase equilibria and solidification behavior of Sn-Cu-Ni alloys with compositions in the range of 0 wt.% to 1.5 wt.% Cu and 0 wt.% to 0.3 wt.% Ni. The isothermal section at 268°C in the Sn-rich corner was determined. No evidence for a ternary phase was found, and the section is in good agreement with past experimental studies that report wide solubility ranges for (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. The vacuum fluidity test was applied to compositions that are liquid at 268°C to map the variation in microstructure and flow behavior with composition in this system. Significant variations in fluidity length were measured among the Sn-Cu-Ni alloys, and the variations correlate with the microstructure that develops during solidification. The generated fluidity map enables the selection of Sn-Cu-Ni solder compositions that exhibit good fluidity behavior during solidification and form near-eutectic microstructures.

  15. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys and intermetallic materials: Phase stability in NbCr{sub 2} Laves phase alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States); Liu, C.T. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases is studied in this paper, using data from binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor (e/a = the average number of electrons per atom outside the closed shells of the component atoms) is the determinate factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves phase structures were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure was stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of transition-metal A{sub 3}B intermetallic compounds and Mg-based Laves phases is also reviewed and compared with the present observations in transition-metal Laves phases.

  16. Room-Temperature Indentation Creep and the Mechanical Properties of Rapidly Solidified Sn-Sb-Pb-Cu Alloys

    Science.gov (United States)

    Kamal, Mustafa; El-Bediwi, A.; Lashin, A. R.; El-Zarka, A. H.

    2016-05-01

    In this paper, we study the room-temperature indentation creep and the mechanical properties of Sn-Sb-Pb-Cu alloys. Rapid solidification from melt using the melt-spinning technique is applied to prepare all the alloys. The experimental results show that the magnitude of the creep displacement increases with the increase in both time and applied load, and the stress exponent increases with the increase in the copper content in the alloys which happens primarily due to the existence of the intermetallic compounds SbSn and Cu6Sn5. The calculated values of the stress exponent are in the range of 2.82 to 5.16, which are in good agreement with the values reported for the Sn-Sb-Pb-Cu alloys. We have also studied and analyzed the structure, elastic modulus, and internal friction of the Sn-Sb-Pb-Cu alloys.

  17. Microstructure of AlSi17Cu5 alloy after overheating over liquidus temperature

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2015-01-01

    Full Text Available The paper presents microstructure tests of alloy AlSi17Cu5. In order to disintegrate the primary grain of silicon the so-called time-temperature transformation TTT was applied which was based on overheating the liquid alloy way over the temperature Tliq., soaking in it for 30 minutes and casting it to a casting mould. It was found that such process causes the achievement of fine-crystalline structure and primary silicon crystals take up the form of pentahedra or frustums of pyramids. With the use of X-ray microanalysis and X-ray diffraction analysis the presence of intermetallic phases Al2Cu, Al4Cu9 which are the ingredients of eutectics α - AlCu - β and phase Al9Fe2Si which is a part of eutectic α - AlFeSi - β was confirmed.

  18. Brazing Alloys Indicate Turbomachinery Temperatures

    Science.gov (United States)

    Schlaff, J. W.

    1985-01-01

    Foils serve as consumable thermometers. Stainless-steel tab with circular window holds brazing-foil sample in place. Tab tacked to object to be tested with capacitive-discharge spot welder operating in range 10 + 1 joules. After measurements, tabs and samples chiseled off, leaving tested object fairly well intact. Technique used on objects made of alloys with iron, nickel, or cobalt as principal ingredients.

  19. Magnesium Diecasting Alloys for High Temperature Applications

    Science.gov (United States)

    Pekguleryuz, Mihriban O.; Kaya, A. Arslan

    New growth area for automotive use of magnesium is powertrain applications such as the transmission case and engine block. These applications see service conditions in the temperature range of 150-200C under 50-70 MPa of tensile and compressive loads. In addition, metallurgical stability, fatigue resistance, corrosion resistance and castability requirements need to be met. A decade of research and development has resulted in a number of creep- resistant magnesium alloys that are potential candidates for elevated-temperature automotive applications. These alloys are mostly based on rare-earth and alkaline earth element additions to magnesium. This paper gives an overview of the various magnesium alloy systems for use in elevated-temperature applications.

  20. Intermetallics: past, present and future

    Directory of Open Access Journals (Sweden)

    Morris, D. G.

    2005-12-01

    Full Text Available Intermetallics have seen extensive world-wide attention over the past decades. For the most part these studies have examined multi-phase aluminide based alloys, because of their high stiffness, combined with reasonable strength and ductility, good structural stability and oxidation resistance, and attempted to improve current Ni-base superalloys, Ti-base alloys, or Fe-base stainless steels for structural aerospace applications. The current status of development and application of such materials is briefly reviewed. Future developments are taking intermetallics from the realm of "improved high-temperature but low-ductility metallic alloys" into the realm of "improved aggressive-environment, high-toughness ceramic-like alloys". Such evolution will be outlined.

    Durante los últimos décadas ha habido un desarrollo de los intermetálicos, sobre todo por aplicaciones estructurales a alta temperatura en aplicaciones aeroespaciales, donde, por su rigidez alta, en combinación con una resistencia mecánica y ductilidad razonable, su buena estabilidad estructural y resistencia a la oxidación, han sido vistos como versiones avanzadas y mejoradas de las aleaciones metálicas como, por ejemplo, las superaleaciones a base de nitrógeno y las aleaciones de titanio. Se discute el desarrollo importante durante las últimas décadas, y también los nuevos desarrollos probables durante los próximos años. Se podrían ver los intermetálicos como versiones mejoradas de los cerámicos.

  1. Effects of intermetallic phases on the electrochemical properties of rapidly-solidified Si-Cr alloys for rechargeable Li-ion batteries

    Science.gov (United States)

    Ha, Jeong Ae; Jo, In Joo; Park, Won-Wook; Sohn, Keun Yong

    2016-09-01

    The microstructures and the electrochemical properties of rapidly-solidified Si-Cr alloys of various compositions were investigated in order to elucidate the effects of intermetallic phases on the cyclic energy capacity of the materials. Rapidly-solidified ribbons of the alloys were prepared by using a melt-spinning process, which is one of the most efficient rapid-solidification processes. The ribbons were fragmented by using a ball-milling process to produce powders of the alloys. To examine the electrochemical characteristics of the alloys, we mixed each of the alloy powders with Ketjenblack®, a conductive material, and a binder dissolved in deionized water and used it to form electrodes. The electrolyte used was 1.5-M LiPF6 dissolved in ethyl carbonate/dimethyl carbonate/fluoroethylene carbonate. The microstructures and the phases of the alloys were analyzed by using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses. The obtained results showed that the microstructures of the rapidly-solidified Si-Cr alloys were composed of Si and CrSi2 phases. Fine Si particles with diameters of 50 - 100 nm were observed in an eutectic constituent while the sizes of the primary Si and CrSi2 phases were relatively larger at 500 - 900 nm. The specific energy capacities ( C) of the Si-Cr alloys decreased linearly with increasing volume fraction ( f) of the CrSi2 phase as follows: C = -1,667 f + 1,978 after the 50th cycle. The Columbic efficiency after the 3rd cycle increased slightly with increasing volume fraction of the CrSi2 phase; this was effective in improving the cycling capacity of the Si particles.

  2. The Solidification Behavior of AA2618 Aluminum Alloy and the Influence of Cooling Rate

    Science.gov (United States)

    Liu, Yulin; Liu, Ming; Luo, Lei; Wang, Jijie; Liu, Chunzhong

    2014-01-01

    In AA2618 aluminum alloy, the iron- and nickel-rich intermetallics formed during solidification are of great effect on the mechanical properties of the alloy at both room temperature and elevated temperatures. However, the solidification behavior of the alloy and the formation mechanism of the intermetallics during solidification of the alloy are not clear. This research fills the gap and contributes to understanding the intermetallic of the alloy. The results showed that cooling rate was of great influence on the formation of the intermetallics. Under the condition of slow cooling, the as-cast microstructures of the alloy were complex with many coarse eutectic compounds including Al9FeNi, Al7(CuNi)5, Si, Al2Cu and Al2CuMg. The phase Al9FeNi was the dominant intermetallic compound, which precipitated at the earlier stage of the solidification by eutectic reaction L → α-Al + Al9FeNi. Increasing the cooling rate would suppress the formation of the coarse eutectic intermetallics. Under the condition of near-rapid cooling, the as-cast microstructures of the alloy consisted of metastable intermetallics Al9FeNi and Al2Cu; the equilibrium eutectic compounds were suppressed. This research concluded that intermetallics could be refined to a great extent by near-rapid cooling. PMID:28788281

  3. The Solidification Behavior of AA2618 Aluminum Alloy and the Influence of Cooling Rate.

    Science.gov (United States)

    Liu, Yulin; Liu, Ming; Luo, Lei; Wang, Jijie; Liu, Chunzhong

    2014-12-09

    In AA2618 aluminum alloy, the iron- and nickel-rich intermetallics formed during solidification are of great effect on the mechanical properties of the alloy at both room temperature and elevated temperatures. However, the solidification behavior of the alloy and the formation mechanism of the intermetallics during solidification of the alloy are not clear. This research fills the gap and contributes to understanding the intermetallic of the alloy. The results showed that cooling rate was of great influence on the formation of the intermetallics. Under the condition of slow cooling, the as-cast microstructures of the alloy were complex with many coarse eutectic compounds including Al₉FeNi, Al₇(CuNi)₅, Si, Al₂Cu and Al₂CuMg. The phase Al₉FeNi was the dominant intermetallic compound, which precipitated at the earlier stage of the solidification by eutectic reaction L → α-Al + Al₉FeNi. Increasing the cooling rate would suppress the formation of the coarse eutectic intermetallics. Under the condition of near-rapid cooling, the as-cast microstructures of the alloy consisted of metastable intermetallics Al₉FeNi and Al₂Cu; the equilibrium eutectic compounds were suppressed. This research concluded that intermetallics could be refined to a great extent by near-rapid cooling.

  4. TEM studies of high temperature corrosion behaviour of TiAl intermetallics with surface modifications

    Energy Technology Data Exchange (ETDEWEB)

    Du, H.L.; Rose, S.R.; Xiang, Z.D.; Datta, P.K. [University of Northumbria, Advanced Materials Research Institute, Ellison Building, Ellison Place, NE1 8 ST Newcastle upon Tyne (United Kingdom); Li, X.Y. [Ion Engieneering Research Institute Corporation, 2-8-1, Tsudayamate, Hirakata, Osaka 513-0128 (Japan)

    2003-04-01

    The oxidation/sulphidation behaviour of a Ti-46.7Al-1.9W-0.5Si alloy with a TiAl{sub 3} diffusion coating was studied in an environment of H{sub 2}/H{sub 2}S/H{sub 2}O at 850{sup o}C. The kinetic results demonstrate that the TiAl{sub 3} coating significantly increased the high temperature corrosion resistance of Ti-46.7Al-1.9W-0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al{sub 2}O{sub 3} scale on the surface of the TiAl{sub 3}-coated sample was responsible for the enhancement of the corrosion resistance. The Ti-46.7Al-1.9W-0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received samples were subjected to cyclic oxidation in an open air at 800{sup o}C. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  5. High Temperature Advanced Structural Composites. Book 1: Executive Summary and Intermetallic Compounds

    Science.gov (United States)

    1993-04-02

    RHIPed at 12500C. 5 . JAa1u’•-_" ., Pib.r OD-. Aligned short fiber composites chn IVmade by cobiting pa r insction molding (powder extrusion) with- a s...Justification ....................... By Di-•t ibution I Availability Codes Avail and I or Dist Special DTIC QUALITY7 uzsPECTED 5 XICURITY...reprints of papers on Intermetallic Compounds. Volume two contains reprints of papers on Ceramic Matrix Composites, Fiber Processi and Properties and

  6. Microstructures and mechanical property of a Fe-Ni-Al-C alloy containing B2 intermetallic compounds

    Science.gov (United States)

    Gao, Si; Bai, Yu; Shibata, Akinobu; Tsuji, Nobuhiro

    2017-07-01

    Specimens of a Fe-24Ni-6Al-0.4C alloy with ultra-fine grained dual phase microstructures composed of FCC austenite and B2 phases were fabricated by cold rolling followed by annealing treatments in the temperature range from 850°C to 1100°C. Tensile tests of these specimens revealed a similar yield stress while the tensile strength was found to vary significantly. The different tensile strength of the samples was considered to be caused by the different volume fractions of the hard B2 phase.

  7. Microstructure and mechanical properties control of γ-TiAl(Nb, Cr, Zr) intermetallic alloy by induction float zone processing

    Energy Technology Data Exchange (ETDEWEB)

    Kartavykh, A.V., E-mail: karta@korolev-net.ru [National University of Science and Technology “MISIS”, Leninsky pr. 4, 119049 Moscow (Russian Federation); Technological Institute for Superhard and Novel Carbon Materials (TISNCM), 7a Centralnaya str., 142190 Troitsk, Moscow (Russian Federation); Asnis, E.A.; Piskun, N.V.; Statkevich, I.I. [The E.O. Paton Electric Welding Institute, 11 Bozhenko str., 03680 Kyiv (Ukraine); Gorshenkov, M.V. [National University of Science and Technology “MISIS”, Leninsky pr. 4, 119049 Moscow (Russian Federation)

    2015-09-15

    Highlights: • Induction float zoning of as-synthesized Ti–44Al–5Nb–3Cr–1.5Zr (at.%) alloy. • Special ordered phase microstructure engineering by FZ conditions. • Refining effect by FZ with respect to dissolved oxygen. • Comparative compression testing. • Drastic enhancement of mechanical properties. - Abstract: Advanced Ti–44Al–5Nb–3Cr–1.5Zr (at.%) structural alloy was previously synthesized by the electron beam semi-continuous casting technique. The rod-shaped blanks of raw alloy with irregular coarse microstructure have been directionally upward re-solidified by the vertical induction float zone (FZ) technique in argon flow. FZ processing led to specific duplex microstructure creation consisting of (γ + α{sub 2}) lamellar colonies and γ grains with minor intergranular fraction of B2 phase. The grain size, interlamellar spacing and ordered axial alignment of lamellae along the applied thermal gradient were controlled by FZ conditions. Structure, phase and elemental composition were analyzed with XRD, SEM, EBSD and hot gas extraction techniques. Mechanical properties were comparatively examined by uniaxial compression testing at ambient temperature. It was shown that (1) fine submicron interlamellar spacing; (2) ordered lamellae alignment; (3) relative volumetric ratio of (γ + α{sub 2})/γ/B2 structural-phase constituents and (4) dissolved oxygen content are the key parameters for controlling the compressive properties of FZ-alloy. Both yield strength, and ultimate compressive strength enhance drastically as a result of the FZ processing, being in correlation with the duplex microstructure development and refining of the material from oxygen.

  8. Development of High-Strength High-Temperature Cast Al-Ni-Cr Alloys Through Evolution of a Novel Composite Eutectic Structure

    Science.gov (United States)

    Pandey, P.; Kashyap, S.; Tiwary, C. S.; Chattopadhyay, K.

    2017-12-01

    Aiming to develop high-strength Al-based alloys with high material index (strength/density) for structural application, this article reports a new class of multiphase Al alloys in the Al-Ni-Cr system that possess impressive room temperature and elevated temperature (≥ 200 °C) mechanical properties. The ternary eutectic and near eutectic alloys display a complex microstructure containing intermetallic phases displaying hierarchically arranged plate and rod morphologies that exhibit extraordinary mechanical properties. The yield strengths achieved at room temperatures are in excess of 350 MPa with compressive plastic strains of more than 30 pct (without fracturing) for these alloys. The stability of the complex microstructure also leads to a yield stress of 191 ± 8 to 232 ± 5 MPa at 250 °C. It is argued that the alloys derive their high strength and impressive plasticity through synergic effects of refined nanoeutectics of two different morphologies forming a core shell type of architecture.

  9. Cast Aluminum Alloy for High Temperature Applications

    Science.gov (United States)

    Lee, Jonathan A.

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties.

  10. Comments on intermetallic thermochemistry

    Directory of Open Access Journals (Sweden)

    Borzone G.

    2002-01-01

    Full Text Available The need of a concerted multi-disciplinary approach in the investigation of intermetallic systems and the role of thermochemistry are underlined. The activity carried out in the Author’s laboratory in the alloy thermodynamics is summarized. The different instruments (calorimeters built in laboratory are briefly presented and their performance discussed. The results obtained in the measurement of the enthalpy of formation mainly of several rare earth alloys are described. The characteristics of the Eu and Yb thermochemistry and crystallochemistry are finally underlined.

  11. EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

    Directory of Open Access Journals (Sweden)

    Prabhu Paulraj

    2015-08-01

    Full Text Available Duplex Stainless Steels (DSS and Super Duplex Stainless Steel (SDSS have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic phases and their effects on corrosion and mechanical properties. First the effect of various alloying elements on DSS and SDSS has been discussed followed by formation of various intermetallic phases. The intermetallic phases affect impact toughness and corrosion resistance significantly. Their deleterious effect on weldments has also been reviewed.

  12. Room temperature deformation of in-situ grown quasicrystals embedded in Al-based cast alloy

    Directory of Open Access Journals (Sweden)

    Boštjan Markoli

    2013-12-01

    Full Text Available An Al-based cast alloy containing Mn, Be and Cu has been chosen to investigate the room temperature deformation behavior of QC particles embedded in Al-matrix. Using LOM, SEM (equipped with EDS, conventional TEM with SAED and controlled tensile and compression tests, the deformation response of AlMn2Be2Cu2 cast alloy at room temperature has been examined. Alloy consisted of Al-based matrix, primary particles and eutectic icosahedral quasicrystalline (QC i-phase and traces of Θ-Al2Cu and Al10Mn3. Tensile and compression specimens were used for evaluation of mechanical response and behavior of QC i-phase articles embedded in Al-cast alloy. It has been established that embedded QC i-phase particles undergo plastic deformation along with the Al-based matrix even under severe deformation and have the response resembling that of the metallic materials by formation of typical cup-and-cone feature prior to failure. So, we can conclude that QC i-phase has the ability to undergo plastic deformation along with the Al-matrix to greater extent contrary to e.g. intermetallics such as Θ-Al2Cu for instance.

  13. Corrosion behavior in high-temperature pressurized water of Zircaloy-4 joints brazed with Zr-Cu-based amorphous filler alloys

    Science.gov (United States)

    Lee, Jung Gu; Lee, Gyoung-Ja; Park, Jin-Ju; Lee, Min-Ku

    2017-05-01

    The compositional effects of ternary Zr-Cu-X (X: Al, Fe) amorphous filler alloys on galvanic corrosion susceptibility in high-temperature pressurized water were investigated for Zircaloy-4 brazed joints. Through an Al-induced microgalvanic reaction that deteriorated the overall nobility of the joint, application of the Zr-Cu-Al filler alloy caused galvanic coupling to develop readily between the Al-bearing joint and the Al-free base metal, finally leading to massive localized corrosion of the joint. Contrastingly, joints prepared with a Zr-Cu-Fe filler alloy showed excellent corrosion resistance comparable to that of the Zircaloy-4 base metal, since the Cu and Fe elements forming fine intermetallic particles with Zr did not influence the electrochemical stability of the resultant joints. The present results demonstrate that Fe is a more suitable alloying element than Al for brazing filler alloys subjected to high-temperature corrosive environments.

  14. Reviewing the class of Al-rich Ti-Al alloys: modeling high temperature plastic anisotropy and asymmetry

    Science.gov (United States)

    Chowdhury, Helal; Altenbach, Holm; Krüger, Manja; Naumenko, Konstantin

    2017-12-01

    In the last decades, the class of Ti-rich TiAl-based intermetallic materials has replaced many contemporary alloys till 900 °C. Due to higher oxidation resistance, 20% lower density and higher (about 150 °C more) operating temperature possibility of Al-rich TiAl alloys over Ti-rich side, phases from the Al-rich region of this alloy system are considered to be highly potential candidates for high temperature structural applications. Although there are a lot of works about Ti-rich alloys, however, investigation from the Al-rich side is very limited. This work reviews the class of Al-rich TiAl alloys in terms of phases, microstructures, morphology, deformation mechanisms, mechanical behaviors along with a possible micromechanical modeling approach. Single crystal like Ti-61.8at.%Al alloy from the Al-rich family has been chosen as an example for modeling high temperature anisotropy and tension-compression asymmetry. A possible comparison with Ti-rich side is also presented.

  15. Platinum Iron Intermetallic Nanoparticles Supported on Carbon Formed In Situ by High-Pressure Pyrolysis for Efficient Oxygen Reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei

    2016-01-01

    Carbon-supported PtFe alloy catalysts are synthesized by the one-step, high-temperature pyrolysis of Pt, Fe, and C precursors. As a result of the high temperature, the formed PtFe nanoparticles possess highly ordered, face-centered tetragonal, intermetallic structures with a mean size of ≈11.8 nm...

  16. Structure and mechanical properties of a eutectic high-temperature Nb-Si alloy grown by directional solidification

    Science.gov (United States)

    Karpov, M. I.; Vnukov, V. I.; Korzhov, V. P.; Stroganova, T. S.; Zheltyakova, I. S.; Prokhorov, D. V.; Gnesin, I. B.; Kiiko, V. M.; Kolobov, Yu. R.; Golosov, E. V.; Nekrasov, A. N.

    2014-04-01

    The structure and the short-term high-temperature strength of Ni-18.7 at % Si (Nb-Nb3Si eutectic) alloys fabricated by vacuum electron-beam zone melting and induction melting in an argon atmosphere are studied. The structure of the samples prepared by vacuum electron-beam zone melting is characterized by the presence of primary Nb5Si3 intermetallic precipitates and the absence of its secondary precipitates. The structure of the samples prepared by induction melting in an argon atmosphere has two characteristic zones, namely, eutectic and eutectoid ones.

  17. Fabrication of Intermetallic Titanium Alloy Based on Ti2AlNb by Rapid Quenching of Melt

    Science.gov (United States)

    Senkevich, K. S.; Serov, M. M.; Umarova, O. Z.

    2017-11-01

    The possibility of fabrication of rapidly quenched fibers from alloy Ti - 22Al - 27Nb by extracting a hanging melt drop is studied. The special features of the production of electrodes for spraying the fibers by sintering mechanically alloyed powdered components of the alloy, i.e., titanium hydride, niobium, and aluminum dust, are studied. The rapidly quenched fibers with homogeneous phase composition and fine-grained structure produced from alloy Ti - 22Al - 27Nb are suitable for manufacturing compact semiproducts by hot pressing.

  18. Intermetallics: past, present and future

    OpenAIRE

    Morris, D. G.; Muñoz-Morris, M. A.

    2005-01-01

    Intermetallics have seen extensive world-wide attention over the past decades. For the most part these studies have examined multi-phase aluminide based alloys, because of their high stiffness, combined with reasonable strength and ductility, good structural stability and oxidation resistance, and attempted to improve current Ni-base superalloys, Ti-base alloys, or Fe-base stainless steels for structural aerospace applications. The current status of development and application of such materia...

  19. Laser Brazing of High Temperature Braze Alloy

    Science.gov (United States)

    Gao, Y. P.; Seaman, R. F.; McQuillan, T. J.; Martiens, R. F.

    2000-01-01

    The Space Shuttle Main Engine (SSME) consists of 1080 conical tubes, which are furnace brazed themselves, manifolds, and surrounding structural jacket making almost four miles of braze joints. Subsequent furnace braze cycles are performed due to localized braze voids between the coolant tubes. SSME nozzle experiences extremely high heat flux (180 mW/sq m) during hot fire. Braze voids between coolant tubes may result in hot combustion gas escape causing jacket bulges. The nozzle can be disqualified for flight or result in mission failure if the braze voids exceed the limits. Localized braze processes were considered to eliminate braze voids, however, damage to the parent materials often prohibited use of such process. Being the only manned flight reusable rocket engine, it has stringent requirement on the braze process. Poor braze quality or damage to the parent materials limits the nozzle service life. The objective of this study was to develop a laser brazing process to provide quality, localized braze joints without adverse affect on the parent materials. Gold (Au-Cu-Ni-Pd-Mn) based high temperature braze alloys were used in both powder and wire form. Thin section iron base superalloy A286 tube was used as substrate materials. Different Laser Systems including CO2 (10.6 micrometers, 1kW), ND:YAG (1.06 micrometers, 4kW). and direct diode laser (808nm. 150W) were investigated for brazing process. The laser process variables including wavelength. laser power, travel speed and angle of inclination were optimized according to bead geometry and braze alloy wetting at minimum heat input level, The properties of laser brazing were compared to that of furnace brazing. Microhardness profiles were used for braze joint property comparison between laser and furnace brazing. The cooling rate of laser brazing was compared to furnace brazing based on secondary dendritic arm spacing, Both optical and Scanning Electron Microscope (SEM) were used to evaluate the microstructures of

  20. New Stainless Steel Alloys for Low Temperature Surface Hardening?

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2015-01-01

    The present contribution showcases the possibility for developing new surface hardenable stainless steels containing strong nitride/carbide forming elements (SNCFE). Nitriding of the commercial alloys, austenitic A286, and ferritic AISI 409 illustrates the beneficial effect of having SNCFE present...... in the stainless steel alloys. The presented computational approach for alloy design enables “screening” of hundreds of thousands hypothetical alloy systems by use of Thermo-Calc. Promising compositions for new stainless steel alloys can be selected based on imposed criteria, i.e. facilitating easy selection...... of candidate alloys designed for low temperature surface hardening....

  1. DEVELOPMENT OF HIGH-TEMPERATURE TITANIUM ALLOY VT9,

    Science.gov (United States)

    The paper describes work, done in 1957-58, in the course of the development of the high-temperature (HT) Ti alloy currently termed BT9(VT9). The...target requirements for the new alloy specified the development of a Ti alloy for forging billets and stamping blanks which at 500 degrees centigrade

  2. On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

    Energy Technology Data Exchange (ETDEWEB)

    Bhanu Sankara Rao, K.; Halford, G.R. (National Aeronautics Space Agency, Cleveland, OH (United States). Lewis Research Center); Schuster, H. (KFA, Juelich (Germany). Inst. for Reactor Materials)

    1994-08-15

    Alloys engineered for high-temperature application are frequently put into use in a thermodynamically unstable condition. Subsequent exposure to service temperatures may promote many thermally-assisted reactions such as formation, coarsening, and/or coalescence of precipitates. Superposition of cyclic straining may accelerate the kinetics of these reactions but also may cause reaction products having specific features not observed under simple thermal exposure. The influence of cyclic strain-induced microstructural changes on the fatigue behavior has to be considered in terms of their effects on both cyclic strength and life. The occurrence of massive (cellular) precipitation of M[sub 23]C[sub 6] on grain boundaries during elevated temperature low cycle fatigue testing has been reported in Type 304 stainless steel, Type 316 stainless steel, and Inconel 617 superalloy, and its presence has already been linked with reduction in high temperature ductility, an important engineering property on which low cycle fatigue (LCF) life depends to a large extent. Massive precipitation may render the austenitic engineering alloys susceptible to corrosion, which would have important bearing on the performance of these alloys in the oxidizing environments. Furthermore, the long term stability of massive M[sub 23]C[sub 6] particles is particularly important since the transformation of such a large structure into a brittle intermetallic phase (such as sigma) could produce a detrimental effect on the mechanical properties. The conditions and the mechanisms responsible for the occurrence of massive precipitation during LCF have not yet been established. This investigation is specifically aimed at understanding the influence of strain rate on massive precipitation and the mechanism responsible for the occurrence of massive M[sub 23]C[sub 6] precipitation in Alloy 800H during elevated temperature LCF testing.

  3. Influence of Intermetallic Phases on Fracture Resistance of Silumins

    Directory of Open Access Journals (Sweden)

    Mityayev O.

    2013-12-01

    Full Text Available In secondary aluminium alloys iron is the main detrimental impurity. It forms intermetallic phases which have lamellar shape, high brittleness and weak crystallographic conformity with the matrix. In the work the influence of intermetallic phases on the initiation and propagation of microcracks, mechanical and service properties of aluminium alloys has been investigated.

  4. Structural considerations of intermetallic electrodes for lithium batteries

    Science.gov (United States)

    Thackeray, M. M.; Vaughey, J. T.; Johnson, C. S.; Kropf, A. J.; Benedek, R.; Fransson, L. M. L.; Edstrom, K.

    Although metal alloys and intermetallic compounds have been researched extensively as possible negative electrodes for lithium batteries, only recently have efforts been made to monitor the phase transitions that occur during their reaction with lithium by in situ X-ray diffraction. These studies have lead to attempts to exploit those systems that show strong structural relationships between a parent structure and its lithiated products. In this paper, an overview of several systems is presented, particularly those that operate by lithium insertion/metal displacement reactions with a host metal array at room temperature. An analogy between these reactions and the high-temperature electrochemical reaction of sodium/nickel chloride cells, which is 100% efficient, is provided. On this basis, a prognosis for using intermetallic electrodes in lithium-ion cells is given.

  5. A review of rapid solidification studies of intermetallic compounds

    Science.gov (United States)

    Koch, C. C.

    1985-01-01

    A review of rapid solidification studies of high-temperature ordered intermetallic compounds is presented. Emphasis is on the nickel - and iron- aluminides which are of potential interest as structural materials. The nickel-base aluminides which have been rapidly solidified exhibit changes in grain size, compositional segregation, and degree of long range order (as reflected in APB size and distribution) which markedly affect mechanical properties. Some experiments indicate the formation of a metastable L1(2) phase in rapidly solidified Fe-(Ni,Mn)-Al-C alloys, while other work observes only a metastable fcc phase in the same composition range. The metastable phases and/or microstructures in both nickel and iron aluminides are destroyed by annealing at temperatures above 750 K, with subsequent degradation of mechanical properties. Rapid solidification studies of several other intermetallic compounds are briefly noted.

  6. High-temperature alloys for high-power thermionic systems

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Kwang S.; Jacobson, D.L.; D' cruz, L.; Luo, Anhua; Chen, Bor-Ling.

    1990-08-01

    The need for structural materials with useful strength above 1600 k has stimulated interest in refractory-metal alloys. Tungsten possesses an extreme high modulus of elasticity as well as the highest melting temperature among metals, and hence is being considered as one of the most promising candidate materials for high temperature structural applications such as space nuclear power systems. This report is divided into three chapters covering the following: (1) the processing of tungsten base alloys; (2) the tensile properties of tungsten base alloys; and (3) creep behavior of tungsten base alloys. Separate abstracts were prepared for each chapter. (SC)

  7. The influence of the surface distribution of Al{sub 6}(MnFe) intermetallic on the electrochemical response of AA5083 aluminium alloy in NaCl solutions

    Energy Technology Data Exchange (ETDEWEB)

    Bethencourt, M.; Botana, F.J.; Calvino, J.J.; Perez, J.; Rodriguez, M.A. [Cadiz Univ. (Spain). Dept. de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica; Marcos, M.

    1998-12-31

    In this paper the behaviour against pitting corrosion of different samples of AA5083 aluminium alloy has been studied. A correlation between the microstructure of the samples and their susceptibility to pitting has been established. Metallographic analysis combined with SEM and EDS techniques have allowed us to detect three intermetallic compounds in the samples. The particle size distribution and surface density of each intermetallic phase have been evaluated for the three AA5083 alloy samples coming from different suppliers. Significant differences in the microstructure of the three samples have been found. Full immersion test carried out in 3.5% aerated aqueous solutions showed that pitting starts at the locations of the Al{sub 6}(MnFe) intermetallic particles. As a consequence of this, the samples with higher Al{sub 6}(MnFe) content showed a higher pit density on its surface. The results of cyclic polarisation tests showed also a good correlation with the microstructural parameters. (orig.) 11 refs.

  8. Correlation of deformation mechanisms with the tensile and compressive behavior of NiAl and NiAl(Zr) intermetallic alloys

    Science.gov (United States)

    Bowman, R. R.; Noebe, R. D.; Raj, S. V.; Locci, I. E.

    1992-01-01

    To identify the mechanisms controlling strength and ductility in powder-extruded NiAl and NiAl + 0.05 at. pct Zr, tensile and compressive testing was performed from 300 to 1300 K for several grain sizes. Grain size refinement significantly increased yield stress in both alloys and, in some cases, slightly lowered the ductile-to-brittle transition temperature (DBTT), although no room-temperature tensile ductility was observed even in the finest grain size specimens. The small Zr addition increased the DBTT and changed the low-temperature fracture mode from intergranular in NiAl to a combination of intergranular and transgranular in the Zr-doped alloy. Scanning electron microscopy of compression specimens deformed at room temperature revealed the presence of grain-boundary cracks in both alloys. These cracks were due to the incompatibility of strain in the polycrystalline material, owing to the lack of five independent slip systems. The tendency to form grain-boundary cracks, in addition to the low fracture stress of these alloys, contributed to the lack of tensile ductility at low temperatures.

  9. Microstructural features associated with the effect of temperature on the dimensional stability of an automotive Al-A319 alloy

    Directory of Open Access Journals (Sweden)

    Hugo F. Lopez

    2016-05-01

    Full Text Available In this work an automotive Al-A319 was given a solid solution heat treatment (T4 at 753 K (480 °C for 4.5 hours and an ageing treatment (T7 at 513 K (240 °C for various times up to 3.0 h. The alloy in the T4 condition was dilatometrically tested at various temperatures in order to measure its relative dimensional changes. It was found that the dimensional changes are due to both, alloy thermal expansion and nucleation and growth of second phases. In addition, in the T7 condition the alloy strength and ductility were determined as a function of ageing times. Ageing promoted alloy strength but at the expenses of a rather poor alloy ductility (down to 1%. Apparently, Cu rich intermetallic phases and regions provided a brittle path for fracturing. In particular, microstructural characterization using high resolution transmission electron microscopy indicated that not all the Cu in the matrix was dissolved during the T4 treatment. Hence, after ageing (T7 these Cu-rich regions seemed to coarsen into spherical particles.

  10. Effect of Bonding Temperature on the Joining of Ti-6Al-4V Alloy Using Cu Coatings and Sn Interlayers

    Science.gov (United States)

    AlHazaa, Abdulaziz N.; AlGharbi, Sultan H.; Nishikawa, Hiroshi

    2017-01-01

    Titanium alloy Ti-6Al-4V samples were bonded together using Cu coatings and Sn interlayers. The bonding of titanium samples was successful at various temperatures (700-950 °C) which are below the β-transus temperature of Ti-6Al-4V alloy. An applied uniaxial pressure of 1 MPa and a short bonding time of 15 min were selected as bonding parameters. Scanning electron microscope and energy-dispersive spectroscopy showed that the dissolution of Ti in the joint region increases with the increase in bonding temperature. X-ray diffraction analysis of the fractured surfaces revealed that Sn5Ti6, Sn3Ti5 and SnTi3 intermetallic compounds (IMCs) were formed and dominated the joint structure. The shear strengths of the bonds increase with the increase in bonding temperature and reaches a maximum of 478 MPa for bond made at 950 °C. The microhardness analysis of the fractured surfaces compared to the base alloy confirmed the presence of the IMCs. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Ti at the top surface of the fractured bonds made at 700 °C which confirmed a successful joint evolution even at the lowest bonding temperature used. Atomic force microscopy observations for bonds made at 700 and 950 °C coincide with the XRD and XPS analysis and were able to reveal the remaining Cu particles on the substrates.

  11. Alliages intermétalliques du magnésium, anodes pour MAFC ? Magnesium intermetallic alloys, anodes for MAFC?

    Directory of Open Access Journals (Sweden)

    Montagné Pierre

    2013-11-01

    Full Text Available Des composés intermétalliques sélectionnés ont été étudiés en vue d'une utilisation en remplacement de l'anode métallique dans des batteries de type métal air. Ces composés présentent des structures cristallines très différentes : structure lamellaire pour MgB2, structure covalente simple pour Mg2Si et structure complexe basée sur un empilement compact de polyèdres pour Mg2Al3. Les meilleurs résultats sont obtenus pour ce dernier composé avec une réactivité vis-à-vis des électrolytes testés sensiblement inférieure à celle du magnésium et une cinétique de réaction plus lente. Le potentiel en fonctionnement au sein de la batterie est sensiblement plus faible que celui du magnésium mais il présente une stabilité remarquable au cours du temps. Selected intermetallic compounds have been studied as anodic materials in metal air fuel cells. These compounds have different structural types, MgB2 displays a lamellar structure, Mg2Si a simple covalent structure while Mg2Al3 has a complex structure based on compact polyhedral packing. Best electrochemical results are obtained for the latter, with a lower reactivity towards magnesium in the two electrolytes and with lower kinetics of reaction. The operating potential of the battery with a Mg2Al3 anode is noticeably lower than with a Mg anode, but it presents a very good stability over time.

  12. Study on the Mechanical Properties and Corrosion Behaviors of Fe-(20, 45) wt%Gd Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Bo Kyeong; Baik, Youl; Choi, Yong [Dankook University, Chungnam (Korea, Republic of); Moon, Byung Moon [Korea Institute of Industrial Technology, Incheon (Korea, Republic of)

    2017-02-15

    Fe-(20, 45 wt%) Gd intermetallics were vacuum arc melted as the mother alloy of a neutron shielding and absorbing material. The structure of the cast Fe-20 wt%Gd intermetallics had primary dendrites with a short width of about 2 μm, which became coarse with increasing Gd content. The final compositions of the Fe-20 wt%Gd and Fe-45 wt%Gd intermetallics determined by Rietveld refinement were mainly Fe{sub 3}Gd with 26.6 at%Fe{sub 2}Gd, and Fe{sub 3}Gd with various intermetallics like 13.9 at%Fe{sub 2}Gd, 7.3 at%Fe{sub 9}Gd and 3.9 at%Fe{sub 17}Gd{sub 2}, respectively. The micro-hardnesses, yield strength, ultimate compressive strength and elongation of the Fe-20 wt%Gd intermetallics were 629±12 Hv, 753 MPa, 785 MPa and 4%, respectively, and those of the Fe-45 wt%Gd intermetallics were 741±13 Hv, 772 MPa, 823 MPa and 3%. Passivity was not present in artificial sea water at room temperature. The corrosion potentials and the corrosion rates of the Fe-20 wt%Gd and Fe-45 wt%Gd intermetallics were –624 mV{sub SHE}, 2.771 mA/cm{sup 2} , and –804 mV{sub SHE}, 3.397 mA/cm{sup 2} , respectively. The corroded surface of the Fe-Gd intermetallics contained corrosion products like gadolinium with iron, which detached to leave a trail of pits.

  13. Intermetallic compound formation at Sn-3.0Ag-0.5Cu-1.0Zn lead-free solder alloy/Cu interface during as-soldered and as-aged conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Feng-Jiang [Department of Materials Science and Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China)]. E-mail: wangfjy@yahoo.com.cn; Yu, Zhi-Shui [Department of Materials Science and Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Qi, Kai [Department of Materials Science and Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China)

    2007-07-12

    Intermetallic formations of Sn-3.0Ag-0.5Cu solder alloy with additional 1.0 wt% Zn were investigated for Cu-substrate during soldering and isothermal aging. During soldering condition, the Cu{sub 5}Zn{sub 8} compound with granular-type morphology is the interfacial IMC for Sn-3.0Ag-0.5Cu-1.0Zn solder, while the Cu{sub 6}Sn{sub 5} compound with scallop-type morphology is the interfacial IMC for Sn-3.0Ag-0.5Cu solder. During thermal aging, the final interfacial structure for Sn-3.0Ag-0.5Cu-1.0Zn solder is solder/Cu{sub 5}Zn{sub 8}/Cu{sub 6}Sn{sub 5}/Cu{sub 3}Sn/Cu, different from the solder/Cu{sub 6}Sn{sub 5}/Cu{sub 3}Sn/Cu for Sn-3.0Ag-0.5Cu solder. The thickness of Cu-Sn IMC layers increases, while the thickness of Cu{sub 5}Zn{sub 8} compound layer decreases with increasing aging time due to the decomposition of the Cu{sub 5}Zn{sub 8} layer by the diffusion of Cu and Zn atoms into the solder and Cu{sub 6}Sn{sub 5} at higher aging temperature. For Sn-3.0Ag-0.5Cu-1.0Zn solder, at higher aging temperature of 150 or 175 {sup o}C, with the formation of Cu{sub 3}Sn at Cu{sub 6}Sn{sub 5}/Cu, Kirkendall voids can be observed at the interface of Cu{sub 3}Sn/Cu.

  14. High Bismuth Alloys as Lead-Free Alternatives for Interconnects in High-Temperature Electronics

    Science.gov (United States)

    Mallampati, Sandeep

    Predominant high melting point solders for high-temperature electronics (operating temperatures from 200 to 250°C) are Pb-based which are being banned from usage due to their toxic nature. In this study, high bismuth alloy compositions (Bi-14Cu-8Sn, Bi-20Sb-10Cu, Bi-15Sb-10Cu and Bi-10Sb-10Cu) were designed, cast, and characterized to understand their potential as replacements. The desirable aspect of Bi is its high melting temperature, which is 271°C. Alloying elements Sn, Sb and Cu were added to improve some of its properties such as thermal conductivity, plasticity, and reactivity with Cu and Ni surface. Metallographic sectioning and microstructure analysis were performed on the bulk alloys to compare the evolution of phases predicted from equilibrium phase diagrams. Reflow processes were developed to make die-attach samples out of the proposed alloys and die-shear testing was carried out to characterize mechanical integrity of the joint. Thermal shock between -55°C to 200°C and high temperature storage at 200°C were performed on the assembled die-attach samples to study microstructure evolution and mechanical behavior of the reflowed alloys under accelerated testing conditions. In addition, heat dissipation capabilities, using flash diffusivity, were measured on the bulk alloys and also on the die-attach assembly. Finally, tensile testing was performed on the dogbone specimens to identify the potential for plastic deformation and electron backscatter diffraction (EBSD) analysis was used to study the grain orientations on the fracture surfaces and their influence on the crack propagation. Bi-14Cu-8Sn has formed BiNi by on the die backside metallization and the reaction with Cu was poor. This has resulted in weaker substrate side interface. It was observed that Bi-Sb alloys have strong reactivity with Ni (forming Bi3Ni, BiNi and NiSb intermetallic phases), and with Cu (forming Cu2Sb, Cu4Sb). Spallation was observed in NiSb interfacial intermetallic layer and

  15. NASA vane alloy boasts high-temperature strength

    Science.gov (United States)

    Waters, W. J.; Freche, J. C.

    1975-01-01

    The higher inlet-gas temperatures in new aircraft turbine engines make it necessary to use improved superalloys in engine design. Such superalloys are provided by WAZ alloys. NASA has explored the Ni-W-Al system in an attempt to find higher-strength nickel-based alloys for use as stator vane materials. Critical performance goals have been met with the new alloy WAZ-16. With suitable protective coatings, WAZ-16 appears to have considerable potential for high-temperature stator vane applications.

  16. Microstructure Characterization and Wear-Resistant Properties Evaluation of an Intermetallic Composite in Ni-Mo-Si System.

    Science.gov (United States)

    Huang, Boyuan; Song, Chunyan; Liu, Yang; Gui, Yongliang

    2017-02-04

    Intermetallic compounds have been studied for their potential application as structural wear materials or coatings on engineering steels. In the present work, a newly designed intermetallic composite in a Ni-Mo-Si system was fabricated by arc-melting process with commercially pure metal powders as starting materials. The chemical composition of this intermetallic composite is 45Ni-40Mo-15Si (at %), selected according to the ternary alloy diagram. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and the wear-resistant properties at room temperature were evaluated under different wear test conditions. Microstructure characterization showed that the composite has a dense and uniform microstructure. XRD results showed that the intermetallic composite is constituted by a binary intermetallic compound NiMo and a ternary Mo₂Ni₃Si metal silicide phase. Wear test results indicated that the intermetallic composite has an excellent wear-resistance at room-temperature, which is attributed to the high hardness and strong atomic bonding of constituent phases NiMo and Mo₂Ni₃Si.

  17. High temperature hardness of steels and iron-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Torres, H., E-mail: torres@ac2t.at; Varga, M.; Ripoll, M. Rodríguez

    2016-08-01

    Hot hardness, related to the mechanical strength and wear resistance of materials at high temperatures, has been measured from room temperature up to 800 °C for a comprehensive set of iron-based alloys having different microstructures and chemical compositions. The results obtained suggest the existence of several softening regimes with increasing temperatures, also with a massive hardness drop observed to begin at temperatures close to 0.5 times the melting temperature for most of the chosen alloys. Austenitic steel grades were also observed to show a significant softening behaviour at moderate temperatures compared to ferritic and martensitic alloys, attributed to the dislocation dynamics of face cubic centred alloys. The exact nature of the temperature dependence shown by hardness has been proposed to adopt the form of an exponential Arrhenius equation. Another model suggested in the available literature is also discussed within this context. Additionally, the role of alloying elements has been correlated to the softening behaviour. Molybdenum or boron were found to slow down the softening behaviour, while carbide-forming elements such as vanadium and tungsten were found to be beneficial for room temperature hardness.

  18. Spectral emissivity of candidate alloys for very high temperature reactors in high temperature air environment

    Energy Technology Data Exchange (ETDEWEB)

    Cao, G., E-mail: gcao@wisc.edu; Weber, S.J.; Martin, S.O.; Sridharan, K.; Anderson, M.H.; Allen, T.R.

    2013-10-15

    Emissivity measurements for candidate alloys for very high temperature reactors were carried out in a custom-built experimental facility, capable of both efficient and reliable measurements of spectral emissivities of multiple samples at high temperatures. The alloys studied include 304 and 316 austenitic stainless steels, Alloy 617, and SA508 ferritic steel. The oxidation of alloys plays an important role in dictating emissivity values. The higher chromium content of 304 and 316 austenitic stainless steels, and Alloy 617 results in an oxide layer only of sub-micron thickness even at 700 °C and consequently the emissivity of these alloys remains low. In contrast, the low alloy SA508 ferritic steel which contains no chromium develops a thicker oxide layer, and consequently exhibits higher emissivity values.

  19. Spectral emissivity of candidate alloys for very high temperature reactors in high temperature air environment

    Science.gov (United States)

    Cao, G.; Weber, S. J.; Martin, S. O.; Sridharan, K.; Anderson, M. H.; Allen, T. R.

    2013-10-01

    Emissivity measurements for candidate alloys for very high temperature reactors were carried out in a custom-built experimental facility, capable of both efficient and reliable measurements of spectral emissivities of multiple samples at high temperatures. The alloys studied include 304 and 316 austenitic stainless steels, Alloy 617, and SA508 ferritic steel. The oxidation of alloys plays an important role in dictating emissivity values. The higher chromium content of 304 and 316 austenitic stainless steels, and Alloy 617 results in an oxide layer only of sub-micron thickness even at 700 °C and consequently the emissivity of these alloys remains low. In contrast, the low alloy SA508 ferritic steel which contains no chromium develops a thicker oxide layer, and consequently exhibits higher emissivity values.

  20. Effect of Al alloying on the martensitic temperature in Ti-Ta shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Alberto; Rogal, Jutta; Drautz, Ralf [Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universitaet Bochum (Germany)

    2017-07-01

    Ti-Ta-based alloys are promising candidates as high temperature shape memory alloys (HTSMAs) for actuators and superelastic applications. The shape memory mechanism involves a martensitic transformation between the low-temperature α'' phase (orthorhombic) and the high-temperature β phase (body-centered cubic). In order to prevent the degradation of the shape memory effect, Ti-Ta needs to be alloyed with further elements. However, this often reduces the martensitic temperature M{sub s}, which is usually strongly composition dependent. The aim of this work is to analyze how the addition of a third element to Ti-Ta alloys affects M{sub s} by means of electronic structure calculations. In particular, it will be investigated how alloying Al to Ti-Ta alters the relative stability of the α'' and β phases. This understanding will help to identify new alloy compositions featuring both a stable shape memory effect and elevated transformation temperatures.

  1. Identification of Intermetallic Compounds and Its Formation Mechanism in Boron Steel Hot-Dipped in Al-7 wt.% Mn Alloy

    Directory of Open Access Journals (Sweden)

    Sung-Yun Kwak

    2017-12-01

    Full Text Available In laser welding and hot stamping Al-Si-coated boron steel, there is a problem that the strength of the joint is lowered due to ferrite formation in the fusion zone. The purpose of this study is to develop an Al-7 wt.% Mn hot-dip coating in which Mn, an austenite stabilizing element, replaces the ferrite stabilizing element Si. The nucleation and formation mechanism of the reaction layer was studied in detail by varying the dipping time between 0 and 120 s at 773 °C. The microstructure and phase constitution of the reaction layer were investigated by various observational methods. Phase formation is discussed using a phase diagram calculated by Thermo-CalcTM. Under a 30 s hot-dipping process, no reaction occurred due to the formation of a Fe3O4 layer on the steel surface. The Fe3O4 layer decomposed by a reduction reaction with Al-Mn molten alloy, constituent elements of steel dissolved into a liquid, and the reaction-layer nucleus was formed toward the liquid phase. A coated layer consists of a solidified layer of Al and Al6Mn and a reactive layer formed beneath it. The reaction layer is formed mainly by inter-diffusion of Al and Fe in the solid state, which is arranged on the steel in the order of Al11Mn4 → FeAl3 (θ → Fe2Al5 (η phases, and the Fe3AlC (κ in several nm bands formed at the interface between the η-phase and steel.

  2. Nonequilibrium Phase Chemistry in High Temperature Structure Alloys

    Science.gov (United States)

    Wang, R.

    1991-01-01

    Titanium and nickel aluminides of nonequilibrium microstructures and in thin gauge thickness were identified, characterized and produced for potential high temperature applications. A high rate sputter deposition technique for rapid surveillance of the microstructures and nonequilibrium phase is demonstrated. Alloys with specific compositions were synthesized with extended solid solutions, stable dispersoids, and specific phase boundaries associated with different heat treatments. Phase stability and mechanical behavior of these nonequilibrium alloys were investigated and compared.

  3. High temperature alloy chloridation at 850 C

    Energy Technology Data Exchange (ETDEWEB)

    Chevalier, S.; Bekaddour, A. [Laboratoire de Recherches sur la Reactivite des Solides, UMR 5613 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, 21078 Dijon (France); Ched' Homme, S. [DTM/SRPU/LPPU, CEA Valduc, 21120 Is-sur-Tille (France); Amilain-Basset, K.; Buisson, L. [Interface Caracterisation des Materiaux, Universite de Bourgogne, 21078 Dijon (France)

    2007-05-15

    The resistance of eight alloys against chloridation was tested at 850 C in Ar/Cl{sub 2} (2.5% Cl{sub 2}) for 15 min. Pre-oxidation treatments were performed for 1 h and 8 h at 850 C in order to produce a thin, adherent and protective oxide scale able to improve the chloridation behaviour of the tested materials. The chloridised sample morphologies were compared to the morphologies observed on the non pre-oxidised samples. The alloys containing a large amount of iron did not exhibit any chloridation resistance, even after pre-oxidation, and were severely damaged. The nickel based alloys gave interesting results but were also attacked by chloride, probably by the ''active oxidation'' mechanism. The duration of the pre-oxidation treatment plays an important role, since the 8 h pre-oxidation appears more beneficial than the 1 h pre-oxidation, to delay the chloridation, probably because of the best quality of the oxide layer grown during 8 h. For the nickel based materials, the effects of chloride appear less severe than for the iron-based alloys, but are not stopped. The ''active oxidation'' mechanism is proposed to be responsible for the degradation of the tested materials. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  4. High temperature fracture characteristics of a nanostructured ferritic alloy (NFA)

    Science.gov (United States)

    Byun, Thak Sang; Kim, Jeoung Han; Yoon, Ji Hyun; Hoelzer, David T.

    2010-12-01

    The nanostructured ferritic alloys (NFAs) have been developed to improve high temperature strength and radiation resistance by refining grains and including nanoclusters. Among the key properties of NFAs needed to be assessed for advanced reactor applications the cracking resistance at high temperatures has not been well known. In this work, therefore, the high temperature fracture behavior has been investigated for the latest nanostructured ferritic alloy 14YWT (SM10). The fracture toughness of the alloy was above 140 MPa √m at low temperatures, room temperature (RT) and 200 °C, but decreased to a low fracture toughness range of 52-82 MPa √m at higher temperatures up to 700 °C. This behavior was explained by the fractography results indicating that the unique nanostructure of 14YWT alloy produced shallow plasticity layers at high temperatures and a low-ductility grain boundary debonding occurred at 700 °C. The discussion also proposes methods to improve resistance to cracking.

  5. High temperature strain of metals and alloys. Physical fundamentals

    Energy Technology Data Exchange (ETDEWEB)

    Levitin, V. [National Technical Univ., Zaporozhye (Ukraine)

    2006-07-01

    The author shows how new in-situ X-ray investigations and transmission electron microscope studies lead to novel explanations of high-temperature deformation and creep in pure metals, solid solutions and super alloys. This approach is the first to find unequivocal and quantitative expressions for the macroscopic deformation rate by means of three groups of parameters: substructural characteristics, physical material constants and external conditions. Creep strength of the studied uptodate single crystal super alloys is greatly increased over conventional polycrystalline super alloys. The contents of this book include: macroscopic characteristics of strain at high temperatures; experimental equipment and technique of in situ X-ray investigations; experimental data and structural parameters in deformed metals; sub-boundaries as dislocation sources and obstacles; the physical mechanism of creep and the quantitative structural model; simulation of the parameters evolution; system of differential equations; high-temperature deformation of industrial super alloys; single crystals of super alloys; effect of composition, orientation and temperature on properties; and creep of some refractory metals.

  6. Anelasticity in Fe-Al-Cr alloys at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Golovin, I.S., E-mail: i.golovin@misis.ru [Physics of Metals Department, National University ' Moscow Institute of Steel and Alloys' , Moscow (Russian Federation); Physics of Metals Department and Materials Science, Tula State University, Tula (Russian Federation); Riviere, A. [LMPM-UMR CNRS 6617, ENSMA, F-86961 Futuroscope Chasseneuil Cedex (France)

    2009-09-15

    Several (Fe,Cr){sub 3}Al alloys with Cr content from 3 to 25% have been studied in the temperature range from 680 to 930 K using isothermal frequency dependent tests (from 10{sup -4} to 10{sup 2} Hz). Three relaxation peaks were observed in this range. The Zener relaxation (P1 peak) caused by reorientation of pairs of substitute atoms in Fe is observed in all studied alloys and used to evaluate the activation parameters of substitute atom jumps in Fe. Activation parameters of the Zener peak in Fe-26Al-Cr depend not too much on Cr content (H = 275-290 kJ/mol, {tau}{sub 0} = 10{sup -19} to 10{sup -20} s), while the relaxation strength increases with the increase in Al + Cr content. The second internal friction peak (P2) at higher temperatures with similar activation energies but higher {tau}{sub 0} (10{sup -17} to 10{sup -19} s) is observed only in Cr containing alloys but not in Fe-25Al binary alloy. Most probably this peak is controlled by dislocations motion in Fe-26Al-Cr alloys. The third peak, denoted as P3 (H = 428 kJ/mol, {tau}{sub 0} = 10{sup -25} s), was observed only in the Fe-25Al-25Cr alloy and was classified as a grain boundary peak.

  7. Internal gettering by metal alloy clusters

    Science.gov (United States)

    Buonassisi, Anthony; Heuer, Matthias; Istratov, Andrei A.; Pickett, Matthew D.; Marcus, Mathew A.; Weber, Eicke R.

    2010-07-27

    The present invention relates to the internal gettering of impurities in semiconductors by metal alloy clusters. In particular, intermetallic clusters are formed within silicon, such clusters containing two or more transition metal species. Such clusters have melting temperatures below that of the host material and are shown to be particularly effective in gettering impurities within the silicon and collecting them into isolated, less harmful locations. Novel compositions for some of the metal alloy clusters are also described.

  8. Intermetallic titanium aluminides as innovative high temperature lightweight structural materials. How materialographic methods have contributed to their development; Intermetallische Titanaluminide als innovative Hochtemperaturleichtbauwerkstoffe. Wie materialographische Methoden zu ihrer Entwicklung beigetragen haben

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Helmut; Mayer, Svea [Montanuniversitaet Leoben (Austria). Dept. Metallkunde und Werkstoffpruefung

    2015-07-01

    The present article is considered the continuation of the two review articles ''Intermetallische γ-Titanaluminid-Basislegierungen aus metallographischer Sicht'' (''Intermetallic γ titanium aluminide based alloys from a metallographic point of view'') by H. Clemens and F. Jeglitsch in Pract. Metallogr. 37 (2000) 194 - 217 and ''Intermetallische γ-Titanaluminid-Basislegierungen aus metallographischer Sicht - eine Fortsetzung'' (''Intermetallic γ titanium aluminide based alloy from a metallographic point of view - a continuation'') by H. Clemens and S. Mayer in Pract. Metallogr. 48 (2011) 64 - 100. With reference to a γ TiAl based alloy specifically developed for aircraft engines, the so-called TNM alloy, this third and concluding part describes how materialographic methods, in combination with a targeted use of complementary investigation methods, have contributed to their development, manufacture, and processing, and, eventually, to their industrial launch. In this context, the alloy development strategy is discussed and representative microstructures and nanostructures are shown and described after different processing and heat treatment processes. Selected case studies from materialographic examinations are presented and interpreted using, for each and every of these aspects, approaches from the fields of physical metallurgy und metal physics.

  9. Formation of abrasion-resistant coatings of the AlSiFexMny intermetallic compound type on the AISI 304L alloy

    Directory of Open Access Journals (Sweden)

    Martínez-Perales, Laura G.

    2016-03-01

    Full Text Available The α-Al9FeMnSi and β-Al9FeMn2Si intermetallics formed by reactive sintering of Al, Si, Mn, Fe, Cr and Ni powders have been used in AISI 304L steels to enhance microhardness. Processing variables of the reactive sintering treatment were temperature (600, 650, 700, 750 and 800 °C, pressure (5, 10 y 20 MPa and holding time (3600, 5400 y 7200 seconds. Experimental results show that temperature is the most important variable affecting the substrate/coating formation, while pressure does not appear to have a significant effect. The results show the optimum conditions of the reactive sintering that favor the substrate/coating formation are 800 °C, 20 MPa and 7200 seconds. Under these conditions, the reaction zone between the substrate and coating is more compacted and well-adhered, with a microhardness of 1300 Vickers. The results of SEM and X-Ray diffraction confirmed the formation of α-Al9FeMnSi and β-Al9FeMn2Si intermetallics in the substrate/coating interface as well as the presence of Cr and Ni, indicating diffusion of these two elements from the substrate to the interface.Los intermetálicos α-Al9FeMnSi y β-Al9FeMn2Si formados por sinterización reactiva de polvos Al, Si, Mn, Fe, Cr, Ni se han utilizado en aceros AISI 304L para mejorar la microdureza. Las variables de procesamiento de sinterización reactiva fueron temperatura (600, 650, 700, 750, y 800 °C, presión (5, 10 y 20 MPa y el tiempo de retención (3600, 5400 7200 segundos. Los resultados experimentales muestran que la temperatura es la variable más importante que afecta a la formación del sustrato/recubrimiento, mientras que la presión no parece tener un efecto significativo una influencia significativa. Los resultados muestran las condiciones óptimas de la sinterización reactiva que favorecen la formación del sustrato/recubrimiento a 800 °C, 20 MPa y 7200 segundos. En estas condiciones, la zona de reacción entre el sustrato y el recubrimiento es más compacta y bien

  10. Synthesis of Fe-Al-Ti Based Intermetallics with the Use of Laser Engineered Net Shaping (LENS

    Directory of Open Access Journals (Sweden)

    Monika Kwiatkowska

    2015-04-01

    Full Text Available The Laser Engineered Net Shaping (LENS technique was combined with direct synthesis to fabricate L21-ordered Fe-Al-Ti based intermetallic alloys. It was found that ternary Fe-Al-Ti alloys can be synthesized using the LENS technique from a feedstock composed of a pre-alloyed Fe-Al powder and elemental Ti powder. The obtained average compositions of the ternary alloys after the laser deposition and subsequent annealing were quite close to the nominal compositions, but the distributions of the elements in the annealed samples recorded over a large area were inhomogeneous. No traces of pure Ti were observed in the deposited alloys. Macroscopic cracking and porosity were observed in all investigated alloys. The amount of porosity in the samples was less than 1.2 vol. %. It seems that the porosity originates from the porous pre-alloyed Fe-Al powders. Single-phase (L21, two-phase (L21-C14 and multiphase (L21-A2-C14 Fe-Al-Ti intermetallic alloys were obtained from the direct laser synthesis and annealing process. The most prominent feature of the ternary Fe-Al-Ti intermetallics synthesized by the LENS method is their fine-grained structure. The grain size is in the range of 3–5 μm, indicating grain refinement effect through the highly rapid cooling of the LENS process. The Fe-Al-Ti alloys synthesized by LENS and annealed at 1000 °C in the single-phase B2 region were prone to an essential grain growth. In contrast, the alloys annealed at 1000 °C in the two-phase L21-C14 region exhibited almost constant grain size values after the high-temperature annealing.

  11. Structure Defect Property Relationships in Binary Intermetallics

    Science.gov (United States)

    Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

    2015-03-01

    Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

  12. High Temperature Strength and Hot Working Technology for As-Cast Mg–1Zn–1Ca (ZX11 Alloy

    Directory of Open Access Journals (Sweden)

    Kamineni Pitcheswara Rao

    2017-10-01

    Full Text Available Cast Mg–1Zn–1Ca alloy (ZX11 has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260–500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg–3Sn–2Ca (TX32 between 25 °C and 200 °C, and exhibits a plateau between 100 °C and 175 °C, similar to TX32. This is attributed to Mg2Ca particles present at grain boundaries that reduce their sliding. The processing map, developed between 260 and 420 °C in the strain rate limits of 0.0003 s−1 to 1 s−1, exhibited two domains in the ranges: (1 280–330 °C and 0.0003–0.01 s−1 and (2 330–400 °C and 0.0003–0.1 s−1. In these domains, dynamic recrystallization occurs, with basal slip dominating in the first domain and prismatic slip in the second, while the recovery mechanism being climb of edge dislocations in both. The activation energy estimated using standard kinetic rate equation is 191 kJ/mol, which is higher than the value for lattice self-diffusion in magnesium indicating that a large back stress is created by the presence of Ca2Mg6Zn3 intermetallic particles in the matrix. It is recommended that the alloy be best processed at 380 °C and 0.1 s−1 at which prismatic slip is favored due to Zn addition. At higher strain rates, the alloy exhibits flow instability and adiabatic shear band formation at <340 °C while flow localization and cracking at grain boundaries occurs at temperatures >400 °C.

  13. Amorphous Alloy Membranes for High Temperature Hydrogen Separation

    Energy Technology Data Exchange (ETDEWEB)

    Coulter, K. [Southwest Research Inst. (SwRI), San Antonio, TX (United States)

    2013-09-30

    At the beginning of this project, thin film amorphous alloy membranes were considered a nascent but promising new technology for industrial-scale hydrogen gas separations from coal- derived syngas. This project used a combination of theoretical modeling, advanced physical vapor deposition fabricating, and laboratory and gasifier testing to develop amorphous alloy membranes that had the potential to meet Department of Energy (DOE) targets in the testing strategies outlined in the NETL Membrane Test Protocol. The project is complete with Southwest Research Institute® (SwRI®), Georgia Institute of Technology (GT), and Western Research Institute (WRI) having all operated independently and concurrently. GT studied the hydrogen transport properties of several amorphous alloys and found that ZrCu and ZrCuTi were the most promising candidates. GT also evaluated the hydrogen transport properties of V, Nb and Ta membranes coated with different transition-metal carbides (TMCs) (TM = Ti, Hf, Zr) catalytic layers by employing first-principles calculations together with statistical mechanics methods and determined that TiC was the most promising material to provide catalytic hydrogen dissociation. SwRI developed magnetron coating techniques to deposit a range of amorphous alloys onto both porous discs and tubular substrates. Unfortunately none of the amorphous alloys could be deposited without pinhole defects that undermined the selectivity of the membranes. WRI tested the thermal properties of the ZrCu and ZrNi alloys and found that under reducing environments the upper temperature limit of operation without recrystallization is ~250 °C. There were four publications generated from this project with two additional manuscripts in progress and six presentations were made at national and international technical conferences. The combination of the pinhole defects and the lack of high temperature stability make the theoretically identified most promising candidate amorphous alloys

  14. Structural stability of high entropy alloys under pressure and temperature

    DEFF Research Database (Denmark)

    Ahmad, Azkar S.; Su, Y.; Liu, S. Y.

    2017-01-01

    The stability of high-entropy alloys (HEAs) is a key issue before their selection for industrial applications. In this study, in-situ high-pressure and high-temperature synchrotron radiation X-ray diffraction experiments have been performed on three typical HEAs Ni20Co20Fe20Mn20Cr20, Hf25Nb25Zr25Ti...

  15. Oxidation resistant iron and nickel alloys for high temperature use

    Science.gov (United States)

    Hill, V. L.; Misra, S. K.; Wheaton, H. L.

    1970-01-01

    Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

  16. Corrosion of Alloy 617 in high-temperature gas environments

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Tsung-Kuang [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chang, Hao-Ping [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Wang, Mei-Ya, E-mail: meywang@mx.nthu.edu.tw [Nuclear Science and Technology Development Center, National Tsing Hua University, Hsinchu 300, Taiwan (China); Yuan, Trai [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Kai, Ji-Jung [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan (China)

    2014-05-01

    High-temperature gas-cooled reactors (HTGRs) with helium gas as the primary coolant have been considered as one type of the Generation IV nuclear power reactor systems. Several nickel-based superalloys, including Alloy 617, are potential structural materials to serve as pressure boundary components, such as the intermediate heat exchanger (IHX) in an HTGR. Impurities in a helium coolant, such as H{sub 2}O and O{sub 2}, can interact with structural materials at working temperatures of >900 °C, leading to serious degradation on these materials. In addition, defects in IHX surface coatings would allow these species to reach and interact with the external surfaces of these components, leading to similar or even more serious degradation. In this study we investigated the oxidation behavior of Alloy 617 in high-temperature, gaseous environments with various levels of O{sub 2} and H{sub 2}O. A series of general corrosion tests were conducted at test temperatures of 650 °C, 750 °C, 850 °C and 950 °C under various coolant compositions of dry air, 1% O{sub 2}, 10% relative humidity (RH), and 50% RH. Preliminary results showed that the surface morphologies of the Alloy 617 samples exhibited distinct evidence of intergranular corrosion. Compact chromium oxide layers were observed on the sample surfaces. The oxidation mechanisms of this alloy in the designated environments are discussed.

  17. High temperature oxidation of iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, Lars

    2003-06-15

    The high temperature oxidation of the ferritic alloy Fe78Cr22 has been investigated in the present work. The effect of small alloying additions of cerium and/or silicon was also investigated. The alloys were oxidized at 973, 1173 and 1373 K in either air or a hydrogen/argon mixture. The various reaction atmospheres contained between 0.02 and 50% water vapour. The oxide scales formed on the various alloys at 973 K consisted of thin chromia layers. The oxide scales grown on the alloys at 1173 K also consisted of a chromia layer. The microstructure of the chromia scales was found to depend on the reaction atmosphere. The chromia scales grown in hydrogen/argon atmospheres formed oxide whiskers and oxide ridges at the surface of the scales, while the chromia scales grown in air formed larger oxide grains near the surface. This difference in oxide microstructure was due to the vaporization of chromium species from the chromia scales grown in air. Two different growth mechanisms are proposed for the growth of oxide whiskers. The growth rate of the chromia scales was independent of the oxygen activity. This is explained by a growth mechanism of the chromia scales, where the growth is governed by the diffusion of interstitial chromium. The addition of silicon to the iron-chromium alloy resulted in the formation of silica particles beneath the chromia scale. The presence of silicon in the alloy was found to decrease the growth rate of the chromia scale. This is explained by a blocking mechanism, where the silica particles beneath the chromia scale partly block the outwards diffusion of chromium from the alloy to the chromia scale. The addition of cerium to the iron-chromium alloy improved the adhesion of the chromia scale to the alloy and decreased the growth rate of chromia. It was observed that the minimum concentration of cerium in the alloy should be 0.3 at.% in order to observe an effect of the cerium addition. The effect of cerium is explained by the &apos

  18. Temperature dependence of the magnetic properties of ferromagnetic amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, P.

    1979-01-01

    The magnetic hysteresis properties of amorphous alloys have recently been discussed in terms of an exchange-enhanced applied field. This absolute-zero model is here extended to finite temperatures. The modified treatment predicts a remanent magnetization which is unaffected by thermal activation while the coercive force falls (finally to zero) as temperature increases. Comparison with experiment for TbFe/sub 2/ suggests that regions of volume approx. =7500 A/sup 3/ reverse coherently.

  19. Properties of Free-Machining Aluminum Alloys at Elevated Temperatures

    Science.gov (United States)

    Faltus, Jiří; Karlík, Miroslav; Haušild, Petr

    In areas close to the cutting tool the workpieces being dry machined could be heated up to 350°C and they may be impact loaded. Therefore it is of interest to study mechanical properties of corresponding materials at elevated temperatures. Free-machining alloys of Al-Cu and Al-Mg-Si systems containing Pb, Bi and Sn additions (AA2011, AA2111B, AA6262, and AA6023) were subjected to Charpy U notch impact test at the temperatures ranging from 20 to 350°C. The tested alloys show a sharp drop in notch impact strength KU at different temperatures. This drop of KU is caused by liquid metal embrittlement due to the melting of low-melting point dispersed phases which is documented by differential scanning calorimetry. Fracture surfaces of the specimens were observed using a scanning electron microscope. At room temperature, the fractures of all studied alloys exhibited similar ductile dimple fracture micromorphology, at elevated temperatures, numerous secondary intergranular cracks were observed.

  20. Chemistry and Properties of Complex Intermetallics from Metallic Fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Kanatzidis, Mercouri G. [Northwestern Univ., Evanston, IL (United States)

    2015-03-28

    This project investigated the reaction chemistry and synthesis of new intermetallic materials with complex compositions and structures using metallic fluxes as solvents. It was found that the metallic fluxes offer several key advantages in facilitating the formation and crystal growth of new materials. The fluxes mostly explored were liquid aluminum, gallium and indium. The main purpose of this project was to exploit the potential of metallic fluxes as high temperature solvent for materials discovery in the broad class of intermetallics. This work opened new paths to compound formation. We discovered many new Si (or Ge)-based compounds with novel structures, bonding and physicochemical properties. We created new insights about the reaction chemistry that is responsible for stabilizing the new materials. We also studied the structural and compositional relationships to understand their properties. We investigated the use of Group-13 metals Al, Ga and In as solvents and have generated a wide variety of new results including several new ternary and quaternary materials with fascinating structures and properties as well as new insights as to how these systems are stabilized in the fluxes. The project focused on reactions of metals from the rare earth element family in combination with transition metals with Si and Ge. For example molten gallium has serves both as a reactive and non-reactive solvent in the preparation and crystallization of intermetallics in the system RE/M/Ga/Ge(Si). Molten indium behaves similarly in that it too is an excellent reaction medium, but it gives compounds that are different from those obtained from gallium. Some of the new phase identified in the aluminide class are complex phases and may be present in many advanced Al-matrix alloys. Such phases play a key role in determining (either beneficially or detrimentally) the mechanical properties of advanced Al-matrix alloys. This project enhanced our basic knowledge of the solid state chemistry

  1. Temperature compensation in piezoelectric energy harvesters using shape memory alloys

    Science.gov (United States)

    Rhimi, Mohamed; Lajnef, Nizar

    2011-04-01

    Harvested vibration energy is typically considered as an alternative power source for sensors' networks for health and usage monitoring in civil and mechanical structures. The longevity, and hence the efficacy, of these sensors is severely limited by the levels of generated power. Piezoelectric vibration harvesters have been widely used given their energy conversion ability and relatively high mechanical to electrical coupling properties. Several techniques can be applied to improve these properties and to cancel external environmental effects such as temperature variations. In this paper, the temperature compensation of the response characteristics of a bimorph cantilever Lead zirconate titanate (PZT) piezoelectric beam, through a combination with shape memory alloys, is studied. A mathematical model, based on onedimensional linear piezoelectricity equations and one dimensional constitutive behavior of shape memory alloys, is derived. The model describes the effect of temperature deviations on the theoretical harvestable energy levels as well as the compensation methodology. Proof of concept experimental results are also presented. The voltage response transfer functions are measured at different temperatures to show the induced effect by shape memory alloys.

  2. Elevated temperature crack growth in aluminum alloys: Tensile deformation of 2618 and FVS0812 aluminum alloys

    Science.gov (United States)

    Leng, Yang; Gangloff, Richard P.

    1990-01-01

    Understanding the damage tolerance of aluminum alloys at elevated temperatures is essential for safe applications of advanced materials. The objective of this project is to investigate the time dependent subcritical cracking behavior of powder metallurgy FVS0812 and ingot metallurgy 2618 aluminum alloys at elevated temperatures. The fracture mechanics approach was applied. Sidegrooved compact tension specimens were tested at 175, 250, and 316 C under constant load. Subcritical crack growth occurred in each alloy at applied stress intensity levels (K) of between about 14 and 25 MPa/m, well below K (sub IC). Measured load, crack opening displacement and displacement rate, and crack length and growth rate (da/dt) were analyzed with several continuum fracture parameters including, the C-integral, C (sub t), and K. Elevated temperature growth rate data suggest that K is a controlling parameter during time dependent cracking. For FVS0812, da/dt is highest at 175 C when rates are expressed as a function of K. While crack growth rate is not controlled by C (sub t) at 175 C, da/dt appears to better correlate with C (sub t) at higher temperatures. Creep brittle cracking at intermediate temperatures, and perhaps related to strain aging, is augmented by time dependent transient creep plasticity at higher temperatures. The C (sub t) analysis is, however, complicated by the necessity to measure small differences in the elastic crack growth and creep contributions to the crack opening displacement rate. A microstructural study indicates that 2618 and FVS0812 are likely to be creep brittle materials, consistent with the results obtained from the fracture mechanics study. Time dependent crack growth of 2618 at 175 C is characterized by mixed transgranular and intergranular fracture. Delamination along the ribbon powder particle boundaries occurs in FVS0812 at all temperatures. The fracture mode of FVS0812 changes with temperature. At 175 C, it is characterized as dimpled rupture

  3. Intermetallic diffusion coatings for enhanced hot-salt oxidation resistance of nitrogen-containing austenitic stainless steels

    Science.gov (United States)

    Mudali, U. Kamachi; Bhuvaneswaran, N.; Shankar, P.; Khatak, H. S.; Raj, B.

    2004-06-01

    This article presents the preparation, characterization, and hot-salt oxidation behavior of nitrogen-containing type 316L stainless steel (SS), surface modified with intermetallic coatings. Three different types of intermetallic coating systems, containing aluminum, titanium, and titanium/aluminum multilayers, were formed by diffusion annealing of type 316L austenitic SS containing 0.015, 0.1, 0.2, and 0.56 pct nitrogen. Analysis by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and secondary ion mass spectroscopy (SIMS) confirmed the formation of various intermetallic phases such as AIN, Al13Fe4, FeAl2, FeTi, Ti2N, and Ti3Al in the coatings. Hot salt oxidation behavior of the uncoated and surface-modified stainless steels was assessed by periodic monitoring of the weight changes of NaCl salt-applied alloys kept in an air furnace at 1023 K up to 250 hours. The oxide scales formed were examined by XRD and stereomicroscopy. Among the various surface modifications investigated in the present study, the results indicate that the titanium-modified alloys show the best hot-salt oxidation resistance with the formation of an adherent, protective, thin, and continuous oxide layer. Among the four N-containing alloys investigated, the titanium and Ti/Al multilayer modified 0.56 pct N alloy showed the best hot-salt oxidation resistance as compared to uncoated alloys. The slower corrosion kinetics and adherent scale morphology indicate that the surface-modified titanium intermetallic coatings could provide high-temperature service applications up to 1073 K, particularly in chloride containing atmospheres, for austenitic stainless steels.

  4. Non-alloyed Ni3Al based alloys – preparation and evaluation of mechanical properties

    Directory of Open Access Journals (Sweden)

    J. Malcharcziková

    2013-07-01

    Full Text Available The paper reports on the fabrication and mechanical properties of Ni3Al based alloy, which represents the most frequently used basic composition of nickel based intermetallic alloys for high temperature applications. The structure of the alloy was controlled through directional solidification. The samples had a multi-phase microstructure. The directionally solidified specimens were subjected to tensile tests with concurrent measurement of acoustic emission (AE. The specimens exhibited considerable room temperature ductility before fracture. During tensile testing an intensive AE was observed.

  5. Micro-mechanisms of Surface Defects Induced on Aluminum Alloys during Plastic Deformation at Elevated Temperatures

    Science.gov (United States)

    Gali, Olufisayo A.

    Near-surface deformed layers developed on aluminum alloys significantly influence the corrosion and tribological behavior as well as reduce the surface quality of the rolled aluminum. The evolution of the near-surface microstructures induced on magnesium containing aluminum alloys during thermomechanical processing has been investigated with the aim generating an understanding of the influence of individual forming parameters on its evolution and examine the microstructure of the roll coating induced on the mating steel roll through material transfer during rolling. The micro-mechanisms related to the various features of near-surface microstructure developed during tribological conditions of the simulated hot rolling process were identified. Thermomechanical processing experiments were performed with the aid of hot rolling (operating temperature: 550 to 460 °C, 4, 10 and 20 rolling pass schedules) and hot forming (operating temperature: 350 to 545 °C, strain rate: 4 x 10-2 s-1) tribo-simulators. The surface, near-surface features and material transfer induced during the elevated temperature plastic deformation were examined and characterized employing optical interferometry, SEM/EDS, FIB and TEM. Near-surface features characterized on the rolled aluminum alloys included; cracks, fractured intermetallic particles, aluminum nano-particles, oxide decorated grain boundaries, rolled-in oxides, shingles and blisters. These features were related to various individual rolling parameters which included, the work roll roughness, which induced the formation of shingles, rolling marks and were responsible for the redistribution of surface oxide and the enhancements of the depth of the near-surface damage. The enhanced stresses and strains experienced during rolling were related to the formation and propagation of cracks, the nanocrystalline structure of the near-surface layers and aluminum nano-particles. The mechanism of the evolution of the near-surface microstructure were

  6. The temperature variation of hydrogen diffusion coefficients in metal alloys

    Science.gov (United States)

    Danford, M. D.

    1990-01-01

    Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.

  7. Reduced-Temperature Transient-Liquid-Phase Bonding of AluminaUsing a Ag-Cu-Based Brazing Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Moo; Glaeser, Andreas M.

    2005-12-19

    The mechanical properties and microstructural evolution ofmetal-ceramic bonds produced using a transient liquid phase (TLP) aredescribed. Alumina (Al2O3) was joined at 500 degrees C, 600 degrees C,and 700 degrees C using a multilayer In/Cusil-ABA (R) (commercialcopper-silver eutectic brazing alloy)/In interlayer. The introduction ofthin In cladding layers allows the system to bond at much lowertemperatures than those typically used for brazing with Cusil-ABA (R),thereby protecting temperature-sensitive components. After chemicalhomogenization, the interlayers retain an operating temperature rangesimilar to that of the brazed joints. TLP bonds made at 500 degrees C,600 degrees C, and 700 degrees C with holding times ranging from as lowas 1.5 h to 24 h had average fracture strengths above 220 MPa. Theeffects of bonding temperature and time on fracture strength aredescribed. Preliminary analysis of the interlayers shows that the Ag-Inor Cu-In intermetallic phases do not form. Considerations unique tosystems with two-phase core layers are discussed. Experiments usingsingle-crystal sapphire indicate rapid formation of a reaction layer at700 degrees C, suggesting the possibility of making strong bonds usinglower temperatures and/or shorter processing times.

  8. Mo-Si alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Heatherly, L.; Wright, J.L. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  9. Phase constitution and corrosion resistance of Al–Co alloys

    Energy Technology Data Exchange (ETDEWEB)

    Palcut, Marián, E-mail: marian.palcut@gmail.com; Priputen, Pavol; Šalgó, Kristián; Janovec, Jozef

    2015-09-15

    Al–24Co, Al–25Co, Al–26Co, Al–27Co and Al–28Co alloys (composition in atomic percent) were prepared by arc-melting in high purity argon. Each alloy was found to consist of several microstructure constituents. Precipitation sequences of different intermetallic compounds were described based on a previously published Al–Co phase diagram and non-equilibrium processes taking place during casting. Electrochemical corrosion was investigated by potentiodynamic polarization in aqueous NaCl solution at room temperature. A large amount of pitting is observed, with some of the phases being preferentially corroded. The nobility of Al–Co intermetallic compounds is discussed in terms of chemical composition and crystal structure. Conclusions towards the alloy stability are provided. - Highlights: • Al–24Co to Al–28Co alloys were prepared by arc-melting in high purity argon. • Precipitation sequences of different intermetallic compounds have been observed. • Anodic alloy dissolution takes place by galvanic mechanism. • Nobility of Al–Co intermetallic compounds increases with increasing Co concentration.

  10. An evaluation of mechanical and high-temperature corrosion properties of Ni-Cr alloy with composition of alloying elements

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Sujin; Kim, Dongjin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Helium is used as a coolant in a VHTR owing to its high thermal conductivity, inertness, and low neutron absorption. However, helium inevitably includes impurities that create an imbalance in the surface reactivity at the interface of the coolant and the exposed materials. As the Alloy 617 has been exposed to high temperatures at 950 .deg. C in the impure helium environment of a VHTR, degradation of material is accelerated and mechanical properties decreased. An alloy superior to alloy 617 should be developed. In this study, the mechanical and high-temperature corrosion properties for Ni-Cr alloys fabricated in laboratory were evaluated as a function of the grain boundary strengthening and alloying element composition. The mechanical property and corrosion property for Ni-Cr alloys fabricated in a laboratory were evaluated as a function of the main element composition. The ductility was increased and decreased by increasing the amount of Mo and Cr, respectively. Surface oxide was detached during the corrosion test, because there was not aluminum element in the alloy. Aluminum seems to act as an anti-corrosive role in Ni-based alloy. In conclusion, the addition of Al into the alloy is required to improvement of high temperature corrosion resistance.

  11. Study of the high temperature characteristics of hydrogen storage alloys

    CERN Document Server

    Rong, Li; Shaoxiong, Zhou; Yan, Qi; 10.1016/j.jallcom.2004.07.006

    2005-01-01

    In this work, the phase structure of as-cast and melt-spun (MmY)/sub 1/(NiCoMnAl)/sub 5/ alloys (the content of yttrium is 0-2.5wt.%) and their electrochemical properties were studied with regard to discharge capacity at different temperatures (30-80 degrees C) and cycling life at 30 degrees C. It is found that the substitution of yttrium increase the electrochemical capacity of the compounds and decrease the difference in capacity between as-cast and as-quenched compounds at 30 degrees C. When increasing the yttrium concentration from 0 to 2.5wt.%, the cycling life of both the as-cast and the melt- spun compounds deteriorated, although the latter have a slightly longer cycle life than the former. The remarkable feature of the alloys obtained by yttrium substitution is the improvement of the high temperature electrochemical properties. It shows that the stability of the hydrides is increased. Compared with the as-cast alloys, the melt-spun ribbons have higher electrochemical charge /discharge capacity in the ...

  12. Advances in Solid State Joining of High Temperature Alloys

    Science.gov (United States)

    Ding, Jeff; Schneider, Judy

    2011-01-01

    Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

  13. Effects of alloying elements and temperature on the elastic properties of W-based alloys by first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yong-Jie, E-mail: yoh5120@psu.edu [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Shang, Shun-Li; Wang, Yi [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Darling, Kristopher A.; Butler, Brady G.; Kecskes, Laszlo J. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005 (United States); Liu, Zi-Kui [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2016-06-25

    The influence of various transition alloying elements (X's) on the elastic properties of W-based alloys has been studied via first-principles calculations on the basis of density functional theory. Here, nineteen transition metal alloying elements (X) are considered: Ti, V, Cr, Fe, Co, Ni, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, Re, Os, Ir, and Pt. It is found that (i) the bulk modulus of the dilute W-X alloy decreases with increasing its equilibrium volume, particularly, for the alloying elements in the same period; (ii) all of the alloying elements decrease the shear modulus of BCC W; and (iii) the largest decrease of elastic properties of W is due to alloying element Y. In addition, it is shown that the changes of elastic properties of W caused by the alloying elements are traceable from the electron charge density distribution, resulting in a bonding distortion between W and the alloying atoms. Using the quasi-static approach based on the Debye model, the elastic properties of these W-X alloys at finite temperatures are predicted. Calculated properties of BCC W and the W-X alloys are in favorable agreement with available experimental measurements. - Highlights: • The effects of nineteen metal elements on the elastic properties of W are studied. • The elastic properties at finite temperatures are predicted by the Debye model. • The alloying effects can be traceable from the changes of electronic structure. • The possibly promising alloying elements to soften BCC W are suggested.

  14. Effect of Nb Doping on High Temperature Oxidation Resistance of Ti-Al Alloyed Coatings

    Directory of Open Access Journals (Sweden)

    DAI Jing-jie

    2017-02-01

    Full Text Available Ti-Al alloyed coatings with different Nb doping contents were fabricated on TC4 titanium alloy by laser surface alloying to improve high temperature oxidation resistance of the alloy. Structures and high temperature oxidation behaviors of the alloyed coatings were analyzed and tested by X-ray diffraction (XRD, scanning electron microscope (SEM, energy dispersive spectrometer (EDS and box-type resistance furnace. The results show that the alloyed coatings consist of TiAl and Ti3Al, and no niobium compound are formed in Ti-Al-Nb alloyed coatings. The alloyed coatings are uniform and exhibit excellent metallurgical bonding with the substrates. A large amount of surface cracks and a few penetrating cracks are formed in Ti-Al alloyed coating without Nb doping, while no obvious cracks are formed in Ti-Al alloyed coating with Nb doping. The oxidation mass gains of all the alloyed coatings were significantly lower than those of the substrate. The alloyed coatings with Nb doping exhibit more excellent high temperature oxidation resistance due to the beneficial machanism of Nb doping. The mechanism of Nb doping on improving high temperature oxidation resistance of Ti-Al alloyed coatings includes reducing the defect concentration of TiO2, refining oxide grains and promoting the formation of Al2O3.

  15. Synthesis of Ternary Nitrides From Intermetallic Precursors: Modes of Nitridation in Model Cr3Pt Alloys to Form Cr3PtN Perovskite and Applications to Other Systems

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [ORNL; Wrobel, Sarah [University of Tennessee, Knoxville (UTK); Lograsso, Tom [Ames Laboratory; Payzant, E Andrew [ORNL; Hoelzer, David T [ORNL; Horton Jr, Joe A [ORNL; Walker, Larry R [ORNL

    2004-01-01

    The use of intermetallic alloy precursors is explored as a new means to synthesize complex transition and refractory metal nitrides, carbides, and related phases. The conditions under which model single-phase Cr{sub 3}Pt and two-phase Cr{sub 3}Pt-dispersed Cr alloys form Cr{sub 3}PtN antiperovskite when thermally nitrided were studied. Phenomenological experiments suggest that the key variable to achieving single-phase Cr{sub 3}PtN surface layers is the Cr{sub 3}Pt phase composition. In two-phase {beta}-Cr-Cr{sub 3}Pt alloys, the formation of single-phase Cr{sub 3}PtN at Cr{sub 3}Pt precipitates by in-place internal nitridation was found to be a strong function of the size of the Cr{sub 3}Pt dispersion in the microstructure. Nanoscale Cr{sub 3}Pt dispersions were readily converted to near single-phase Cr{sub 3}PtN, whereas nitridation of coarse Cr{sub 3}Pt particles resulted in a cellular or discontinuous-type reaction to form a lath mixture of Cr{sub 3}PtN and a more Cr-rich Cr{sub 3}Pt or {beta}-Cr. The potential for using such external/internal oxidation phenomena as a synthesis approach to layered or composite surfaces of ternary ceramic phases (nitrides, carbides, borides, etc.) of technological interest such as the Ti{sub 3}AlC{sub 2} phase, bimetallic nitride, and carbide catalysts (Co{sub 3}Mo{sub 3}N and Co{sub 3}Mo{sub 3}C and related phases), and magnetic rare earth nitrides (Fe{sub 17}Sm{sub 2}N{sub x} or Fe{sub 17}Nd{sub 2}N{sub x}) is discussed.

  16. High Strength Aluminum Alloy For High Temperature Applications

    Science.gov (United States)

    Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

    2005-01-01

    A cast article from an aluminum alloy has improved mechanical properties at elevated temperatures. The cast article has the following composition in weight percent: Silicon 6.0-25.0, Copper 5.0-8.0, Iron 0.05-1.2, Magnesium 0.5-1.5, Nickel 0.05-0.9, Manganese 0.05-1.2, Titanium 0.05-1.2, Zirconium 0.05-1.2, Vanadium 0.05-1.2, Zinc 0.05-0.9, Strontium 0.001-0.1, Phosphorus 0.001-0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10-25, and the copper-to-magnesium ratio is 4-15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2 crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix containing up to about 60% by volume of a secondary filler material.

  17. Development of powder metallurgy Al alloys for high temperature aircraft structural applications, phase 2

    Science.gov (United States)

    Chellman, D. J.

    1982-01-01

    In this continuing study, the development of mechanically alloyed heat resistant aluminum alloys for aircraft were studied to develop higher strength targets and higher service temperatures. The use of higher alloy additions to MA Al-Fe-Co alloys, employment of prealloyed starting materials, and higher extrusion temperatures were investigated. While the MA Al-Fe-Co alloys exhibited good retention of strength and ductility properties at elevated temperatures and excellent stability of properties after 1000 hour exposure at elevated temperatures, a sensitivity of this system to low extrusion strain rates adversely affected the level of strength achieved. MA alloys in the Al-Li family showed excellent notched toughness and property stability after long time exposures at elevated temperatures. A loss of Li during processing and the higher extrusion temperature 482 K (900 F) resulted in low mechanical strengths. Subsequent hot and cold working of the MA Al-Li had only a mild influence on properties.

  18. High-temperature tribological behaviors of a Cr-Si co-alloyed layer on TA15 alloy

    Directory of Open Access Journals (Sweden)

    Haifeng Lu

    2017-04-01

    Full Text Available A Cr-Si co-alloyed layer was successfully deposited on TA15 alloy by the double glow plasma surface technology to improve its poor wear resistance at elevated temperature. The microstructure, composition, and phase structure of the layer were investigated by SEM, EDS, and XRD. The tribological behaviors of the Cr-Si co-alloyed layer at 20 °C and 500 °C were analyzed in details. The results indicated that the friction coefficient and wear rate of the Cr-Si co-alloyed layer at 20 °C and 500 °C were much lower than those of the substrate, which was due to higher hardness and superior elastic modulus. This layer may become an approach to effectively improving the wear resistance of TA15 alloy at elevated temperature.

  19. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    Science.gov (United States)

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Sputter deposition of aluminum and other alloys at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D.L.; Wan, C.T.; Susi, G.T.; Taylor, K.A.

    1989-05-01

    Structures of thin films deposited at ambient temperatures are similar to those of the bulk material whereas at lower temperatures films have significantly reduced grain size and may become amorphouslike. A two-stage cryorefrigerator was installed in a sputtering system to allow thin films of aluminum and aluminum--copper alloy to be deposited onto substrates cooled to cryogenic temperatures less than 30 K. Gases used for sputtering were argon, neon, and helium at pressures ranging from 0.40 to 2.0 Pa. A standard planar magnetron cathode was used. Vapor pressure--temperature data for gases show that argon will not cryocondense on substrate surfaces at temperatures greater than 40 K and neon will not cryocondense at temperatures above 11 K. Helium is considered for sputtering at substrate temperatures below 11 K. The purpose of this work is to determine the deposition rates using argon, neon, and helium and microstructure changes occurring when thin films are deposited onto cryogenically cooled substrates. Deposition rates are determined using surface profilometry and microstructure was determined by transmission electron microscopy.

  1. Evaluation of precipitates used in strainer head loss testing: Part II. Precipitates by in situ aluminum alloy corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Bahn, Chi Bum, E-mail: bahn@anl.go [Argonne National Laboratory, Lemont, IL 60439 (United States); Kasza, Ken E.; Shack, William J.; Natesan, Ken [Argonne National Laboratory, Lemont, IL 60439 (United States); Klein, Paul [The United States Nuclear Regulatory Commission, Rockville, MD 20852 (United States)

    2011-05-15

    Graphical abstract: Display Omitted Research highlights: Sump strainer head loss testing to evaluate chemical effects. Aluminum hydroxide precipitates by in situ Al alloy corrosion caused head loss. Intermetallic particles released from Al alloy can also cause significant head loss. When evaluating Al effect on head loss, intermetallics should be considered. - Abstract: Vertical loop head loss tests were performed with 6061 and 1100 aluminum (Al) alloy plates immersed in borated solution at pH = 9.3 at room temperature and 60 {sup o}C. The results suggest that the potential for corrosion of an Al alloy to result in increased head loss across a glass fiber bed may depend on its microstructure, i.e., the size distribution and number density of intermetallic particles that are present in Al matrix and FeSiAl ternary compounds, as well as its Al release rate. Per unit mass of Al removed from solution, the WCAP-16530 aluminum hydroxide (Al(OH){sub 3}) surrogate was more effective in increasing head loss than the Al(OH){sub 3} precipitates formed in situ by corrosion of Al alloy. However, in choosing a representative amount of surrogate for plant specific testing, consideration should be given to the potential for additional head losses due to intermetallic particles and the apparent reduction in the effective solubility of Al(OH){sub 3} when intermetallic particles are present.

  2. Beneficial Role of Copper in the Enhancement of Durability of Ordered Intermetallic PtFeCu Catalyst for Electrocatalytic Oxygen Reduction.

    Science.gov (United States)

    Arumugam, Balamurugan; Tamaki, Takanori; Yamaguchi, Takeo

    2015-08-05

    Design of Pt alloy catalysts with enhanced activity and durability is a key challenge for polymer electrolyte membrane fuel cells. In the present work, we compare the durability of the ordered intermetallic face-centered tetragonal (fct) PtFeCu catalyst for the oxygen reduction reaction (ORR) relative to its counterpart bimetallic catalysts, i.e., the ordered intermetallic fct-PtFe catalyst and the commercial catalyst from Tanaka Kikinzoku Kogyo, TKK-PtC. Although both fct catalysts initially exhibited an ordered structure and mass activity approximately 2.5 times higher than that of TKK-Pt/C, the presence of Cu at the ordered intermetallic fct-PtFeCu catalyst led to a significant enhancement in durability compared to that of the ordered intermetallic fct-PtFe catalyst. The ordered intermetallic fct-PtFeCu catalyst retained more than 70% of its mass activity and electrochemically active surface area (ECSA) over 10 000 durability cycles carried out at 60 °C. In contrast, the ordered intermetallic fct-PtFe catalyst maintained only about 40% of its activity. The temperature of the durability experiment is also shown to be important: the catalyst was more severely degraded at 60 °C than at room temperature. To obtain insight into the observed enhancement in durability of fct-PtFeCu catalyst, a postmortem analysis of the ordered intermetallic fct-PtFeCu catalyst was carried out using scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) line scan. The STEM-EDX line scans of the ordered intermetallic fct-PtFeCu catalyst over 10 000 durability cycles showed a smaller degree of Fe and Cu dissolution from the catalyst. Conversely, large dissolution of Fe was identified in the ordered intermetallic fct-PtFe catalyst, indicating a lesser retention of Fe that causes the destruction of ordered structure and gives rise to poor durability. The enhancement in the durability of the ordered intermetallic fct-PtFeCu catalyst is ascribed to

  3. Suppressors made from intermetallic materials

    Energy Technology Data Exchange (ETDEWEB)

    Klett, James W; Muth, Thomas R; Cler, Dan L

    2014-11-04

    Disclosed are several examples of apparatuses for suppressing the blast and flash produced as a projectile is expelled by gases from a firearm. In some examples, gases are diverted away from the central chamber to an expansion chamber by baffles. The gases are absorbed by the expansion chamber and desorbed slowly, thus decreasing pressure and increasing residence time of the gases. In other examples, the gases impinge against a plurality of rods before expanding through passages between the rods to decrease the pressure and increase the residence time of the gases. These and other exemplary suppressors are made from an intermetallic material composition for enhanced strength and oxidation resistance at high operational temperatures.

  4. Addition of iron for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase in an Al-7.5Si-3.6Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Belmares-Perales, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon (Mexico); Zaldivar-Cadena, A.A., E-mail: azaldiva70@hotmail.com [Facultad de Ingenieria Civil, Departamento de Ecomateriales y Energia, Instituto de Ingenieria Civil, Av. Fidel Velasquez and Av. Universidad S/N, Cd. Universitaria, San Nicolas de los Garza, N.L. 66450 (Mexico)

    2010-10-25

    Addition of iron into the molten metal for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase has been studied. Solidification conditions and composition determine the final microstructure and mechanical properties of a casting piece. It is known that increasing the iron content will produce an increasing of the {alpha}-AlFeSi and {beta}-AlFeSi phases. This phenomenon was confirmed with calculations made by Thermo-Calc{sup TM} software and validated with experimental results, however, the technique of iron addition in this study plays an important role on the solidification kinetics of these iron phases because the refining of {alpha}-AlFeSi and removal of {beta}-AlFeSi phases can be improved. Final results showed an improvement in mechanical properties by removal and refining of {beta}-AlFeSi and {alpha}-AlFeSi phases, respectively. This study shows a new method of removal of {beta}-AlFeSi that could be adopted in the aluminum smelting industry in aluminum alloys with a low cooling rate with a secondary dendritic spacing of about 37 {mu}m.

  5. Study on growth factors of intermetallic layer within hot-dipped

    Indian Academy of Sciences (India)

    Al-Zn-Si coating with regard to general seawater corrosion protection. This study deals with the interfacial intermetallic layer's growth, which affects considerably the corrosion resistance and mechanical properties of 25%Al-Zn alloy coatings, ...

  6. Dynamic high-temperature characterization of an iridium alloy in tension

    Energy Technology Data Exchange (ETDEWEB)

    Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nelson, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Jin, Helena [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bignell, John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ulrich, G. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); George, E. P. [Ruhr Univ., Bochum (Germany)

    2015-09-01

    Iridium alloys have been utilized as structural materials for certain high-temperature applications, due to their superior strength and ductility at elevated temperatures. The mechanical properties, including failure response at high strain rates and elevated temperatures of the iridium alloys need to be characterized to better understand high-speed impacts at elevated temperatures. A DOP-26 iridium alloy has been dynamically characterized in compression at elevated temperatures with high-temperature Kolsky compression bar techniques. However, the dynamic high-temperature compression tests were not able to provide sufficient dynamic high-temperature failure information of the iridium alloy. In this study, we modified current room-temperature Kolsky tension bar techniques for obtaining dynamic tensile stress-strain curves of the DOP-26 iridium alloy at two different strain rates (~1000 and ~3000 s-1) and temperatures (~750°C and ~1030°C). The effects of strain rate and temperature on the tensile stress-strain response of the iridium alloy were determined. The DOP-26 iridium alloy exhibited high ductility in stress-strain response that strongly depended on both strain rate and temperature.

  7. Improvement of the surface properties of aluminium by the formation of intermetallic phases and metal matrix composites during laser surface alloying

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2011-05-01

    Full Text Available Aluminium is widely used in industry due to its low cost, light weight and excellent workability, but is lacking in wear resistance and hardness. Laser alloying is used to improve the surface properties, such as hardness, by modifying...

  8. Composite Layers “MgAl Intermetalic Layer / PVD Coating” Obtained On The AZ91D Magnesium Alloy By Different Hybrid Surface Treatment Methods

    Directory of Open Access Journals (Sweden)

    Smolik J.

    2015-06-01

    Full Text Available Magnesium alloys have very interesting physical properties which make them ‘materials of the future’ for tools and machine components in many industry areas. However, very low corrosion and tribological resistance of magnesium alloys hampers the implementation of this material in the industry. One of the methods to improve the properties of magnesium alloys is the application of the solutions of surface engineering like hybrid technologies. In this paper, the authors compare the tribological and corrosion properties of two types of “MgAlitermetalic / PVD coating” composite layers obtained by two different hybrid surface treatment technologies. In the first configuration, the “MgAlitermetalic / PVD coating” composite layer was obtained by multisource hybrid surface treatment technology combining magnetron sputtering (MS, arc evaporation (AE and vacuum heating methods. The second type of a composite layer was prepared using a hybrid technology combined with a diffusion treatment process in Al-powder and the electron beam evaporation (EB method. The authors conclude, that even though the application of „MgAlitermetalic / PVD coating” composite layers can be an effective solution to increase the abrasive wear resistance of magnesium alloys, it is not a good solution to increase its corrosion resistance.

  9. Thermal aging modeling and validation on the Mo containing Fe-Cr-Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Busby, Jeremy T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-04-01

    Thermodynamics of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical knowledge to understand thermal aging effect on the phase stability of Mo-containing austenitic steels, which subsequently facilitates alloy design/improvement and degradation mitigation of these materials for reactor applications. Among the intermetallic phases, Chi (χ), Laves, and Sigma (σ) are often of concern because of their tendency to cause embrittlement of the materials. The focus of this study is thermal stability of the Chi and Laves phases as they were less studied compared to the Sigma phase. Coupled with thermodynamic modeling, thermal stability of intermetallic phases in Mo containing Fe-Cr-Ni alloys was investigated at 1000, 850 and 700 C for different annealing times. The morphologies, compositions and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Three key findings resulted from this study. First, the Chi phase is stable at high temperature, and with decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. Thirdly, in situ transformation from Chi phase to Laves phase was directly observed, which increased the local strain field, generated dislocations in the intermetallic phases, and altered the precipitate phase orientation relationship with the austenitic matrix. The thermodynamic models that were developed and validated were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  10. Heat resistant magnesium alloys for automotive powertrain applications

    Energy Technology Data Exchange (ETDEWEB)

    Anyanwu, I.A.; Gokan, Y.; Nozawa, S.; Kamado, S.; Kojima, Y. [Dept. of Mechanical Engineering, Nagaoka Univ. of Technology, Nagaoka, Niigata (Japan); Takeda, S.; Ishida, T. [Ahresty Corp., Magnesium Products Mfg. Div., Tochigi (Japan)

    2003-07-01

    The suitability of new Mg-Zn-Al-Ca-RE alloys for automotive power train applications are evaluated. Zinc and aluminum contents of the alloys were systematically varied in order to determine alloys with a combination of good diecasting characteristics and high heat resistance. Addition of large amounts of zinc to the alloys results in the formation of intermetallic compounds that crystallize at lower temperatures relative to the matrix, and consequently, fluidity is improved, but hot tearing occurs during diecasting. However, one of the new alloys, Mg-0.5%Zn-6%Al-1%Ca-3%RE alloy is found to exhibit good diecastability and comparable heat resistance with the conventional aluminum alloy, ADC12 that is currently used for diecasting of automotive powertrain parts. (orig.)

  11. Materials Properties Database for Selection of High-Temperature Alloys and Concepts of Alloy Design for SOFC Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z Gary; Paxton, Dean M.; Weil, K. Scott; Stevenson, Jeffry W.; Singh, Prabhakar

    2002-11-24

    To serve as an interconnect / gas separator in an SOFC stack, an alloy should demonstrate the ability to provide (i) bulk and surface stability against oxidation and corrosion during prolonged exposure to the fuel cell environment, (ii) thermal expansion compatibility with the other stack components, (iii) chemical compatibility with adjacent stack components, (iv) high electrical conductivity of the surface reaction products, (v) mechanical reliability and durability at cell exposure conditions, (vii) good manufacturability, processability and fabricability, and (viii) cost effectiveness. As the first step of this approach, a composition and property database was compiled for high temperature alloys in order to assist in determining which alloys offer the most promise for SOFC interconnect applications in terms of oxidation and corrosion resistance. The high temperature alloys of interest included Ni-, Fe-, Co-base superal

  12. Effect of pouring temperature on the properties of Al-8%Si alloy sand ...

    African Journals Online (AJOL)

    This study was conducted to produce sand castings and determine the effect of pouring temperature on the properties of sand cast products from Al-8%Si alloy. Molten alloy was poured into prepared sand moulds at pouring temperatures of 650, 700, 750, 800 and 850°C. The density of each casting was determined based ...

  13. Calculation of the high-temperature strength of complexly alloyed nickel alloys using equations of the system of nonpolarized ionic radii

    Science.gov (United States)

    Ovsepyan, S. V.; Lomberg, B. S.; Baburina, E. V.

    1995-06-01

    Modern complexly alloyed high-temperature nickel-base alloys contain up to 14 alloying elements. The complex composition ensures fulfillment of strict and often contradictory requirements imposed on the materials of critical parts of gas turbine engines (GTE). However, multi-component alloying creates considerable difficulties in the development of new compositions with specified characteristics or in the optimization of existing alloys. The present work is devoted to calculating the high-temperature strength of nickel alloys by means of the system of nonpolarized ionic radii (SNIR).

  14. Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under temperature gradient

    Science.gov (United States)

    Zhao, N.; Zhong, Y.; Huang, M. L.; Ma, H. T.; Dong, W.

    2015-08-01

    The growth behavior of intermetallic compounds (IMCs) at the liquid-solid interfaces in Cu/Sn/Cu interconnects during reflow at 250 °C and 280 °C on a hot plate was investigated. Being different from the symmetrical growth during isothermal aging, the interfacial IMCs showed clearly asymmetrical growth during reflow, i.e., the growth of Cu6Sn5 IMC at the cold end was significantly enhanced while that of Cu3Sn IMC was hindered especially at the hot end. It was found that the temperature gradient had caused the mass migration of Cu atoms from the hot end toward the cold end, resulting in sufficient Cu atomic flux for interfacial reaction at the cold end while inadequate Cu atomic flux at the hot end. The growth mechanism was considered as reaction/thermomigration-controlled at the cold end and grain boundary diffusion/thermomigration-controlled at the hot end. A growth model was established to explain the growth kinetics of the Cu6Sn5 IMC at both cold and hot ends. The molar heat of transport of Cu atoms in molten Sn was calculated as + 11.12 kJ/mol at 250 °C and + 14.65 kJ/mol at 280 °C. The corresponding driving force of thermomigration in molten Sn was estimated as 4.82 × 10-19 N and 6.80 × 10-19 N.

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

    Directory of Open Access Journals (Sweden)

    J.B. Ferguson

    2016-02-01

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

  16. Prediction of intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Burkhanov, Gennady S; Kiselyova, N N [A A Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow (Russian Federation)

    2009-06-30

    The problems of predicting not yet synthesized intermetallic compounds are discussed. It is noted that the use of classical physicochemical analysis in the study of multicomponent metallic systems is faced with the complexity of presenting multidimensional phase diagrams. One way of predicting new intermetallics with specified properties is the use of modern processing technology with application of teaching of image recognition by the computer. The algorithms used most often in these methods are briefly considered and the efficiency of their use for predicting new compounds is demonstrated.

  17. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.; Easton, D.S.; Heatherly, L.

    1996-06-01

    The objective of this work is to develop a new generation of structural materials based on intermetallic alloys for use at high temperatures in advanced fossil energy conversion systems. Target applications of such ultrahigh strength alloys include hot components (for example, air heat exchangers) in advanced energy conversion systems and heat engines. However, these materials may also find use as wear-resistant parts in coal handling systems (for example, nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. One potential class of such alloys is that based on Cr-Cr{sub 2}Nb alloys. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for initial development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), and excellent high-temperature strength (at 1000 to 1250{degrees}C). This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions.

  18. High Work Output Ni-Ti-Pt High Temperature Shape Memory Alloys and Associated Processing Methods

    Science.gov (United States)

    Noebe, Ronald D. (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Garg, Anita (Inventor)

    2009-01-01

    According to the invention, compositions of Ni-Ti-Pt high temperature, high force, shape memory alloys are disclosed that have transition temperatures above 100 C.; have narrow hysteresis; and produce a high specific work output.

  19. High Temperature Properties and Recent Research Trend of Mg-RE Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Soo Woo [Korea Institute of Science and Technology Information, Seoul (Korea, Republic of)

    2017-04-15

    For the applications in automotive, aircraft, aerospace, and electronic industries, the lightest structural Mg alloys have received much attention since 2000. There has been some progress for the improvement of the mechanical properties such as room temperature strength, formability and mechanical anisotropy. However, the high temperature strength of Mg alloys is very low to be used for the parts and structures of high temperature conditions. For the last decade, considerable efforts are concentrated for the development of Mg alloys to be used at high temperature. Newly developing Mg-RE alloys are the good examples for the high temperature use. In this regard, this review paper introduces the recent research trends for the development of Mg-RE alloys strengthened with some precipitates and the long period stacking ordered (LPSO) structures related RE elements.

  20. High temperature oxidation of slurry coated interconnect alloys

    DEFF Research Database (Denmark)

    Persson, Åsa Helen

    with this interaction mechanism mainly give a geometrical protection against oxidation by blocking oxygen access at the surface of the oxide scale. The protecting effect is gradually reduced as the oxide scale grows thicker than the diameter of the coating particles. Interaction mechanism B entails a chemical reaction.......85Sr0.15)CoO3 + 10% Co3O4, LSC, coatings were found to be relatively successful in decreasing the oxidation rate, the chromium content in the outermost part of ii the dense scale, and the electrical resistance in the growing oxide scales when applied onto Crofer 22APU. But, the positive effects......In this project, high temperature oxidation experiments of slurry coated ferritic alloys in atmospheres similar to the atmosphere found at the cathode in an SOFC were conducted. From the observations possible interaction mechanisms between the slurry coatings and the growing oxide scale...

  1. High-pressure structural stability of the ductile intermetallic ...

    Indian Academy of Sciences (India)

    Administrator

    . Introduction. Intermetallic compounds hold much potential to improve the performance of engineering systems owing to their low density, good oxidation resistance and high strength and stiffness at elevated temperature (Fleischer and Zabala.

  2. Applications of high-temperature powder metal aluminum alloys to small gas turbines

    Science.gov (United States)

    Millan, P. P., Jr.

    1982-01-01

    A program aimed at the development of advanced powder-metallurgy (PM) aluminum alloys for high-temperature applications up to 650 F using the concepts of rapid solidification and mechanical alloying is discussed. In particular, application of rapidly solidified PM aluminum alloys to centrifugal compressor impellers, currently used in auxiliary power units for both military and commercial aircraft and potentially for advanced automotive gas turbine engines, is examined. It is shown that substitution of high-temperature aluminum for titanium alloy impellers operating in the 360-650 F range provides significant savings in material and machining costs and results in reduced component weight, and consequently, reduced rotating group inertia requirements.

  3. Dendrite Growth Kinetics in Undercooled Melts of Intermetallic Compounds

    Directory of Open Access Journals (Sweden)

    Dieter M. Herlach

    2015-09-01

    Full Text Available Solidification needs an undercooling to drive the solidification front. If large undercoolings are achieved, metastable solid materials are solidified from the undercooled melt. Containerless processing provides the conditions to achieve large undercoolings since heterogeneous nucleation on container walls is completely avoided. In the present contribution both electromagnetic and electrostatic levitation are applied. The velocity of rapidly advancing dendrites is measured as a function of undercooling by a High-Speed-Camera. The dendrite growth dynamics is investigated in undercooled melts of intermetallic compounds. The Al50Ni50 alloy is studied with respect to disorder trapping that leads to a disordered superlattice structure if the melt is undercooled beyond a critical undercooling. Disorder trapping is evidenced by in situ energy dispersive diffraction using synchrotron radiation of high intensity to record full diffraction pattern on levitated samples within a short time interval. Experiments on Ni2B using different processing techniques of varying the level of convection reveal convection-induced faceting of rapidly growing dendrites. Eventually, the growth velocity is measured in an undercooled melt of glass forming Cu50Zr50 alloy. A maximum in the growth velocity–undercooling relation is proved. This is understood by the fact that the temperature dependent diffusion coefficient counteracts the thermodynamic driving force for rapid growth if the temperature of the undercooled melt is approaching the temperature regime above the glass transition temperature. The analysis of this result allows for determining the activation energy of atomic attachment kinetics at the solid–liquid interface that is comparable to the activation energy of atomic diffusion as determined by independent measurements of the atomic diffusion in undercooled Cu50Zr50 alloy melt.

  4. Ultrasonic investigations in intermetallics

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 72; Issue 2. Ultrasonic investigations in intermetallics. Devraj Singh D K Pandey. Research Articles ... Author Affiliations. Devraj Singh1 D K Pandey1. Department of Applied Physics, AMITY School of Engineering and Technology, Bijwasan, New Delhi 110 061, India ...

  5. INFLUENCE OF TEMPERATURE REGIME OF MELTING ON CHARACTERISTICS OF CAST ALIMINIUM ALLOYS

    Directory of Open Access Journals (Sweden)

    I. V. Rafalski

    2005-01-01

    Full Text Available Temperature dependence of the melts properties of the system Al-Si with content of silicon up to 16% (masses and influence of the temperature regime of the alloys melting in liquid phase on the structure and properties of cast metal is studied. The temperature regimes of preparation of cast aluminium alloys in liquid phase providing dispersible phases at crystallizing and increase of mechanical properties of cast metal are established. Modification of form, sizes and character of distribution of primary and eutectic phases is the result of the regime of the temperature processing of alloy in liquid state. The formalized model of evolutions of the metal system condition is offered.

  6. Iron-aluminum alloys having high room-temperature and method for making same

    Science.gov (United States)

    Sikka, V.K.; McKamey, C.G.

    1993-08-24

    A wrought and annealed iron-aluminum alloy is described consisting essentially of 8 to 9.5% aluminum, an effective amount of chromium sufficient to promote resistance to aqueous corrosion of the alloy, and an alloying constituent selected from the group of elements consisting of an effective amount of molybdenum sufficient to promote solution hardening of the alloy and resistance of the alloy to pitting when exposed to solutions containing chloride, up to about 0.05% carbon with up to about 0.5% of a carbide former which combines with the carbon to form carbides for controlling grain growth at elevated temperatures, and mixtures thereof, and the balance iron, wherein said alloy has a single disordered [alpha] phase crystal structure, is substantially non-susceptible to hydrogen embrittlement, and has a room-temperature ductility of greater than 20%.

  7. Niobium-Based Intermetallics for Affordable In-Space Propulsion Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort proposes an innovative class of refractory metal intermetallic composites as alternatives to high temperature metallic materials presently...

  8. Nonstoichiometry of Al-Zr intermetallic phases

    Energy Technology Data Exchange (ETDEWEB)

    Radmilovic, V.; Thomas, G.

    1994-06-01

    Nonstoichiometry of metastable cubic {beta}{prime} and equilibrium tetragonal {beta} Al-Zr intermetallic phases of the nominal composition Al{sub 3}Zr in Al-rich alloys has been extensively studied. It is proposed that the ``dark contrast`` of {beta}{prime} core in {beta}{prime}/{sigma}{prime} complex precipitates, in Al-Li-Zr based alloys, is caused by incorporation of Al and Li atoms into the {beta}{prime} phase on Zr sublattice sites, forming nonstoichiometric Al-Zr intermetallic phases, rather than by Li partitioning only. {beta}{prime} particles contain very small amounts of Zr, approximately 5 at.%, much less than the stoichiometric 25 at.% in the Al{sub 3}Zr metastable phase. These particles are, according to simulation of high resolution images, of the Al{sub 3}(Al{sub 0.4}Li{sub 0.4}Zr{sub 0.2}) type. Nonstoichiometric particles of average composition Al{sub 4}Zr and Al{sub 6}Zr are observed also in the binary Al-Zr alloy, even after annealing for several hours at 600{degree}C.

  9. Spark plasma sintering of titanium aluminide intermetallics and its composites

    Science.gov (United States)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  10. Chemical effect on diffusion in intermetallic compounds

    Science.gov (United States)

    Chen, Yi-Ting

    With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

  11. 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

  12. A Review on the Properties of Iron Aluminide Intermetallics

    Directory of Open Access Journals (Sweden)

    Mohammad Zamanzade

    2016-01-01

    Full Text Available Iron aluminides have been among the most studied intermetallics since the 1930s, when their excellent oxidation resistance was first noticed. Their low cost of production, low density, high strength-to-weight ratios, good wear resistance, ease of fabrication and resistance to high temperature oxidation and sulfurization make them very attractive as a substitute for routine stainless steel in industrial applications. Furthermore, iron aluminides allow for the conservation of less accessible and expensive elements such as nickel and molybdenum. These advantages have led to the consideration of many applications, such as brake disks for windmills and trucks, filtration systems in refineries and fossil power plants, transfer rolls for hot-rolled steel strips, and ethylene crackers and air deflectors for burning high-sulfur coal. A wide application for iron aluminides in industry strictly depends on the fundamental understanding of the influence of (i alloy composition; (ii microstructure; and (iii number (type of defects on the thermo-mechanical properties. Additionally, environmental degradation of the alloys, consisting of hydrogen embrittlement, anodic or cathodic dissolution, localized corrosion and oxidation resistance, in different environments should be well known. Recently, some progress in the development of new micro- and nano-mechanical testing methods in addition to the fabrication techniques of micro- and nano-scaled samples has enabled scientists to resolve more clearly the effects of alloying elements, environmental items and crystal structure on the deformation behavior of alloys. In this paper, we will review the extensive work which has been done during the last decades to address each of the points mentioned above.

  13. Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures

    Directory of Open Access Journals (Sweden)

    Hesham Ahmed

    2016-08-01

    Full Text Available Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the “Reduction-Sintering” process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H2, CH4 and N2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures

  14. Thermographic Study of Chip Temperature in High-Speed Dry Milling Magnesium Alloys

    Directory of Open Access Journals (Sweden)

    Kuczmaszewski Józef

    2016-06-01

    Full Text Available This paper presents an overview of the state of knowledge on temperature measurement in the cutting area during magnesium alloy milling. Additionally, results of own research on chip temperature measurement during dry milling of magnesium alloys are included. Tested magnesium alloys are frequently used for manufacturing elements applied in the aerospace industry. The impact of technological parameters on the maximum chip temperature during milling is also analysed. This study is relevant due to the risk of chip ignition during the machining process.

  15. New Equation for Prediction of Martensite Start Temperature in High Carbon Ferrous Alloys

    Science.gov (United States)

    Park, Jihye; Shim, Jae-Hyeok; Lee, Seok-Jae

    2018-02-01

    Since previous equations fail to predict M S temperature of high carbon ferrous alloys, we first propose an equation for prediction of M S temperature of ferrous alloys containing > 2 wt pct C. The presence of carbides (Fe3C and Cr-rich M 7C3) is thermodynamically considered to estimate the C concentration in austenite. Especially, equations individually specialized for lean and high Cr alloys very accurately reproduce experimental results. The chemical driving force for martensitic transformation is quantitatively analyzed based on the calculation of T 0 temperature.

  16. Influence of temperature, grain size and cobalt content on the hardness of WC-Co alloys

    CSIR Research Space (South Africa)

    Milman, YV

    1999-01-01

    Full Text Available The Vickers hardness of WC-Co alloys has been measured at temperatures ranging from -196 to 900 degrees C. The cobalt content of the alloys ranged from 10 to 24 vol% and the grain size from 0.5 to 2.3 um. It was found that, at all cobalt contents...

  17. Copper modified austenitic stainless steel alloys with improved high temperature creep resistance

    Science.gov (United States)

    Swindeman, R.W.; Maziasz, P.J.

    1987-04-28

    An improved austenitic stainless steel that incorporates copper into a base Fe-Ni-Cr alloy having minor alloying substituents of Mo, Mn, Si, T, Nb, V, C, N, P, B which exhibits significant improvement in high temperature creep resistance over previous steels. 3 figs.

  18. Summary of workshop on alloys for very high-temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    In current fossil energy systems, the maximum operating temperatures experienced by critical metal structures do not exceed approximately 732{degrees}C and the major limitation on the use of the alloys typically is corrosion resistance. In systems intended for higher performance and higher efficiency, increasingly higher working fluid temperatures will be employed, which will require materials with higher-temperature capabilities, in particular, higher creep strength and greater environmental resistance. There have been significant developments in alloys in recent years, from modifications of currently-used wrought ferritic and austenitic alloys with the intent of improving their high-temperature capabilities, to oxide dispersion-strengthened alloys targeted at extremely high-temperature applications. The aim of this workshop was to examine the temperature capability of these alloys compared to current alloys, and compared to the needs of advanced fossil fuel combustion or conversion systems, with the goals of identifying where modified/new alloys would be expected to find application, their limitations, and the information/actions required or that are being taken to qualify them for such use.

  19. Development of a Brazing Alloy for the Mechanically Alloyed High Temperature Sheet Material INCOLOY Alloy MA 956.

    Science.gov (United States)

    1981-09-01

    OF CONTENTS Section Pge 1. INTRODUCTION AND PW)GRAM E OBJECTIVE 7 2. ALLOYING APROACH AND RATIONALE 9 2.1 Approach 9 2.2 Selection of Suitable Alloy...At the time of writing this final summary report only limited success has been achieved by Allied Chemicals but it is reported as follows so that the

  20. Development of Mg-Al-Zn based diecasting alloys for elevated temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.M.; Park, B.K.; Jun, J.H.; Kim, K.T.; Jung, W.J. [Advanced Materials Development Center, Korea Inst. of Industrial Technology, Incheon (Korea); Shin, K. [Dept. of Metallurgy and Materials Science, Changwon National Univ., Changwon (Korea)

    2005-07-01

    Effort has been devoted to develop new heat resistant diecasting alloys based on Mg-Al-Zn system in this research. Small amounts of cerium-rich misch metal and antimony additions to AZ91 alloy could enhance the tensile strength at an elevated temperature while keeping the good castability. The increase of Zn content in Mg-8(wt%)Al-xZn-0.5RE-0.5Sb alloys, was observed to significantly increase the yield strength at 175 C although the castability such as fluidity and hot cracking resistance was slightly decreased. Intensive microstructural investigation on the new Mg-Al-Zn diecasting alloys was also carried out. (orig.)

  1. Tensile deformation of 2618 and Al-Fe-Si-V aluminum alloys at elevated temperatures

    Science.gov (United States)

    Leng, Y.; Porr, W. C., Jr.; Gangloff, R. P.

    1990-01-01

    The present study experimentally characterizes the effects of elevated temperature on the uniaxial tensile behavior of ingot metallurgy 2618 Al alloy and the rapidly solidified FVS 0812 P/M alloy by means of two constitutive formulations: the Ramberg/Osgood equation and the Bodner-Partom (1975) incremental formulation for uniaxial tensile loading. The elastoplastic strain-hardening behavior of the ingot metallurgy alloy is equally well represented by either formulation. Both alloys deform similarly under decreasing load after only 1-5 percent uniform tensile strain, a response which is not described by either constitutive relation.

  2. Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Seehra, M.S.; Babu, V.S. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    1996-05-01

    X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

  3. Forging of FeAl intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L. [UNAM, Cuernavaca (Mexico). Lab. de Cuernavaca; Schneibel, J.H. [Oak Ridge National Lab., TN (United States)

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  4. Properties of aluminum alloys tensile, creep, and fatigue data at high and low temperatures

    CERN Document Server

    1999-01-01

    This book compiles more than 300 tables listing typical average properties of a wide range of aluminum alloys. The individual test results were compiled, plotted in various ways, and analyzed. The average values from the tensile and creep tests were then normalized to the published typical room-temperature tensile properties of the respective alloys for easy comparison. This extensive project was done by Alcoa Laboratories over a period of several years. The types of data presented include: Typical Mechanical Properties of Wrought and Cast Aluminum Alloys at Various Temperatures, including tensile properties at subzero temperatures, at temperature after various holding times at the test temperature, and at room temperature after exposure at various temperatures for various holding times; creep rupture strengths for various times at various temperatures; stresses required to generate various amounts of creep in various lengths of time; rotating-beam fatigue strengths; modulus of elasticity as a function of t...

  5. New tungsten alloy has high strength at elevated temperatures

    Science.gov (United States)

    1966-01-01

    Tungsten-hafnium-carbon alloy has tensile strengths of 88,200 psi at 3000 deg F and 62,500 psi at 3500 deg F. Possible industrial applications for this alloy would include electrical components such as switches and spark plugs, die materials for die casting steels, and heating elements.

  6. Low temperature heat capacity of lutetium and lutetium hydrogen alloys

    Energy Technology Data Exchange (ETDEWEB)

    Thome, David Keith [Iowa State Univ., Ames, IA (United States)

    1977-10-01

    The heat capacity of high purity electrotransport refined lutetium was measured between 1 and 20°K. Results for thetaD were in excellent agreement with theta values determined from elastic constant measurements. The heat capacity of a series of lutetium-hydrogen solid solution alloys was determined and results showed an increase in γ to about 11.3 mJ/g-atom-K2 for hydrogen content increasing from zero to about one atomic percent. Above one percent hydrogen γ decreased with increasing hydrogen contents. The C/T data showed an increase with temperature decreasing below about 2.5°K for samples with 0.1 to 1.5 atomic percent hydrogen. This accounts for a large amount of scatter in thetaD versus hydrogen content in this range. The heat capacity of a bulk sample of lutetium dihydride was measured between 1 and 20°K and showed a large increase in thetaD and a large decrease in ..gamma.. compared to pure lutetium.

  7. Self-brazing Mechanism of Aluminum Alloy at Medium Temperature

    Directory of Open Access Journals (Sweden)

    CHENG Fang-jie

    2018-01-01

    Full Text Available ZnCl2 and SnCl2 were added to the AlF3-CsF eutectic flux, which can be used for connecting aluminum alloy sheet by self-brazing at medium temperature. The influence of the amount of ZnCl2 and SnCl2 and the size of the T-joint area on the interface microstructure and the self-brazing joint mechanical properties was investigated. The interface microstructure, chemical compositions, defects and tensile fractography of the self-brazing joints were analyzed by metallographic microscope, scanning electron microscope and energy dispersive spectroscopy. The results show that the joints are soundly bonded when both the mass fractions of ZnCl2 and SnCl2 are about 4%; the replacement reactions between Zn2+, Sn2+ of flux and Al atoms of base metal occur during brazing, then the liquid metals of Sn and Zn appear, a great degree of Zn which has high solid solution with Al spreads rapidly to the base metal; Sn is distributed along the interface forming a low melting point metal layer with Zn and Al; the brazing of joints with small area can be realized easily; there are a lot of dimples on the fracture surface and the tensile strength of the brazing joint reaches (58±5MPa.

  8. Development of Creep Resistant Mg-Al-Sr Alloys

    Science.gov (United States)

    Pekguleryuz, Mihriban O.; Baril, Eric

    There have been attempts since in the 70's to develop creep resistant magnesium diecasting alloys for automotive applications such as automatic-transmission case and engine components. The earliest die casting alloys developed as a result of these activities were the Mg-Al- RE and Mg-Al-Si systems (AE and AS alloys). The shortcomings of these two alloy systems related to high cost or borderline properties have led to renewed activity in the 90's in the development of magnesium alloys with improved elevaied-temperature properties. This paper presents the development of a new family of creep-resistant Mg alloys based on the Mg-Al-Sr system. Creep resistance, the tensile yield strength and the bolt-load-retention of these alloys at 150°C and 175°C show improvement over Mg-Al-RE and Mg-Al-Si system. The microstructure of the alloys is characterized by Al-Sr-(Mg) containing intermetallic second phases. The absence of the Mg17Al12 phase in the microstructure, either creep-induced or as-cast, is one of the factors that contribute to improved creep-resistance of these alloys over the Mg-Al based diecasting alloys. Furthermore, the alloys exhibit better salt-spray corrosion resistance (0.09-0.15mg/cm2/day) than other commercial magnesium diecasting alloys such as AM60B, AS41, AE42 and the aluminum diecasting alloy A380.

  9. First-principles prediction of high-entropy-alloy stability

    Science.gov (United States)

    Feng, Rui; Liaw, Peter K.; Gao, Michael C.; Widom, Michael

    2017-11-01

    High entropy alloys (HEAs) are multicomponent compounds whose high configurational entropy allows them to solidify into a single phase, with a simple crystal lattice structure. Some HEAs exhibit desirable properties, such as high specific strength, ductility, and corrosion resistance, while challenging the scientist to make confident predictions in the face of multiple competing phases. We demonstrate phase stability in the multicomponent alloy system of Cr-Mo-Nb-V, for which some of its binary subsystems are subject to phase separation and complex intermetallic-phase formation. Our first-principles calculation of free energy predicts that the configurational entropy stabilizes a single body-centered cubic (BCC) phase from T = 1700 K up to melting, while precipitation of a complex intermetallic is favored at lower temperatures. We form the compound experimentally and confirm that it develops as a single BCC phase from the melt, but that it transforms reversibly at lower temperatures.

  10. Design and fabrication of a mechanical alloying system for preparing intermetallic, nanocrystalline, amorphous and quasicrystalline compounds; Diseno y fabricacion de un sistema de aleado mecanico para preparar compuestos intermetalicos, nanocristalinos, amorfos y cuasicristalinos

    Energy Technology Data Exchange (ETDEWEB)

    Bonifacio M, J.; Iturbe G, J.L.; Castaneda J, G. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2002-07-01

    In this work a grinding system was designed and fabricated which allowed to improve the operation conditions in time, frequency, temperature and selection of the grinding media and that allow the contamination decrease of the compounds. By means of this method of mechanical alloying new metallic compounds can be produced, starting from elemental powders, with fine and controlled microstructures. These compounds prepared by this method are going to be used as materials for the hydrogen storage. (Author)

  11. Effect of Thermal Exposure on the Tensile Properties of Aluminum Alloys for Elevated Temperature Service

    Science.gov (United States)

    Edahl, Robert A., Jr.; Domack, Marcia

    2004-01-01

    Tensile properties were evaluated for four aluminum alloys that are candidates for airframe applications on high speed transport aircraft. These alloys included the Al-Cu-Mg-Ag alloys C415 and C416 and the Al-Cu-Li-Mg-Ag alloys RX818 and ML377. The Al-Cu-Mg alloys CM001, which was used on the Concorde SST, and 1143, which was modified from the alloy used on the TU144 Russian supersonic aircraft, were tested for comparison. The alloys were subjected to thermal exposure at 200 F, 225 F and 275 F for times up to 30,000 hours. Tensile tests were performed on thermally-exposed and as-received material at -65 F, room temperature, 200 F, 225 F and 275 F. All four candidate alloys showed significant tensile property improvements over CM001 and 1143. Room temperature yield strengths of the candidate alloys were at least 20% greater than for CM001 and 1143, for both the as-received and thermally-exposed conditions. The strength levels of alloy RX818 were the highest of all materials investigated, and were 5-10% higher than for ML377, C415 and C416 for the as-received condition and after 5,000 hours thermal exposure. RX818 was removed from this study after 5,000 hours exposure due to poor fracture toughness performance observed in a parallel study. After 30,000 hours exposure at 200 F and 225 F, the alloys C415, C416 and ML377 showed minor decreases in yield strength, tensile strength and elongation when compared to the as-received properties. Reductions in tensile strength from the as-received values were up to 25% for alloys C415, C416 and ML377 after 15,000 hours exposure at 275 F.

  12. 46 CFR 54.25-15 - Low temperature operation-high alloy steels (modifies UHA-23(b) and UHA-51).

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Low temperature operation-high alloy steels (modifies... (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-15 Low temperature operation—high alloy steels (modifies UHA-23(b) and UHA-51). (a) Toughness...

  13. Peculiar high temperature corrosion of martensite alloy under impact of Estonian oil shale fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Tallermo, H.; Klevtsov, I. [Thermal Engineering Department of Tallinn Technical University, Tallinn (Estonia)

    1998-12-31

    The superheaters` surfaces of oil shale steam boiler made of pearlitic and austenitic alloys, are subject to intensive corrosion, mainly due to presence of chlorine in external deposits. The applicability of martensitic alloys X1OCrMoVNb91 and X20CrMoV121 for superheaters is examined here and empirical equations allowing to predict alloys` corrosion resistance in the range of operational temperatures are established. Alloy X1OCrMoVNb91 is found been most perspective for superheaters of boilers firing fossil fuel that contain alkaline metals and chlorine. The abnormal dependence of corrosion resistance of martensitic alloys on temperature is revealed, namely, corrosion at 580 deg C in presence of oil shale fly ash is more intensive than at 620 deg C. (orig.) 2 refs.

  14. Modified ferritic iron alloys with improved high-temperature mechanical properties and oxidation resistance

    Science.gov (United States)

    Oldrieve, R. E.

    1975-01-01

    An alloy modification program was conducted in which the compositions of two existing Fe-Cr-Al alloys (Armco 18SR and GE-1541) were changed to achieve either improved high-temperature strength or improved fabricability. Only modifications of Armco 18SR were successful in achieving increased strength without loss of fabricability or oxidation resistance. The best modified alloy, designated NASA-18T, had twice the rupture strength of Armco 18SR at 800 and 1000 C. The NASA-18T alloy also had better oxidation resistance than Armco 18SR and comparable fabricability. The nominal composition of NASA-18T is Fe-18Cr-2Al-1Si-1.25Ta. All attempted modifications of the GE-1541 alloy were unsuccessful in terms of achieving better fabricability without sacrificing high-temperature strength and oxidation resistance.

  15. Commercialization of NASA's High Strength Cast Aluminum Alloy for High Temperature Applications

    Science.gov (United States)

    Lee, Jonathan A.

    2003-01-01

    In this paper, the commercialization of a new high strength cast aluminum alloy, invented by NASA-Marshall Space Flight Center, for high temperature applications will be presented. Originally developed to meet U.S. automotive legislation requiring low- exhaust emission, the novel NASA aluminum alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (450 F-750 F), which can lead to reducing part weight and cost as well as improving performance for automotive engine applications. It is an ideal low cost material for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. NASA alloy also offers greater wear resistance, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys, and the new alloy can be produced economically from sand, permanent mold and investment casting. Since 2001, this technology was licensed to several companies for automotive and marine internal combustion engines applications.

  16. Thermal Stir Welding of High Strength and High Temperature Alloys for Aerospace Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Keystone and MSU team propose to demonstrate the feasibility of solid-state joining high strength and temperature alloys utilizing the Thermal Stir Welding...

  17. Iron-niobium-aluminum alloy having high-temperature corrosion resistance

    Science.gov (United States)

    Hsu, Huey S.

    1988-04-14

    An alloy for use in high temperature sulfur and oxygen containing environments, having aluminum for oxygen resistance, niobium for sulfur resistance and the balance iron, is discussed. 4 figs., 2 tabs.

  18. Effect of Rare Earth Metals on the Microstructure of Al-Si Based Alloys

    Directory of Open Access Journals (Sweden)

    Saleh A. Alkahtani

    2016-01-01

    Full Text Available The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting temperature with no marked change in the temperature of Al-Si eutectic precipitation. Additionally, rare earth metals have no modification effect up to 1.5 wt %. In addition, La and Ce tend to react with Sr leading to modification degradation. In order to achieve noticeable modification of eutectic Si particles, the concentration of rare earth metals should exceed 1.5 wt %, which simultaneously results in the precipitation of a fairly large volume fraction of insoluble intermetallics. The precipitation of these complex intermetallics is expected to have a negative effect on the alloy performance.

  19. Fatigue and Fracture Characterization of HPDC AM6OB Magnesium Alloy at Cold Temperature

    Science.gov (United States)

    Nur Hossain, Md.; Taheri, Farid

    2011-12-01

    An investigation of the fatigue and fracture characterization of the high pressure die cast (HPDC) AM60B magnesium alloy at -40 °C temperature was conducted by means of the constant load amplitude fatigue test. The results demonstrated that low temperature had a significant influence on alloy's fatigue life; the life increased at -40 °C temperature as compared to that at room temperature. The fracture surfaces of the tested specimens were observed under a scanning electron microscope (SEM) to further understand the fracture phenomenon at low temperature.

  20. Effect of mechanical alloying on FeCrC reinforced Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, S. Osman [Univ. of Namik Kemal, Tekirdag (Turkey); Teker, Tanju [Adiyaman Univ. (Turkey). Dept. of Metallurgical and Materials Engineering; Demir, Fatih [Batman Univ. (Turkey)

    2016-05-01

    Mechanical alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing and rewelding of powder particles in a high-energy ball mill. In the present study, the intermetallic matrix composites (IMCs) of Ni-Al reinforced by M{sub 7}C{sub 3} were produced by powder metallurgical routes via solid state reaction of Ni, Al and M{sub 7}C{sub 3} particulates by mechanical alloying processes. Ni, Al and M{sub 7}C{sub 3} powders having 100 μm were mixed, mechanical alloyed and the compacts were combusted in a furnace. The mechanically alloyed (MAed) powders were investigated by X-ray diffraction (XRD), microhardness measurement, optic microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The presence of the carbides depressed the formation of unwanted NiAl intermetallic phases. The mechanical alloyed M{sub 7}C{sub 3} particles were unstable and decomposed partially within the matrix during alloying and sintering, and the morphology of the composites changed with the dissolution ratio of M{sub 7}C{sub 3} and sintering temperature.

  1. Functional and structural fatigue of titanium tantalum high temperature shape memory alloys (HT SMAs)

    Energy Technology Data Exchange (ETDEWEB)

    Niendorf, T., E-mail: Thomas.Niendorf@iwt.tu-freiberg.de [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, 09599 Freiberg (Germany); Krooß, P. [Lehrstuhl für Werkstoffkunde (Materials Science), University of Paderborn, 33098 Paderborn (Germany); Batyrsina, E. [Institut für Werkstoffkunde (Materials Science), Leibniz Universität Hannover, 30823 Garbsen (Germany); Paulsen, A.; Motemani, Y.; Ludwig, A.; Buenconsejo, P.; Frenzel, J.; Eggeler, G. [Institut für Werkstoffe, Ruhr-Universität Bochum, 44801 Bochum (Germany); Maier, H.J. [Institut für Werkstoffkunde (Materials Science), Leibniz Universität Hannover, 30823 Garbsen (Germany)

    2015-01-03

    Due to their high work output and good mechanical properties, actuators made from shape memory alloys (SMAs) are used in numerous applications. Unfortunately, SMAs such as nickel–titanium (Ni–Ti) can only be employed at temperatures up to about 100 °C. Lately, high-temperature shape memory alloys (HT SMAs) have been introduced to overcome this limitation. Ternary systems based on Ni–Ti have been intensively characterized and alloys are available that can operate at elevated temperatures. However, these alloys either contain substantial amounts of expensive noble elements like platinum and palladium, or the materials are brittle. The titanium–tantalum (Ti–Ta) system has been developed to overcome these issues. Binary Ti–Ta provides relatively high M{sub S} temperature combined with excellent workability, but it suffers from fast cyclic degradation. By alloying with third elements this drawback can be overcome: The ternary Ti–Ta–Al alloy shows overall promising properties as will be shown in the present work. In-situ thermo-mechanical cycling experiments were conducted and allowed for evaluation of the factors affecting the functional and structural fatigue of this alloy. Functional fatigue is dominated by ω-phase evolution, while structural fatigue is triggered by an interplay of ω-phase induced embrittlement and deformation constraints imposed by unsuitable texture. In addition, a concept for fatigue life extension proposed very recently for binary Ti–Ta, is demonstrated to be also applicable for the ternary Ti–Ta–Al.

  2. Study on hydrogen absorption/desorption properties of uranium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Hiroshi; Yamaguchi, Kenji; Yamawaki, Michio [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.

    1996-10-01

    Hydrogen absorption/desorption properties of two U-Mn intermetallic compounds, U{sub 6}Mn and UMn{sub 2}, were investigated. U{sub 6}Mn absorbed hydrogen and the hydrogen desorption pressure of U{sub 6}Mn obtained from this experiment was higher than that of U, which was considered to be the effect of alloying, whereas UMn{sub 2} was not observed to absorb hydrogen up to 50 atm at room temperature. (author)

  3. Dynamic High-Temperature Characterization of an Iridium Alloy in Compression at High Strain Rates

    Energy Technology Data Exchange (ETDEWEB)

    Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Experimental Environment Simulation Dept.; Nelson, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials Dept.; Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Nuclear Fuel Cycle Technology Dept.; Bignell, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Structural and Thermal Analysis Dept.; Ulrich, G. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program; George, E. P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program

    2014-06-01

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 – 10000 s-1) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.

  4. Formation of amorphous alloys by mechanical alloying for platinum group metal-M(M=Zr or Al) system; Mechanical alloying ni yoru kikinzoku (Pd,Pt) to M(Zr aruiwa Al) tono kongo funmatsu no hishoshitsuka

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzuki, T.; Arakawa, T. [Kinki Univ., Higashi-Osaka, Osaka (Japan)

    1998-08-15

    The intermetallic compounds containing precious metals such as platinum white gold are widely used in chemistry or industry as catalysts. These alloy catalysts are mainly used in grinding the materials prepared by solidifying liquids. The authors of the paper attempt to prepare alloy powders of precious metal with Zr or Al by mechanical alloying (MA). As an object of applying them on a catalyst, alloy powders of precious metals (Pd and Pt) and M (Zr or Al) are regulated by the mechanical alloying reaction, and the results show that the Pd and Pt show different MA reaction while using Al as the M, the former generates an intermetallic compound as PdAl during the halfway point of the MA reaction, but the later generates amorphous powders. But, each of them generates amorphous alloys only while using Zr and the M. As a result of differential thermal analysis and electrical resistivity measurement investigating the crystalline process of the obtained amorphous alloys, it is clarified that the Pt-Al base alloy shows higher crystalline temperature compared with the other alloys. 8 refs., 6 figs.

  5. Application of Combined Sustained and Cyclic Loading Test Results to Alloy 617 Elevated Temperature Design Criteria

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yanli [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jetter, Robert I [Global Egineering and Technology, LLC, Coral Gables, FL (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-08-25

    Alloy 617 is a reference structural material for very high temperature components of advanced-gas cooled reactors with outlet temperatures in the range of 900-950°C . In order for designers to be able to use Alloy 617 for these high temperature components, Alloy 617 has to be approved for use in Section III (the nuclear section) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. A plan has been developed to submit a draft code for Alloy 617 to ASME Section III by 2015. However, the current rules in Subsection NH for the evaluation of strain limits and creep-fatigue damage using simplified methods based on elastic analysis have been deemed inappropriate for Alloy 617 at temperatures above 1200°F (650°C). The rationale for this exclusion is that at higher temperatures it is not feasible to decouple plasticity and creep deformation, which is the basis for the current simplified rules. This temperature, 1200 °F, is well below the temperature range of interest for this material in High Temperature Gas Cooled Reactor (HTGR) applications. The only current alternative is, thus, a full inelastic analysis which requires sophisticated material models which have been formulated but not yet verified. To address this issue, proposed code rules have been developed which are based on the use of elastic-perfectly plastic (EPP) analysis methods and which are expected to be applicable to very high temperatures.

  6. Materials corrosion of high temperature alloys immersed in 600C binary nitrate salt.

    Energy Technology Data Exchange (ETDEWEB)

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-03-01

    Thirteen high temperature alloys were immersion tested in a 60/40 binary nitrate salt. Samples were interval tested up to 3000 hours at 600ÀC with air as the ullage gas. Chemical analysis of the molten salt indicated lower nitrite concentrations present in the salt, as predicted by the equilibrium equation. Corrosion rates were generally low for all alloys. Corrosion products were identified using x-ray diffraction and electron microprobe analysis. Fe-Cr based alloys tended to form mixtures of sodium and iron oxides, while Fe-Ni/Cr alloys had similar corrosion products plus oxides of nickel and chromium. Nickel based alloys primarily formed NiO, with chromium oxides near the oxide/base alloy interface. In625 exhibited similar corrosion performance in relation to previous tests, lending confidence in comparisons between past and present experiments. HA230 exhibited internal oxidation that consisted of a nickel/chromium oxide. Alloys with significant aluminum alloying tended to exhibit superior performance, due formation of a thin alumina layer. Soluble corrosion products of chromium, molybdenum, and tungsten were also formed and are thought to be a significant factor in alloy performance.

  7. Corrosion of high temperature alloys in solar salt at 400, 500, and 680ÀC.

    Energy Technology Data Exchange (ETDEWEB)

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-09-01

    Corrosion tests at 400, 500, and 680ÀC were performed using four high temperature alloys; 347SS, 321SS In625, and HA230. Molten salt chemistry was monitored over time through analysis of nitrite, carbonate, and dissolved metals. Metallography was performed on alloys at 500 and 680ÀC, due to the relatively thin oxide scale observed at 400ÀC. At 500ÀC, corrosion of iron based alloys took the form of chromium depletion and iron oxides, while nickel based alloys also had chromium depletion and formation of NiO. Chromium was detected in relatively low concentrations at this temperature. At 680ÀC, significant surface corrosion occurred with metal losses greater than 450microns/year after 1025hours of exposure. Iron based alloys formed complex iron, sodium, and chromium oxides. Some data suggests grain boundary chromium depletion of 321SS. Nickel alloys formed NiO and metallic nickel corrosion morphologies, with HA230 displaying significant internal oxidation in the form of chromia. Nickel alloys both exhibited worse corrosion than iron based alloys likely due to preferential dissolution of chromium, molybdenum, and tungsten.

  8. Effect of pouring temperature on the properties of Al-8%Si alloy sand ...

    African Journals Online (AJOL)

    It was found that the density and mechanical properties of the sand castings decrease with increase in pouring temperature, particularly at 800-850°C, although the fluidity of the molten alloy increases with increase with temperature. The study, therefore, recommended pouring temperatures of 650-700°C in order to obtain ...

  9. Investigation of Martensite Formation in Fe Based Alloys During Heating From Boiling Nitrogen Temperature

    DEFF Research Database (Denmark)

    Villa, Matteo; Christiansen, Thomas L.; Hansen, Mikkel F.

    2015-01-01

    he austenite-to-martensite transformation at temperatures below room temperature was investigated in situ by magnetometry in Fe-N, Fe-Cr-C and Fe-Cr-Ni based alloys. After quenching to room temperature, samples were immersed in boiling nitrogen and martensite formation was followed during...

  10. Surfaces of complex intermetallic compounds: insights from density functional calculations.

    Science.gov (United States)

    Hafner, Jürgen; Krajčí, Marian

    2014-11-18

    CONSPECTUS: Complex intermetallic compounds are a class of ordered alloys consisting of quasicrystals and other ordered compounds with large unit cells; many of them are approximant phases to quasicrystals. Quasicrystals are the limiting case where the unit cell becomes infinitely large; approximants are series of periodic structures converging to the quasicrystal. While the unique properties of quasicrystals have inspired many investigations of their surfaces, relatively little attention has been devoted to the surface properties of the approximants. In general, complex intermetallic compounds display rather irregular, often strongly corrugated surfaces, making the determination of their atomic structure a very complex and challenging task. During recent years, scanning tunneling microscopy (STM) has been used to study the surfaces of several complex intermetallic compounds. If atomic resolution can be achieved, STM permits visualization of the local atomistic surface structure. However, the interpretation of the STM images is often ambiguous and sometimes even impossible without a realistic model of the structure of the surface and the distribution of the electronic density above the surface. Here we demonstrate that ab initio density functional theory (DFT) can be used to determine the energetics and the geometric and electronic structures of the stable surfaces of complex intermetallic compounds. Calculations for surfaces with different chemical compositions can be performed in the grand canonical ensemble. Simulated cleavage experiments permit us to determine the formation of the cleavage planes requiring the lowest energy. The investigation of the adsorption of molecular species permits a comparison with temperature-programmed thermal desorption experiments. Calculated surface electronic densities of state can be compared with the results of photoelectron spectroscopy. Simulations of detailed STM images can be directly confronted with the experimental results

  11. High-temperature corrosion and applications of nickel and iron aluminides in coal-conversion power systems

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K. [Argonne National Lab., IL (United States); Tortorelli, P.F. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Nickel and iron aluminide intermetallics are being developed for use as structural materials and/or as cladding for conventional engineering alloys. In addition to strength advantages, these materials exhibit excellent resistance to corrosion in single- and multioxidant environments at elevated temperatures by the formation of slow-growing, adherent alumina scales. Corrosion resistance in a given environment is strongly dependent on the composition of the alloy and on the nature of the corrosive species prevalent in the service environment. This paper presents a comprehensive review of the current status of the corrosion performance of these intermetallics in oxidizing, sulfidizing, and multicomponent gas environments of typical coal-conversion systems. Mechanisms of scale development/breakdown, performance envelopes for long-term usage of these materials, approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics, and in-service experience with these materials are emphasized.

  12. Thermocouples of tantalum and rhenium alloys for more stable vacuum-high temperature performance

    Science.gov (United States)

    Morris, J. F. (Inventor)

    1977-01-01

    Thermocouples of the present invention provide stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor wherein each metal of the sensor is selected from a group of metals comprising tantalum and rhenium and alloys containing only those two metals. The tantalum, rhenium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibilities and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys of the present invention result in improved emf, temperature properties and thermocouple hot junction performance. The thermocouples formed of the tantalum, rhenium alloys exhibit reliability and performance stability in systems involving high temperatures and vacuums and are adaptable to space propulsion and power systems and nuclear environments.

  13. Intermetallic: A Pseudoelement for Catalysis.

    Science.gov (United States)

    Tsai, A P; Kameoka, S; Nozawa, K; Shimoda, M; Ishii, Y

    2017-12-19

    A clear correlation between electronic structure and CO2 selectivity for steam reforming of methanol (SRM) was obtained with PdZn, PtZn, NiZn, and PdCd intermetallics on the basis of experiments and calculations. In order to rule out the effects of oxide supports, the intermetallic powders were simply prepared by alloying in an arc furnace followed by crushing in a mortar. PdZn and PdCd exhibit valence electronic densities of states similar to that of Cu and significant chemical shifts (larger than 1 eV) of Pd 3d states with respect to pure Pd, as verified by high-resolution hard X-ray photoelectron spectroscopy (HXPS) measurements and density functional theory (DFT) calculations. Consequently, they show the similar high selectivity of CO2 for the SRM reaction. However, this is not the case for PtZn and NiZn because of the slight differences in their valence electronic structures from that of PdZn. The interval between the Fermi level and the top of the d band is closely related to the selectivity of CO2 for the SRM: the larger the interval is, the higher is the selectivity of CO2. According to DFT calculations for bulk PdZn performed by Chen et al. ( Phys. Rev. B 2003 , 68 , 075417 ), the (111) and (100) surfaces exposing Zn and Pd in an equimolar ratio are more stable than the (001) or (110) surfaces terminated by alternative Zn or Pd layers. First-principles slab calculations for PdZn, PtZn, and NiZn show that bond breaking on the surface leads to a reduction in the d bandwidth but that the d band for stable (111) or (100) surfaces remains essentially unchanged from that of the bulk. It is intriguing that PdZn and PdCd do not contain Cu but show similar valence electronic structure and catalytic selectivity, and hence, a concept is proposed where PdZn and PdCd are regarded as pseudoelements of Cu. The basis of this concept is like electronic structure, like catalysis, which has been demonstrated by experiments and calculations. This is a logical way to enable us

  14. Critical Assessment 14: High Entropy Alloys and Their Development as Structural Materials (Postprint)

    Science.gov (United States)

    2015-01-01

    competing intermetallic compounds.1–3 The rationale often given to support this strategy is that intermetallic phases can embrittle structural alloys...better than one It is often stated that the motivation for HEAs is to avoid intermetallic phases , which might embrittle structural alloys.1–3...that rely on significant volume fractions of intermetallic or ceramic phases . Pearlite is a common microstructural element in steels, where the soft

  15. Mechanical Properties of Discontinuous Precipitated Al-Zn Alloys after Drawing at Room and Cryogenic Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Soo; Lee, Jehyun [Changwon National University, Changwon (Korea, Republic of); Han, Seung Zeon; Ahn, Jee Hyuk [Korea Institute of Materials Science, Changwon (Korea, Republic of); Lim, Sung Hwan [Kangwon National University, Chuncheon (Korea, Republic of); Kim, Kwang Ho [Pusan National University, Pusan (Korea, Republic of); Kim, Sang sik [Gyeongsang National University, Jinju (Korea, Republic of)

    2017-02-15

    In order to study the effect of microstructural change on the tensile properties of discontinuous precipitated Al-Zn binary alloy, four different Al-Zn alloys(25, 30, 35, 45 wt%Zn) were aged at 160 ℃ for different aging times(0, 5, 15, 30, 60, 120, 360 min) after being solution treated at 400 ℃, and successively drawn at room and cryogenic temperatures(-197 ℃). Discontinuous precipitation was formed during aging in the Al matrix(which contained more than 30 wt%Zn) in Al alloys containing more than 30 wt%Zn. The tensile strength of continuous precipitated Al-35Zn alloy decreased with increasing drawing ratio, however, the tensile strength of discontinuous precipitated Al-35Zn alloy increased with further drawing. The strength and ductility combination, 350 MPa-36%was achieved by drawning discontinuous precipitated Al-Zn alloy at room temperature. The discontinuous precipitated Al-Zn alloy drawn at cryogenic temperature showed a higher value of tensile strength, over 500 MPa, although ductility decreased.

  16. Wireless and passive temperature indicator utilizing the large hysteresis of magnetic shape memory alloys

    Science.gov (United States)

    Bergmair, Bernhard; Liu, Jian; Huber, Thomas; Gutfleisch, Oliver; Suess, Dieter

    2012-07-01

    An ultra-low cost, wireless magnetoelastic temperature indicator is presented. It comprises a magnetostrictive amorphous ribbon, a Ni-Mn-Sn-Co magnetic shape memory alloy with a highly tunable transformation temperature, and a bias magnet. It allows to remotely detect irreversible changes due to transgressions of upper or lower temperature thresholds. Therefore, the proposed temperature indicator is particularly suitable for monitoring the temperature-controlled supply chain of, e.g., deep frozen and chilled food or pharmaceuticals.

  17. Basic research for alloy design of Nb-base alloys as ultra high temperature structural materials; Chokoon kozoyo niobuki gokin no gokin sekkei no tame no kisoteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Miura, E. [Tohoku University, Sendai (Japan); Yoshimi, K.; Hanada, S. [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals

    1997-02-01

    This paper describes an influence of additional elements on the high temperature deformation behavior of Nb-base solid solution alloys. Highly concentrated solid solution single crystals of Nb-Ta and Nb-Mo alloys were prepared. Compression test and strain rate sudden change test were conducted in the vacuum at temperatures ranging from 77 to 1773 K, to determine the strain rate sensitivity index. Yield stress of the Nb-Ta alloy was similar to that of Nb alloy at temperatures over 0.3{times}T{sub M}, where T{sub M} is fusing point of Nb. While, the yield stress increased with increasing the impurity oxygen concentration at temperatures below 0.3{times}T{sub M}. The yield stress became much higher than that of Nb alloy. The strain rate sensitivity index showed positive values in the whole temperature range. On the other hand, the yield stress of Nb-Mo alloy was higher than that of Nb alloy in the whole temperature range, and increased with increasing the Mo concentration. The strain rate sensitivity index showed negative values at the temperature range from 0.3{times}T{sub M} to 0.4{times}T{sub M}. It was found that serration occurred often for Nb-40Mo alloys. 1 ref., 4 figs., 1 tab.

  18. Joining of Aluminium Alloy and Steel by Laser Assisted Reactive Wetting

    Science.gov (United States)

    Liedl, Gerhard; Vázquez, Rodrigo Gómez; Murzin, Serguei P.

    2017-12-01

    Compounds of dissimilar materials, like aluminium and steel offer an interesting opportunity for the automotive industry to reduce the weight of a car body. Thermal joining of aluminium and steel leads to the formation of brittle intermetallic compounds, which negatively affects the properties of the welded joint. Amongst others, growth of such intermetallic compounds depends on maximum temperature and on the time at certain temperatures. Laser welding with its narrow well seam and its fast heating and cooling cycles provides an excellent opportunity to obtain an ultrathin diffusion zone. Joining of sheet metal DC01 with aluminium alloy AW6016 has been chosen for research. The performed experimental studies showed that by a variation of the beam power and scanning speed it is possible to obtain an ultrathin diffusion zone with narrow intermetallic interlayers. With the aim of supporting further investigation of laser welding of the respective and other dissimilar pairings a multi-physical simulation model has been developed.

  19. Intermetallic semiconducting films

    CERN Document Server

    Wieder, H H

    1970-01-01

    Intermetallic Semiconducting Films introduces the physics and technology of AшВv compound films. This material is a type of a polycrystalline semiconductor that is used for galvanomagnetic device applications. Such material has a high electron mobility that is ideal for generators and magnetoresistors. The book discusses the available references on the preparation and identification of the material. An assessment of its device applications and other possible use is also enumerated. The book describes the structures and physical parts of different films. A section of the book covers the three t

  20. Considerations of Alloy N for Fluoride Salt-Cooled High-Temperature Reactor Applications

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju [ORNL; Muralidharan, Govindarajan [ORNL; Wilson, Dane F [ORNL; Holcomb, David Eugene [ORNL

    2011-01-01

    Fluoride Salt-Cooled High-Temperature Reactors (FHRs) are a promising new class of thermal-spectrum nuclear reactors. The reactor structural materials must possess high-temperature strength and chemical compatibility with the liquid fluoride salt as well as with a power cycle fluid such as supercritical water while remaining resistant to residual air within the containment. Alloy N was developed for use with liquid fluoride salts and it possesses adequate strength and chemical compatibility up to about 700 C. A distinctive property of FHRs is that their maximum allowable coolant temperature is restricted by their structural alloy maximum service temperature. As the reactor thermal efficiency directly increases with the maximum coolant temperature, higher temperature resistant alloys are strongly desired. This paper reviews the current status of Alloy N and its relevance to FHRs including its design principles, development history, high temperature strength, environmental resistance, metallurgical stability, component manufacturability, ASME codification status, and reactor service requirements. The review will identify issues and provide guidance for improving the alloy properties or implementing engineering solutions.

  1. Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; DeVan, J.H.

    1994-09-01

    Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb were examined on the basis of isothermal exposures to air at 950 C. Additions of either Re and Al or Fe, Ni, and Al had relatively little effect on weight gains relative to the Cr-6% Nb binary alloy. One alloying element that improved the mechanical behavior of Cr-Cr{sub 2}Nb alloys substantially increased the oxidation rates and spallation susceptibilities of Cr-6 and -12% Nb alloys. However, the addition of another element completely offset these deleterious effects. The presence of this latter element resulted in the best overall oxidation behavior (in terms of both weight gains and spallation tendencies) of all Cr-Cr{sub 2}Nb compositions. Its beneficial effect can be attributed to improvement in the oxidation resistance of the Cr-rich phase.

  2. Toughness testing and high-temperature oxidation evaluations of advanced alloys for core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [ORNL; Pint, Bruce A [ORNL; Chen, Xiang [ORNL

    2016-09-16

    Alloy X-750 was procured from Carpenter Technology and Bodycote in this year. An appropriate TMT was developed on Alloy 439 to obtain materials with refined grain size for property screening tests. Charpy V-notch impact tests were completed for the three ferritic steels Grade 92, Alloy 439, and 14YWT. Fracture toughness tests at elevated temperatures were completed for 14YWT. The tests will be completed for the other alloys in next fiscal year. Steam oxidation tests of the three ferritic steels, 316L, and Zr–2.5Nb have been completed. The steam tests of the Ni-based superalloys and the other austenitic stainless steels will be continued and finished in next fiscal year. Performance ranking in terms of steam oxidation resistance and impact/fracture toughness of the alloys will be deduced.

  3. Strengthening mechanisms of indirect-extruded Mg–Sn based alloys at room temperature

    Directory of Open Access Journals (Sweden)

    Wei Li Cheng

    2014-12-01

    Full Text Available The strength of a material is dependent on how dislocations in its crystal lattice can be easily propagated. These dislocations create stress fields within the material depending on their intrinsic character. Generally, the following strengthening mechanisms are relevant in wrought magnesium materials tested at room temperature: fine-grain strengthening, precipitate strengthening and solid solution strengthening as well as texture strengthening. The indirect-extruded Mg–8Sn (T8 and Mg–8Sn–1Al–1Zn (TAZ811 alloys present superior tensile properties compared to the commercial AZ31 alloy extruded in the same condition. The contributions to the strengthen of Mg–Sn based alloys made by four strengthening mechanisms were calculated quantitatively based on the microstructure characteristics, physical characteristics, thermomechanical analysis and interactions of alloying elements using AZ31 alloy as benchmark.

  4. Heat treatment influence on the structural and magnetic properties of the intermetallic Fe56.25Al43.75 alloy prepared by mechanical alloying and arc-melted

    Science.gov (United States)

    Trujillo Hernández, J. S.; Tabares, J. A.; Pérez Alcázar, G. A.

    2014-04-01

    Alloys of the Fe56.25Al43.75 system were prepared by mechanical alloying (MA) using a high energy planetary ball mill, with milling times in the range from 12 up to 96 h named MA0 samples. The sample milled for 48 hours was heat treated at 700 °C for 9 days. Then this sample was milled for times of 1, 4, 8, 12, 24, and 48 h, named MA1 samples. Additionally, and for comparison, it was prepared a Fe56.25Al43.75 sample by arc-melting method. For all samples, the structural and magnetic study was conducted by X-rays diffraction (XRD) and Mössbauer spectrometry (MS). The XRD results show that the system is nanostructured and the MA0 samples present only the BCC disordered phase, whose lattice parameter remains relatively constant with milling time. For MA1 samples it was identify the FeAl, Fe3Al, FeO and α-Fe phases. The Mössbauer spectra for all samples were fitted by using a hyperfine magnetic field distribution (HMFD), and a paramagnetic site for all the times used here. The ferromagnetism increases when milling time increases, and this is a consequence of the structural disorder induced by mechanical alloying.

  5. Effects of heat treatment on mechanical and tribological properties of cobalt-base tribaloy alloys

    Science.gov (United States)

    Liu, Rong; Yao, Matthew X.; Patnaik, Prakash C.; Wu, Xijia

    2005-10-01

    Cobalt-base Tribaloy alloys are important wear-resistant materials, especially for high-temperature applications, because of the outstanding properties of the strengthened cobalt solid solution and the hard Laves intermetallic phase that make up the alloys. The Laves intermetallic phase is so abundant (35-70 vol.%) in these alloys that its presence governs all of the material properties. Heat treatment may alter the volume fraction, the size/shape, and the distribution of the Laves phase in the microstructures as well as the phase and structure of the cobalt solid solution, thus influencing the mechanical and tribological properties of the alloys. In this work, the effects of heat treatment on two cobalt-based Tribaloy alloys, T-400 and T-200, were studied. The former is a well-known Tribaloy alloy, and the latter is a newly developed one. These two alloys were heat treated in different conditions. The phases and microstructures of the alloys before and after the heat treatments were analyzed using x-ray and scanning electron microscopy. The mechanical and tribological properties of the alloys were investigated using a nano-indentation technique and a pin-on-disc tribometer, respectively.

  6. Long-Term Cyclic Oxidation Behavior of Wrought Commercial Alloys at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bingtao [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    The oxidation resistance of a high-temperature alloy is dependent upon sustaining the formation of a protective scale, which is strongly related to the alloying composition and the oxidation condition. The protective oxide scale only provides a finite period of oxidation resistance owing to its eventual breakdown, which is especially accelerated under thermal cycling conditions. This current study focuses on the long-term cyclic oxidation behavior of a number of commercial wrought alloys. The alloys studied were Fe- and Ni-based, containing different levels of minor elements, such as Si, Al, Mn, and Ti. Oxidation testing was conducted at 1000 and 1100 C in still air under both isothermal and thermal cycling conditions (1-day and 7-days). The specific aspects studied were the oxidation behavior of chromia-forming alloys that are used extensively in industry. The current study analyzed the effects of alloying elements, especially the effect of minor element Si, on cyclic oxidation resistance. The behavior of oxide scale growth, scale spallation, subsurface changes, and chromium interdiffusion in the alloy were analyzed in detail. A novel model was developed in the current study to predict the life-time during cyclic oxidation by simulating oxidation kinetics and chromium interdiffusion in the subsurface of chromia-forming alloys.

  7. Synthesis, Characterization and Properties of Nanoparticles of Intermetallic Compounds

    Energy Technology Data Exchange (ETDEWEB)

    DiSalvo, Francis J. [Cornell Univ., Ithaca, NY (United States)

    2015-03-12

    The research program from 2010 to the end of the grant focused on understanding the factors important to the synthesis of single phase intermetallic nano-particles (NPs), their size, crystalline order, surface properties and electrochemical activity. The synthetic method developed is a co-reduction of mixtures of single metal precursors by strong, soluble reducing agents in a non-protic solvent, tetrahydrofuran (THF). With some exceptions, the particles obtained by room temperature reduction are random alloys that need to be annealed at modest temperatures (200 to 600 °C) in order to develop an ordered structure. To avoid significant particle size growth and agglomeration, the particles must be protected by surface coatings. We developed a novel method of coating the metal nanoparticles with KCl, a by-product of the reduction reaction if the proper reducing agents are employed. In that case, a composite product containing individual metal nanoparticles in a KCl matrix is obtained. The composite can be heated to at least 600 °C without significant agglomeration or growth in particle size. Washing the annealed product in the presence of catalyst supports in ethylene glycol removes the KCl and deposits the particles on the support. Six publications present the method and its application to producing and studying new catalyst/support combinations for fuel cell applications. Three publications concern the use of related methods to explore new lithium-sulfur battery concepts.

  8. Evaluation of Aluminum Alloy 2050-T84 Microstructure and Mechanical Properties at Ambient and Cryogenic Temperatures

    Science.gov (United States)

    Hafley, Robert A.; Domack, Marcia S.; Hales, Stephen J.; Shenoy, Ravi N.

    2011-01-01

    Aluminum alloy 2050 is being considered for the fabrication of cryogenic propellant tanks to reduce the mass of future heavy-lift launch vehicles. The alloy is available in section thicknesses greater than that of the incumbent aluminum alloy, 2195, which will enable designs with greater structural efficiency. While ambient temperature design allowable properties are available for alloy 2050, cryogenic properties are not available. To determine its suitability for use in cryogenic propellant tanks, tensile, compression and fracture tests were conducted on 4 inch thick 2050-T84 plate at ambient temperature and at -320degF. Various metallurgical analyses were also performed in order to provide an understanding of the compositional homogeneity and microstructure of 2050.

  9. Size, shape and temperature dependent surface energy of binary alloy nanoparticles

    Science.gov (United States)

    Jabbareh, Mohammad Amin

    2017-12-01

    Surface energy has an important role in determining the properties of nanoparticles. Even though, extensive research has been done on the surface energy of pure nanoparticles, the surface energy of alloy nanoparticles has not been considered enough. In this work, based on the liquid drop model for surface energy of pure nanoparticles and Butler's equation, a model for size dependent surface energy of alloy nanoparticles has been developed. In addition to size and concentration, the model can describe the effects of shape and temperature on surface energy of alloy nanoparticles. Cu - Ag and Cu - Au systems have been studied as two examples and the results have been compared with other theoretical models and available simulated data. Reasonable agreements between the results were observed. The results show that the decreasing particle size decreases surface energy of alloy nanoparticles but decreasing temperature and shape factor increases the value of surface energy.

  10. Transition in Deformation Mechanism of AZ31 Magnesium Alloy during High-Temperature Tensile Deformation

    Directory of Open Access Journals (Sweden)

    Masafumi Noda

    2011-01-01

    Full Text Available Magnesium alloys can be used for reducing the weight of various structural products, because of their high specific strength. They have attracted considerable attention as materials with a reduced environmental load, since they help to save both resources and energy. In order to use Mg alloys for manufacturing vehicles, it is important to investigate the deformation mechanism and transition point for optimizing the material and vehicle design. In this study, we investigated the transition of the deformation mechanism during the high-temperature uniaxial tensile deformation of the AZ31 Mg alloy. At a test temperature of 523 K and an initial strain rate of 3×10−3 s-1, the AZ31 Mg alloy (mean grain size: ~5 μm exhibited stable deformation behavior and the deformation mechanism changed to one dominated by grain boundary sliding.

  11. Structural transformations and temperature state of rotating blades of E1893 alloy under operation

    Energy Technology Data Exchange (ETDEWEB)

    Pigrova, G.D.; Rybnikov, A.I.; Kryukov, I.I. [Polzunov Central Boiler and Turbine Institute, St. Petersburg (Russian Federation)

    1998-12-31

    The composition and quantity of different phase component of EI893 alloy after long term operation as base metal for rotating blades of gas turbines GT-6, GTN-9, GTK-10 and GT-100 types were studied. The obtained date were analysed with regard to the chemical composition of alloys and of initial condition of heat treatment. Data of metal phase analysis owned alter operation can provide the basis for evaluation of tempera field of rotating blades in the course of operation since structural condition of phase components and redistribution of alloying elements are being specified by temperature and in-service time. (orig.)

  12. Mechanisms Governing the Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Vijay [Univ. of Cincinnati, OH (United States); Carroll, Laura [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-04-06

    This research project, which includes collaborators from INL and ORNL, focuses on the study of alloy 617 and alloy 800H that are candidates for applications as intermediate heat exchangers in GEN IV nuclear reactors, with an emphasis on the effects of grain size, grain boundaries and second phases on the creep properties; the mechanisms of dislocation creep, diffusional creep and cavitation; the onset of tertiary creep; and theoretical modeling for long-term predictions of materials behavior and for high temperature alloy design.

  13. Influence of Ultrasonic Melt Treatment and Cooling Rates on the Microstructural Development and Elevated Temperature Mechanical Properties of a Hypereutectic Al-18Si-4Cu-3Ni Piston Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jea-Hee; Cho, Young-Hee; Jung, Jae-Gil; Lee, Jung-Moo [Korea Institute of Materials Science (KIMS), Changwon (Korea, Republic of); Park, Ik Min [Pusan National University, Busan (Korea, Republic of)

    2017-06-15

    The influence of ultrasonic melt treatment (UST) combined with a change in cooling rates on the microstructure and elevated temperature mechanical properties of a hypereutectic Al-18Si-4Cu-3Ni piston alloy was investigated. Microstructural observation confirmed that UST effectively refined the sizes of primary Si and intermetallic compounds (e.g. ε-Al{sub 3}Ni) while promoting their homogeneous distribution. Besides the refinement of the constituent phases, the size of the dendrite arm spacing (DAS), which was hardly affected by UST, significantly deceased with increasing cooling rates. The refinement of the solidification structure in the alloy achieved through both UST and increased cooling rates resulted in an improvement in tensile properties, ultimate tensile strength and elongation in particular, after T5 heat treatment followed by overaging at 350 ℃. However, the elevated temperature yield strength of the alloy was not associated with the refinement, but was rather correlated with the 3-D interconnectivity, morphology and volume fraction of the primary Si.

  14. The Application of CPA to Calculations of the Mean Magnetic Moment in the Gd1-xNi, Gd1-xFe, Gd1xCox, and Y1-xCox Intermetallic Compounds

    DEFF Research Database (Denmark)

    Szpunar, B.; Kozarzewski, B.

    1977-01-01

    with a narrow d-band is considered. The magnetic moment of the alloy at zero temperature is calculated within the molecular field and Hartree-Fock approximations. Disorder is treated in the coherent potential approximation. Results are in good agreement with the experimental data obtained for the crystalline......Calculations are made of the mean magnetic moment per atom of the transition metal and the rare-earth metal in the intermetallic compounds, Gd1-x,Nix, Gd1-x Fex, Gd1-x Cox, and Y1-x Cox. A simple model of the disordered alloy consisting of spins localized on the rare-earth atoms and interacting...

  15. Fracture toughness of TiAl-Cr-Nb-Mo alloys produced via centrifugal casting

    Directory of Open Access Journals (Sweden)

    A. Brotzu

    2012-10-01

    Full Text Available Fracture toughness of a TiAl base intermetallic alloy has been investigated at room temperature. The Ti-48Al-2.5Cr-0.5Nb-2Mo (at. % alloy produced via centrifugal casting exhibits fine nearly lamellar microstructures, consisting mainly of fine lamellar grains, together with a very small quantity of residual β phases along lamellar colony boundaries. In order to determine the alloy fracture toughness compact tension specimens were tested and the results were compared with those available in literature.

  16. Corrosion behavior of Fe3Al intermetallics with addition of lithium, cerium and nickel in 2.5 % SO2+N2 at 900 °C

    Directory of Open Access Journals (Sweden)

    González-Rodríguez, J. G.

    2012-12-01

    Full Text Available The corrosion behavior of Fe3Al-type intermetallic alloys with addition of 1 at. % cerium, lithium and nickel at high temperature has been studied. The various alloys were exposed to an environment composed of 2.5 % SO2+N2 at 900 °C for 48 h. For all the intermetallic tested, the corrosion kinetics showed a parabolic behavior. The alloy, which showed less corrosion rate, was the Fe3AlNi alloy, being Fe3AlCeLi the alloy with the highest corrosion rate. For the various alloys, energy dispersive X-ray spectroscopy analysis, EDS, on the developed scale only detected aluminum, oxygen, and traces of iron and cerium, suggesting the formation of alumina as main component. The intermetallic alloys showed oxide cracking and spalling. The intermetallic chemical composition played an important role in defining the oxide scale morphology and the extent of damage.Se estudió el comportamiento a la corrosión a alta temperatura de intermetálicos tipo Fe3Al con adición de 1at. % de cerio, litio y níquel. Las diferentes aleaciones fueron expuestas bajo un ambiente compuesto de 2,5 % SO2+N2 a 900 °C durante 48 h. Para todos los intermetálicos ensayados, la cinética de corrosión presentó un comportamiento parabólico. La aleación que mostró la menor velocidad de corrosión fue el intermetálico Fe3AlNi, siendo el intermetálico Fe3AlCeLi el de mayor velocidad de corrosión. Los análisis mediante espectroscopía de dispersión de rayos X, EDS, sobre la costra formada identificaron únicamente aluminio, oxígeno y trazas de hierro y cerio, lo que sugiere la formación de alúmina como el componente principal. Los intermetálicos mostraron agrietamiento y desprendimiento de la costra de óxido. La composición química de los intermetálicos tuvo un papel importante en la definición de la morfología del óxido formado y el grado de daño.

  17. Dynamic mechanical response and a constitutive model of Fe-based high temperature alloy at high temperatures and strain rates.

    Science.gov (United States)

    Su, Xiang; Wang, Gang; Li, Jianfeng; Rong, Yiming

    2016-01-01

    The effects of strain rate and temperature on the dynamic behavior of Fe-based high temperature alloy was studied. The strain rates were 0.001-12,000 s(-1), at temperatures ranging from room temperature to 800 °C. A phenomenological constitutive model (Power-Law constitutive model) was proposed considering adiabatic temperature rise and accurate material thermal physical properties. During which, the effects of the specific heat capacity on the adiabatic temperature rise was studied. The constitutive model was verified to be accurate by comparison between predicted and experimental results.

  18. Pressure-concentration-temperature characterization of St909 getter alloy with hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Ghezzi, F. [Consiglio Nazionale delle Ricerche, Milan (Italy). Lab. di Fisica del Plasma; Boffito, C. [SAES Getters S.p.A., Milan (Italy)

    1996-06-01

    One of the major issues related to the next generation of fusion reactors is tritium recovery and recycling from tritiated water. Among the various approaches proposed, chemical dissociation of tritiated water over active beds based on reactive alloys appears to be a promising solution. It enables, in fact, safe recovery of tritium by exploiting the relatively high equilibrium pressures, even at low concentrations and operating temperature, of selected alloys. This paper presents the results of pressure-temperature-composition measurements carried out on a Zr-Mn-Fe alloy, named St909, candidate for such an application. Equilibrium isotherms have been determined between room temperature and 400{sup o}C for low hydrogen concentrations, and at room temperature for higher concentrations, exploring the bi-phasic region. Sieverts` law appears to be obeyed in the low concentration range, at H/A ratios of less than 0.03. (Author).

  19. Analysis of Structure and Abrasion Resistance of the Metal Composite Based on an Intermetallic FeAl Phase with VC and TiC Precipitates

    Directory of Open Access Journals (Sweden)

    Kopyciński D.

    2013-09-01

    Full Text Available Metal alloys with matrix based on an Fe-Al system are generally considered materials for high-temperature applications. Their main advantages are compact crystallographic structure, long-range ordering and structural stability at high temperatures. These materials are based on an intermetallic phase of FeAl or Fe3Al, which is stable in the range from room temperature up to the melting point of 1240°C. Their application at high temperatures is also beneficial because of the low cost of production, very good resistance to oxidation and corrosion, and high mechanical strength. The casting alloy the structure of which includes the FeAl phase is, among others, highaluminium cast iron. This study has been devoted to the determination of the effect of vanadium and titanium on the transformation of the high-aluminium cast iron structure into an in-situ FeAl-VC composite.

  20. Thermogravimetric study of oxidation of a PdCr alloy used for high-temperature sensors

    Science.gov (United States)

    Boyd, Darwin L.; Zeller, Mary V.

    1994-01-01

    In this study, the oxidation of Pd-13 weight percent Cr, a candidate alloy for high-temperature strain gages, was investigated by thermogravimetry. Although the bulk alloy exhibits linear electrical resistivity versus temperature and stable resistivity at elevated temperatures, problems attributed to oxidation occur when this material is fabricated into strain gages. In this work, isothermal thermogravimetry (TG) was used to study the oxidation kinetics. Results indicate that the oxidation of Pd-13 weight percent Cr was approximately parabolic in time at 600 C but exhibited greater passivation from 700 to 900 C. At 1100 C, the oxidation rate again increased.

  1. Toughening and creep in multiphase intermetallics through ...

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    alloys through alloying to introduce beneficial, second phase effects. .... The second emerged as a consequence of slower reaction kinetics of diffusion- .... Aging stabilizes the microstructure in a temperature range spanning potential service temperatures of the material. Forging below the bcc transus offers the option of bcc ...

  2. Nickel-base alloy forgings for advanced high temperature power plants

    Energy Technology Data Exchange (ETDEWEB)

    Donth, B.; Diwo, A.; Blaes, N.; Bokelmann, D. [Saarschmiede GmbH Freiformschmiede, Voelklingen (Germany)

    2008-07-01

    The strong efforts to reduce the CO{sub 2} emissions lead to the demand for improved thermal efficiency of coal fired power plants. An increased thermal efficiency can be realised by higher steam temperatures and pressures in the boiler and the turbine. The European development aims for steam temperatures of 700 C which requires the development and use of new materials and also associated process technology for large components. Temperatures of 700 C and above are too high for the application of ferritic steels and therefore only Nickel-Base Alloys can fulfill the required material properties. In particular the Nickel-Base Alloy A617 is the most candidate alloy on which was focused the investigation and development in several German and European programs during the last 10 years. The goal is to verify and improve the attainable material properties and ultrasonic detectability of large Alloy 617 forgings for turbine rotors and boiler parts. For many years Saarschmiede has been manufacturing nickel and cobalt alloys and is participating the research programs by developing the manufacturing routes for large turbine rotor forgings up to a maximum diameter of 1000 mm as well as for forged tubes and valve parts for the boiler side. The experiences in manufacturing and testing of very large forgings made from nickel base alloys for 700 C steam power plants are reported. (orig.)

  3. Erosion-Corrosion of Iron and Nickel Alloys at Elevated Temperature in a Combustion Gas Environment

    Energy Technology Data Exchange (ETDEWEB)

    Tylczak, Joseph [National Energy Technology Lab. (NETL), Albany, OR (United States)

    2014-05-02

    This paper reports on the results of a study that compares the erosion-corrosion behavior of a variety of alloys (Fe- 2¼Cr 1Mo, 304 SS, 310 SS, Incoloy 800, Haynes 230 and a Fe3Al) in a combustion environment. Advanced coal combustion environments, with higher temperatures, are driving re-examination of traditional and examination of new alloys in these hostile environments. In order to simulate conditions in advanced coal combustion boilers, a special erosion apparatus was used to allow for impingement of particles under a low abrasive flux in a gaseous environment comprised of 20 % CO2, 0.05 % HCl, 77 % N2, 3 % O2, and 0.1 % SO2. Tests were conducted at room temperature and 700 °C with ~ 270 μm silica, using an impact velocity of 20 m/s in both air and the simulated combustion gas environment. The erosion-corrosion behavior was characterized by gravimetric measurements and by examination of the degraded surfaces optically and by scanning electron microscopy (SEM). At room temperature most of the alloys had similar loss rates. Not surprisingly, at 700 °C the lower chrome-iron alloy had a very high loss rate. The nickel alloys tended to have higher loss rates than the high chrome austenitic alloys.

  4. Effect of mold temperature on the microstructure and corrosion properties of a 14-karat gold alloy.

    Science.gov (United States)

    Koiso, Kazuo; Saito, Takahiro; Kawashima, Isao

    2012-01-01

    The objective of this research was to investigate the effect of mold temperature on grain interior and grain boundary reactions in a14-karat gold alloy. The alloy (Au-15%Ag-3%Pd-24 mass%Cu) was cast into an investment with different mold temperatures (22, 250,400, and 700°C) and then analyzed using SEM, X-ray diffraction, and potentiodynamic polarization tests. Lower mold temperatures(22 and 250°C) retarded a grain boundary reaction evidently present when using higher mold temperatures (400 and 700°C). Phase separation, which was manifested as a dual phase grain boundary nodular formation, was observed at a higher degree at 400°C mold temperature than at 700°C. The corrosion potentials of alloys cast at lower mold temperatures were more noble than those cast at higher mold temperatures, suggesting improved corrosion properties. Results of this study showed that the microstructure, crystalline phases present, and corrosion properties of 14-karat gold alloy were keenly influenced by the mold temperature, which controls and influences the cooling rate.

  5. Development of High-Temperature Ferritic Alloys and Performance Prediction Methods for Advanced Fission Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    G. RObert Odette; Takuya Yamamoto

    2009-08-14

    Reports the results of a comprehensive development and analysis of a database on irradiation hardening and embrittlement of tempered martensitic steels (TMS). Alloy specific quantitative semi-empirical models were derived for the dpa dose, irradiation temperature (ti) and test (Tt) temperature of yield stress hardening (or softening) .

  6. Influence of Cryogenic Temperatures on the Microstructure and Mechanical Properties of Magnesium Alloys: A Review

    Directory of Open Access Journals (Sweden)

    Hajo Dieringa

    2017-01-01

    Full Text Available Magnesium alloys have been used in the automotive industry and 3C (computer, communication, and consumer electronics for many years. Their room temperature properties combined with their low density offer a wide range of applications, especially when processed by High Pressure Die Casting (HPDC. The use of magnesium alloys at higher temperatures is well-studied; special creep resistant alloys containing the rare earth elements silver or yttrium are needed. However, when it comes to very low temperatures, only a few studies have been performed to determine the property-microstructure relationship. The possible fields of application at low temperatures are aerospace and satellite parts and tanks for liquefied gases. This review shall not only examine mechanical properties at low temperatures, but also the permanent effects of cyclic or long-lasting cryogenic treatment on the microstructure and mechanical properties. It was found that cryogenic treatment is able to influence the precipitate concentration and grain orientation in some magnesium alloys. Reduction in the number of brittle phases is improving ductility in some cases. It is well-known that high speed tool steels, in particular, can be influenced by cryogenic treatment. Whether this is possible with magnesium alloys and what the mechanisms are shall be reviewed.

  7. Effects of Temperature and Current Stressing on the Intermetallic Compounds Growth Characteristics of Cu Pillar/Sn-3.5Ag Microbump

    Science.gov (United States)

    Kwak, Byoung-Hyun; Jeong, Myeong-Hyeok; Park, Young-Bae

    2012-05-01

    The mechanical and electrical reliability of Cu/Sn-3.5Ag microbumps under both annealing and current-stressing conditions were systematically evaluated. Intermetallic compound (IMC) growth was controlled by a diffusion-dominant mechanism and a chemical reaction-dominant mechanism with annealing and current-stressing time, respectively. The transition time for IMC phase change had an inverse relationship with current density because of the electron wind force under current stressing conditions. The shear strength and IMC thickness increased monotonically with annealing time at 150 °C, while the amount of solder decreased. It was clearly revealed that strong correlations exist between IMC growth kinetics, shear strength, and fracture modes in Cu/solder microbumps.

  8. Fatigue Characteristics and Compressive Residual Stress of Shot Preened Alloy 600 Under High Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Cheon; Cheong, Seong Kyun [Seoul Nat' l Univ. of Science and Technology, Seoul (Korea, Republic of); Cho, Hong Seok [KEPCO Plant Service and Engineering co., Ltd., Seongnam (Korea, Republic of)

    2013-03-15

    The compressive residual stress and fatigue behavior of shot preened alloy 600 under a high-temperature environment is investigated in this study. Alloy 600 is used in the main parts of nuclear power plants, and the compressive residual stress induced by the shot peening process is considered to prevent Succ (stress corrosion cracking). To obtain practical results, the fatigue characteristics and compressive residual stress are evaluated under the actual operating temperature of a domestic nuclear power plant, as well as a high-temperature environment. The experimental results show that the peening effects are valid at a high temperature lower than approximately 538 .deg. C,, which is the threshold temperature. The fatigue life was maintained at temperatures lower than 538 .deg. C, and the compressive residual stress at 538 .deg. C was 68.2% of that at room temperature. The present results are expected to be used to obtain basic safety and reliability data.

  9. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    Science.gov (United States)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  10. Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.

    Science.gov (United States)

    Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Casagrande, Angelo

    2010-01-01

    A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders. Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation.

  11. Iron atoms redistribution in oxide films of Zr-Fe, Zr-Fe-Cu alloys during corrosion in autoclave at 350°C

    Science.gov (United States)

    Filippov, V.; Bateev, A.

    2016-04-01

    The data on changes of iron atoms state in the oxide films of binary Zr-1.24 mas.%Fe and ternary Zr-1.39 mas.%Fe-0.60 mas.%Cu zirconium alloys are obtained. Alloys are subjected to corrosion tests under autoclave conditions at 350°C temperature in a steam-water environment under pressure p = 16.8 MPa. In initial specimens of the alloys the iron atoms are in the form of intermetallic compounds. In oxide films the decomposition of intermetallic compounds and formation of new compounds occurs with structural phase distortion. In the oxide films metallic the metallic iron particles α-Fe, iron oxide in the form of hematite α-Fe2O3, solid solutions of iron ions in ZrO2 are formed. The phase composition of the oxide films depends on the alloy composition and changes during the growth process of the oxide film.

  12. Low-Temperature Forming of Beta Titanium Alloys

    Science.gov (United States)

    Kaneko, R. S.; Woods, C. A.

    1983-01-01

    Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

  13. GRCop-84: A High-Temperature Copper Alloy for High-Heat-Flux Applications

    Science.gov (United States)

    Ellis, David L.

    2005-01-01

    GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) is a new high-temperature copper-based alloy. It possesses excellent high-temperature strength, creep resistance and low-cycle fatigue up to 700 C (1292 F) along with low thermal expansion and good conductivity. GRCop-84 can be processed and joined by a variety of methods such as extrusion, rolling, bending, stamping, brazing, friction stir welding, and electron beam welding. Considerable mechanical property data has been generated for as-produced material and following simulated braze cycles. The data shows that the alloy is extremely stable during thermal exposures. This paper reviews the major GRCop-84 mechanical and thermophysical properties and compares them to literature values for a variety of other high-temperature copper-based alloys.

  14. Magnetic susceptibility of Inconel alloys 718, 625, and 600 at cryogenic temperatures

    Science.gov (United States)

    Goldberg, Ira B.; Mitchell, Michael R.; Murphy, Allan R.; Goldfarb, Ronald B.; Loughran, Robert J.

    1990-01-01

    After a hydrogen fuel bleed valve problem on the Discovery Space Shuttle was traced to the strong magnetization of Inconel 718 in the armature of the linear variable differential transformer near liquid hydrogen temperatures, the ac magnetic susceptibility of three samples of Inconel 718 of slightly different compositions, one sample of Inconel 625, and on sample of Inconel 600 were measured as a function of temperature. Inconel 718 alloys are found to exhibit a spin glass state below 16 K. Inconel 600 exhibits three different magnetic phases, the lowest-temperature state (below 6 K) being somewhat similar to that of Inconel 718. The magnetic states of the Inconel alloys and their magnetic susceptibilities appear to be strongly dependent on the exact composition of the alloy.

  15. Temperature dependence of the photoluminescence polarization of ordered III-V semiconductor alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T.; Makarov, N. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, 72050 Puebla, Pue. (Mexico); Attolini, G. [IMEM/CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy)

    2016-03-21

    We studied the linear polarization of the photoluminescence (PL) emission of atomically ordered GaInAsP and GaInP alloys with different ordering parameters in the temperature range from 10 to 300 K. The epitaxial layers of these alloys were grown on GaAs and Ge (001) substrates by metal organic vapor phase epitaxy. The polarization of the PL emission propagating along different crystallographic axes depends on the value of biaxial strain in the layer and changes with temperature. We calculated the PL polarization patterns for different propagation directions as a function of biaxial strain using an existing model developed for ternary atomically ordered III-V alloys. Comparing the calculated PL polarization patterns with those obtained experimentally, we separated the variation of the PL polarization due to change of biaxial strain with temperature.

  16. Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Stubbins, James [Univ. of Illinois, Urbana-Champaign, IL (United States); Heuser, Brent [Univ. of Illinois, Urbana-Champaign, IL (United States); Robertson, Ian [Kyushu Univ. (Japan); Sehitoglu, Huseyin [Univ. of Illinois, Urbana-Champaign, IL (United States); Sofronis, Petros [Kyushu Univ. (Japan); Gewirth, Andrew [Kyushu Univ. (Japan)

    2015-04-22

    This “Blue Sky” project was directed at exploring the opportunities that would be gained by developing Oxide Dispersion Strengthened (ODS) alloys based on the Fe-Cr-Ni austenitic alloy system. A great deal of research effort has been directed toward ferritic and ferritic/martensitic ODS alloys which has resulted in reasonable advances in alloy properties. Similar gains should be possible with austenitic alloy which would also take advantage of other superior properties of that alloy system. The research effort was aimed at the developing an in-depth understanding of the microstructural-level strengthening effects of ODS particles in austentic alloys. This was accomplished on a variety of alloy compositions with the main focus on 304SS and 316SS compositions. A further goal was to develop an understanding other the role of ODS particles on crack propagation and creep performance. Since these later two properties require bulk alloy material which was not available, this work was carried out on promising austentic alloy systems which could later be enhanced with ODS strengthening. The research relied on a large variety of micro-analytical techniques, many of which were available through various scientific user facilities. Access to these facilities throughout the course of this work was instrumental in gathering complimentary data from various analysis techniques to form a well-rounded picture of the processes which control austenitic ODS alloy performance. Micromechanical testing of the austenitic ODS alloys confirmed their highly superior mechanical properties at elevated temperature from the enhanced strengthening effects. The study analyzed the microstructural mechanisms that provide this enhanced high temperature performance. The findings confirm that the smallest size ODS particles provide the most potent strengthening component. Larger particles and other thermally- driven precipitate structures were less effective contributors and, in some cases, limited

  17. Room temperature synthesis of Ni-based alloy nanoparticles by radiolysis.

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina Maria; Berry, Donald T.; Lu, Ping; Leung, Kevin; Provencio, Paula Polyak; Stumpf, Roland Rudolph; Huang, Jian Yu; Zhang, Zhenyuan

    2009-09-01

    Room temperature radiolysis, density functional theory, and various nanoscale characterization methods were used to synthesize and fully describe Ni-based alloy nanoparticles (NPs) that were synthesized at room temperature. These complementary methods provide a strong basis in understanding and describing metastable phase regimes of alloy NPs whose reaction formation is determined by kinetic rather than thermodynamic reaction processes. Four series of NPs, (Ag-Ni, Pd-Ni, Co-Ni, and W-Ni) were analyzed and characterized by a variety of methods, including UV-vis, TEM/HRTEM, HAADF-STEM and EFTEM mapping. In the first focus of research, AgNi and PdNi were studied. Different ratios of Ag{sub x}- Ni{sub 1-x} alloy NPs and Pd{sub 0.5}- Ni{sub 0.5} alloy NP were prepared using a high dose rate from gamma irradiation. Images from high-angle annular dark-field (HAADF) show that the Ag-Ni NPs are not core-shell structure but are homogeneous alloys in composition. Energy filtered transmission electron microscopy (EFTEM) maps show the homogeneity of the metals in each alloy NP. Of particular interest are the normally immiscible Ag-Ni NPs. All evidence confirmed that homogeneous Ag-Ni and Pd-Ni alloy NPs presented here were successfully synthesized by high dose rate radiolytic methodology. A mechanism is provided to explain the homogeneous formation of the alloy NPs. Furthermore, studies of Pd-Ni NPs by in situ TEM (with heated stage) shows the ability to sinter these NPs at temperatures below 800 C. In the second set of work, CoNi and WNi superalloy NPs were attempted at 50/50 concentration ratios using high dose rates from gamma irradiation. Preliminary results on synthesis and characterization have been completed and are presented. As with the earlier alloy NPs, no evidence of core-shell NP formation occurs. Microscopy results seem to indicate alloying occurred with the CoNi alloys. However, there appears to be incomplete reduction of the Na{sub 2}WO{sub 4} to form the W

  18. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    Science.gov (United States)

    Ellis, D. L.; Michal, G. M.; Dreshfield, R. L.

    1995-01-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

  19. Experimental Analysis of the Behaviour of Aluminium Alloy EN 6082AW T6 at High Temperature

    Directory of Open Access Journals (Sweden)

    Neno Torić

    2017-04-01

    Full Text Available The paper presents test results for the mechanical and creep properties of European aluminium alloy EN 6082AW T6 at high temperatures. Mechanical properties of the aluminium alloy were determined by means of two types of test: constant stress-rate and stationary creep tests. Mechanical properties were determined up to a temperature of 350 °C, while the creep tests were conducted within the temperature interval 150–300 °C. The creep tests conducted identified the critical temperature interval for creep development, which represents an important factor when analysing creep behaviour of aluminium structures. This temperature interval was found to be within the range 200–300 °C. Test results for stress at 0.2% strain and modulus of elasticity at different temperatures showed good agreement with the codified values from Eurocode 9 and with other comparable studies.

  20. Influence of yttria surface modification on high temperature corrosion of porous Ni22Cr alloy

    DEFF Research Database (Denmark)

    Karczewski, Jakub; Dunst, Katarzyna; Jasinski, Piotr

    2017-01-01

    Protective coatings for porous alloys for high temperature use are relatively new materials. Their main drawback is high temperature corrosion. In this work protective coatings based the on Y-precursor infiltrated into the sintered Ni22Cr alloys are studied at 700°C. Effects of the amount...... of the protective phase on the resulting corrosion properties are evaluated in air and humidified hydrogen. Weight gain of the samples, their open porosities and microstructures are analyzed and compared. Results show, that by the addition of even a minor amount of the Y-precursor corrosion rates can be decreased...

  1. Niobium and chromium rich coatings tailored by laser alloying: XRD analysis at high temperatures

    Directory of Open Access Journals (Sweden)

    Adilson Rodrigues da Costa

    2004-03-01

    Full Text Available Laser treatment technologies have been widely used to modify superficial layers of different materials. In this work we prepare Nb and Cr rich coatings according to laser alloying technique using cast iron as substrate material. Nb and Cr are intensive used in order to overcome challenges like good chemical and mechanical performance at high temperatures. Following laser alloying the surface-modified samples were submitted to an "in situ" XRD analysis under controlled high temperature and atmosphere. The phase transitions registered point to transformations that do not implies formation of fragile phases or cracks induced by high volumes modifications.

  2. Debye temperature for binary alloys and its relationship with cohesive energy

    Science.gov (United States)

    Tang, Kewei; Wang, Tianran; Qi, Weihong; Li, Yejun

    2018-02-01

    The cohesive energy, formation enthalpies, and elastic constants of AgAl, AuAg, AuPd, AuPt, CuNi, CuPt, NiPb, NiPd, NiPt, and PtPd alloys are calculated by molecular dynamics simulation and first-principle calculation. It is found that the calculated formation enthalpies generally agree with the availible experimental data. The Debye temperatures of these alloys with different compositions are computed from the obtained elastic constants. An empirical relationship between Debye temperature and cohesive energy is developed, which is confirmed by both the simulation and calculation.

  3. High-temperature mechanical properties of aluminium alloys reinforced with boron carbide particles

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J. [Dept. Ingenieria y Ciencia de los Materiales, ETSI Industriales, Universidad Politecnica de Madrid, c/Jose Gutierrez Abascal 2, 28006 Madrid (Spain)], E-mail: javier.onoro@upm.es; Salvador, M.D. [Dept. Ingenieria Mecanica y de Materiales, ETSI Industriales, Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia (Spain); Cambronero, L.E.G. [Dept. Ingenieria de Materiales, ETSI Minas, Universidad Politecnica de Madrid, c/Rios Rosas 21, 28003 Madrid (Spain)

    2009-01-15

    The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys (6061 and 7015) at high temperatures were studied. Boron carbide particles were used as reinforcement. All composites were produced by hot extrusion. The tensile properties and fracture analysis of these materials were investigated at room temperature and at high temperature to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy.

  4. Simulation of Ti-Al intermetallic compound synthesis using cold spraying

    Science.gov (United States)

    Kiselev, S. P.; Ryashin, N. S.; Maximovsky, E. A.; Kiselev, V. P.; Filippov, A. A.; Polukhin, A. A.

    2017-10-01

    The results of the experiment and numerical simulation of Ti-Al intermetallic compound synthesis using cold gas-dynamic spraying and heat postprocessing in an oven at a temperature above the aluminum melting temperature are presented. Ti-Al-type intermetallic systems were obtained at heating temperatures from 930 to 1620 K and phase composition and crystal structure of the compounds were studied. Numerical simulation of the intermetallic synthesis process performed by the molecular dynamics method had shown that the kinetics of the process at these temperatures is determined by the diffusion and dissolution processes of titanium in molten aluminum.

  5. Effect of Temperature on Thermogalvanic Coupling of Alloy 31 in Libr Solutions Studied by Means of Imposed Potential Measurements

    OpenAIRE

    Fernández Domene, Ramón Manuel; Blasco-Tamarit, E.; García-García, D.M.; Garcia-Anton, Jose

    2011-01-01

    Corrosion resistance of Alloy 31, a highly alloyed stainless steel (UNS N08031) were studied in heavy brine LiBr solutions (400, 700 and 992 g/l) at different temperatures using electrochemical techniques. The mixed potential theory was used to evaluate thermogalvanic corrosion of Alloy 31 in the studied LiBr solutions. Potentiodynamic curves indicate that high temperatures favoured both cathodic and anodic processes, increasing passive current densities and decreasing the pitting potential. ...

  6. 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.

  7. Martensite formation in Fe-C alloys at cryogenic temperatures

    DEFF Research Database (Denmark)

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

    2017-01-01

    Magnetometry was applied to quantify the fraction of austenite retained in Fe-C alloys subjected to various treatments. These treatments consisted of: (i) water quenching; (ii) water quenching followed by immersion in boiling nitrogen and again in water; (iii) as for (ii) but re-heating from 77 K...... at a rate of 0.0083 K s− 1; (iv) as for (iii) but (re-)heating at 0.167 K s− 1 interrupted by an isothermal step. Data was coupled with hardness measurements and demonstrates that the re-heating conditions from 77 K significantly influence the fraction of austenite retained at the end of the thermal cycle....

  8. Characterization of second-phase plates in a Gd₅Ge₃ intermetallic compound.

    Science.gov (United States)

    Cao, Q; Chumbley, L S

    2013-12-01

    Rare-earth compounds based on the stoichiometry R₅(Si(x)Ge(1-x))₄ (R = rare-earth elements) exhibit many unusual features, including possessing R₅(Si(x)Ge(1-x))3 thin plates which always precipitate from the matrix despite efforts to suppress their formation. In an effort to better understand the unique relationship between these two intermetallic alloy systems, the bulk microstructure of the compound Gd₅Ge₃ was examined using scanning (SEM) and transmission electron microscopy (TEM) and optical microscopy. Surprisingly, SEM examination revealed a series of thin plates present in the Gd₅Ge₃ matrix similar to what is seen in Gd₅Ge₄. TEM observation revealed that a role reversal had occurred, with the thin plates possessing the orthorhombic structure and composition of Gd₅Ge₄. The orientation relationship between Gd₅Ge₄ thin plates and the Gd₅Ge₃ matrix was determined to be [1 0 1 0 ](1 2 1 1)(m)||[0 1 0](1 0 2)(p), the same relationship reported for Gd₅Ge₃ plates precipitating from a Gd₅Ge₄ matrix. However, by exchanging the respective roles of the phases as regards matrix vs. precipitate, the total number of precipitation variants seen can be increased from two to six. The persistence with which these two intermetallic systems co-exist is truly unique. However, understanding exactly the kinetic and thermodynamic conditions that lead to their unique relationship is hampered by the high formation temperatures at which the observed reaction occurs.

  9. Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

  10. Mechanistic basis of temperature-dependent dwell fatigue in titanium alloys

    Science.gov (United States)

    Zheng, Zebang; Balint, Daniel S.; Dunne, Fionn P. E.

    2017-10-01

    The temperature-dependent dwell sensitivity of Ti-6242 and Ti-6246 alloys has been assessed over a temperature range from - 50∘ C to 390 °C using discrete dislocation plasticity which incorporates both thermal activation of dislocation escape from obstacles and slip transfer across grain boundaries. The worst-case load shedding in Ti-6242 alloy is found to be at or close to 120 °C under dwell fatigue loading, which diminishes and vanishes at temperatures lower than - 50∘ C or higher than 230 °C. Load shedding behaviour is predicted to occur in alloy Ti-6246 also but over a range of higher temperatures which are outside those relevant to in-service conditions. The key controlling dislocation mechanism with respect to load shedding in titanium alloys, and its temperature sensitivity, is shown to be the time constant associated with the thermal activation of dislocation escape from obstacles, with respect to the stress dwell time. The mechanistic basis of load shedding and dwell sensitivity in dwell fatigue loading is presented and discussed in the context of experimental observations.

  11. Effect of sulfur on the protective layers on alloys 600 and 690 in low and high temperature environments

    Energy Technology Data Exchange (ETDEWEB)

    Combrade, P.; Foucault, M.; Vancon, D. (Unirec, 42 - Firminy (FR)); Marcus, P.; Grimal, J.M. (Ecole Nationale Superieure de Chimie, 75 - Paris (FR)); Gelpi, A. (Societe Franco-Americaine de Constructions Atomiques (Framatome), 92 - Courbevoie (FR))

    The effect of the presence of sulfide dissolved in the environment on the dissolution and film repair was studied on alloy 600, alloy 690 and nickel exposed to neutral and caustic deaerated solutions at 290{sup 0}C. Comparison with the effect of adsorbed sulfur on the dissolution and film built up on high purity alloy 600 and nickel in acidic solutions at room temperature shows strong analogies. In both cases the beneficial effect of chromium is clearly shown and this is consistent with the better behaviour of alloy with increased chromium content such as alloy 690.

  12. Hardness evolution of AZ80 magnesium alloy processed by HPT at different temperatures

    Directory of Open Access Journals (Sweden)

    Saad A. Alsubaie

    2017-10-01

    Full Text Available Discs of an extruded AZ80 magnesium alloy were processed by high-pressure torsion (HPT using 6.0 GPa up to 10 turns at different temperatures (296 K and 473 K. The disc surfaces and cross-sectional planes were examined before and after processing using scanning electron microscopy (SEM and Vickers microhardness (Hv. The microhardness results at the surface show differences in the strength of the material as a function of distance from the disc centres up to saturation, as well as a function of distance from the bottom to the surface in the cross-sectional plane. This study analyses the effect of processing temperature on the evolution of microhardness in the AZ80 magnesium alloy processed by high-pressure torsion. Keywords: Hardness, High-pressure torsion, Magnesium alloy, Severe plastic deformation

  13. Bonding evolution with sintering temperature in low alloyed steels with chromium

    Directory of Open Access Journals (Sweden)

    Fuentes-Pacheco L.

    2009-01-01

    Full Text Available At present, high performance PM steels for automotive applications follow a processing route that comprises die compaction of water-atomized powder, followed by sintering and secondary treatments, and finishing operations. This study examines Cr-alloyed sintered steels with two level of alloying. In chromium-alloyed steels, the surface oxide on the powder is of critical importance for developing the bonding between the particles during sintering. Reduction of this oxide depends mainly on three factors: temperature, dew point of the atmosphere, and carbothermic reduction provided by the added graphite. The transformation of the initial surface oxide evolves sequence as temperature increases during sintering, depending on the oxide composition. Carbothermic reduction is supposed to be the controlling mechanism, even when sintering in hydrogen-containing atmospheres. The effect of carbothermic reduction can be monitored by investigating the behavior of the specimens under tensile testing, and studying the resultant fracture surfaces.

  14. Effect of Mn Content and Solution Annealing Temperature on the Corrosion Resistance of Stainless Steel Alloys

    Directory of Open Access Journals (Sweden)

    Ihsan-ul-Haq Toor

    2014-01-01

    Full Text Available The corrosion behavior of two specially designed austenitic stainless steels (SSs having different Nickel (Ni and Manganese (Mn contents was investigated. Prior to electrochemical tests, SS alloys were solution-annealed at two different temperatures, that is, at 1030°C for 2 h and 1050°C for 0.5 h. Potentiodynamic polarization (PD tests were carried out in chloride and acidic chloride, whereas linear polarization resistance (LPR and electrochemical impedance spectroscopy (EIS was performed in 0.5 M NaCl solution at room temperature. SEM/EDS investigations were carried out to study the microstructure and types of inclusions present in these alloys. Experimental results suggested that the alloy with highest Ni content and annealed at 1050°C/0.5 hr has the highest corrosion resistance.

  15. Mechanical Properties of WE43 Magnesium Alloy Joint at Elevated Temperature / Właściwości Mechaniczne Złączy Ze Stopu Magnezu WE43 W Podwyższonej Temperaturze

    Directory of Open Access Journals (Sweden)

    Turowska A.

    2015-12-01

    Full Text Available The WE43 cast magnesium alloy, containing yttrium and rare earth elements, remains stable at temperatures up to 300°C, according to the manufacturer, and therefore it is considered for a possible application in the aerospace and automotive. Usually, it is cast gravitationally into sand moulds and used for large-size castings that find application in the aerospace industry. After the casting process any possible defects that might appear in the casting are repaired with the application of welding techniques. These techniques also find application in renovation of the used cast elements and in the process of joining the cast parts into complex structures. An important factor determining the validity of the application of welding techniques for repairing or joining cast magnesium alloys is the structural stability and the stability of the properties of the joint in operating conditions. In the literature of the subject are information on the properties of the WE43 alloy or an impact of heat treatment on the structure and properties of the alloy, however, there is a lack of information concerning the welded joints produced from this alloy. This paper has been focused on the analysis the microstructure of the welded joints and their mechanical properties at elevated temperatures. To do this, tensile tests at temperatures ranging from 20°C to 300°C were performed. The tests showed, that up to the temperature of 150°C the crack occurred in the base material, whereas above this temperature level the rapture occurred within the weld. The loss of cohesion resulted from the nucleation of voids on grain boundaries and their formation into the main crack. The strength of the joints ranged from 150 MPa to 235 MPa, i.e. around 90 % of strength of the WE43 alloy after heat treatment (T6. Also performed a profilometric examination was to establish the shape of the fracture and to analyze how the temperature affected a contribution of phases in the process of

  16. The effect of pressure on the Curie temperature in Fe-Ni Invar mechanical alloys

    CERN Document Server

    Wei, S; Zach, R; Matsushita, M; Takahashi, A; Inoue, H; Ono, F; Maeta, H; Iwase, A; Endo, S

    2002-01-01

    Measurements of the temperature dependence of the AC susceptibility were made for Fe-Ni Invar mechanical alloys under hydrostatic pressures up to 1.5 GPa. The Curie temperatures decreased linearly with pressure. The rate of decrease became larger for specimens annealed at higher temperatures. The temperature of annealing after ball milling has been directly related to the extent of the chemical concentration fluctuation, and the extent becomes smaller for specimens annealed at higher temperature. This tendency can be explained by assuming a Gaussian distribution function.

  17. Ambient-temperature high damping capacity in TiPd-based martensitic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Dezhen [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Zhou, Yumei, E-mail: zhouyumei@mail.xjtu.edu.cn [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ding, Xiangdong [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Otsuka, Kazuhiro [Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Sun, Jun [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ren, Xiaobing [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan)

    2015-04-24

    Shape memory alloys (SMAs) have attracted considerable attention for their high damping capacities. Here we investigate the damping behavior of Ti{sub 50}(Pd{sub 50−x}D{sub x}) SMAs (D=Fe, Co, Mn, V) by dynamic mechanical analysis. We find that these alloys show remarkably similar damping behavior. There exists a sharp damping peak associated with the B2–B19 martensitic transformation and a high damping plateau (Q{sup −1}~0.02–0.05) over a wide ambient-temperature range (220–420 K) due to the hysteretic twin boundary motion. After doping hydrogen into the above alloys, a new relaxation-type damping peak appears in the martensite phase over 270–360 K. Such a peak is considered to originate from the interaction of hydrogen atoms with twin boundaries and the corresponding damping capacity (Q{sup −1}~0.05–0.09) is enhanced by roughly twice that of the damping plateau for each alloy. Moreover, the relaxation peaks are at higher temperatures for the TiPd-based alloys (270–370 K) than for the TiNi-based alloys (190–260 K). We discuss the influence of hydrogen diffusion, mobility of twin boundaries and hydrogen–twin boundary interaction on the temperature range of the relaxation peak. Our results suggest that a martensite, with appropriate values for twinning shear and hydrogen doping level, provides a route towards developing high damping SMAs for applications in desired temperature ranges.

  18. Inhibition of the formation of intermetallic compounds in aluminum-steel welded joints by friction stir welding; Inhibicion de la formacion de compuestos intermetalicos en juntas aluminio-acero soldadas por friccion-agitacion

    Energy Technology Data Exchange (ETDEWEB)

    Torres Lopez, E. A.; Ramirez, A. J.

    2015-07-01

    Formation of deleterious phases during welding of aluminum and steel is a challenge of the welding processes, for decades. Friction Stir Welding (FSW) has been used in an attempt to reduce formation of intermetallic compounds trough reducing the heat input. In this research, dissimilar joint of 6063-T5 aluminum alloy and AISI-SAE 1020 steel were welded using this technique. The temperature of welded joints was measured during the process. The interface of the welded joints was characterized using optical microscopy, scanning and transmission electron microscopy. Additionally, composition measurements were carried out by X-EDS and DRX. The experimental results revealed that the maximum temperature on the joint studied is less than 360 degree centigrade. The microstructural characterization in the aluminum-steel interface showed the absence of intermetallic compounds, which is a condition attributed to the use of welding with low thermal input parameters. (Author)

  19. Absorbed Energy Distribution of Ductile Ni-resist Alloyed Iron Under Instrumented Impact Load at Low Temperatures

    National Research Council Canada - National Science Library

    Ke, Jiang; Yingdong, Qu; Junhua, You; Rongde, Li

    2016-01-01

    In this study, in order to investigate the absorbed energy distribution on the low-temperature impact fracture process of ductile Ni-resist alloyed iron, the low-temperature impact tests of ductile Ni...

  20. Microstructure and high temperature stability of age hardenable AA2219 aluminium alloy modified by Sc, Mg and Zr additions

    Energy Technology Data Exchange (ETDEWEB)

    Naga Raju, P. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)], E-mail: puvvala_nagaraju@yahoo.com; Srinivasa Rao, K. [Metallurgical Engineering Department, Andhra University, Visakapatnam 530003 (India); Reddy, G.M. [Defence Metallurgical Research Laboratory, Hyderabad 500258 (India); Kamaraj, M.; Prasad Rao, K. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)

    2007-08-25

    The present work pertains to the improvement of high temperature stability of age hardenable AA2219 aluminium-copper (6.3%) alloy. Addition of scandium, magnesium and zirconium to the base metal AA2219 was adopted to improve this high temperature stability. These additions were systematically varied by preparing alloys of different composition using gas tungsten arc melting. Long time ageing studies and impression creep technique were used to study the high temperature stability of the alloys. These modified compositions of the alloy resulted in fine equiaxed grains, refined eutectics, large number of high temperature stable and finer precipitates. Among all the compositions, 0.8% Sc + 0.45% Mg + 0.2% Zr addition was found to be significant in improving the high temperature stability of AA2219 alloy. This may be attributed to the possible microstructural changes, solute enrichment of the matrix and pinning of the grain boundaries by the finer precipitates.

  1. Study of the properties and the choice of alloys for bladed disks (blisks) and a method for their joining

    Science.gov (United States)

    Povarova, K. B.; Valitov, V. A.; Obsepyan, S. V.; Drozdov, A. A.; Bazyleva, O. A.; Valitova, E. V.

    2014-09-01

    The choice of materials for the bladed disks (blisks) that are intended for next-generation aviation gas turbine engines is grounded. As blade materials, single crystals of light heterophase γ' + γ VKNA-type alloys based on the γ'(Ni3Al) intermetallic compound with an ordered structure are proposed. The choice of novel deformable EP975-type nickel superalloys, which are intended for operation at 800-850°C, as the disk material is grounded. It is shown that the most effective method for forming one-piece joints of an Ni3Al-based alloy and a high-alloy EP975-type nickel superalloy is the new process of solid-phase pressure welding under conditions of high-temperature superplasticity. Solid-phase joints are formed for heterophase Ni3Al-based alloy single crystals and deformable EK61 and EP975 nickel alloys. The gradient structures in the zone of the solid-phase joints that form under the conditions of low- and high-temperature superplasticity at homologous temperatures of ˜0.6 T m and 0.9 T m are studied. The character and direction of the diffusion processes at the joint of an intermetallic alloy single crystal and a deformable polycrystalline alloy are determined.

  2. Effects of metallic nanoparticle doped flux on the interfacial intermetallic compounds between lead-free solder ball and copper substrate

    Energy Technology Data Exchange (ETDEWEB)

    Sujan, G.K., E-mail: sgkumer@gmail.com; Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my; Afifi, A.B.M., E-mail: amalina@um.edu.my

    2014-11-15

    Lead free solders currently in use are prone to develop thick interfacial intermetallic compound layers with rough morphology which are detrimental to the long term solder joint reliability. A novel method has been developed to control the morphology and growth of intermetallic compound layers between lead-free Sn–3.0Ag–0.5Cu solder ball and copper substrate by doping a water soluble flux with metallic nanoparticles. Four types of metallic nanoparticles (nickel, cobalt, molybdenum and titanium) were used to investigate their effects on the wetting behavior and interfacial microstructural evaluations after reflow. Nanoparticles were dispersed manually with a water soluble flux and the resulting nanoparticle doped flux was placed on copper substrate. Lead-free Sn–3.0Ag–0.5Cu solder balls of diameter 0.45 mm were placed on top of the flux and were reflowed at a peak temperature of 240 °C for 45 s. Angle of contact, wetting area and interfacial microstructure were studied by optical microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that the angle of contact increased and wetting area decreased with the addition of cobalt, molybdenum and titanium nanoparticles to flux. On the other hand, wettability improved with the addition of nickel nanoparticles. Cross-sectional micrographs revealed that both nickel and cobalt nanoparticle doping transformed the morphology of Cu{sub 6}Sn{sub 5} from a typical scallop type to a planer one and reduced the intermetallic compound thickness under optimum condition. These effects were suggested to be related to in-situ interfacial alloying at the interface during reflow. The minimum amount of nanoparticles required to produce the planer morphology was found to be 0.1 wt.% for both nickel and cobalt. Molybdenum and titanium nanoparticles neither appear to undergo alloying during reflow nor have any influence at the solder/substrate interfacial reaction. Thus, doping

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

    Energy Technology Data Exchange (ETDEWEB)

    Palma, Rodrigo H. [Departamento de Ingenieria Mecanica, Universidad de Chile, Beauchef 850, 4 deg. Piso, Santiago 6511261 (Chile)]. E-mail: rhpalma@ing.uchile.ct; Sepulveda, Aquiles [Departamento de Ingenieria Mecanica, Universidad de Chile, Beauchef 850, 4 deg. Piso, Santiago 6511261 (Chile); Espinoza, Rodrigo [Departamento de Ingenieria Mecanica, Universidad de Chile, Beauchef 850, 4 deg. Piso, Santiago 6511261 (Chile); Dianez, M. Jesus [Instituto de Ciencia de Materiales de Sevilla, Americo Vespucio s/n, Isla de La Cartuja, Sevilla (Spain); Criado, Jose M. [Instituto de Ciencia de Materiales de Sevilla, Americo Vespucio s/n, Isla de La Cartuja, Sevilla (Spain); Sayagues, M. Jesus [Instituto de Ciencia de Materiales de Sevilla, Americo Vespucio s/n, Isla de La Cartuja, Sevilla (Spain)

    2005-01-25

    The hot mechanical behaviour and microstructure of Cu-5 vol.% TiC, Cu-5 vol.% ZrO{sub 2} and Cu-2.5 vol.% TiC-2.5 vol.% ZrO{sub 2} alloys prepared by reaction milling were studied. After a test of 1 h annealing at 1173 K, the Cu-5 vol.% ZrO{sub 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{sup -3} and 0.85 x 10{sup -4} s{sup -1} were performed. The Cu-2.5 vol.% TiC-2.5 vol.% ZrO{sub 2} and the Cu-5 vol.% ZrO{sub 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{sub 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.

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

    Directory of Open Access Journals (Sweden)

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

    2013-01-01

    Full Text Available 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.

  5. Compression Deformation Behavior of AZ81 Magnesium Alloy at Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Xiaoping Luo

    2014-01-01

    Full Text Available The hot deformation behavior of an AZ81 magnesium alloy was investigated by hot compressive testing on a Gleeble-1500 thermal mechanical simulator in the temperature range from 200 to 400°C and in the strain rate range of 0.001–5 s−1. The relationships among flow stress, strain rate, and deformation temperature were analyzed, and the deformation activation energy and stress exponent were calculated. The microstructure evolution of the AZ81 magnesium alloy under high deformation was examined. The results indicated that the maximum value of the flow stress increased with the decrease of deformation temperature and the increase of strain rate. When the deformation temperature is constant, the flow stress of the AZ81 magnesium alloy increases with the increase of strain rate, which can be demonstrated by a Zener-Hollomon parameter in a hyperbolic-sine-type equation with a hot compression deformation activation energy of 176.01 KJ/mol and basic hot deformation material factors A, n, and a in the analytical expression of the AZ81 magnesium alloy flow stress of 3.21227×1014 s−1, 7.85, and 0.00866 MPa, respectively.

  6. Temperature dependence of the bulk and surface properties of liquid Zn-Cd alloys

    Energy Technology Data Exchange (ETDEWEB)

    Awe, O.E. [University of Ibadan, Department of Physics, Ibadan (Nigeria); Azeez, A.A. [African University of Science and Technology, Abuja (Nigeria)

    2017-05-15

    The effects of temperature on the bulk and surface properties of liquid Zn-Cd alloys have been theoretically investigated, using a combination of self association model, Darken's thermodynamic equation for diffusion, empirical model for viscosity and a statistical mechanics model. The results from this study show that change in temperature resulted in cross-over effects in bulk and surface properties. We also found that with an increase in temperature, a pronounced asymmetry of viscosity isotherm is significantly reduced, and viscosity isotherm exhibited anomalous behaviour. Our results reveal that the homocoordination tendency in Zn-Cd liquid alloys is not strong and reduces with increasing temperature. The study further suggests a pronounced segregation of Cd-atoms at the surface of Zn-Cd liquid alloys and the extent of segregation reduces with temperature. We as well found that, in addition to the reported understanding that size-factor determines the compositional location of asymmetry of the viscosity isotherm, temperature is an operating parameter that has effect, not only on the composition of asymmetry, but also on the magnitude of asymmetry. In all the properties investigated, the most pronounced effect of temperature (52.9 %) is on the viscosity while the least effect (7.1 %) is on the surface tension. (orig.)

  7. Study on microstructure and properties of Mg-alloy surface alloying layer fabricated by EPC

    Directory of Open Access Journals (Sweden)

    Chen Dongfeng

    2010-02-01

    Full Text Available AZ91D surface alloying was investigated through evaporative pattern casting (EPC technology. Aluminum powder (0.074 to 0.104 mm was used as the alloying element in the experiment. An alloying coating with excellent properties was fabricated, which mainly consisted of adhesive, co-solvent, suspending agent and other ingredients according to desired proportion. Mg-alloy melt was poured under certain temperature and the degree of negative pressure. The microstructure of the surface layer was examined by means of scanning electron microscopy. It has been found that a large volume fraction of network new phases were formed on the Mg-alloy surface, the thickness of the alloying surface layer increased with the alloying coating increasing from 0.3 mm to 0.5 mm, and the microstructure became compact. Energy dispersive X-ray (EDX analysis was used to determine the chemical composition of the new phases. It showed that the new phases mainly consist of β-Mg17Al12, in addition to a small quantity of inter-metallic compounds and oxides. A micro-hardness test and a corrosion experiment to simulate the effect of sea water were performed. The result indicated that the highest micro-hardness of the surface reaches three times that of the matrix. The corrosion rate of alloying samples declines to about a fifth of that of the as-cast AZ91D specimen.

  8. Characterization of Al-Mg Alloy Aged at Low Temperatures

    Science.gov (United States)

    Yi, Gaosong; Cullen, David A.; Littrell, Kenneth C.; Golumbfskie, William; Sundberg, Erik; Free, Michael L.

    2017-04-01

    Long-term aged [343 K (70 °C) for 30 months and natural exposure for over 10 years] Al 5456 H116 samples were characterized using electron backscatter diffraction (EBSD), scanning transmission electron microscopy (STEM), state-of-the-art energy-dispersive X-ray spectroscopy (EDS) systems, and small-angle neutron scattering (SANS). ASTM G-67 mass loss tests of the sensitized Al 5456 alloy samples were conducted. Intragranular Mg-rich precipitates, such as Guinier-Preston (GP) zones, were confirmed in Al 5456 H116 aged at 343 K (70 °C) for 30 months, and the volume of these precipitates is 1.39 pct. β' phase is identified at the grain boundary of a navy ship sample, while high-resolution STEM results reveal no intragranular precipitates. Intergranular corrosion (IGC) of Al 5456 was found to be related to the continuity of intergranular precipitates.

  9. A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Liming Liu

    2014-05-01

    Full Text Available Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC such as Mg17Al12 and Mg2Al3. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research.

  10. A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys

    Science.gov (United States)

    Liu, Liming; Ren, Daxin; Liu, Fei

    2014-01-01

    Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC) such as Mg17Al12 and Mg2Al3. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research. PMID:28788646

  11. Corrosion and Creep of Candidate Alloys in High Temperature Helium and Steam Environments for the NGNP

    Energy Technology Data Exchange (ETDEWEB)

    Was, Gary; Jones, J. W.

    2013-06-21

    This project aims to understand the processes by which candidate materials degrade in He and supercritical water/steam environments characteristic of the current NGNP design. We will focus on understanding the roles of temperature, and carbon and oxygen potential in the 750-850 degree C range on both uniform oxidation and selective internal oxidation along grain boundaries in alloys 617 and 800H in supercritical water in the temperature range 500-600 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature rang 750-850 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature range 750-850 degree C over a range of oxygen and carbon potentials in helium. Combined, these studies wil elucidate the potential high damage rate processes in environments and alloys relevant to the NGNP.

  12. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-06-01

    Iron aluminides containing greater than about 20-25 @ % Al have oxidation/sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. In addition to alloying modifications for improved creep resistance of wrought material, this strength limitation is being addressed by development of oxide-dispersion- strengthened (ODS) iron aluminides and by evaluation of Fe{sub 3}Al alloy compositions as coatings or claddings on higher-strength, less corrosion-resistant materials. As part of these efforts, the high-temperature corrosion behavior of iron-aluminide weld overlays and ODS alloys is being characterized and compared to previous results for ingot-processed material.

  13. New eutectic alloys and their heats of transformation

    Science.gov (United States)

    Farkas, D.; Birchenall, C. E.

    1985-01-01

    Eutectic compositions and congruently melting intermetallic compounds in binary and multicomponent systems among common elements such as Al, Ca, Cu, Mg, P, Si, and Zn may be useful for high temperature heat storage. In this work, heats of fusion of new multicomponent eutectics and intermetallic phases are reported, some of which are competitive with molten salts in heat storage density at high temperatures. The method used to determine unknown eutectic compositions combined results of differential thermal analysis, metallography, and microprobe analysis. The method allows determination of eutectic compositions in no more than three steps. The heats of fusion of the alloys were measured using commercial calorimeters, a differential thermal analyzer, and a differential scanning calorimeter.

  14. Tensile behaviour of aluminium 7017 alloy at various temperatures and strain rates

    Directory of Open Access Journals (Sweden)

    Ravindranadh Bobbili

    2016-04-01

    Full Text Available The objective of the present study is to carry out high strain rate tensile tests on 7017 aluminium alloy under different strain rates ranging from 0.01, 500, 1000 and 1500 s−1 and at temperatures of 25, 100, 200 and 300 °C. Quasi-Static tensile stress–strain curves were generated using INSTRON 8500 machine. Johnson-Cook (J-C constitutive model was developed for 7017 aluminium alloy based on high strain rate tensile data generated from split Hopkinson tension bar (SHTB at various temperatures. This study evidently showed an improvement in dynamic strength as the strain rate increases. The predictions of J-C model are observed to be in consistence with the experimental data for all strain rates and temperatures. The fracture surfaces of specimens tested were studied under SEM. The change in fracture mode has been observed at different strain rates. The shear mode of fracture is dominant at lower strain rates (0.01 and 500 s−1; whereas cup- and cone-like surface representing dimple structure is found at the higher strain rates (1000 and 1500 s−1. The numbers of dimples at high strain rates are more than the quasi-static and intermediate strain rates. It is also observed that the flow stress decreases with increase in temperature. The 7017 aluminium alloy demonstrates thermal softening at higher temperatures. So when the temperature is more than 200 °C at these strain rates, thermal softening is predominant mode of deformation mechanism. It is found that when the temperature increases to 200 °C, the number of dimples rises and the dimple size of 7017 aluminium alloy is larger than at lower temperatures.

  15. Phase separation of metastable CoCrFeNi high entropy alloy at intermediate temperatures

    OpenAIRE

    He, Feng; Wang, Zhijun; Wu, Qingfeng; Li, Junjie; Wang, Jincheng; Liu, C T

    2016-01-01

    The CoCrFeNi alloy is widely accepted as an exemplary stable base for high entropy alloys (HEAs). Although various investigations prove it to be stable solid solution, its phase stability is still suspicious. Here, we identified that the CoCrFeNi HEA was thermally metastable at intermediate temperatures, and composition decomposition occurred after annealed at 750oC for 800 hrs. The increased lattice distortion induced by minor addition of Al into the CoCrFeNi base accelerated the composition...

  16. A chemical approach toward low temperature alloying of immiscible iron and molybdenum metals

    Energy Technology Data Exchange (ETDEWEB)

    Nazir, Rabia [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Applied Chemistry Research Centre, Pakistan Council of Scientific and Industrial Research Laboratories Complex, Lahore 54600 (Pakistan); Ahmed, Sohail [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Akhtar, Muhammad Javed; Siddique, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Khan, Nawazish Ali [Material Science Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shah, Muhammad Raza [HEJ Research Institute of Chemistry, University of Karachi, Karachi 75270 (Pakistan); Nadeem, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    2013-11-15

    Graphical abstract: - Highlights: • Low temperature pyrolysis of [Fe(bipy){sub 3}]Cl{sub 2} and [Mo(bipy)Cl{sub 4}] homogeneous powder. • Easy low temperature alloying of immiscible metals like Fe and Mo. • Uniform sized Fe–Mo nanoalloy with particle size of 48–68 nm. • Characterization by EDXRF, AFM, XRPD, magnetometery, {sup 57}Fe Mössbauer and impedance. • Alloy behaves as almost superparamagnetic obeying simple –R(CPE)– circuit. - Abstract: The present research is based on a low temperature operated feasible method for the synthesis of immiscible iron and molybdenum metals’ nanoalloy for technological applications. The nanoalloy has been synthesized by pyrolysis of homogeneous powder precipitated, from a common solvent, of the two complexes, trisbipyridineiron(II)chloride, [Fe(bipy){sub 3}]Cl{sub 2}, and bipyridinemolybedenum(IV) chloride, [Mo(bipy)Cl{sub 4}], followed by heating at 500 °C in an inert atmosphere of flowing argon gas. The resulting nanoalloy has been characterized by using EDXRF, AFM, XRD, magnetometery, {sup 57}Fe Mössbauer and impedance spectroscopies. These results showed that under provided experimental conditions iron and molybdenum metals, with known miscibility barrier, alloy together to give (1:1) single phase material having particle size in the range of 48–66 nm. The magnetism of iron is considerably reduced after alloy formation and shows its trend toward superparamagnetism. The designed chemical synthetic procedure is equally feasible for the fabrication of other immiscible metals.

  17. Low-temperature relaxation in NiTi-based shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Torrens-Serra, Joan; Salas, Daniel; Cesari, Eduard; Kustov, Sergey [Departament de Fisica, Universitat de les Illes Balears, cra. de Valldemossa km 7.5, E-07122, Palma de Mallorca (Spain)

    2011-07-01

    We have studied the structural changes occurring in different Ni-Ti and Ni-Ti-Fe alloys over the temperature range from 13 to 300 K by means of mechanical spectroscopy, calorimetry (DSC) and electrical resistivity measurements. Several binary and ternary alloys were used with different thermal and mechanical history, which demonstrate distinct transformation paths: B2-B19', B2-R and B2-R-B19'. Temperature dependence of the internal friction (IF) was studied over the range 90-137 kHz for different strain amplitudes from 3{sup *}10E-7 to 5{sup *}10E-5. In addition to the martensitic and intermartensitic transformations, the IF curves showed a peak at about 90 K in annealed and water-quenched samples independently of their composition which can not be detected by DSC or electrical resistivity measurements. The thermally activated nature of the relaxation has been confirmed using different measurement frequencies. Since the IF peak is observed for ultrasonic frequencies at temperatures of around 90 K, it corresponds to a new relaxation phenomenon, not reported so far in Ni-Ti family of alloys, with the activation energy of the order of only 0.01 eV. On the other hand, no relaxation is found in deformed alloys not subjected to annealing heat treatments. The origin of this relaxation may be attributed to the presence of interstitial hydrogen atoms.

  18. The Effects of Test Temperature, Temper, and Alloyed Copper on the Hydrogen-Controlled Crack Growth Rate of an Al-Zn-Mg-(Cu) Alloy

    Energy Technology Data Exchange (ETDEWEB)

    G.A. Young, Jr.; J.R. Scully

    2000-09-17

    The hydrogen embrittlement controlled stage II crack growth rate of AA 7050 (6.09 wt.% Zn, 2.14 wt% Mg, 2.19 wt.% Cu) was investigated as a function of temper and alloyed copper level in a humid air environment at various temperatures. Three tempers representing the underaged, peak aged, and overaged conditions were tested in 90% relative humidity (RH) air at temperatures between 25 and 90 C. At all test temperatures, an increased degree of aging (from underaged to overaged) produced slower stage II crack growth rates. The stage II crack growth rate of each alloy and temper displayed Arrhenius-type temperature dependence with activation energies between 58 and 99 kJ/mol. For both the normal copper and low copper alloys, the fracture path was predominantly intergranular at all test temperatures (25-90 C) in each temper investigated. Comparison of the stage II crack growth rates for normal (2.19 wt.%) and low (0.06 wt.%) copper alloys in the peak aged and overaged tempers showed the beneficial effect of copper additions on stage II crack growth rate in humid air. In the 2.19 wt.% copper alloy, the significant decrease ({approx} 10 times at 25 C) in stage II crack growth rate upon overaging is attributed to an increase in the apparent activation energy for crack growth. IN the 0.06 wt.% copper alloy, overaging did not increase the activation energy for crack growth but did lower the pre-exponential factor, {nu}{sub 0}, resulting in a modest ({approx} 2.5 times at 25 C) decrease in crack growth rate. These results indicate that alloyed copper and thermal aging affect the kinetic factors that govern stage II crack growth rate. Overaged, copper bearing alloys are not intrinsically immune to hydrogen environment assisted cracking but are more resistant due to an increased apparent activation energy for stage II crack growth.

  19. Passivation and corrosion of the high performance materials alloy 33, alloy 31 and nickel in LiBr solution at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Igual Munoz, A.; Garcia Anton, J.; Guinon, J.L.; Perez Herranz, V. [Departamento de Ingenieria Quimica y Nuclear. E.T.S. Industriales, Universidad Politecnica de Valencia, P.O. Box 22012, E-46071 Valencia (Spain)

    2004-07-01

    Aqueous solutions containing high concentrations of Lithium Bromide are employed as absorbent solutions for almost all types of heating and refrigerating absorption systems that use natural gas or steam as energy sources. LiBr solutions can cause serious corrosion problems in common metallic components. The objective of the present work was to study the corrosion resistance of new high alloyed materials in commercial LiBr heavy brine solution (which contains chromate as inhibitor), at different temperatures (25, 30, 40, 50, 60, 70 and 80 deg. C). The materials tested were stainless steels Alloy 33 (UNS R20033), a new corrosion resistant austenitic material alloyed with nominally (wt%) 33 Cr, 32 Fe, 31 Ni; Nicrofer 3127 hMo-alloy 31 (UNS N08031), an iron-nickel-chromium-molybdenum alloy with nitrogen; and pure Nickel. Corrosion resistance was estimated from the cyclic potentiodynamic polarization curves, comparing OCP values, calculating corrosion potentials and current rates from Tafel analysis; in order to characterize the passivating behaviour of the alloys the study was completed with the analysis of the pitting potentials, passivating current and re-passivating properties at the temperatures under study. Passivating properties are well observed in all the samples in commercial LiBr solution at all temperatures. In these cases, passivation properties decrease with temperature. (authors)

  20. High plasma-flux elevated temperature sputtering of Cu-Li alloys

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, A.R.; Gruen, D.M.; Mendelsohn, M.H.; Conn, R.; Goebel, D.; Hirooka, Y.; Leung, K.

    1986-01-01

    Copper-lithium alloys ranging in composition from 3 to 12 at. % Li have been exposed to sputtering by 3 x 10/sup 16/ - 6 x 10/sup 17/ 100 eV He+/cm/sup 2/-sec at temperatures of 300 to 500/sup 0/C at the UCLA PISCES plasma device. Weight loss and optical spectroscopy techniques were used to determine the sputtering-induced erosion of the binary alloys relative to pure copper. It was found that the weight loss of the alloy and the amount of copper in the plasma as measured by emission spectroscopy never exceeded that of pure copper and in some cases was reduced by a factor of five or more. Post-irradiation analysis by Auger electron spectroscopy and scanning electron microscopy show a correlation between lithium surface depletion, surface roughening, weight loss, and partial erosion yields as measured by plasma emission spectroscopy.

  1. Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

    Science.gov (United States)

    Stein, Frank; Philips, Noah

    2017-09-01

    High-melting Nb-based alloys hold significant promise for the development of novel high-temperature materials for structural applications. In order to understand the effect of alloying elements Al and Fe, the Nb-rich part of the ternary Nb-Al-Fe system was investigated. A series of Nb-rich ternary alloys were synthesized from high-purity Nb, Al, and Fe metals by arc melting. Solidification paths were identified and the liquidus surface of the Nb corner of the ternary system was established by analysis of the as-melted microstructures and thermal analysis. Complementary analysis of heat-treated samples yielded isothermal sections at 1723 K and 1873 K (1450 °C and 1600 °C).

  2. Au-Ge based Candidate Alloys for High-Temperature Lead-Free Solder Alternatives

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2009-01-01

    Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The influence of the low melting point metals namely In, Sb and Sn to the Au-Ge eutectic with respect to the microstructure...... was primarily strengthened by the refined (Ge) dispersed phase. The distribution of phases played a relatively more crucial role in determining the ductility of the bulk solder alloy. In the present work it was found that among the low melting point metals, the addition of Sb to the Au-Ge eutectic would...... and microhardness has been extensively reported. Furthermore, the effects of thermal aging on the microstructure and its corresponding microhardness of these promising candidate alloys have been investigated in this work. After thermal aging at 200°C for different durations ranging from 1 day to 3 weeks...

  3. High Strength and Wear Resistant Aluminum Alloy for High Temperature Applications

    Science.gov (United States)

    Lee, Jonathan A.; Chen, Po Shou

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent thermal growth stability, surface hardness and wear resistant properties.

  4. Metals Technology for Aerospace Applications in 2020: Development of High Temperature Aluminum Alloys For Aerospace Applications

    Science.gov (United States)

    Dicus, Dennis (Technical Monitor); Starke, Edgar A., Jr.

    2003-01-01

    The role of trace additions on the nucleation and stability of the primary strengthening phase, omega, is of paramount importance for the enhancement of mechanical properties for moderate temperature application of Al-Cu-Mg-(Ag) alloys. In order to better understand the competition for solute, which governs the microstructural evolution of these alloys, a series of Al-Cu-Mg-Si quaternary alloys were prepared to investigate the role of trace Si additions on the nucleation of the omega phase. Si additions were found to quell omega nucleation in conjunction with the enhanced matrix precipitation of competing phases. These initial results indicate that it is necessary to overcome a critical Mg/Si ratio for omega precipitation, rather than a particular Si content.

  5. EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

    OpenAIRE

    Prabhu Paulraj; Rajnish Garg

    2015-01-01

    Duplex Stainless Steels (DSS) and Super Duplex Stainless Steel (SDSS) have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic pha...

  6. Magneto-caloric effect in the pseudo-binary intermetallic YPrFe{sub 17} compound

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Pablo [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Gorria, Pedro, E-mail: pgorria@uniovi.es [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Sanchez Llamazares, Jose L. [Division de Materiales Avanzados, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San Jose 2055, CP 78216, San Luis Potosi (Mexico); Perez, Maria J. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Franco, Victorino [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Reiffers, Marian; Kovac, Jozef [Institute of Experimental Physics, Watsonova 47, SK-04001 Kosice (Slovakia); Puente-Orench, Ines [Institute Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble (France); Blanco, Jesus A. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer YPrFe{sub 17} exhibits a broad {Delta}S{sub M}(T) associated with the ferro-to-paramagnetic phase transition (T{sub C} Almost-Equal-To 290 K). Black-Right-Pointing-Pointer We obtain |{Delta}S{sub M}| Almost-Equal-To 2.3 J kg{sup -1} K{sup -1} and RCP Almost-Equal-To 100 J kg{sup -1}for a magnetic field change of 1.5 T. Black-Right-Pointing-Pointer A single master curve for {Delta}S{sub M} is found when compared with other isostructural R{sub 2}Fe{sub 17} binary alloys. - Abstract: We have synthesized the intermetallic YPrFe{sub 17} compound by arc-melting. X-ray and neutron powder diffraction show that the crystal structure is rhombohedral with R3{sup Macron }m space group (Th{sub 2}Zn{sub 17}-type). The investigated compound exhibits a broad isothermal magnetic entropy change {Delta}S{sub M}(T) associated with the ferro-to-paramagnetic phase transition (T{sub C} Almost-Equal-To 290 K). The |{Delta}S{sub M}| ( Almost-Equal-To 2.3 J kg{sup -1} K{sup -1}) and the relative cooling power ( Almost-Equal-To 100 J kg{sup -1}) have been calculated for applied magnetic field changes up to 1.5 T. A single master curve for {Delta}S{sub M} under different values of the magnetic field change can be obtained by a rescaling of the temperature axis. The results are compared and discussed in terms of the magneto-caloric effect in the isostructural R{sub 2}Fe{sub 17} (R = Y, Pr and Nd) binary intermetallic alloys.

  7. High temperature deformation behavior and microstructural evolutions of a high Zr containing WE magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Asqardoust, Sh.; Zarei-Hanzaki, A. [School of Metallurgical & Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Fatemi, S.M., E-mail: mfatemi@ut.ac.ir [Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of); Moradjoy-Hamedani, M. [School of Metallurgical & Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2016-06-05

    Magnesium alloys containing RE elements (WE grade) are considered as potential materials for high temperature structural applications. To this end, it is crucial to study the flow behavior and the microstructural evolution of these alloys at high temperatures. In present work, the hot compression testing was employed to investigate the deformation behavior of a rolled WE54 magnesium alloy at elevated temperatures. The experimental material failed to deform to target strain of 0.6 at 250 and 300 °C, while the straining was successfully performed at 350 °C. A flow softening was observed at 350 °C, which was related to the depletion of RE strengthener elements, particularly Y atoms, from the solid solution and dynamic precipitation of β phases. It was suggested that the Zener pinning effect of the latter precipitates might retard the occurrence of dynamic recrystallization. As the temperature increased to 450 and 500 °C, the RE elements dissolved in the matrix and thus dynamic recrystallization could considerably progress in the microstructure. The comparative study of specimens cut along transverse ad normal direction (TD and ND specimens) implied that the presence of RE elements might effectively reduce the yield anisotropy in WE54 rolled alloy. Microstructural observations indicated a higher fraction of dynamically-recrystallized grains for the ND specimens. This was discussed relying on the different shares of deformation mechanism during compressing the TD and ND specimens. - Highlights: • Deformation behavior of a high Zr WE alloy was addressed at low strain rate. • Dynamic precipitation was realized at 350 °C. • The occurrence of DRX was retarded due to Zener pinning effect. • A higher DRX fraction was obtained in ND specimens comparing with TD ones.

  8. Creep Crack Growth Behavior of Alloys 617 and 800H in Air and Impure Helium Environments at High Temperatures

    Science.gov (United States)

    Grierson, D. S.; Cao, G.; Brooks, P.; Pezzi, P.; Glaudell, A.; Kuettel, D.; Fischer, G.; Allen, T.; Sridharan, K.; Crone, W. C.

    2017-03-01

    The environmental degradation of intermediate heat exchanger (IHX) materials in impure helium has been identified as an area with major ramifications on the design of very high-temperature reactors (VHTR). It has been reported that in some helium environments, non-ductile failure is a significant failure mode for Alloy 617 with long-term elevated-temperature service. Non-ductile failure of intermediate exchangers can result in catastrophic consequences; unfortunately, the knowledge of creep crack initiation and creep crack growth (CCG) in candidate alloys is limited. Current codes and code cases for the candidate alloys do not provide specific guidelines for effects of impure helium on the high-temperature behavior. The work reported here explores creep crack growth characterization of Alloy 617 and Alloy 800H at elevated temperatures in air and in impure helium environments, providing information on the reliability of these alloys in VHTR for long-term service. Alloy 617 was found to exhibit superior CCG resistance compared to Alloy 800H. For Alloy 617 tested at 973 K (700 °C), a notable increase in the resistance to crack growth was measured in air compared to that measured in the helium environment; CCG results for Alloy 800H suggest that air and helium environments produce similar behavior. Testing of grain boundary-engineered (GBE) Alloy 617 samples revealed that, although the technique produces superior mechanical properties in many respects, the GBE samples exhibited inferior resistance to creep crack growth compared to the other Alloy 617 samples tested under similar conditions. Grain size is noted as a confounding factor in creep crack growth resistance.

  9. Rapid solidification of an Al-5Ni alloy processed by spray forming

    Directory of Open Access Journals (Sweden)

    Conrado Ramos Moreira Afonso

    2012-10-01

    Full Text Available Recently, intermetallic compounds have attracted much attention due to their potential technological applications as high-temperature materials. In particular the intermetallic compounds, associated with the Al-Ni binary system stand out as promising candidates for high-temperature materials for the use in harsh environments. It is expected that a bulk Al-Ni alloy may exceed the strength of many commercial materials. The great challenge in developing these alloys is to manipulate the solidification thermal parameters in order to obtain the desired microstructural features. One of the indicated routes to obtain very refined intermetallic phases dispersed in the microstructure is the spray forming process. The dendritic and eutectic growth dependences on cooling rate are already known for directionally solidified (DS hypoeutectic Al-Ni alloys. In the case of rapidly solidified (RS samples, extrapolations of such experimental laws are needed, which can be very helpful to estimate realistic values of high cooling rates imposed during the spray forming process. The present study aims to compare directionally solidified and spray-formed Al-5wt. (%Ni alloy samples with a view to providing a basis for understanding how to control solidification parameters and the as-cast microstructure. The Al-5.0wt. (%Ni alloy was shown to have a cellular morphology for the overspray powder size range examined (up to 500 µm. The mean cell spacing decreased from 5.0 to 1.1 µm with the decrease in the powder average diameter. It was found that the experimental cooling rates imposed during the atomization step of the overspray powder solidification varied from 10³ to 2.10(4 K/s. The DSC trace depicted a crystallization peak of an amorphous structure fraction in the smallest Al-5.0wt. (%Ni alloy powder size range (<32 µm estimating a 15 µm critical diameter of amorphous powder in the binary Al97.5Ni2.5 (at% alloy.

  10. Microstructure and wear behavior of γ/Al 4C 3/TiC/CaF 2 composite coating on γ-TiAl intermetallic alloy prepared by Nd:YAG laser cladding

    Science.gov (United States)

    Liu, Xiu-Bo; Shi, Shi-Hong; Guo, Jian; Fu, Ge-Yan; Wang, Ming-Di

    2009-03-01

    As a further step in obtaining high performance elevated temperature self-lubrication anti-wear composite coatings on TiAl alloy, a novel Ni-P electroless plating method was adopted to encapsulate the as-received CaF 2 in the preparation of precursor NiCr-Cr 3C 2-CaF 2 mixed powders with an aim to decrease its mass loss and increase its compatibility with the metal matrix during a Nd:YAG laser cladding. The microstructure of the coating was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) and the friction and wear behavior of the composite coatings sliding against the hardened 0.45% C steel ring was evaluated using a block-on-ring wear tester at room temperature. It was found that the coating had a unique microstructure consisting of primary dendrites TiC and block Al 4C 3 carbides reinforcement as well as fine isolated spherical CaF 2 solid lubrication particles uniformly dispersed in the NiCrAlTi ( γ) matrix. The good friction-reducing and anti-wear abilities of the laser clad composite coating was suggested to the Ni-P electroless plating and the attendant reduction of mass loss of CaF 2 and the increasing of it's wettability with the NiCrAlTi ( γ) matrix during the laser cladding process.

  11. TA [B] Predicting Microstructure-Creep Resistance Correlation in High Temperature Alloys over Multiple Time Scales

    Energy Technology Data Exchange (ETDEWEB)

    Tomar, Vikas [Purdue Univ., West Lafayette, IN (United States)

    2017-03-06

    DoE-NETL partnered with Purdue University to predict the creep and associated microstructure evolution of tungsten-based refractory alloys. Researchers use grain boundary (GB) diagrams, a new concept, to establish time-dependent creep resistance and associated microstructure evolution of grain boundaries/intergranular films GB/IGF controlled creep as a function of load, environment, and temperature. The goal was to conduct a systematic study that includes the development of a theoretical framework, multiscale modeling, and experimental validation using W-based body-centered-cubic alloys, doped/alloyed with one or two of the following elements: nickel, palladium, cobalt, iron, and copper—typical refractory alloys. Prior work has already established and validated a basic theory for W-based binary and ternary alloys; the study conducted under this project extended this proven work. Based on interface diagrams phase field models were developed to predict long term microstructural evolution. In order to validate the models nanoindentation creep data was used to elucidate the role played by the interface properties in predicting long term creep strength and microstructure evolution.

  12. Temperature effects on the chemical composition of nickel-phosphorus alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Oguocha, I.N.A., E-mail: iko340@mail.usask.c [Department of Mechanical Engineering, Engineering Building, 57 Campus Drive, University of Saskatchewan, Saskatoon, SK, S7N 5A9 (Canada); Taheri, R.; Yannacopoulos, S. [School of Engineering, University of British Columbia Okanagan, 3333 University Way, Kelowna, B.C. V1V 1V7 (Canada); Uju, W.A. [Department of Mechanical Engineering, Engineering Building, 57 Campus Drive, University of Saskatchewan, Saskatoon, SK, S7N 5A9 (Canada); Sammynaiken, R., E-mail: r.sammynaiken@usask.c [Saskatchewan Structural Science Centre, University of Saskatchewan, 110 Science Place, Saskatoon, SK, S7N 5C9 (Canada); Wettig, S. [School of Pharmacy, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1 (Canada); Hu, Y.-F. [Canadian Light Source Inc., 101 Perimeter Road, Saskatoon, SK, S7N 0X4 (Canada)

    2010-02-01

    Electroless Ni-P (EN) alloys are widely used as coating materials. Their properties depend on the level of phosphorus present and the extent of thermal treatment. We report the results of two complimentary electronic structure techniques, X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS), and the site-specific surface chemistry in EN alloys of different phosphorus compositions and thermal treatments. In XANES experiment, absorption at the Ni L{sub 3,2} edge and the P K edge were measured and the P 2p, Ni 2p, and Ni 3p bands were measured by XPS. Heating EN alloys to high temperatures result in a competitive reaction between phosphorus and nickel on the surface for oxygen. There is an increase in the level of phosphates and other forms of phosphorus oxides and a decrease in the oxidized nickel on the surface of the EN alloy thin film. Changes in the electronic structure and chemical composition in the bulk of the EN alloy are not obvious.

  13. Nickel Alloy Catalysts for the Anode of a High Temperature PEM Direct Propane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Shadi Vafaeyan

    2014-01-01

    Full Text Available High temperature polymer electrode membrane fuel cells that use hydrocarbon as the fuel have many theoretical advantages over those that use hydrogen. For example, nonprecious metal catalysts can replace platinum. In this work, two of the four propane fuel cell reactions, propane dehydrogenation and water dissociation, were examined using nickel alloy catalysts. The adsorption energies of both propane and water decreased as the Fe content of Ni/Fe alloys increased. In contrast, they both increased as the Cu content of Ni/Cu alloys increased. The activation energy for the dehydrogenation of propane (a nonpolar molecule changed very little, even though the adsorption energy changed substantially as a function of alloy composition. In contrast, the activation energy for dissociation of water (a molecule that can be polarized decreased markedly as the energy of adsorption decreased. The different relationship between activation energy and adsorption energy for propane dehydrogenation and water dissociation alloys was attributed to propane being a nonpolar molecule and water being a molecule that can be polarized.

  14. Effect of pre-oxidation on high temperature sulfidation behavior of FeCr and FeCrAl alloys

    Directory of Open Access Journals (Sweden)

    Pillis Marina Fuser

    2004-01-01

    Full Text Available High temperature corrosion of structural alloys in sulfur bearing environments is many orders of magnitude higher than in oxidizing environments. Efforts to increase sulfidation resistance of these alloys include addition of alloying elements. Aluminum additions to iron-chromium alloys bring about increase in sulfidation resistance. This paper reports the effect of pre-oxidation on the sulfidation behavior of Fe-20Cr and Fe-20Cr-5Al alloys in H2-2% H2S environment at 800 °C. The surfaces of sulfidized specimens were also examined. Pre-oxidation of the two alloys results in an incubation period during subsequent sulfidation. After this incubation period, the Fe-20Cr alloy showed sulfidation behavior similar to that when the alloy was not pre-oxidized. The incubation period during sulfidation of the Fe-20Cr-5Al alloy was significantly longer, over 45 h, compared to 2 h for the Al free alloy. Based on the microscopic and gravimetric data a mechanism for sulfidation of these alloys with pre-oxidation has been proposed.

  15. Influence of temperature on oxidation behaviour of ZE41 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, M.D., E-mail: mariadolores.lopez@urjc.e [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Munez, C.J. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Carboneras, M. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Rodrigo, P.; Escalera, M.D.; Otero, E. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain)

    2010-02-18

    The influence of temperature on the oxidation behaviour of commercial ZE41 magnesium alloy has been studied. Thermogravimetric tests were carried out to determine the oxidation kinetics in the 350-500 {sup o}C range. Morphology and growth of the oxidation films were analysed by Scanning Electronic Microscopy (SEM), Energy Dispersive X-Ray Spectrometry (EDS) and X-Ray Diffraction (XRD). It was found that the oxidation kinetics initially follow a parabolic law, following a linear law for higher exposure times. Results also showed that the protective nature of the oxide layer depends on the oxidation temperature. At temperatures in the range of 350-450 {sup o}C the ZE41 alloy is covered by a protective oxide layer, very thin and compact, whereas the oxide layer formed at 500 {sup o}C exhibits a non-protective nature, showing an 'oxide sponges' morphology.

  16. Phase evolution and thermal stability of 2 Mg–Cu alloys processed by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Martínez, C., E-mail: carola.martinezu@usach.cl [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile); Ordoñez, S., E-mail: stella.ordonez@usach.cl [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile); Guzmán, D. [Departamento de Ingeniería en Metalurgia, Facultad de Ingeniería, Universidad de Atacama y CRIDESAT, Av. Copayapu 485, Casilla de Correo 240, Copiapó (Chile); Serafini, D. [Departamento de Física, Facultad de Ciencia, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 307, Santiago (Chile); Iturriza, I. [CEIT, Manuel de Lardizábal 15, 20018 San Sebastián, España (Spain); Bustos, O. [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile)

    2013-12-25

    Highlights: •Study of phase evolution of elemental powders Mg and Cu by mechanical alloying. •The presence of an amorphous precursor which crystallizes to Mg{sub 2}Cu can be observed. •Establishing the sequence of phase transformations leading to the formation of Mg{sub 2}Cu. •The feasibility to obtain Mg{sub 2}Cu by means two possible routes has been established. -- Abstract: Phase evolution during mechanical alloying (MA) of elemental Mg and Cu powders and their subsequent heat treatment is studied. Elemental Mg and Cu powders in a 2:1 atomic ratio were mechanically alloyed in a SPEX 8000D mill using a 10:1 ball-to-powder ratio. X-ray diffraction (XRD) shows that the formation of the intermetallic Mg{sub 2}Cu takes place between 3 and 4 h of milling, although traces of elemental Cu are still present after 10 h of milling. The thermal behavior of different powder mixtures was evaluated by differential scanning calorimetry (DSC). The combination of DSC, heat treatment and XRD has shown a sequence of phase transformations that results in the intermetallic Mg{sub 2}Cu from an amorphous precursor. This amorphous phase is converted into Mg{sub 2}Cu by heating at low temperature (407 K). Short MA times and the formation of the amorphous precursor, together with its subsequent transformation into Mg{sub 2}Cu at low temperatures; represent an advantageous alternative route for its preparation.

  17. Processing Map of Powder Metallurgy Al-W Alloys at Elevated Temperatures

    Science.gov (United States)

    Xue, Yong; Du, Yue; Zhang, Zhimin; Huang, Youwang; Guo, Lafeng

    2017-07-01

    An Al-0.71 wt.% W alloy was prepared via powder metallurgy (PM) using a room-temperature pressing process and a subsequent hot-pressing process. Studies of the deformation behavior of the PM Al-W alloy were conducted using hot-compression tests in the temperature range from 420 to 570 °C and a strain rate range from 0.001 to 5 s-1. After the stress-strain data were acquired as a function of temperature and strain rate, processing maps that depict the variation in the power dissipation efficiency were constructed and interpreted via the dynamic materials model. The optimum temperature and strain rate combination for PM billet conditioning were demonstrated to be 560-570 °C and 0.001 s-1, respectively. Additionally, a secondary metal working process with a higher production efficiency on the PM billet was conducted at a higher strain rate from 0.01 to 0.1 s-1 and at a low temperature from 500 to 540 °C. The PM Al-W alloy was successfully extruded at 540 °C with a ram speed of 2 mm min-1 and an extrusion ratio of 5:1. The ultimate tensile strength and elongation of the test sample taken from the 15-mm-diameter as-extruded rods were 478 MPa and 15.4%, respectively.

  18. Some statistics on intermetallic compounds.

    Science.gov (United States)

    Dshemuchadse, Julia; Steurer, Walter

    2015-02-02

    It is still largely unknown why intermetallic phases show such a large variety of crystal structures, with unit cell sizes varying between 1 and more than 20 000 atoms. The goal of our study was, therefore, to get a general overview of the symmetries, unit cell sizes, stoichiometries, most frequent structure types, and their stability fields based on the Mendeleev numbers as ordering parameters. A total of 20829 structures crystallizing in 2166 structure types have been studied for this purpose. Thereby, the focus was on a subset of 6441 binary intermetallic compounds, which crystallize in 943 structure types.

  19. Diffusion Bonding Behavior and Characterization of Joints Made Between 316L Stainless Steel Alloy and AZ31 Magnesium Alloy

    Science.gov (United States)

    Elthalabawy, Waled Mohamed

    The 316L austenitic stainless steel and AZ31 magnesium alloy have physical and mechanical properties which makes these alloys suitable in a number of high technology based industries such as the aerospace and automotive sectors. However, for these alloys to be used in engineering applications, components must be fabricated and joined successfully. The differences in the physical and metallurgical properties between these two alloys prevents the use of conventional fusion welding processes commonly employed in aerospace and transport industry. Therefore, alternative techniques need to be developed and diffusion bonding technology is a process that has considerable potential to join these two dissimilar alloys. In this research work both solid-state and transient liquid phase (TLP) bonding processes were applied. The solid-state bonding of 316L steel to AZ31 magnesium alloy was possible at a bonding temperature of 550°C for 120 minutes using a pressure of 1.3 MPa. The interface characterization of the joint showed a thin intermetallic zone rich in Fe-Al was responsible for providing a metallurgical bond. However, low joint shear strengths were recorded and this was attributed to the poor surface to surface contact. The macro-deformation of the AZ31 alloy prevented the use of higher bonding pressures and longer bonding times. In order to overcome these problems, the TLP bonding process was implemented using pure Cu and Ni foils as interlayers which produced a eutectic phase at the bonding temperature. This research identified the bonding mechanism through microstructural and differential scanning calorimetry investigations. The microstructural characterization of the TLP joints identified intermetallics which became concentrated along the 316L steel/AZ31 bond interface due to the "pushing effect" of the solid/liquid interface during isothermal solidification stage of bonding. The size and concentration of the intermetallics had a noticeable effect on the final joint

  20. Friction welding of intermetallic titanium aluminides. Microstructural evolution and mechanical properties; Reibschweissen von intermetallischen Titanaluminiden. Gefuegeentwicklung und mechanische Eigenschaften

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Svea; Clemens, Helmut [Montanuniv. Leoben (Austria). Dept. Metallkunde und Werkstoffpruefung; Appel, Ludwig; Cramer, Heidi [GSI mbH, Muenchen (Germany). Niederlassung Schweisstechnische Lehr- und Versuchsanstalt SLV

    2011-07-01

    Intermetallic titanium aluminides have the potential to replace currently used nickel-based superalloys in high temperature applications in the medium term owing to their attractive properties profile. They will mainly be used for aircraft and automobile engines. The production of individual components of aircraft or automobile engines requires an easily applicable and reliable joining technology in order to produce complex component structures as a consequence of costs incurred for machining them from solid. Friction welding plays a key role when it comes to an economical use of titanium aluminide materials in lightweight constructions and high temperature applications. The present work describes this pressure welding technique using an extruded {gamma}-TiAl-based alloy Ti-43.5Al-4Nb-1Mo-0.1B (at%). It compares and discusses the microstructural evolution and mechanical properties of joints of the same kind. (orig.)

  1. Effect of heat-treatment on phase transition temperatures of a superelastic NiTi alloy for medical use

    Energy Technology Data Exchange (ETDEWEB)

    Yeung, K.W.K.; Cheung, K.M.C.; Lu, W.W.; Luk, K.D.K. [Univ. of Hong Kong (China). Dept. of Orthopaedic Surgery; Chung, C.Y. [City Univ. of Hong Kong, Kowloon (China). Dept. of Physics and Materials Science

    2002-07-01

    Surgical correction of scoliosis typically uses stainless steel or titanium alloy spinal instrumentation to straighten the scoliotic spine by 70% only. Our aim is to develop a method to overcome this by using an implantable superelastic (SE) nickel-titanium (NiTi) alloy rod, which will impose a continuous gradual correction force to the spine after the surgery so as to achieve a superior correction. More than 75 specimens made of a Ti-50.0 at% Ni alloy were treated by different heat treatment routes. The Austenitic transition temperature of the NiTi alloy can be adjusted to be available at 37.5 C by altering the heat treatment parameters: time and temperature of heat treatment. The experimental results showed that the heat treatment temperature should set between 400-500 C and the heat treatment time should be less than 60 minutes for the alloy. (orig.)

  2. Influence of Sc on Microstructure and Mechanical Properties of High Zn-Containing Mg Alloy

    Directory of Open Access Journals (Sweden)

    Lidong Wang

    2014-01-01

    Full Text Available Microstructures and mechanical properties of Mg-11Zn and Mg-11Zn-1Sc (wt% alloys were investigated. The main secondary phase of Mg-11Zn and Mg-11Zn-1Sc alloys is MgZn2 phase. Rare earth Sc element is an effective grain refiner and the grain size of Mg-11Zn-1Sc alloy is greatly refined. The mechanical properties of the Mg-11Zn alloy were greatly improved with incorporation of 1 wt% Sc, especially for the elevated temperature strength. Such mechanical property enhancement is ascribed to the refinement and pinning mechanism of high heat-resistant Sc and Sc-containing intermetallic particles in Mg alloy.

  3. Competing mechanisms for ordering tendencies in BCC CuAuZn{sub 2} and FCC AuFe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.D.; Althoff, J.D. [Sandia National Labs., Livermore, CA (United States); Staunton, J.B.; Ling, M.F. [Warwick Univ., Coventry (United Kingdom). Dept. of Physics; Pinski, F.J. [Cincinnati Univ, OH (United States). Dept. of Physics

    1995-07-01

    We have briefly discussed the ASRO (atomic short-range order) in AuFe and CuAuZn{sub 2}. General points are that (1) we have implemented a first-principles theory of ASRO in N-component alloys which allows determination of the electronic origins of said ASRO; (2) such calculations can provide much information on the high- and (sometimes) low-temperature alloys; and (3) this approach has identified the origin for the novel special-point ASRO in AuFe. Displacement effects, i.e., non-rigid lattice effects, as well as the other contributions beyond band-energy, are being incorporated into the multicomponent alloy calculations. Such improvements will allow us to investigate other alloys, where charge effects may play a role, to ``design`, for example, higher temperature intermetallics through alloying.

  4. Adiabatic Shear Localization and Microstructure in Ultrafine Grained Aluminum Alloy at Cryogenic Temperature

    Science.gov (United States)

    Ma, Rui; Wang, Bingfeng; Zhang, Xiaoyong; Zhou, Bingqing

    2018-01-01

    Adiabatic shear localization plays an important role in the deformation and failure of ultrafine grained 6061 aluminum alloy processed by friction stir processing. To understand the effects of temperature and strain on adiabatic shear localization in the ultrafine grained 6061 aluminum alloy, it has been investigated dynamic mechanical behavior of ultrafine grained 6061 aluminum alloy under the controlled shock loading experiments. Deformation characteristics and microstructures in the shear band were performed by optical microscopy and transmission electron microscopy. The shear band in the ultrafine grained aluminum alloy is a long and straight band distinguished from the matrix. The width of the shear band decreases with increasing nominal strain. The results show that the grains in the boundary of the shear band are highly elongated along the shear direction and form the elongated cell structures (0.2 μ in width), and the core of the shear band consists of a number of recrystallized equiaxed grains 0.2-0.3 μ in diameters and the second phases distribute in both the boundary and the inner of the equiaxed new grains. The calculated temperature in the shear band is about 692 K. Rotational dynamic recrystallization mechanism is responsible for the formation of the microstructure in the shear band.

  5. A Research Status on High-Temperature Creep of Alloy 617 for Use in VHTR System

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Gon; Park, Jae-Young; Kim, Eung-Seon; Kim, Yong-Wan; Kim, Min-Hwan [KAERI, Daejeon (Korea, Republic of); Kim, Seon-Jin [Pukyong National Univ., Busan (Korea, Republic of)

    2016-05-15

    In this study, a research status on creep works of Alloy 617 conducting at KAERI was introduced and summarized. Various experimental creep data and creep constants obtained in the air/helium environments and base/weld metals were presented and discussed using various creep equations and parameters. The draft Code Case is a modification from ASME Section III Subsection NH that was put forth by a special task force of the ASME subgroup that deals with elevated temperature design. The primary intended application of the draft Code Case is a VHTR. Presently, various creep data for Alloy 617 are being accumulated through Generation-IV forum (GIF) Material Handbook Database of a next-generation nuclear plant research and development. As per this, a new Alloy 617 Code Case is planned to be approved by 2017. However, to do so, various creep data and creep constants in air/helium environments, and base/weld metals etc. should be obtained to help draft the new Code Case, and creep behavior should be investigated through systematic analysis of a wide range of creep temperature and stress conditions. Using various creep equations and parameters, the creep constants were determined for design use of Alloy 617. The stress of the He environment was more reduced than that of the air one. As the stress increases, the creep rate of WM was significantly lower than that of BM. The reason for this was that the rupture elongation of WM was largely reduced compared with that of BM.

  6. Aluminum-Silicon Alloy Having Improved Properties at Elevated Temperatures and Articles Cast Therefrom

    Science.gov (United States)

    Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

    2002-01-01

    An aluminum alloy suitable for high temperature applications, such as heavy duty pistons and other internal combustion applications. having the following composition, by weight percent (wt %): Silicon: 11.0-14.0; Copper: 5.6-8.0; Iron: 0-0.8; Magnesium: 0.5-1.5; Nickel: 0.05-0.9; Manganese: 0.5-1.5; Titanium: 0.05-1.2; Zirconium: 0.12-1.2; Vanadium: 0.05-1.2; Zinc: 0.005-0.9; Strontium: 0.001-0.1; Aluminum: balance. In this alloy the ratio of silicon:magnesium is 10-25, and the ratio of copper:magnesium is 4-15. After an article is cast from this alloy, the article is treated in a solutionizing step which dissolves unwanted precipitates and reduces any segregation present in the original alloy. After this solutionizing step, the article is quenched, and is then aged at an elevated temperature for maximum strength.

  7. Synthesis and characterization of Ni–Cu alloy nanoparticles with a tunable Curie temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ferk, Gregor [Faculty of Chemistry and Chemical Engineering, University of Maribor (Slovenia); Stergar, Janja [Faculty of Medicine, University of Maribor (Slovenia); Makovec, Darko [Department for Materials Synthesis, Jožef Stefan Institute, Ljubljana (Slovenia); Hamler, Anton [Faculty of Electrical Engineering and Computer Science, University of Maribor (Slovenia); Jagličić, Zvonko [Institute of Mathematics, Physics and Mechanics and Faculty of Civil and Geodetic Engineering, University of Ljubljana (Slovenia); Drofenik, Miha [Faculty of Chemistry and Chemical Engineering, University of Maribor (Slovenia); Department for Materials Synthesis, Jožef Stefan Institute, Ljubljana (Slovenia); Ban, Irena [Faculty of Chemistry and Chemical Engineering, University of Maribor (Slovenia); Center of Excellence NAMASTE, Ljubljana (Slovenia)

    2015-11-05

    A series of nickel–copper alloy magnetic nanoparticles with a range of Curie points from 51 °C to 63 °C were prepared by the reduction of intimately mixed nickel and copper oxides in a silica matrix using the sol–gel method. The silica matrix was subsequently removed with an etching solution, assisted by sonication. The alloy nanoparticles were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA/SDTA), thermomagnetic analysis (TMA), transmission electron microscopy (TEM), magnetic measurements (SQUID, vibrating-sample magnetometer) and specific absorption rate measurements (SAR). The synthesized nanoparticles show a size in the range 15–20 nm, exhibited superparamagnetic behavior with a blocking temperature (T{sub B}) of approximately 135 K and a room-temperature magnetization of 3–9 emu/g, depending on the composition. The nanoparticles showed a relatively high effective anisotropy constant (K{sub eff}) and a significant heating ability in an alternating magnetic field. The synthesis method is straightforward and allows the preparation of homogeneous Ni–Cu alloy nanoparticles with a relatively narrow particle size distribution. - Highlights: • Straightforward so-gel synthesis of homogeneous Ni–Cu alloy nanoparticles. • Narrow particle size distribution and controlled Curie point. • Applications in “self-regulating magnetic fluid hyperthermia”. • Heating efficiency of nanoparticles as a function of composition and size.

  8. Temperature-Dependent Nickel Release from Nickel-Alloys

    DEFF Research Database (Denmark)

    Menne, T.; Solgaard, Per Bent

    1979-01-01

    Ni release from Danish 1 krone coins and metal buttons from jeans was measured at 20.degree. C in distilled water and at 35.degree. C in distilled water and synthetic sweat. The temperature elevation increased the Ni release from the coins and 2 of the 9 metal buttons investigated. The sensitivity...

  9. Design of lead-free candidate alloys for high-temperature soldering based on the Au–Sn system

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hattel, Jesper Henri; Hald, John

    2010-01-01

    of the Au–Sn binary system were explored in this work. Furthermore, the effects of thermal aging on the microstructure and microhardness of these promising Au–Sn based ternary alloys were investigated. For this purpose, the candidate alloys were aged at a lower temperature, 150°C for up to 1week...

  10. Effect of REE on the Phase Composition and Properties of a New Refractory Magnesium Alloy of the Mg - Zn - Zr - REE System

    Science.gov (United States)

    Kablov, E. N.; Volkova, E. F.; Filonova, E. V.

    2017-11-01

    A novel high-strength refractory alloy VMD16 of the Mg - Zn - Zr - REE system is described. The advantages of the alloy with respect to the counterparts are considered. The processes of formation of phase composition and of structural evolution are studied. A fine dispersed subgrain structure is shown to exist in the deformable magnesium alloy. The combination of the specific morphology and topology of the intermetallic phases with their thermal stability provides a high level of strength properties at room and elevated (300 - 350°C) temperatures at a low anisotropy.

  11. Impact of temperature and nitrogen composition on the growth of GaAsPN alloys

    Science.gov (United States)

    Yamane, Keisuke; Mugikura, Shun; Tanaka, Shunsuke; Goto, Masaya; Sekiguchi, Hiroto; Okada, Hiroshi; Wakahara, Akihiro

    2018-03-01

    This paper presents the impact of temperature and nitrogen-composition on the growth mode and crystallinity of GaAsPN alloys. Reflection high-energy electron diffraction results combined with transmission electron microscopy analysis revealed that maintaining two-dimensional (2-D) growth required higher temperatures when nitrogen composition increased. Outside the 2-D growth windows, stacking faults and micro-twins were preferentially formed at {1 1 1} B planes rather than at the {1 1 1} A planes and anomalous growth was observed. The photoluminescence spectra of GaAsPN layers implies that the higher temperature growth is effective for reducing the nitrogen-related point defects.

  12. Application of neutron diffraction in characterization of texture evolution during high-temperature creep in magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Sven C [Los Alamos National Laboratory; Sediako, Dimitry [CANADIAN NEUTRON BEAM; Shook, S [APPLIED MAGNESIUM INTERNATIONAL; Sediako, A [MCGILL UNIV

    2010-01-01

    A good combination of room-temperature and elevated temperature strength and ductility, good salt-spray corrosion resistance and exceUent diecastability are frequently among the main considerations in development of a new alloy. Unfortunately, there has been much lesser effort in development of wrought-stock alloys for high temperature applications. Extrudability and high temperature performance of wrought material becomes an important factor in an effort to develop new wrought alloys and processing technologies. This paper shows some results received in creep testing and studies of in-creep texture evolution for several wrought magnesium alloys developed for use in elevated-temperature applications. These studies were performed using E3 neutron spectrometer of the Canadian Neutron Beam Centre in Chalk River, ON, and HIPPO time-of-flight (TOF) spectrometer at Los Alamos Neutron Science Center, NM.

  13. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, Victor Hugo C. de, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Melo, Tadeu Antonio de A, E-mail: tadeu@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Gomes, Rodinei M., E-mail: gomes@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Lima, Severino Jackson G. de, E-mail: jackson@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica (DEMec)/Instituto de Engenharia Mecanica e Gestao Industrial INEGI, Rua Dr. Roberto Frias, S/N 4200-465 Porto (Portugal)

    2010-11-25

    Research highlights: {yields} This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. {yields} The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. {yields} Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. {yields} First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. {yields} The results are of relevant value to enhance the understanding of the CuAlBe alloy. - Abstract: This work is a study of the influence of grain size and temperature on the toughness of CuAlBe shape memory alloys with (CuAlBeNbNi) and without NbNi (CuAlBe) grain refiner elements. The toughness analysis was based on the V-notch Charpy impact test under temperatures of -150, -100, -50, 0, 50, 100 and 150 deg. C. A statistical analysis of the results led to the conclusion that the toughness of both alloys was influenced by temperature and grain size. The CuAlBeNbNi alloy absorbed higher impact energy than the CuAlBe alloy showing that the refining elements improved the toughness of the alloy. To confirm and complement these findings, the fracture surfaces were evaluated by stereomicroscopy. Smooth homogeneous surfaces and rough heterogonous surfaces were detected for the CuAlBeNbNi and CuAlBe alloys, respectively. Predominately brittle zones were confirmed by scanning electron microscopy in both alloys. Furthermore, to determine the phase transformation temperatures and the associated microstructures, the alloys were assessed by conventional differential scanning calorimetry (DSC) and DSC with optical microscopy.

  14. Orthodontic silver brazing alloys.

    Science.gov (United States)

    Brockhurst, P J; Pham, H L

    1989-10-01

    Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy.

  15. Radiation Tolerance of Controlled Fusion Welds in High Temperature Oxidation Resistant FeCrAl Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gussev, Maxim N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Field, Kevin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    High temperature oxidation resistant iron-chromium-aluminum (FeCrAl) alloys are candidate alloys for nuclear applications due to their exceptional performance during off-normal conditions such as a loss-of-coolant accident (LOCA) compared to currently deployed zirconium-based claddings [1]. A series of studies have been completed to determine the weldability of the FeCrAl alloy class and investigate the weldment performance in the as-received (non-irradiated) state [2,3]. These initial studies have shown the general effects of composition and microstructure on the weldability of FeCrAl alloys. Given this, limited details on the radiation tolerance of FeCrAl alloys and their weldments exist. Here, the highest priority candidate FeCrAl alloys and their weldments have been investigated after irradiation to enable a better understanding of FeCrAl alloy weldment performance within a high-intensity neutron field. The alloys examined include C35M (Fe-13%Cr-5% Al) and variants with aluminum (+2%) or titanium carbide (+1%) additions. Two different sub-sized tensile geometries, SS-J type and SS-2E (or SS-mini), were neutron irradiated in the High Flux Isotope Reactor to 1.8-1.9 displacements per atom (dpa) in the temperature range of 195°C to 559°C. Post irradiation examination of the candidate alloys was completed and included uniaxial tensile tests coupled with digital image correlation (DIC), scanning electron microscopy-electron back scattered diffraction analysis (SEM-EBSD), and SEM-based fractography. In addition to weldment testing, non-welded parent material was examined as a direct comparison between welded and non-welded specimen performance. Both welded and non-welded specimens showed a high degree of radiation-induced hardening near irradiation temperatures of 200°C, moderate radiation-induced hardening near temperatures of 360°C, and almost no radiation-induced hardening at elevated temperatures near 550°C. Additionally, low-temperature irradiations showed

  16. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    Science.gov (United States)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  17. Effect Of Low-Temperature Annealing On The Properties Of Ni-P Amorphous Alloys Deposited Via Electroless Plating

    Directory of Open Access Journals (Sweden)

    Zhao Guanlin

    2015-06-01

    Full Text Available Amorphous Ni-P alloys were prepared via electroless plating and annealing at 200°C at different times to obtain different microstructures. The effects of low-temperature annealing on the properties of amorphous Ni-P alloys were studied. The local atomic structure of the annealed amorphous Ni-P alloys was analyzed by calculating the atomic pair distribution function from their X-ray diffraction patterns. The results indicate that the properties of the annealed amorphous Ni-P alloys are closely related to the order atomic cluster size. However, these annealed Ni-P alloys maintained their amorphous structure at different annealing times. The variation in microhardness is in agreement with the change in cluster size. By contrast, the corrosion resistance of the annealed alloys in 3.5 wt% NaCl solution increases with the decrease in order cluster size.

  18. Formation of GeSn alloy on Si(100) by low-temperature molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Talochkin, A. B., E-mail: tal@isp.nsc.ru [A. V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Mashanov, V. I. [A. V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation)

    2014-12-29

    GeSn alloys grown on Si(100) by the low-temperature (100 °C) molecular beam epitaxy are studied using scanning tunneling microscopy and Raman spectroscopy. It is found that the effect of Sn as a surfactant modifies substantially the low-temperature growth mechanism of Ge on Si. Instead of the formation of small Ge islands surrounded by amorphous Ge, in the presence of Sn, the growth of pure Ge islands appears via the Stranski-Krastanov growth mode, and a partially relaxed Ge{sub 1−x}Sn{sub x} alloy layer with the high Sn-fraction up to 40 at. % is formed in the area between them. It is shown that the observed growth mode induced by high surface mobility of Sn and the large strain of the pseudomorphic state of Ge to Si ensures the minimum elastic-strain energy of the structure.

  19. MODELING HIGH TEMPERATURE FLOW BEHAVIOR OF AN AL 6061 ALUMINIUM ALLOY

    Directory of Open Access Journals (Sweden)

    E. Badami

    2014-12-01

    Full Text Available Hot deformation behavior of a medium Cr/Mn Al6061 aluminum alloy was studied by isothermal compression test at temperatures range of 320 to 480 °C and strain rates range of 0.001 to 0.1 s −1. The true stresstrue strain curves were analyzed to characterize the flow stress of Al6061. Plastic behavior, as a function of both temperature and strain rate for Al6061, was also modeled using a hyperbolic sinusoidal type equation. For different values of material constant α in the range of 0.001 to 0.4, values of A, n and Q were calculated based on mathematical relationships. The best data fit with minimum error was applied to define constitutive equation for the alloy. The predicted results of the proposed model were found to be in reasonable agreement with the experimental results, which could be used to predict the required deformation forces in hot deformation processes

  20. Literature Survey on the Stress Corrosion Cracking of Low-Alloy Steels in High Temperature Water

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.P

    2002-02-01

    The present report is a summary of a literature survey on the stress corrosion cracking (SCC) behaviour/ mechanisms in low-alloy steels (LAS) in high-temperature water with special emphasis to primary-pressure-boundary components of boiling water reactors (BWR). A brief overview on the current state of knowledge concerning SCC of low-alloy reactor pressure vessel and piping steels under BWR conditions is given. After a short introduction on general aspects of SCC, the main influence parameter and available quantitative literature data concerning SCC of LAS in high-temperature water are discussed on a phenomenological basis followed by a summary of the most popular SCC models for this corrosion system. The BWR operating experience and service cracking incidents are discussed with respect to the existing laboratory data and background knowledge. Finally, the most important open questions and topics for further experimental investigations are outlined. (author)

  1. Lithium based alloy-thionyl chloride cells for applications at temperatures to 200 C

    Science.gov (United States)

    Kane, P.; Marincic, N.; Epstein, J.; Lindsey, A.

    A long-life lithium battery for industrial applications at temperatures up to 200 C was developed by combining Li-based alloy anodes with oxyhalide electrolytes. Cathodes were fabricated by rolling the blend of polycarbonomonofluoride, a conductive carbon additive, and a binder, while anodes were fabricated as those used in oxyhalide cells, incorporating a modified anode current collector designed to prevent the formation of 'lithium islands' at the end of discharge; nonwoven glass fiber separators were pretreated to remove excessive binders and lubricants. Various active electrode surface areas were combined with a corresponding thickness of electrodes and separators, matched in capacity. Tests of the high-rate electrode structure, using Li-Mg alloy anode in conjunction with thionyl chloride electrolyte, have demonstrated that the battery with this anode can be used under abusive conditions such as short circuit and external heating (at 175 C). Raising the operating temperature to 200 C did require some modifications of regular cell hardware.

  2. High strain rate behavior of alloy 800H at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Shafiei, E., E-mail: shafiei.ehsan.mse@gmail.com

    2016-05-15

    In this paper, a new model using linear estimation of strain hardening rate vs. stress, has been developed to predict dynamic behavior of alloy 800H at high temperatures. In order to prove the accuracy and competency of the presented model, Johnson–Cook model pertaining modeling of flow stress curves was used. Evaluation of mean error of flow stress at deformation temperatures from 850 °C to 1050 °C and at strain rates of 5 S{sup −1} to 20 S{sup −1} indicates that the predicted results are in a good agreement with experimentally measured ones. This analysis has been done for the stress–strain curves under hot working condition for alloy 800H. However, this model is not dependent on the type of material and can be extended for any similar conditions.

  3. High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lulu, E-mail: lli18@ncsu.edu; Saber, Mostafa; Xu, Weizong; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

    2014-09-08

    The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.

  4. Modeling of anisotropic and asymmetric behaviour of magnesium alloys at elevated temperature coupled with ductile damage

    Science.gov (United States)

    Zhang, K.; Badreddine, H.; Labergere, C.; Saanouni, K.

    2017-09-01

    Poor formability of Magnesium alloys at room temperature is due to their Hexagonal Closed Packed (HCP) crystal structure. These materials also have a pronounced Strength Differential (SD) effect. In the present work, an improved constitutive model of thermo-elasto-Dviscoplasticity with mixed nonlinear isotropic and kinematic hardening strongly coupled with isotropic ductile damage is developed. The induced anisotropy as well as tension compression asymmetry are carefully considered including their interaction with thermal effects. The numerical implementation of the developed model into ABAQUS/Explicit FE is made through the user subroutine VUMAT. The proposed model is used to simulate material responses of AZ31 Magnesium alloy during sheet metal forming processes at elevated temperature.

  5. The Temperature Effect on the Compressive Behavior of Closed-Cell Aluminum-Alloy Foams

    Science.gov (United States)

    Movahedi, Nima; Linul, Emanoil; Marsavina, Liviu

    2018-01-01

    In this research, the mechanical behavior of closed-cell aluminum (Al)-alloy foams was investigated at different temperatures in the range of 25-450 °C. The main mechanical properties of porous Al-alloy foams are affected by the testing temperature, and they decrease with the increase in the temperature during uniaxial compression. From both the constant/serrated character of stress-strain curves and macro/microstructural morphology of deformed cellular structure, it was found that Al foams present a transition temperature from brittle to ductile behavior around 192 °C. Due to the softening of the cellular structure at higher temperatures, linear correlations of the stress amplitude and that of the absorbed energy with the temperature were proposed. Also, it was observed that the presence of inherent defects like micropores in the foam cell walls induced further local stress concentration which weakens the cellular structure's strength and crack propagation and cell-wall plastic deformation are the dominant collapse mechanisms. Finally, an energy absorption study was performed and an optimum temperature was proposed.

  6. The Role of Surface Protection for High-Temperature Performance of TiAl Alloys

    Science.gov (United States)

    Schütze, Michael

    2017-09-01

    In the temperature range where TiAl alloys are currently being used in jet engine and automotive industries, surface reaction with the operating environment is not yet a critical issue. Surface treatment may, however, be needed in order to provide improved abrasion resistance. Development routes currently aim at a further increase in operation temperatures in gas turbines up to 800°C and higher, and in automotive applications for turbocharger rotors, even up to 1050°C. In this case, oxidation rates may reach levels where significant metal consumption of the load-bearing cross-section can occur. Another possibly even more critical issue can be high-temperature-induced oxygen and nitrogen up-take into the metal subsurface zone with subsequent massive ambient temperature embrittlement. Solutions for these problems are based on a deliberate phase change of the metal subsurface zone by diffusion treatments and by using effects such as the halogen effect to change the oxidation mechanism at high temperatures. Other topics of relevance for the use of TiAl alloys in high-temperature applications can be high-temperature abrasion resistance, thermal barrier coatings on TiAl and surface quality in additive manufacturing, in all these cases-focusing on the role of the operation environment. This paper addresses the recent developments in these areas and the requirements for future work.

  7. The Temperature Effect on the Compressive Behavior of Closed-Cell Aluminum-Alloy Foams

    Science.gov (United States)

    Movahedi, Nima; Linul, Emanoil; Marsavina, Liviu

    2017-12-01

    In this research, the mechanical behavior of closed-cell aluminum (Al)-alloy foams was investigated at different temperatures in the range of 25-450 °C. The main mechanical properties of porous Al-alloy foams are affected by the testing temperature, and they decrease with the increase in the temperature during uniaxial compression. From both the constant/serrated character of stress-strain curves and macro/microstructural morphology of deformed cellular structure, it was found that Al foams present a transition temperature from brittle to ductile behavior around 192 °C. Due to the softening of the cellular structure at higher temperatures, linear correlations of the stress amplitude and that of the absorbed energy with the temperature were proposed. Also, it was observed that the presence of inherent defects like micropores in the foam cell walls induced further local stress concentration which weakens the cellular structure's strength and crack propagation and cell-wall plastic deformation are the dominant collapse mechanisms. Finally, an energy absorption study was performed and an optimum temperature was proposed.

  8. The Role of Surface Protection for High-Temperature Performance of TiAl Alloys

    Science.gov (United States)

    Schütze, Michael

    2017-12-01

    In the temperature range where TiAl alloys are currently being used in jet engine and automotive industries, surface reaction with the operating environment is not yet a critical issue. Surface treatment may, however, be needed in order to provide improved abrasion resistance. Development routes currently aim at a further increase in operation temperatures in gas turbines up to 800°C and higher, and in automotive applications for turbocharger rotors, even up to 1050°C. In this case, oxidation rates may reach levels where significant metal consumption of the load-bearing cross-section can occur. Another possibly even more critical issue can be high-temperature-induced oxygen and nitrogen up-take into the metal subsurface zone with subsequent massive ambient temperature embrittlement. Solutions for these problems are based on a deliberate phase change of the metal subsurface zone by diffusion treatments and by using effects such as the halogen effect to change the oxidation mechanism at high temperatures. Other topics of relevance for the use of TiAl alloys in high-temperature applications can be high-temperature abrasion resistance, thermal barrier coatings on TiAl and surface quality in additive manufacturing, in all these cases-focusing on the role of the operation environment. This paper addresses the recent developments in these areas and the requirements for future work.

  9. Strain rate and temperature effects on crack initiation of direct aged 718 Alloy

    OpenAIRE

    Perrais Maxime; Burteau Anthony; Seror Alexandre; Poquillon Dominique; Andrieu Eric

    2014-01-01

    During mechanical tests at high temperature in an oxidizing atmosphere, the effects of strain rate on crack initiation are noticeable. This effect is due to a coupling between local mechanical loading and oxidation. Samples were machined in a turbine disk made of direct aged alloy 718. Tests were performed to understand the effect of these couplings on crack initiation and to ensure lifetime is optimized. This study compared the cracking resistance of two different specimen geometries at a gi...

  10. New features of the low temperature ductile shear failure observed in bulk amorphous alloys

    NARCIS (Netherlands)

    Bengus, VZ; Tabachnikova, ED; Miskuf, J; Csach, K; Johnson, WL; Molokanov, VV; Ocelik, Vaclav

    2000-01-01

    Fractographic studies of ductile shear failure under the uniaxial compression for rod-like samples of the Zr(41.2)Ti(13.8)Ni(10)Cu(12.5)Be(22.5) and Cu(50)Zr(35)Ti(8)Hf(5)Ni(2) bulk amorphous alloys at temperatures 300 and 77 K are presented. The mechanisms of shear deformation and failure appeared

  11. Analyses of heterogeneous deformation and subsurface fatigue crack generation in alpha titanium alloy at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Umezawa, Osamu [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501 (Japan); Morita, Motoaki [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533 (Japan); Yuasa, Takayuki [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Nippon Steel and Sumitomo Metal, Kashima, 314-0014 (Japan); Morooka, Satoshi [Department of Mechanical Engineering and Materials Science, Yokohama National University 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan and Now Tokyo Metropolitan University, Hino, Tokyo 191-0065 (Japan); Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047 (Japan)

    2014-01-27

    Subsurface crack initiation in high-cycle fatigue has been detected as (0001) transgranular facet in titanium alloys at low temperature. The discussion on the subsurface crack generation was reviewed. Analyses by neutron diffraction and full constraints model under tension mode as well as crystallographic identification of the facet were focused. The accumulated tensile stress along <0001> may be responsible to initial microcracking on (0001) and the crack opening.

  12. Temperature-dependent viscosities of eutectic Al-Si alloys modified with Sr and P

    Energy Technology Data Exchange (ETDEWEB)

    Song Xigui [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China)], E-mail: sxglm@126.com; Bian Xiufang; Zhang Jingxiang; Zhang Jie [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan, 250061 (China)

    2009-06-24

    The viscosities of eutectic Al-12 wt.%Si alloy and those modified with Sr and P were investigated using high-temperature torsional oscillation viscometer. Strontium decreased melt's viscosity, while phosphorus increased viscosity. Both additional level and means of addition affected the variation of viscosity. The activation energy of viscous flow was strengthened after modification, but the influence of modification on the molar volume was perplexing.

  13. Structure and mechanical properties of Fe–Ni–Zr oxide-dispersion-strengthened (ODS) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Darling, K.A., E-mail: Kristopher.darling.civ@mail.mil [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, MD 21005-5069 (United States); Kapoor, M. [The University of Alabama, Department of Metallurgical & Materials Engineering Tuscaloosa, AL 35487-0202 (United States); Kotan, H. [Necmettin Erbakan University, Department of Metallurgical & Materials Engineering, Konya, 42090 (Turkey); Hornbuckle, B.C.; Walck, S.D. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, MD 21005-5069 (United States); Thompson, G.B. [The University of Alabama, Department of Metallurgical & Materials Engineering Tuscaloosa, AL 35487-0202 (United States); Tschopp, M.A.; Kecskes, L.J. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, MD 21005-5069 (United States)

    2015-12-15

    A series of bulk nanostructured Fe–Ni–Zr oxide-dispersion-strengthened (ODS) alloys were synthesized using high energy mechanical alloying and consolidated using high temperature equal channel angular extrusion. The resultant microstructures are composed of nano/ultrafine or micrometer-sized grains with larger intermetallic precipitates and small Zr oxide clusters (<10 nm diameter, measured and confirmed by atom probe tomography). The ODS alloys possess elevated compression properties, e.g., 1.2 and 2.4 GPa compressive yield stress at room temperature for samples consolidated at 700 °C and 1000 °C, respectively. This work highlights the relationship between processing, microstructure, and properties for this class of ferritic ODS alloys.

  14. Brazing composite intermetallic TiAl with structural materials

    Energy Technology Data Exchange (ETDEWEB)

    Sevryukov, O.N.; Fedotov, V.T.; Kalin, B.A.; Golikov, M.Y. [MIFI-AMENTO, Moscow (Russian Federation)

    2007-07-01

    The intermetallic alloys based on a titanium aluminide have a high strength, a low specific weight, and a chemical and thermal stability. Owing to a similar combination of physical and chemical properties, the given type of materials can be considered as an alternative to the traditional materials used for the manufacture of units of the thermonuclear reactor first wall. The technology to manufacture samples of composite alloys based on a titanium aluminide intermetallide has been improved in the present work with subsequent tests of brazed joints by thermo cycling tests. To estimate the possibility of using this intermetallic alloy as a structural material, brazed joints of Ti-48at.%Al with bronze and titanium were produced. Brazing was carried out by the STEMET 1202 registered filler metal of the Ti-Cu-Zr-Ni-V-Be system. The distribution of chemical elements in the brazed seam was investigated by X-ray spectrum analysis. It has been found that the distribution of the main and doping elements is sufficiently uniform in the contact zone of the filler metal with brazed materials; inclusions, cracks, and delamination are absent. (orig.)

  15. Study of the high-temperature corrosion of heat-resisting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wada, K.

    1986-01-01

    An experimental study is reported of the corrosion resistance of the heat-resistant materials which play such an important role in the development of high-efficiency coal gasification combined-cycle power generation. Specifically, a study was made of the high-temperature and molten salt corrosion of nickel base alloys in coal combustion gas environments. The authors outline various types of high-temperature corrosion which occur: oxidation, sulfidation, decarburization and carburizing, nitridation, hot corrosion and halogenation. The mechanisms involved in molten salt corrosion are explained with reference to various models and currently available data. Finally, a study of electro-chemical measuring methods is reported. The authors conclude that future work on corrosion in coal gasification combined cycle power generation systems should concentrate on the following items: 1) elucidating the conditions under which molten salts form; 2) developing methods for predicting the quantity of molten salts which will form, and for assessing their contribution to corrosion; 3) evaluating the corrosion resistance of specific alloys to molten salts of given composition; 4) clarifying the effect of alloy surface temperature on corrosion resistance and local corrosion; and 5) developing techniques for predicting the amount of corrosion. 24 references, 28 figures, 7 tables.

  16. GRCop-84: A High Temperature Copper-based Alloy For High Heat Flux Applications

    Science.gov (United States)

    Ellis, David L.

    2005-01-01

    While designed for rocket engine main combustion chamber liners, GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) offers potential for high heat flux applications in industrial applications requiring a temperature capability up to approximately 700 C (1292 F). GRCop-84 is a copper-based alloy with excellent elevated temperature strength, good creep resistance, long LCF lives and enhanced oxidation resistance. It also has a lower thermal expansion than copper and many other low alloy copper-based alloys. GRCop-84 can be manufactured into a variety of shapes such as tubing, bar, plate and sheet using standard production techniques and requires no special production techniques. GRCop-84 forms well, so conventional fabrication methods including stamping and bending can be used. GRCop-84 has demonstrated an ability to be friction stir welded, brazed, inertia welded, diffusion bonded and electron beam welded for joining to itself and other materials. Potential applications include plastic injection molds, resistance welding electrodes and holders, permanent metal casting molds, vacuum plasma spray nozzles and high temperature heat exchanger applications.

  17. Kinetics of passivation of a nickel-base alloy in high temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Machet, A. [Laboratoire de Physico-Chimie des Surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Universite Pierre et Marie Curie, F-75231 Paris cedex 05 (France)]|[Framatome ANP, Tour AREVA, F-92084 Paris-la-Defense (France); Galtayries, A.; Zanna, S.; Marcus, P. [Laboratoire de Physico-Chimie des Surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Universite Pierre et Marie Curie, F-75231 Paris cedex 05 (France); Jolivet, P.; Scott, P. [Framatome ANP, Tour AREVA, F-92084 Paris-la-Defense (France); Foucault, M.; Combrade, P. [Framatome ANP, Centre Technique, F-71205 Le Creusot (France)

    2004-07-01

    The kinetics of passivation and the composition of the surface oxide layer, in high temperature and high pressure water, of a nickel-chromium-iron alloy (Alloy 600) have been investigated by X-ray Photoelectron Spectroscopy (XPS). The samples have been exposed for short (0.4 - 8.2 min) and longer (0 - 400 hours) time periods to high temperature (325 deg. C) and high pressure water (containing boron and lithium) under controlled hydrogen pressure. The experiments were performed in two types of autoclaves: a novel autoclave dedicated to short time periods and a classic static autoclave for the longer exposures. In the initial stage of passivation, a continuous ultra-thin layer of chromium oxide (Cr{sub 2}O{sub 3}) is rapidly formed on the surface with an external layer of chromium hydroxide. For longer times of passivation, the oxide layer is in a duplex form with an internal chromium oxide layer and an external layer of nickel hydroxide. The growth of the internal Cr{sub 2}O{sub 3} oxide layer has been fitted by three classical models (parabolic, logarithmic and inverse logarithmic laws) for the short passivation times, and the growth curves have been extrapolated to longer passivation periods. The comparison with the experimental results reveals that the kinetics of passivation of Alloy 600 in high temperature and high pressure water, for passivation times up to 400 hours, is well fitted by a logarithmic growth law. (authors)

  18. Using the PSCPCSP computer software for optimization of the composition of industrial alloys and development of new high-temperature nickel-base alloys

    Science.gov (United States)

    Rtishchev, V. V.

    1995-11-01

    Using computer programs some foreign firms have developed new deformable and castable high-temperature nickel-base alloys such as IN, Rene, Mar-M, Udimet, TRW, TM, TMS, TUT, with equiaxial, columnar, and single-crystal structures for manufacturing functional and nozzle blades and other parts of the hot duct of transport and stationary gas-turbine installations (GTI). Similar investigations have been carried out in Russia. This paper presents examples of the use of the PSCPCSP computer software for a quantitative analysis of structural und phase characteristics and properties of industrial alloys with change (within the grade range) in the concentrations of the alloying elements for optimizing the composition of the alloys and regimes of their heat treatment.

  19. Microstructure and mechanical properties of a novel rapidly solidified, high-temperature Al-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Overman, N.R., E-mail: Nicole.Overman@pnnl.gov [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); Mathaudhu, S.N. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); University of California, Riverside, 3401 Watkins Dr., Riverside, CA 92521 (United States); Choi, J.P.; Roosendaal, T.J.; Pitman, S. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)

    2016-02-15

    Rapid solidification (RS) processing, as a production method, offers a variety of unique properties based on far-from-equilibrium microstructures obtained through rapid cooling rates. In this study, we seek to investigate the microstructures and properties of a novel Al-alloy specifically designed for high temperature mechanical stability. Synthesis of, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} (wt.%), was performed by two approaches: rotating cup atomization (“shot”) and melt spinning (“flake”). These methods were chosen because of their ability to produce alloys with tailored microstructures due to their inherent differences in cooling rate. The as-solidified precursor materials were microstructurally characterized with electron microscopy. The results show that the higher cooling rate flake material exhibited the formation of nanocrystalline regions as well additional phase morphologies not seen in the shot material. Secondary dendritic branching in the flake material was on the order of 0.1–0.25 μm whereas branching in the shot material was 0.5–1.0 μm. Consolidated and extruded material from both precursor materials was mechanically evaluated at both ambient and high (300 °C) temperature. The consolidated RS flake material is shown to exhibit higher strengths than the shot material. The ultimate tensile strength of the melt spun flake was reported as 544.2 MPa at room temperature and 298.0 MPa at 300 °C. These results forecast the ability to design alloys and processing approaches with unique non-equilibrium microstructures with robust mechanical properties at elevated temperatures. - Highlights: • A novel alloy, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} was fabricated by rapid solidification. • Room temperature yield strength exceeded 500 MPa. • Elevated temperature (300 °C) yield strength exceeded 275 MPa. • Forging, after extrusion of the alloy resulted in microstructural coarsening. • Decreased strength and ductility was

  20. Theoretical energy release of thermites, intermetallics, and combustible metals

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, S.H.; Grubelich, M.C.

    1998-06-01

    Thermite (metal oxide) mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability, and possess insensitive ignition properties. In this paper, the authors review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

  1. Temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys

    Science.gov (United States)

    Touraghe, O.; Khatami, M.; Menny, A.; Lassri, H.; Nouneh, K.

    2008-06-01

    The temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum Tmin. In addition, the resistivity shows quadratic temperature behavior in the interval Tmin< T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity α shows a change in structural short range occurring in the composition range 8-9 at%.

  2. Studies of hydrogen absorption and desorption processes in advanced intermetallic hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Masashi

    2005-07-01

    This work is a part of the research program performed in the Department of Energy Systems, Institute for Energy Technology (Kjeller, Norway), which is focused on the development of the advanced hydrogen storage materials. The activities are aimed on studies of the mechanisms of hydrogen interactions with intermetallic alloys with focus on establishing an interrelation between the crystal structure, thermodynamics and kinetics of the processes in the metal-hydrogen systems, on the one hand, and hydrogen storage properties (capacity, rates of desorption, hysteresis). Many of the materials under investigation have potential to be applied in applications, whereas some already have been commercialised in the world market. A number of metals take up considerable amounts of hydrogen and form chemical compounds with H, metal hydrides. Unfortunately, binary hydrides are either very stable (e.g. for the rare earth metals [RE], Zr, Ti, Mg: metal R) or are formed at very high applied pressures of hydrogen gas (e.g. for the transition metals, Ni, Co, Fe, etc.: Metal T). However, hydrogenation process becomes easily reversible at very convenient from practical point of view conditions, around room temperature and at H2 pressures below 1 MPa for the two-component intermetallic alloys R{sub x}T{sub y}. This raised and maintains further interest to the intermetallic hydrides as solid H storage materials. Materials science research of this thesis is focused on studies of the reasons staying behind the beneficial effect of two non-transition elements M(i.e., In and Sn) contributing to the formation of the ternary intermetallic alloys R{sub x}T{sub y}M{sub 2}., on the hydrogen storage behaviours. Particular focus is on two aspects where the remarkable improvement of ordinary metal hydrides is achieved via introduction of In and Sn: a) Increase of the volume density of stored hydrogen in solid materials to the record high level. b) Improvement of the kinetics of hydrogen charge and

  3. Pressure- and Temperature-Dependent Study of Heusler Alloys Cu2MGa (M = Cr and V)

    Science.gov (United States)

    Gupta, Dinesh C.; Ghosh, Sukriti

    2017-04-01

    Full-potential computation of the electronic, magnetic, elastic and thermodynamic properties of Cu2MGa (M = Cr and V) alloys has been performed in the most stable Fm-3 m phase. The equilibrium lattice parameter is 5.9660 Å for Cu2CrGa and 5.9629 Å for Cu2VGa in the stable state. The application of mBJ potential has also found no energy gap in these alloys in either of the spin channels, hence they are metallic. The total and partial density of states, second-order elastic constants and their combinations are computed to show the electronic, magnetic, stability and brittle or ductile nature of these alloys, which are reported for the first time. Cauchy's pressure and Pugh's index predict Cu2CrGa to be brittle and Cu2VGa to be ductile. Both the materials are stiff enough to break. We have found that both the compounds are anisotropic, ferromagnetic and metallic in nature. We have used quasi-harmonic approximations to study the pressure and temperature variation of the thermodynamic properties of these alloys.

  4. KCl-induced high temperature corrosion of selected commercial alloys. Part I: chromia-formers

    DEFF Research Database (Denmark)

    Kiamehr, Saeed; Dahl, Kristian Vinter; Montgomery, Melanie

    2015-01-01

    Laboratory testing of selected chromia-forming alloys was performed to rank the materials and gain further knowledge on the mechanism of KCl-induced high temperature corrosion. The investigated alloys were stainless steels EN1.4021, EN1.4057, EN1.4521, TP347H (coarse-grained), TP347HFG (fine......-grained), Sanicro 28 and the nickel-based alloys 625, 263 and C276. Exposure was performed at 600 °C for 168 h in flowing N2(g)+5%O2(g)+15% H2O(g) (vol.%). Samples were covered with KCl powder prior to exposure. A salt-free exposure was also performed for comparison. Corrosion morphology and products were studied...... with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). It was observed that in the salt-free exposure, stainless steels TP347H (coarse-grained) and EN1.4521 failed to form a thin protective oxide layer compared to the oxide formed on the other alloys...

  5. On elevated temperature stability of high carbon Fe-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baligidad, R.G.; Prakash, U.; Radha Krishna, A. [Defence Metallurgical Research Lab., Hyderabad (India)

    1999-06-15

    Ingots of Fe-Al alloys containing 1.1 wt.% C each and 8.5, 16 and 20 wt% Al, respectively were prepared by a combination of air induction melting and electroslag remelting. These ESR ingot samples were placed in a hearth furnace at 1273 K for 24 h and then furnace cooled to room temperature. The ESR ingots exhibited a significant amount of precipitation of Fe{sub 3}AlC{sub 0.5} phase. Fe-16 wt% Al-1.1wt% C and Fe-20 wt% Al-1.1 wt% C ESR ingots exhibited coarse columnar grains along the ingot axis. No significant change in microstructure was observed in these ingots after heat treatment. Dendritic solidification was observed in ESR ingots of the Fe-8.5 wt% Al-1.1 wt% C alloy with copious precipitation of fine Fe{sub 3}AlC{sub 0.5} phase in the interdendritic region. After heat treatment some coarsening of the interdendritic precipitates and precipitation within the dendrites was observed leading to a more homogeneous microstructure. Fe-8.5 wt% Al-1.1 wt% C alloy samples were badly oxidized after the heat treatment. This was accompanied by significant decarburization in regions near the sample surfaces leading to a localised loss in hardness. It would appear from the present work that high carbon Fe-Al alloys containing 16 wt% Al or more are resistant to oxidation and decarburization. (orig.) 19 refs.

  6. Cyclic degradation of titanium-tantalum high-temperature shape memory alloys - The role of dislocation activity and chemical decomposition

    OpenAIRE

    Niendorf, T.; Krooß, P.; Somsen, C.; Rynko, R.; Paulsen, A.; Batyrshina, E.; Frenzel, J.; G. Eggeler; Maier, Hans Jürgen

    2015-01-01

    Titanium-tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel-titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium-tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation ...

  7. Analysis of Temperature Field, Heat and Fluid Flow of Two-Phase Zone Continuous Casting Cu–Sn Alloy Wire

    OpenAIRE

    Luo J.; Liu X; Wang X

    2016-01-01

    Cu–4.7 wt. % Sn alloy wire with Ø10 mm was prepared by two-phase zone continuous casting technology, and the temperature field, heat and fluid flow were investigated by the numerical simulated method. As the melting temperature, mold temperature, continuous casting speed and cooling water temperature is 1200 °C, 1040 °C, 20 mm/min and 18 °C, respectively, the alloy temperature in the mold is in the range of 720 °C–1081 °C, and the solid/liquid interface is in the mold. In the center of the mo...

  8. Elimination of Iron Based Particles in Al-Si Alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2015-03-01

    Full Text Available This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by chrome. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich phases. It is impossible to remove iron from melt by standard operations, but it is possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful type. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of chrome as iron corrector of iron based phases. By experimental work were used three different amounts of AlCr20 master alloy a three different temperature of chill mold. Our experimental work confirmed that chrome can be used as an iron corrector in Al-Si alloy, due to the change of intermetallic phases and shortening their length.

  9. Elevated Temperature Creep Properties of Conventional 50Au-50Cu and 47Au 50Cu-3Ni Braze Alloys

    Energy Technology Data Exchange (ETDEWEB)

    STEPHENS JR.,JOHN J.; SCHMALE,DAVID T.

    2000-12-18

    The elevated temperature creep properties of the 50Au-50Cu wt% and 47Au-50Cu-3Ni braze alloys have been evaluated over the temperature range 250-850 C. At elevated temperatures, i.e., 450-850 C, both alloys were tested in the annealed condition (2 hrs. 750 C/water quenched). The minimum strain rate properties over this temperature range are well fit by the Garofalo sinh equation. At lower temperatures (250 and 350 C), power law equations were found to characterize the data for both alloys. For samples held long periods of time at 375 C (96 hrs.) and slowly cooled to room temperature, an ordering reaction was observed. For the case of the 50Au-50Cu braze alloy, the stress necessary to reach the same, strain rate increased by about 15% above the baseline data. The limited data for ordered 47Au-50Cu-3Ni alloy reflected a,smaller strength increase. However, the sluggishness of this ordering reaction in both alloys does not appear to pose a problem for braze joints cooled at reasonable rates following brazing.

  10. Transformation Temperatures, Shape Memory and Magnetic Properties of Hafnium Modified Ti-Ta Based High Temperature Shape Memory Alloys

    Science.gov (United States)

    Khan, W. Q.; Wang, Q.; Jin, X.

    2017-02-01

    In this study the modification effect of Hf content on the shape memory properties and magnetic permeability of a 75.5-77Ti-20Ta-3-4.5Hf alloy system has been systematically studied by DSC, three-point bend test, vector network analyzer and XRD. The martensitic transformation temperature, heat of reaction and recovery strain increases with the increase of hafnium and tantalum content. A stable high temperature shape memory effect was observed (Ms = 385-390 °C) during the two thermal cycles between 20 °C and 725 °C. Transformation temperatures and heats of reaction were determined by DSC measurements. Recovery strain was determined by three-point bend testing. Also an alloy, 70Ti-26Ta-4Hf, with higher tantalum content was produced to observe the effect of Ta on the shape memory properties. Permeability increases gradually from 1.671 to 1.919 with increasing content of hafnium modification and remains stable in the frequency range of 450 MHz to 1 GHz.

  11. Analysis of formability of Ca-added magnesium alloy sheets at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Se-Jong; Lee, Young-Seon; Kim, Daeyong, E-mail: daeyong@kims.re.kr

    2016-03-15

    The formability of sheets of the Ca-added magnesium alloy AZX311 was analyzed. The parameters affecting the sheet formability, such as the strain-hardening rate and the strain-rate sensitivity, did not seem to be higher in the alloy AZX311 at temperatures of room temperature (RT) and 200 °C. In addition, the critical stress for fracture at RT was lower in AZX311 than in AZ31. However, AZX311 exhibited higher stretchability and formability at low temperatures than AZ31. Electron back-scattered diffraction microscopy revealed that AZX311 had a weaker basal texture as well as broadened basal poles along the transverse direction. Polycrystal plasticity simulations confirmed that this weaker basal texture increases the activity of basal slip over thickness strain, resulting in the higher formability of AZX311. - Highlights: • A weak basal texture with broadening basal poles along the TD in AZX311 • Lower critical stress for fracture at RT in AZX311 than in AZ31 • Lower strain-hardening rates at low temperatures in the AZX311 than in the AZ31 • Higher formability at low temperatures in AZX311 because of the weak basal texture.

  12. Fabrication of Fe-Al Intermetallic Foams via Organic Compounds Assisted Sintering

    Directory of Open Access Journals (Sweden)

    Krzysztof Karczewski

    2015-04-01

    Full Text Available The influence of the addition of organic compounds, such as palmitic acid and cholesteryl myristate, on the porous structure of Fe-Al intermetallics formation has been investigated in detail in this paper. It was found that additives have a significant effect on the final porosity of the obtained sinters. Formed gaseous products from combustion play the role of the foaming agent during Fe-Al intermetallic alloy sintering. The influence of these additives is also clearly noticeable in chemical composition changes of the final products through the increase of carbon content in the porous structure. This is attributed to the thermal decomposition, namely combustion, of the organic additives.

  13. Structure and phase transformations in copper-alloyed rapidly melt-quenched Ni50Ti32Hf18-based alloys with high-temperature shape memory effect

    Science.gov (United States)

    Pushin, A. V.; Pushin, V. G.; Kuranova, N. N.; Kourov, N. I.; Kuntsevich, T. E.; Makarov, V. V.; Uksusnikov, A. N.

    2017-10-01

    Methods of transmission and scanning electron microscopy, chemical microanalysis, electron diffraction, and X-ray diffraction have been used to carry out the comparative study of the structure and chemical and phase composition of thin ribbons of four quasi-binary alloys (Ni50Ti32Hf18, Ni45Ti32Hf18Cu5, Ni35Ti32Hf18Cu15, and Ni25Ti32Hf18Cu25) obtained in the amorphous state by rapid quenching from the melt by jet spinning. The critical temperatures of the devitrification and B2 ↔ B19' martensitic transformation of the alloys have been determined based on the data of temperature dependences of the electrical resistivity. The specific features of the formation of the ultrafine-grained structure upon the devitrification and of the phase transformations have been studied depending on the heat-treatment regimes and chemical composition of the alloys (concentration of copper atoms).

  14. Summary of workshop on high temperature materials based on Laves phases

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    The Offices of Fossil Energy and Basic Energy Sciences of the Department of Energy jointly sponsored the Workshop on High Temperature Materials Based on Laves Phases in conjunction with the Tenth Annual Conference on Fossil Energy Materials held at the Radisson Summit Hill Hotel in Knoxville, Tennessee on May 14-16, 1996. The objective of this workshop was to review the current status and to address critical issues in the development of new-generation high-temperature structural materials based on Laves phases. The one-day workshop included two sessions of overview presentations and a session of discussion on critical scientific and technological issues. The Laves phases represent an abundant class of intermetallic alloys with possible high-temperature structural applications. Laves phases form at or near the AB{sub 2} composition, and there are over 360 binary Laves phases. The ability of these alloys to dissolve considerable amounts of ternary alloying additions provides over 900 combined binary and ternary Laves phases. Many Laves phases have unique properties which make them attractive for high-temperature structural use. At half their homologous temperature, they retain >0.85 of their ambient yield strength, which is higher than all other intermetallics. Many of the Laves phases also have high melting temperatures, excellent creep properties, reasonably low densities, and for alloys containing Cr, Al, Si or Be, good oxidation resistance. Despite these useful properties, the tendency for low-temperature brittleness has limited the potential application of this large class of alloys.

  15. Tensile behavior of directionally solidified Ni3Al intermetallics with different Al contents and solidification rates

    Science.gov (United States)

    Lu, Yun; Gu, Jiho; Kim, Sangshik; Hong, Hyunuk; Choi, Heekyu; Lee, Jehyun

    2014-03-01

    Despite the excellent high temperature mechanical properties of the Ni3Al intermetallic compound, its application is still limited due to its inherently weak grain boundary. Recent research advances have demonstrated that the tensile ductility can be enhanced by controlling the grain morphology using a directional solidification. In this study, a series of directional solidification experiments were carried out to increase both the tensile ductility and the strength of Ni3Al alloys by arraying either the ductile phase of γ-Ni-rich dendrite fibers or the hard phase of β-NiAl dendrite fibers in the γ'-Ni3Al matrix. The dendrite arm spacing could be controlled by the solidification rate, and the volume fraction of the γ or β phase could be altered by the Al content, ranging from 23 at.% to 27 at.%. With an increasing Al content, the γ dendritic microstructure was transformed into the β dendrite in the γ' matrix, thereby reducing the tensile ductility by increasing the volume fraction of brittle β dendrites in the γ' matrix. With an increasing solidification rate, the dendrite arm spacing decreased and the tensile properties of Ni3Al varied in a complex manner. The microstructural evolution affecting the tensile behavior of directionally solidified Ni3Al alloy specimens with different solidification rates and Al contents is discussed.

  16. Fabrication of intermetallic NiAl by self-propagating high-temperature synthesis reaction using aluminium nanopowder under high pressure

    CERN Document Server

    Dong Shu Shan; Cheng Hai Yong; Yang Hai Bin; Zou Guang Tian

    2002-01-01

    By using aluminium nanopowder prepared by wire electrical explosion, pure monophase NiAl compound with fine crystallites (<=10 mu m) and good densification (98% of the theoretical green density) was successfully fabricated by means of self-propagating high-temperature synthesis (SHS) under a high pressure of 50 MPa. Investigation shows that, due to the physical and chemical characteristics of the nanoparticles, the SHS reaction mode and mechanism are distinct from those when using conventional coarse-grained reactants. The SHS reaction process depends on the thermal conditions related to pressure and can occur at a dramatically low temperature of 308 sup o C, which cannot be expected in conventional SHS reaction. With increasing pressure, the SHS explosive ignition temperature (T sub i sub g) of forming NiAl decreases due to thermal and kinetic effects.

  17. Intermetallic Growth Retardation with the Addition of Graphene in the Sn-3.5Ag Lead-free Solder

    Science.gov (United States)

    Mayappan, R.; Salleh, A.

    2017-06-01

    In this study, the effect of 0.07 wt.% graphene nanosheets (GNSs) on the thermal, microstructure and intermetallic compounds (IMC) growth kinetics were investigated. Experimental results showed that addition of GNSs to the Sn-3.5Ag solder alloy slightly increased the melting temperature. Scanning electron microscope (SEM) micrograph revealed that with the addition of GNSs has transformed the morphologies of the interfacial IMC from scalloped to more planar-shaped after isothermal aging for 500 hours. Growth kinetics calculations show that the k value was reduced from 9.08 × 10-14 cm2/s to 5.73 × 10-14 cm2/s with the addition of graphene. Thereby, it indicates that the addition of GNSs suppressed the growth of the IMC layers hence retarded the IMC’s growth.

  18. Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

    Science.gov (United States)

    1995-01-01

    A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu

  19. Pitting Corrosion of Ni3(Si,Ti Intermetallic Compound at Various Chloride Concentrations

    Directory of Open Access Journals (Sweden)

    Gadang Priyotomo

    2013-10-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti intermetallic compound was investigated as function of chloride concentration by using electrochemical method and scanning electron microscope in sodium chloride solutions at 293 K.  In addition, the pitting corrosion of type C276 alloy was also studied under the same experimental condition for comparison.  The pitting potential obtained for the intermetallic compound decreased with increasing chloride concentration.  The specific pitting potential and pitting potential of Ni3(Si,Ti were lower than those of C276 alloy, which means that the pitting corrosion resistance of C276 alloy was higher than that of Ni3(Si,Ti.

  20. Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy

    Directory of Open Access Journals (Sweden)

    Deng Zhenghua

    2013-03-01

    Full Text Available Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in the formation of surface oxide film. In this present work, the ignition temperature and the surface tension of Mg-9wt.%Al alloy with different Ce concentrations were studied. Surface tensions was measured using the maximum bubble pressure method (MBPM. Ignition temperature was measured using NiCr-NiSi type thermocouples and was monitored and recorded via a WXT-604 desk recording device. The results show that the ignition point of Mg-9wt.%Al alloy can be effectively elevated by adding Ce. The ignition temperature reaches its highest point of 720 ℃ when the addition of Ce is 1wt.%. The surface tension of the molten Mg-9wt.%Al alloy decreases exponentially with the increase of Ce addition at the same temperature. Similarly, the experiment also shows that the surface tension of Mg-9wt.%Al alloy decreases exponentially with the increase of temperature.

  1. Effect of electron count and chemical complexity in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor.

    Science.gov (United States)

    von Rohr, Fabian; Winiarski, Michał J; Tao, Jing; Klimczuk, Tomasz; Cava, Robert Joseph

    2016-11-15

    High-entropy alloys are made from random mixtures of principal elements on simple lattices, stabilized by a high mixing entropy. The recently discovered body-centered cubic (BCC) Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor appears to display properties of both simple crystalline intermetallics and amorphous materials; e.g., it has a well-defined superconducting transition along with an exceptional robustness against disorder. Here we show that the valence electron count dependence of the superconducting transition temperature in the high-entropy alloy falls between those of analogous simple solid solutions and amorphous materials and test the effect of alloy complexity on the superconductivity. We propose high-entropy alloys as excellent intermediate systems for studying superconductivity as it evolves between crystalline and amorphous materials.

  2. Improved corrosion protection of aluminum alloys by low-temperature plasma interface engineering

    Science.gov (United States)

    Reddy, Chandra Mudupu

    The System Approach Interface Engineering (SAIE) concept was employed to develop corrosion protection processes for aluminum (Al) alloys by application of a low temperature plasma interface engineering technique with a cathodic electrocoat (E-coat) as the primary layer coating. The SAIE concept emphasizes that the corrosion protection property of the coated system for Al alloys depends on the total system rather than any good corrosion protection component of the system. The cathodic E-coated SAIE plasma pretreatments on Alclad 2024-T3, 2024-T3 bare and 7075-T6 bare alloys showed excellent corrosion resistance property when tested by SO2 and Prohesion salt spray tests. These systems out performed the conventional conversion coated controls, chromate conversion coated then Deft primer coated (CC Deft) and chromate conversion coated then cathodic E-coated (CC E-coat) in both the corrosion testes. The corrosion protection by SAIE systems depends on three major factors; (1) improved barrier characteristics of E-coat, (2) water insensitive adhesion of E-coat to plasma polymers deposited in a DC discharge and (3) creating a stable surface oxide layer by plasma treatment or chemical cleaning. Different chemical pretreatments were employed to create a stable barrier type aluminum oxide layer on the surfaces of the substrates prior to plasma polymer deposition. The surface analysis showed that these pretreatments depend on the type of alloy and surface chemistry. As received surfaces with acetone wipe and plasma cleaning of the organic contaminants was found to be best for Alclad 2024-T3 alloy. Chemical alkaline cleaning for 2024-T3 bare and alkaline cleaning followed by deoxidization for 7075-T6 bare alloy were necessary. The adhesion of the cathodic E-coat was improved by surface energy matching techniques by deposition of various plasma polymer films of trimethylsilane (TMS) and mixtures of TMS with O2, H2, and N2. The adhesion performance evaluated by the N

  3. Increasing of founding properties of secondary aluminium alloys

    Directory of Open Access Journals (Sweden)

    O.V. Lyutova

    2013-06-01

    Full Text Available Purpose. To study the influence of metallurgical factors of production on casting properties of secondary aluminum alloy АК9М2. Methodology. For the experimental melts shaving amount in a charge, iron content and the quantity of modifier additive were chosen as independent variables. The components of modifier were being changed in the intervals of 25…40 % Na2CO3, 12…20 % SiC, 3…8 % Ti, the other – S. The microstructure of alloys was investigated under a light microscope, using the method of quantitative metallography. Influence analysis of certain parameters of alloys was conducted by mathematical statistics methods. The influence of shaving additions, iron and modifier amount on liquidity and porosity of the resulting alloys was studied. Findings. The paper shows that the increase of shaving content in the charge from 1 to 19 % and iron content in alloy from 0.66 to 2.34 % resulted in the decline of alloy liquidity on 30…35 %. Simultaneously the linear shrinkage reduction for 18…20 % and the porosity increase from 0.5 to 2.5 points were observed. The presented changes of alloy casting properties are conditioned by the amount of intermetallic phases of unfavorable form and its capacity for aeration. Increase of modifier additive from 0.02 to 0.15 % resulted in the liquidity increase on 10…15 %, the increase of linear shrinkage on 30…35 % and porosity decline from 2.5 to 0.5 points. At the same time a change of form of intermetallic phases and increase of their evenness were observed. Originality. The increase of iron concentration in silumin composition is accompanied by the decline of its liquidity. Thus, the rate of decline of alloy liquidity is proportional to the amount of dissolved iron. The character of iron influence is caused by formation of high temperature intermetallic compounds of the type Al3Fe, Al5SiFe, which promote the metal viscidity. Practical value. Practical use of the obtained scientific results would

  4. Experimental-calculation study of ion-plasma thermal barrier coatings for turbine blades made of intermetallic nickel superalloys

    Science.gov (United States)

    Budinovskii, S. A.; Matveev, P. V.; Zhivushkin, A. A.; Tikhomirova, E. A.; Belyaeva, L. A.; Balakin, S. M.

    2017-06-01

    The ion-plasma thermal barrier coatings deposited onto samples and blades made of intermetallic VKNA-1V and VKNA-25 alloys are tested in a laboratory. The external ceramic layer of the thermal barrier coatings (TBC) is formed by magnetron sputtering of zirconium alloy targets and has a columnar structure. The influence of NiCrAlY(Re, Ta, Hf) + AlNiY(Hf) + ZrYGdO TBC on the long-term strength at a test temperature of 1200°C and on the high-cycle fatigue at a temperature of 900°C is studied. Blades with TBC are subjected to thermal cycling tests in the temperature range 950 ↔ 400°C and 1050 ↔ 400°C during air cooling and in the range 950 ↔ 200°C during water cooling at 500 cycles. The temperature fields in the cross section of a blade airfoil during thermal cycling are calculated. The laws of formation of fracture zones and the development of thermal fatigue cracks under the conditions that are close to the operating conditions of nozzle TBC-containing blades are investigated.

  5. Microstructure and Mechanical Properties of a Novel Rapidly Solidified, High-Temperature Al-Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Overman, Nicole R.; Mathaudhu, Suveen; Choi, Jung-Pyung; Roosendaal, Timothy J.; Pitman, Stan G.

    2016-02-12

    Rapid solidification (RS) processing, as a production method, offers a variety of unique properties based on far-from-equilibrium microstructures obtained through rapid cooling rates. In this study, we seek to investigate the microstructures and properties of a novel Al-alloy specifically designed for high temperature mechanical stability. Synthesis of, AlFe11.4Si1.8V1.6Mn0.9 (wt. %), was performed by two approaches: rotating cup atomization (“shot”) and melt spinning (“flake”). These methods were chosen because of their ability to produce alloys with tailored microstructures due to their inherent differences in cooling rate. The as-solidified precursor materials were microstructurally characterized with electron microscopy. The results show that the higher cooling rate flake material exhibited the formation of nanocrystalline regions as well additional phase morphologies not seen in the shot material. Secondary dendritic branching in the flake material was on the order of 0.1-0.25µm whereas branching in the shot material was 0.5-1.0µm. Consolidated and extruded material from both precursor materials was mechanically evaluated at both ambient and high (300°C) temperature. The consolidated RS flake material is shown to exhibit higher strengths than the shot material. The ultimate tensile strength of the melt spun flake was reported as 544.2MPa at room temperature and 298.0MPa at 300°C. These results forecast the ability to design alloys and processing approaches with unique non-equilibrium microstructures with robust mechanical properties at elevated temperatures.

  6. Solid State Joining of High Temperature Alloy Tubes for USC and Heat-Exchanger Systems

    Energy Technology Data Exchange (ETDEWEB)

    Bimal Kad

    2011-12-31

    The principal objective of this project was to develop materials enabling joining technologies for use in forward looking heat-exchanger fabrication in Brayton cycle HIPPS, IGCC, FutureGen concepts capable of operating at temperatures in excess of 1000{degree}C as well as conventional technology upgrades via Ultra Super-Critical (USC) Rankine-cycle boilers capable of operating at 760{degree}C (1400F)/38.5MPa (5500psi) steam, while still using coal as the principal fossil fuel. The underlying mission in Rankine, Brayton or Brayton-Rankine, or IGCC combined cycle heat engine is a steady quest to improving operating efficiency while mitigating global environmental concerns. There has been a progressive move to higher overall cycle efficiencies, and in the case of fossil fuels this has accelerated recently in part because of concerns about greenhouse gas emissions, notably CO{sub 2}. For a heat engine, the overall efficiency is closely related to the difference between the highest temperature in the cycle and the lowest temperature. In most cases, efficiency gains are prompted by an increase in the high temperature, and this in turn has led to increasing demands on the materials of construction used in the high temperature end of the systems. Our migration to new advanced Ni-base and Oxide Dispersion Strengthened (ODS) alloys poses significant fabrication challenges, as these materials are not readily weldable or the weld performs poorly in the high temperature creep regime. Thus the joining challenge is two-fold to a) devise appropriate joining methodologies for similar/dissimilar Ni-base and ODS alloys while b) preserving the near baseline creep performance in the welded region. Our program focus is on solid state joining of similar and dissimilar metals/alloys for heat exchanger components currently under consideration for the USC, HIPPS and IGCC power systems. The emphasis is to manipulate the joining methods and variables available to optimize joint creep

  7. Role of acidic chemistries in steam treatment of aluminium alloys

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Jellesen, Morten Stendahl; Ambat, Rajan

    2015-01-01

    The effect of acidic chemistry on the accelerated growth of oxide on aluminium alloys Peraluman 706TM and AA6060 under exposure to high temperature steam was investigated. Studied chemistries were based on citrates and phosphates. Results showed that the presence of citrate and phosphate anions...... initiate doxide growth at the intermetallic particles while growth and corrosion performance of oxide was found tobe a function of anions type and their concentration. Further, steam treatment with phosphates exhibited better performance under acetic acid salt spray and filiform corrosion test whereas...

  8. Microstructural observations and thermal stability of a rapidly solidified aluminum-gadolinium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Savage, S.J.; Eliezer, D.; Froes, F.H. (Rapid Solidification Group, Swedish Institute for Metals Research, Drottning Kristinas vag 48, S-114 28 Stockholm (SE))

    1987-08-01

    Rapid solidification processing has significant potential to extend the use of aluminum alloys to higher temperatures (200/sup 0/C to 350/sup 0/C). In particular, alloys based on Al-Fe-X compositions, where X = Ce or Mo, have been studied in detail. Cerium is representative of the family of rare earth, or lanthanide elements, and forms a number of intermetallic compounds with aluminum. Alloys containing rare earths other than cerium have received little attention, although for several reasons they are considered worthy of study. Rapidly solidified ribbons were prepared from this alloy by the chill block melt spinning technique at a peripheral wheel velocity of 20.4 m/s. A melt temperature of --1300/sup 0/C was used to ensure complete dissolution of all intermetallic particles. The ribbons produced were typically about 100 ..mu..m thick and 2 to 3 mm wide. Standard polishing techniques were used to prepare sections for optical microscopy and microhardness measurements. Room temperature Keller's reagent (diluted to 50 vol pct, in water) was used to etch the samples. Thin foils were prepared for TEM by electropolishing from both sides of the ribbon using the window technique.

  9. High-temperature nitridation of Nb-Ti alloys in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Buscaglia, V.; Martinelli, A. [Nat. Res. Council, Genoa (Italy). Inst. of Phys. Chem. of Mater.; Musenich, R. [National Institute of Nuclear Physics, via Dodecaneso 33, I-16146 Genoa (Italy); Mayr, W.; Lengauer, W. [Institute for Chemical Technology of Inorganic Materials, Vienna University of Technology, Getreidemarkt 9/161, A-1060 Vienna (Austria)

    1999-02-01

    Microstructure evolution, phase composition, weight gain and layer growth kinetics of Nb-Ti alloys (10, 47, 63 and 90 at.% Ti) annealed in high-purity nitrogen atmosphere (0.3, 3 and 30 bar) were studied in the temperature range 1300-1600 C. After nitridation, the formation of an external compact nitride layer as well as extensive internal nitride precipitation was observed. The overall nitridation kinetics (weight gain) is invariably parabolic; a deviation from the initial rate law is observed at 1450 and 1600 C for the longer reaction times when the alloy core approaches nitrogen saturation and internal precipitation slows down. The parabolic rate constant is strongly affected by the Nb content in the alloy. The phases detected in the reacted samples are isostructural with those of the Nb-Ti, Nb-N and Ti-N systems. The surface nitride was {delta}-(Ti,Nb)N in any case. The morphology of the internal nitridation zone corresponds to the growth of large, oriented, nitride needles for the three alloys richer in titanium. The needles are composed of {alpha}-(Ti,Nb)(N) in the case of Ti{sub 90}Nb{sub 10} alloy and of {delta}-(Ti,Nb)N{sub 1-x} in the case of Ti{sub 63}Nb{sub 37} and Ti{sub 47}Nb{sub 53}. Such a microstructure is evidence for nucleation difficulty; coarsening of the existing particles is favoured in comparison to the formation of new precipitates. Homogeneous nucleation is hindered by the small chemical Gibbs free energy available and the elastic strain energy related to volume misfit. After initial reaction, microstructure evolution is mainly determined by the fast inward diffusion of nitrogen and the slow Nb-Ti interdiffusion in the {beta}-(Ti,Nb) alloy. Internal nitridation of Ti{sub 10}Nb{sub 90} at 1450 and 1600 C leads to the formation of fine and numerous precipitates of {beta}-(Nb,Ti){sub 2}N. (orig.) 58 refs.

  10. Pulse width modulation-based temperature tracking for feedback control of a shape memory alloy actuator.

    Science.gov (United States)

    Ayvali, Elif; Desai, Jaydev P

    2014-04-01

    This work presents a temperature-feedback approach to control the radius of curvature of an arc-shaped shape memory alloy (SMA) wire. The nonlinear properties of the SMA such as phase transformation and its dependence on temperature and stress make SMA actuators difficult to control. Tracking a desired trajectory is more challenging than controlling just the position of the SMA actuator since the desired path is continuously changing. Consequently, tracking the desired strain directly or tracking the parameters such as temperature and electrical resistance that are related to strain with a model is a challenging task. Temperature-feedback is an attractive approach when direct measurement of strain is not practical. Pulse width modulation (PWM) is an effective method for SMA actuation and it can be used along with a compensator to control the temperature of the SMA. Using the constitutive model of the SMA, the desired temperature profile can be obtained for a given strain trajectory. A PWM-based nonlinear PID controller with a feed-forward heat transfer model is proposed to use temperature-feedback for tracking a desired temperature trajectory. The proposed controller is used during the heating phase of the SMA actuator. The controller proves to be effective in tracking step-wise and continuous trajectories.

  11. Heat resistant nickel base alloy excellent in workability and high temperature strength properties

    Energy Technology Data Exchange (ETDEWEB)

    Susukida, H.; Itoh, H.; Kawai, H.; Kojima, T.; Sahira, K.; Takeiri, T.; Tsuji, I.; Yuge, M.

    1984-10-02

    A heat resistant nickel base alloy which is excellent in not only hot and cold workability but also high temperature strength properties and which also possesses satisfactory oxidation resistance. The nickel base alloy consists essentially of 0.001-0.15 percent carbon, 0.0005-0.05 percent calcium, 20.0-126.0 percent chromium, 4.7-9.4 percent cobalt, 5.0-16.0 percent molybdenum, 0.5-4.0 percent tungsten, with the total of molybdenum plus tungsten being from 9.0 to 16.5 percent, and the balance nickel and inevitable impurities. The alloy may further contain one selected from the group consisting of (1) 0.3-1.5 percent aluminum and 0.1-1.0 percent titanium, (2) 0.001-0.30 percent at least one of yttrium and rare earth elements, and (3) 0.001-1.0 percent at least one of niobium, vanadium and tantalum, whereby the aforementioned characteristics are further enhanced.

  12. A simple route to Cu{sub x}Sn{sub (100−x)} intermetallic nanoparticle catalyst for ultra-phenol hydroxylation

    Energy Technology Data Exchange (ETDEWEB)

    Pithakratanayothin, Sakollapath [The Petroleum and Petrochemical College and Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand); Tongsri, Ruangdaj [Powder Metallurgy Research and Development Unit - PM-RDU, National Metal and Materials Technology Center, Pathum Thani 12120 (Thailand); Chaisuwan, Thanyalak [The Petroleum and Petrochemical College and Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand); Wongkasemjit, Sujitra, E-mail: dsujitra@chula.ac.th [The Petroleum and Petrochemical College and Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand)

    2016-09-15

    A practical methodology and novel, economical materials were proposed to successfully prepare nanoparticle catalysts for phenol hydroxylation. The preparation was carried out via mechanical alloying (MA) of Cu{sub x}Sn{sub (100−x)} powder mixtures (where x = 30, 50, 70, and 100%wt). The mechanical alloyed nanoparticles were characterized using various techniques. X-ray diffraction patterns indicated that η-Cu{sub 6}Sn{sub 5}, ε-Cu{sub 3}Sn, and CuSn phases could be formed in the mechanical alloyed Cu{sub x}Sn{sub (100−x)} materials. Transmission electron micrographs and selected area electron diffraction patterns confirmed the presence of η-Cu{sub 6}Sn{sub 5}, ε-Cu{sub 3}Sn, and CuSn phases. Activity of the catalysts, using the optimal conditions of 70 °C reaction temperature for 1 h, 50 mg of Cu{sub 0.5}Sn{sub 0.5}, and 1:3 phenol:H{sub 2}O{sub 2} ratio, provided more than 98% conversion with 70% catechol (CAT) and 29% hydroquinone (HQ). Experimental results suggested that the presence of the ε-Cu{sub 3}Sn phase gave higher activity while Sn reduced benzoquinone (BQ) to HQ. The catalyst maintained its stability with no structural collapse for more than 24 h. - Highlights: • Cu{sub x}Sn{sub y} intermetallic as a catalyst was successfully synthesized via mechanical alloying. • Cu{sub x}Sn{sub y} intermetallics promoted impressive phenol hydroxylation. • 98% conversion was achieved with high selectivity of catechol.

  13. Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Chu, F.; Thoma, D.J.; He, Y.; Maloy, S.A.; Mitchell, T.E. [Los Alamos National Lab., NM (United States). Materials Science Technology Div.

    1996-09-01

    A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and/or polycrystalline intermetallics, such as Laves phases (C15 HfV{sub 2} and NbCr{sub 2}), Nb-modified titanium aluminides, and transition metal disilicides (C11{sub b} MoSi{sub 2}, C40 NbSi{sub 2} and TaSi{sub 2}). For Laves phases, the elastic properties of HfV{sub 2}-based C15 phases show various anomalies and those of C15 NbCr{sub 2} do not. For Nb-modified titanium aluminides, the elastic properties of O-phase alloys are investigated as a function of alloying content. For transition metal disilicides, single crystal elastic constants of MoSi{sub 2}, NbSi{sub 2}, and TaSi{sub 2} are obtained and compared. Based on the experimentally determined elastic properties, the characteristics of interatomic bonding in these materials are examined and the possible impact of the elastic properties on mechanical behavior is discussed.

  14. Viscoelastoplastic Deformation and Damage Response of Titanium Alloy, Ti-6Al-4V, at Elevated Temperatures

    Science.gov (United States)

    Arnold, Steven M.; Lerch, Bradley A.; Saleeb, Atef F.; Kasemer, Matthew P.

    2013-01-01

    Time-dependent deformation and damage behavior can significantly affect the life of aerospace propulsion components. Consequently, one needs an accurate constitutive model that can represent both reversible and irreversible behavior under multiaxial loading conditions. This paper details the characterization and utilization of a multi-mechanism constitutive model of the GVIPS class (Generalized Viscoplastic with Potential Structure) that has been extended to describe the viscoelastoplastic deformation and damage of the titanium alloy Ti-6Al-4V. Associated material constants were characterized at five elevated temperatures where viscoelastoplastic behavior was observed, and at three elevated temperatures where damage (of both the stiffness reduction and strength reduction type) was incurred. Experimental data from a wide variety of uniaxial load cases were used to correlate and validate the proposed GVIPS model. Presented are the optimized material parameters, and the viscoelastoplastic deformation and damage responses at the various temperatures.

  15. Microstructural stability of wrought, laser and electron beam glazed NARloy-Z alloy at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, J.; Jerman, G.; Bhat, B.; Poorman, R.

    1993-11-01

    Microstructure of wrought, laser, and electron-beam glazed NARloy-Z(Cu-3 wt.% Ag-0.5 wt.% Zr) was investigated for thermal stability at elevated temperatures (539 to 760 C (1,100 to 1,400 F)) up to 94 h. Optical and scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ`s) were observed in the wrought alloy after exposing to temperatures above 605 C (1,120 F). The fine-grained microstructure observed in the laser and electron-beam glazed NARloy-Z was much more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements.

  16. Surface Engineering of Mo-Base Alloys for Elevated-Temperature Environmental Resistance

    Science.gov (United States)

    Perepezko, J. H.

    2015-07-01

    The synthesis of robust coatings that provide protection against environmental attack at ultrahigh temperatures is a difficult challenge. To achieve this goal for Mo-base alloys, the fundamental concepts of reactive diffusion pathway analysis and kinetic biasing are used to design a multilayer Mo-Si-B-base coating with a phase sequencing that allows for structural and thermodynamic compatibility and an underlying diffusion barrier to maintain coating integrity. The coating design concepts have a general applicability. The coating structure evolution during high-temperature exposure facilitates a prolonged lifetime as well as self-healing capability. The borosilicide coatings that can be synthesized by a pack cementation process yield superior environmental resistance for Mo-base systems at temperatures up to at least 1,700°C and can be adapted to apply to other refractory metal and ceramic systems.

  17. Room temperature creep-fatigue response of selected copper alloys for high heat flux applications

    DEFF Research Database (Denmark)

    Li, M.; Singh, B.N.; Stubbins, J.F.

    2004-01-01

    Two copper alloys, dispersion-strengthened CuAl25 and precipitation-hardened CuCrZr, were examined under fatigue and fatigue with hold time loading conditions. Tests were carried out at room temperature and hold times were imposed at maximum tensile and maximum compressive strains. It was found...... that hold times could be damaging even at room temperature, well below temperatures typically associated with creep. Hold times resulted in shorter fatigue lives in the high cycle fatigue, long life regime (i.e., at low strain amplitudes) than those of materials tested under the same conditions without hold...... times. The influence of hold times on fatigue life in the low cycle fatigue, short life regime (i.e., at high strain amplitudes) was minimal. When hold time effects were observed, fatigue lives were reduced with hold times as short as two seconds. Appreciable stress relaxation was observed during...

  18. TEM Study of High-Temperature Precipitation of Delta Phase in Inconel 718 Alloy

    OpenAIRE

    Moukrane Dehmas; Jacques Lacaze; Aliou Niang; Bernard Viguier

    2011-01-01

    Inconel 718 is widely used because of its ability to retain strength at up to 650∘C for long periods of time through coherent metastable   Ni3Nb precipitation associated with a smaller volume fraction of  Ni3Al precipitates. At very long ageing times at service temperature,   decomposes to the stable Ni3Nb phase. This latter phase is also present above the   solvus and is used for grain control during forging of alloy 718. While most works available on precipitation have be...

  19. Analysis of crystallographic slip and grain boundary sliding in a Ti–45Al–2Nb–2Mn (at%)–0.8 vol%TiB{sub 2} alloy by high temperature in situ mechanical testing

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz-Moreno, R. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science and Engineering, Universidad Carlos III de Madrid, Avda. Universidad 30, 28911 Leganés (Spain); Ruiz-Navas, E.M. [Department of Materials Science and Engineering, Universidad Carlos III de Madrid, Avda. Universidad 30, 28911 Leganés (Spain); Boehlert, C.J. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Chemical Engineering and Materials Science, Michigan State University, 2527 Engineering Building, East Lansing, MI 48824 (United States); Llorca, J. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, 28040 Madrid (Spain); Torralba, J.M. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science and Engineering, Universidad Carlos III de Madrid, Avda. Universidad 30, 28911 Leganés (Spain); Pérez-Prado, M.T., E-mail: teresa.perez.prado@imdea.org [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2014-06-01

    This work aims to contribute to a further understanding of the fundamentals of crystallographic slip and grain boundary sliding in the γ-TiAl Ti–45Al–2Nb–2Mn (at%)–0.8 vol%TiB{sub 2} intermetallic alloy, by means of in situ high-temperature tensile testing combined with electron backscatter diffraction (EBSD). Several microstructures, containing different fractions and sizes of lamellar colonies and equiaxed γ-grains, were fabricated by either centrifugal casting or powder metallurgy, followed by heat treatment at 1300 °C and furnace cooling. in situ tensile and tensile-creep experiments were performed in a scanning electron microscope (SEM) at temperatures ranging from 580 °C to 700 °C. EBSD was carried out in selected regions before and after straining. Our results suggest that, during constant strain rate tests, true twin γ/γ interfaces are the weakest barriers to dislocations and, thus, that the relevant length scale might be influenced by the distance between non-true twin boundaries. Under creep conditions both grain/colony boundary sliding (G/CBS) and crystallographic slip are observed to contribute to deformation. The incidence of boundary sliding is particularly high in γ grains of duplex microstructures. The slip activity during creep deformation in different microstructures was evaluated by trace analysis. Special emphasis was placed in distinguishing the compliance of different slip events with the Schmid law with respect to the applied stress.

  20. Effects of pre-strain and Nb content on transformation temperatures in Ti-Ni-Nb shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, T. [Central Research Inst. of Electric Power Industry, Komae (Japan); Mihara, Y. [Graduate School, Univ. of Electro-Communications, Chofu (Japan); Ochi, Y. [Univ. of Electro-Communications, Chofu (Japan); Ozawa, M. [NEC Tokin, Co., Sendai (Japan); Okita, K. [Graduate School, Ehime Univ., Matsuyama (Japan); Okabe, N. [Ehime Univ., Matsuyama (Japan)

    2005-07-01

    Ti-Ni-Nb shape memory alloy has a wide transformation hysteresis, and has been used as coupling devices and so on. However systematic researches of the influence of the amount of Nb addition on transformation temperatures are few. The purpose of this work is to clarify the influences of pre-strain and Nb content on transformation temperatures in Ti-Ni-Nb shape memory alloys. The specimens were Ti-Ni-Nb alloys (Ni/Ti=1.0, Nb=0-15at%), annealed at 1223 K for 0.3 ks. The variation of transformation temperatures with pre-strain and Nb content were investigated experimentally. The variation of A{sub s}, M{sub s} and transformation temperature hysteresis with pre-strain and Nb content will be discussed in relation to the elastic strain energy and the volume fraction of slip-deformed martensite. (orig.)

  1. Effect of temperature on the corrosion resistance and pitting behaviour of Alloy 31 in LiBr solutions

    Energy Technology Data Exchange (ETDEWEB)

    Blasco-Tamarit, E.; Igual-Munoz, A. [Departamento de Ingenieria Quimica y Nuclear, E.T.S.I. Industriales, Universidad Politecnica de Valencia, P.O. Box 22012, E-46071 Valencia (Spain); Anton, J. Garcia [Departamento de Ingenieria Quimica y Nuclear, E.T.S.I. Industriales, Universidad Politecnica de Valencia, P.O. Box 22012, E-46071 Valencia (Spain)], E-mail: jgarciaa@iqn.upv.es; Garcia-Garcia, D. [Departamento de Ingenieria Quimica y Nuclear, E.T.S.I. Industriales, Universidad Politecnica de Valencia, P.O. Box 22012, E-46071 Valencia (Spain)

    2008-07-15

    The corrosion resistance and pitting behaviour of Alloy 31, a high-alloyed austenitic stainless steel (UNS N08031), is studied in two heavy brine LiBr solutions (850 g/l) with and without corrosion inhibitor (lithium chromate) at different temperatures (25 deg. C, 50 deg. C, 75 deg. C and 100 deg. C) using electrochemical techniques. Cyclic potentiodynamic curves indicate that UNS N08031 is less pitting corrosion resistant and it reduces its repassivation properties as temperature increases. Comparison between the results obtained in LiBr solutions with and without inhibitor suggested a decrease in the inhibitor efficiency of lithium chromate at high temperatures.

  2. Study of Intermetallic Nanostructures for Light-Water Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Niels Grobech [Univ. of California, Davis, CA (United States); Asta, Mark D. [Univ. of California, Berkeley, CA (United States); Hosemann, Peter [Univ. of California, Berkeley, CA (United States); Maloy, Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-09-30

    High temperature mechanical measurements were conducted to study the effect of the dynamic precipitation process of PH 13-8 Mo maraging steel. Yield stress, ultimate tensile strength, total elongation, hardness, strain rate sensitivity and activation volume were evaluated as a function of the temperature. The dynamic changes in the mechanical properties at different temperatures were evaluated and a balance between precipitation hardening and annealed softening is discussed. A comparison between hardness and yield stress and ultimate tensile strength over a temperature range from 300 to 600 °C is made. The behavior of the strain rate sensitivity was correlated with the intermetallic precipitates formed during the experiments.

  3. Temperature dependent fracture properties of shape memory alloys: novel findings and a comprehensive model.

    Science.gov (United States)

    Maletta, Carmine; Sgambitterra, Emanuele; Niccoli, Fabrizio

    2016-12-21

    Temperature dependent fracture properties of NiTi-based Shape Memory Alloys (SMAs), within the pseudoelastic regime, were analyzed. In particular, the effective Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature, by a fitting of the William's expansion series, based on Digital Image Correlation (DIC) measurements. It was found that temperature plays an important role on SIF and on critical fast fracture conditions. As a consequence, Linear Elastic Fracture Mechanics (LEFM) approaches are not suitable to predict fracture properties of SMAs, as they do not consider the effects of temperature. On the contrary, good agreements between DIC results and the predictions of an ad-hoc analytical model were observed. In fact, the model takes into account the whole thermo mechanical loading condition, including both mechanical load and temperature. Results revealed that crack tip stress-induced transformations do not represent a toughening effect and this is a completely novel result within the SMA community. Furthremore, it was demonstrated that the analytical model can be actually used to define a temperature independent fracture toughness parameter. Therefore, a new approach is proposed, based on the analytical model, where both mechanical load and temperature are considered as loading parameters in SIF computation.

  4. Reaction kinetics of the formation of intermetallic Fe – Zn during hot - dip galvanizing of steel

    Directory of Open Access Journals (Sweden)

    P. Pokorny

    2016-01-01

    Full Text Available This review article mainly describes the composition of intermetallic Fe - Zn, i.e. zeta (ζ, delta (δ1k + δ1p, gamma1 (Γ1 and gamma (Γ on galvanized steel during low temperature galvanization (t ~ 450 °C. It gives detailed the formation, growth of individual phases during galvanization and their interaction. In terms of the kinetics, the formation of the coating is defined by a parabolic kinetic equation of the growth of different intermetallic phases under ideal conditions. From the available literature the rate constants of the formation of individual intermetallic phases and also for the total coating are cited. The composition of the intermetallic phases, iron content, crystal structure, and group symmetry in which the surface of galvanized steel forms.

  5. Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    Science.gov (United States)

    Wen, Xingshuo

    The Very High Temperature Reactor (VHTR) is one of the leading concepts of the Generation IV nuclear reactor development, which is the core component of Next Generation Nuclear Plant (NGNP). The major challenge in the research and development of NGNP is the performance and reliability of structure materials at high temperature. Alloy 617, with an exceptional combination of high temperature strength and oxidation resistance, has been selected as a primary candidate material for structural use, particularly in Intermediate Heat Exchanger (IHX) which has an outlet temperature in the range of 850 to 950°C and an inner pressure from 5 to 20MPa. In order to qualify the material to be used at the operation condition for a designed service life of 60 years, a comprehensive scientific understanding of creep behavior at high temperature and low stress regime is necessary. In addition, the creep mechanism and the impact factors such as precipitates, grain size, and grain boundary characters need to be evaluated for the purpose of alloy design and development. In this study, thermomechanically processed specimens of alloy 617 with different grain sizes were fabricated, and creep tests with a systematic test matrix covering the temperatures of 850 to 1050°C and stress levels from 5 to 100MPa were conducted. Creep data was analyzed, and the creep curves were found to be unconventional without a well-defined steady-state creep. Very good linear relationships were determined for minimum creep rate versus stress levels with the stress exponents determined around 3-5 depending on the grain size and test condition. Activation energies were also calculated for different stress levels, and the values are close to 400kJ/mol, which is higher than that for self-diffusion in nickel. Power law dislocation climb-glide mechanism was proposed as the dominant creep mechanism in the test condition regime. Dynamic recrystallization happening at high strain range enhanced dislocation climb and

  6. Experimental and Computational Investigation of High Entropy Alloys for Elevated-Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter [Univ. of Tennessee, Knoxville, TN (United States); Zhang, Fan [CompuTherm LLC, Madison, WI (United States); Zhang, Chuan [CompuTherm LLC, Madison, WI (United States); Wang, Gongyao [Univ. of Tennessee, Knoxville, TN (United States); Xie, Xie [Univ. of Tennessee, Knoxville, TN (United States); Diao, Haoyan [Univ. of Tennessee, Knoxville, TN (United States); Kuo, Chih-Hsiang [Univ. of Tennessee, Knoxville, TN (United States); An, Zhinan [Univ. of Tennessee, Knoxville, TN (United States); Hemphill, Michael [Univ. of Tennessee, Knoxville, TN (United States)

    2016-07-30

    To create and design novel structural materials with enhanced creep-resistance, fundamental studies have been conducted on high-entropy alloys (HEAs), using (1) thermodynamic calculations, (2) mechanical tests, (3) neutron diffraction, (4) characterization techniques, and (5) crystal-plasticity finite-element modeling (CPFEM), to explore future candidates for next-generation power plants. All the constituent binary and ternary systems of the Al-Cr-Cu-Fe-Mn-Ni and Al-Co-Cr-Fe-Ni systems were thermodynamically modeled within the whole composition range. Comparisons between the calculated phase diagrams and literature data are in good agreement. Seven types of HEAs were fabricated from Al-Cr-Cu-Fe-Mn-Ni and Al-Co-Cr-Fe-Ni systems. The AlxCrCuFeMnNi HEAs have disordered [face-centered cubic (FCC) + body-centered cubic (BCC)] crystal structures, not FCC or BCC single structure. Excessive alloying of the Al element results in the change of both microstructural and mechanical properties in AlxCoCrFeNi HEAs. There are mainly three structural features in AlxCoCrFeNi: (1) the morphology, (2) the volume fractions of the constitute phases, and (3) existing temperatures of all six phases. After homogenization, the Al0.3CoCrFeNi material is a pure FCC solid solution. After aging at 700 °C for 500 hours, the optimal microstructure combinations, the FCC matrix, needle-like B2 phase within grains, and granular σ phase along grain boundary, is achieved for Al0.3CoCrFeNi. The cold-rolling process is utilized to reduce the grain size of Al0.1CoCrFeNi and Al0.3CoCrFeNi. The chemical elemental partitioning of FCC, BCC, B2, and σphases at different temperatures, before and after mechanical tests, in Al-Cr-Cu-Fe-Mn-Ni and Al-Co-Cr-Fe-Ni systems are quantitatively characterized by both synchrotron X-ray diffraction, neutron diffraction with levitation, scanning electron microscopy (SEM), advanced atom probe

  7. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    Science.gov (United States)

    Kim, Jongjin; Choi, Kyung Joon; Bahn, Chi Bum; Kim, Ji Hyun

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr2O3, NiCr2O4 and Fe3O4 at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  8. Electrochemical properties of the passive film on bulk Zr–Fe–Cr intermetallic fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Yakui [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Ling, Yunhan, E-mail: yhling@mail.tsinghua.edu.cn [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Lai, Wensheng [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Xing, Shupei; Ma, Wen [School of Materials Science and Engineering, Inner Mongolia University of Technology, Huhhot 010051 (China)

    2016-12-01

    Highlights: • SPS was employed to prepare Zr-based intermetallics which were commonly existed in zircaloy. • Zr-based intermetallics act as cathode when they embedded in zirconium matrix. • The passive films on surface of intermetallics behaved as n-type semiconductors. • Carrier concentration of Zr(Fe{sub 3}Cr){sub 2} was much lower than that of other intermetallics. - Abstract: Although Zr-based second phase particles (SPPs) are important factors influencing corrosion resistance of zircaloy cladding materials, the corrosion behavior of SPPs has not been investigated by means of electrochemical method so far. In order to clarify the role of SPPs commonly existed in zircaloy, bulk Zr-based intermetallics were firstly fabricated by spark plasma sintering (SPS) at temperatures 1373 K and an applied pressure of 60 MPa in this work. Both the natural passive film on surface and oxidation behavior of intermetallic has been investigated in this work. X-ray diffraction (XRD) pattern showed that as-prepared intermetallic of crystal structure belongs to Laves phase with AB{sub 2} type. Electrochemical measurement of passive film on surface of bulk Zr-based intermetallic exhibited significant difference with that of zirconium. Potentiodynamic measurements results revealed that intermetallic exhibited higher corrosion potential and lower corrosion current density than that of pure zirconium, implying that Zr-based second phase will act as cathode when they are included in zirconium matrix. Meanwhile, significant improvement of Zr–Fe–Cr intermetallic on the water chemistry corrosion resistance was demonstrated comparing with Zr–Fe and Zr–Cr binary intermetallics.

  9. Effects of hot isostatic pressing temperature on casting shrinkage densification and microstructure of Ti6Al4V alloy

    Directory of Open Access Journals (Sweden)

    Qian Xu

    2017-11-01

    Full Text Available The Ti6Al4V alloy castings were produced by the investment casting process, and the hot isostatic pressing (HIP was used to remove shrinkage from castings. The processing pressure and holding time for HIP were 150 MPa and 20 min, respectively. Four different HIP temperatures were tested, including 750 ºC, 850 ºC, 920 ºC and 950 ºC. To evaluate the effects of temperature on densification and microstructure of Ti6Al4V alloy treated by HIP, non-destructive testing and metallographic observation was performed. The experimental results show that the shrinkage was completely closed at 920 ºC and 950 ºC. The densification of Ti6Al4V alloy increased as the HIP temperature increased below 920 ºC. The lamellae were more uniform, the thickness of lamellae was obviously broadened and the structure was coarsen. Besides, the Norton creep equation was used to simulate the effect of different temperatures on the densification of Ti6Al4V alloy during HIP. The simulation results were in good agreement with the experimental results. It was also found that 920 ºC is a suitable temperature for HIP for Ti6Al4V alloy.

  10. AA6082 to DX56-Steel Laser Brazing: Process Parameter-Intermetallic Formation Correlation

    Science.gov (United States)

    Narsimhachary, D.; Pal, S.; Shariff, S. M.; Padmanabham, G.; Basu, A.

    2017-09-01

    In the present study, laser-brazed AA6082 to DX56-galvanized steel joints were investigated to understand the influence of process parameters on joint strength in terms of intermetallic layer formation. 1.5-mm-thick sheet of aluminum alloy (AA6082-T6) and galvanized steel (DX56) sheet of 0.7 mm thickness were laser-brazed with 1.5-mm-diameter Al-12% Si solid filler wire. During laser brazing, laser power (4.6 kW) and wire feed rate (3.4 m/min) were kept constant with a varying laser scan speed of 3.5, 3, 2.5, 2, 1.5, and 1 m/min. Microstructure of brazed joint reveals epitaxial growth at the aluminum side and intermetallic layer formation at steel interface. Intermetallic layer formation was confirmed by EDS analysis and XRD study. Hardness profile showed hardness drop in filler region, and failure during tensile testing was initiated through the filler region near the steel interface. As per both experimental study and numerical analysis, it was observed that intermetallic layer thickness decreases with increasing brazing speed. Zn vaporization from galvanized steel interface also affected the joint strength. It was found that high laser scan speed or faster cooling rate can be chosen for suppressing intermetallic layer formation or at least decreasing the layer thickness which results in improved mechanical properties.

  11. As-cast microstructures and behavior at high temperature of chromium-rich cobalt-based alloys containing hafnium carbides

    Energy Technology Data Exchange (ETDEWEB)

    Berthod, Patrice, E-mail: Patrice.Berthod@univ-lorraine.fr; Conrath, Elodie

    2014-02-14

    Hafnium is often used to improve the high temperature oxidation resistance of superalloys but not to form carbides for strengthen them against creep. In this work hafnium was added in cobalt-based alloys for verifying that HfC can be obtained in cobalt-based alloys and for characterizing their behavior at a very temperature. Three Co–25Cr–0.25 and 0.50C alloys containing 3.7 and 7.4 Hf to promote HfC carbides, and four Co–25Cr– 0 to 1C alloys for comparison (all contents in wt.%), were cast and exposed at 1200 °C for 50 h in synthetic air. The HfC carbides formed instead chromium carbides during solidification, in eutectic with matrix and as dispersed compact particles. During the stage at 1200 °C the HfC carbides did not significantly evolve, even near the oxidation front despite oxidation early become very fast and generalized. At the same time the chromium carbides present in the Co–Cr–C alloys totally disappeared in the same conditions. Such HfC-alloys potentially bring efficient and sustainable mechanical strengthening at high temperature, but their hot oxidation resistance must be significantly improved. - Highlights: • Co-based alloys containing HfC carbides were successfully obtained by foundry. • HfC are pro-eutectic or form an interdendritic eutectic compound with matrix. • The HfC carbides appear very stable on long time at 1200 °C. • The hot oxidation of the alloys is fast and they require higher Cr contents. • The high stability of HfC may allow Cr-enrichment by pack-cementation.

  12. Microstructure and mechanical properties of rapidly solidified FeAlCr intermetallic compound

    Directory of Open Access Journals (Sweden)

    R. A. Rodríguez‐Díaz

    2009-08-01

    Full Text Available In this work results regarding microstructural characterization of a melt‐spun intermetallic compound Fe40Al5Cr (% at.produced by rapid solidification employing the melt spinning technique at three different tangential wheel speeds (12, 16 and20 ms‐1 are presented. Melt spun ribbons were characterized by optical and scanning electron microscopy (SEM in order toobserve morphology, grain size, ribbon thickness and also fracture surfaces after tensile tests. EDS coupled to SEM wasemployed to perform punctual and scan line chemical analyses on samples, x‐ray diffraction (XRD was utilized to identify crystalstructure and phases. Transmission electron microscopy (TEM was employed to confirm crystal structure and also tocharacterize nanopores formed in the specimens by vacancy clustering. With regard to mechanical properties, micro hardnessVickers measurements as well as tensile tests at room temperature were applied to the rapidly solidified ribbons.The grain size of rapidly solidified Fe40Al5Cr ribbons suffered a drastic reduction as compared with alloys of the samecomposition produced by conventional melting and casting methods, and in melt‐spun ribbons it decreases as the wheel speedincreases. Punctual and line‐scanning chemical analyses revealed that Cr enters in solid solution in FeAl matrix. Hardnessmeasurements revealed a softening in rapidly solidified FeAlCr ribbons as compared with FeAl alloys and tensile test exhibited a(transgranular + intergranular mode of fracture, reaching up to 3 % of elongation in FeAlCr alloys. The presence of porous(meso and nano were also characterized.

  13. R-HPDC of magnesium alloys

    CSIR Research Space (South Africa)

    Curle, UA

    2013-01-01

    Full Text Available liquid segregation is observed in the as-cast microstructure for all three alloys. Minor alloy additions of Mn, in composition specifications, results in the formation of Al8Mn5 intermetallic phase particles dispersed throughout the microstructure. All...

  14. Formability Evaluation of Aluminum Alloy 6061-T6 Sheet at Room and Elevated Temperatures

    Science.gov (United States)

    Chen, Zhu; Fang, Gang; Zhao, Jia-Qing

    2017-09-01

    The formability of aluminum alloy 6061-T6 sheet was evaluated, and the effects of temperature and strain rate on the formability were analyzed. Uniaxial tension tests and Nakajima tests were conducted at room temperature to obtain the constitutive parameters of AA 6061-T6 and establish the forming limit diagram (FLD), respectively. Moreover, uniaxial tension tests were performed at the temperatures ranging between 180 and 380 °C and the strain rates ranging between 0.0005 and 0.05 s-1, and the constitutive equations of AA 6061-T6 were established. Nakajima tests at temperature 330 °C and two forming speeds (15 and 150 mm/min) were carried out to evaluate the formability of AA6061-T6 at elevated temperatures. In consequence, FLDs under different forming conditions were established and compared. Experimental results showed that the forming limit of AA 6061-T6 increased with the increasing temperature and the decreasing forming speed. The present investigation presented the formability of AA 6061-T6 under different forming conditions, which provided a guidance to design the warm/hot forming of AA 6061 sheet. The FLDs and constitutive equations established through these experiments will be used to predict the forming defects in the forming process design.

  15. ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties

    Science.gov (United States)

    Montana, J. W.; Nelson, E. E.

    1972-01-01

    The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.

  16. Unraveling the composition dependence of the martensitic transformation temperature: A first-principles study of Ti-Ta alloys

    Science.gov (United States)

    Chakraborty, Tanmoy; Rogal, Jutta; Drautz, Ralf

    2016-12-01

    The martensitic start temperature Ms is one of the key characteristics of shape memory materials. High-temperature shape memory alloys are a special class of materials where transformation temperatures between the martensite and austenite phase above 373 K are desirable. For the design of new high-temperature shape memory alloys it is therefore important to understand and predict the dependence of Ms on the composition of the material. Using density functional theory in combination with the quasiharmonic Debye model, we evaluate the different contributions to the free energy to determine the transition temperature T0 over a wide range of compositions in Ti-Ta alloys. Our approach provides physical insight into the various contributions that explain the strong composition dependence of Ms that is observed experimentally. Based on our calculations, we identify the relative phase stability at T =0 K and the vibrational entropy difference between the involved phases as critical parameters to predict changes in T0. We propose a simple, one-dimensional descriptor to estimate the transition temperature that can be used in the identification of new alloys suitable for high-temperature shape memory applications.

  17. L10 ordered structures in Al-Cu-(Mg) alloys at the early stages of elevated temperature aging

    Energy Technology Data Exchange (ETDEWEB)

    Fuzhong, X.; Mingpu, W.

    2016-07-01

    This study concerns the precipitation structures of Al-3Cu and Al-3Cu-1.78Mg (wt. %) alloys at the early stages of elevated temperature aging. The Al-3Cu and Al-3Cu-1.78 Mg alloys were solution treated at 540 °C and 500 °C for 2 h, respectively, and then aged at 190 °C for 2 min. The precipitation structures in aged Al-3Cu-(1.78Mg) alloys were characterized by Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HTREM). 001 zone axis Selected area electron diffraction patterns indicate that L10 ordered structures are formed in the two aged alloys. HRTEM experiments reveal the partial dislocations on the interfaces of L10 ordered structures. From comparing experimental results with that in the literature, it is concluded that the L10 ordered structures in aged Al-3Cu alloy consist of Al and Cu atoms, and they are comprised by Al, Cu and Mg atoms together in the aged Al-3Cu-1.78Mg alloy. On the basis of precipitate growing thermodynamics, it is thought the L10 ordered structures act as nuclei for GP zones in Al-Cu-(Mg) alloys during aging. (Author)

  18. Temperature dependence of the kinetic energy in the Zr40Be60 amorphous alloy

    Science.gov (United States)

    Syrykh, G. F.; Stolyarov, A. A.; Krzystyniak, M.; Romanelli, G.; Sadykov, R. A.

    2017-05-01

    The average kinetic energy of the atomic nucleus for each element of the amorphous alloy Zr40Be60 in the temperature range 10-300 K has been measured for the first time using VESUVIO spectrometer (ISIS). The experimental values of have been compared to the partial ZrBe spectra refined by a recursion method based on the data obtained with thermal neutron scattering. The satisfactory agreement has been reached with the calculations using partial spectra based on thermal neutron spectra obtained with recursion method. In addition, the experimental data have been compared to the Debye model. The measurements at different temperatures (10, 200, and 300 K) will provide an opportunity to evaluate the significance of anharmonicity in the dynamics of metallic glasses.

  19. Effect of time and temperature on grain size of V and V-Cr-Ti alloys

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Rink, D.L. [Argonne National Lab., IL (United States)

    1996-10-01

    Grain growth studies were conducted to evaluate the effect of time and temperature on the grain size of pure V, V-4 wt.%Cr-4 wt.%Ti, and V-5 wt.%Cr-5 wt.%Ti alloys. The temperatures used in the study were 500, 650, 800, and 1000{degrees}C, and exposure times ranged between 100 and {approx}5000 h. All three materials exhibited negligible grain growth at 500, 650, and 800{degrees}C, even after {approx}5000 h. At 1000{degrees}C, pure V showed substantial grain growth after only 100 h, and V-4Cr-4Ti showed growth after 2000 h, while V-5Cr-5Ti showed no grain growth after exposure for up to 2000 h.

  20. Additive Manufacturing of NiTiHf High Temperature Shape Memory Alloy

    Science.gov (United States)

    Benafan, Othmane; Bigelow, Glen S.; Elahinia, Mohammad; Moghaddam, Narges Shayesteh; Amerinatanzi, Amirhesam; Saedi, Soheil; Toker, Guher Pelin; Karaca, Haluk

    2017-01-01

    Additive manufacturing of a NiTi-20Hf high temperature shape memory alloy (HTSMA) was investigated. A selective laser melting (SLM) process by Phenix3D Systems was used to develop components from NiTiHf powder (of approximately 25-75 m particle fractions), and the thermomechanical response was compared to the conventionally vacuum induction skull melted counterpart. Transformation temperatures of the SLM material were found to be slightly lower due to the additional oxygen pick up from the gas atomization and melting process. The shape memory response in compression was measured for stresses up to 500 MPa, and transformation strains were found to be very comparable (Up to 1.26 for the as-extruded; up to 1.52 for SLM).

  1. Evaluation of precipitates used in strainer head loss testing : Part II. precipitates by in-situ aluminum alloy corrosion.

    Energy Technology Data Exchange (ETDEWEB)

    Bahn, C.; Kasza, K. E.; Shack, W. J.; Natesan, K. (Nuclear Engineering Division)

    2011-05-01

    Vertical loop head loss tests were performed with 6061 and 1100 aluminum (Al) alloy plates immersed in borated solution at pH = 9.3 at room temperature and 60 C. The results suggest that the potential for corrosion of an Al alloy to result in increased head loss across a glass fiber bed may depend on its microstructure, i.e., the size distribution and number density of intermetallic particles that are present in Al matrix and FeSiAl ternary compounds, as well as its Al release rate. Per unit mass of Al removed from solution, the WCAP-16530 aluminum hydroxide (Al(OH){sub 3}) surrogate was more effective in increasing head loss than the Al(OH)3 precipitates formed in situ by corrosion of Al alloy. However, in choosing a representative amount of surrogate for plant specific testing, consideration should be given to the potential for additional head losses due to intermetallic particles and the apparent reduction in the effective solubility of Al(OH){sub 3} when intermetallic particles are present.

  2. Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

    Science.gov (United States)

    Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

    2005-01-01

    High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

  3. Auger electron spectroscopy study of oxidation of a PdCr alloy used for high-temperature sensors

    Science.gov (United States)

    Boyd, Darwin L.; Zeller, Mary V.; Vargas-Aburto, Carlos

    1993-01-01

    A Pd-13 wt. percent Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical resistance versus temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy was used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13 wt. percent Cr.

  4. Mechanical behavior of tungsten–vanadium–lanthana alloys as function of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, T., E-mail: teresa.palacios@mater.upm.es [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Pastor, J.Y. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Aguirre, M.V. [Departamento de Tecnologías Especiales Aplicadas a la Aeronáutica, Universidad Politécnica de Madrid, E.I. Aeronáutica y del Espacio, 28040 Madrid (Spain); Martín, A. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Monge, M.A.; Muñóz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, Leganés (Spain)

    2013-11-15

    The mechanical behavior of three tungsten (W) alloys with vanadium (V) and lanthana (La{sub 2}O{sub 3}) additions (W–4%V, W–1%La{sub 2}O{sub 3}, W–4%V–1%La{sub 2}O{sub 3}) processed by hot isostatic pressing (HIP) have been compared with pure-W to analyze the influence of the dopants. Mechanical characterization was performed by three point bending (TPB) tests in an oxidizing air atmosphere and temperature range between 77 (immersion tests in liquid nitrogen) and 1273 K, through which the fracture toughness, flexural strength, and yield strength as function of temperature were obtained. Results show that the V and La{sub 2}O{sub 3} additions improve the mechanical properties and oxidation behavior, respectively. Furthermore, a synergistic effect of both dopants results in an extraordinary increase of the flexure strength, fracture toughness and resistance to oxidation compared to pure-W, especially at higher temperatures. In addition, a new experimental method was developed to obtain a very small notch tip radius (around 5–7 μm) and much more similar to a crack through the use of a new machined notch. The fracture toughness results were lower than those obtained with traditional machining of the notch, which can be explained with electron microscopy, observations of deformation in the rear part of the notch tip. Finally, scanning electron microscopy (SEM) examination of the microstructure and fracture surfaces was used to determine and analyze the relationship between the macroscopic mechanical properties and the micromechanisms of failure involved, depending on the temperature and the dispersion of the alloy.

  5. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [ORNL; Yamamoto, Yukinori [ORNL; Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Pankiw, Roman [Duraloy Technologies Inc; Voke, Don [Duraloy Technologies Inc

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  6. Alloying effect on the room temperature creep characteristics of a Ti-Zr-Be bulk metallic glass

    Science.gov (United States)

    Gong, Pan; Wang, Sibo; Li, Fangwei; Wang, Xinyun

    2018-02-01

    The effect of alloying elements (e.g. Fe, Al, and Ni) on the room temperature creep behavior of a lightweight Ti41Zr25Be34 bulk metallic glass (BMG) was investigated via nanoindentation tests. The generalized Kelvin model was adopted to describe the creep curves. The strain rate sensitivity m has been derived as a measure of the creep resistance. The compliance spectrum and retardation spectrum were also derived. The results show that the creep resistance of Ti41Zr25Be34 alloy can be obviously improved with the addition of alloying elements, and the most effective element is found to be Al. The mechanism for enhancing the creep resistance was discussed in terms of the scale variation of the shear transformation zone induced by alloying.

  7. Intermetallics structures, properties, and statistics

    CERN Document Server

    Steurer, Walter

    2016-01-01

    The focus of this book is clearly on the statistics, topology, and geometry of crystal structures and crystal structure types. This allows one to uncover important structural relationships and to illustrate the relative simplicity of most of the general structural building principles. It also allows one to show that a large variety of actual structures can be related to a rather small number of aristotypes. It is important that this book is readable and beneficial in the one way or another for everyone interested in intermetallic phases, from graduate students to experts in solid-state chemistry/physics/materials science. For that purpose it avoids using an enigmatic abstract terminology for the classification of structures. The focus on the statistical analysis of structures and structure types should be seen as an attempt to draw the background of the big picture of intermetallics, and to point to the white spots in it, which could be worthwhile exploring. This book was not planned as a textbook; rather, it...

  8. Current activated tip sintering of Ni-Ti intermetallics

    Science.gov (United States)

    Sharma, Nitin

    This thesis investigated the current activated tip-sintering of reactive mixtures of nickel and titanium to form Ni-Ti intermetallics. The effect of elemental powder composition, heating profile and micro-jet inert gas pressures on the developed macro- and microstructure was investigated. The heating profile brought upon by selective electric current application was found to have a significant effect on whether the reaction is a volumetric combustion or a self-propagating high temperature one. The best results in terms of homogeneity and Ni-Ti intermetallics yield, were obtained for an inert gas pressure of 4 psi under for the nickel rich composition. In addition, surprising results at the higher inert gas pressures show the formation of hollow products, which can give rise future exploration of this technique for combustion synthesizing hollow products of different shapes.

  9. Single crystal growth of the intermetallic compound InPd

    Science.gov (United States)

    Hahne, Michael; Gille, Peter

    2014-09-01

    Quite recently intermetallic compounds have been investigated as catalysts for heterogeneous catalysis as they can be highly active regarding a specific reaction and often show advantages in selectivity and long-term stability. The intermetallic phase InPd (CsCl structure type) is considered to be a possible catalyst for methanol steam reforming. Single crystals are needed to study the basic processes of catalysis. Using the Czochralski technique, InPd single crystals were grown from In-rich solutions as to reduce the vapor pressure of In. The crystals show some unusual rough surface morphology and gradients concerning the main components composition. By adjusting the growth parameters like growth temperature and growth rate we succeeded to get inclusion-free single crystals.

  10. Production of nanograined intermetallics using high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Alhamidi, Ali; Edalati, Kaveh; Horita, Zenji, E-mail: horita@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka (Japan)

    2013-11-01

    Formation of intermetallics is generally feasible at high temperatures when the lattice diffusion is fast enough to form the ordered phases. This study shows that nanograined intermetallics are formed at a low temperature as 573 K in Al- 25 mol% Ni, Al- 50 mol.% Ni and Al- 50 mol% Ti powder mixtures through powder consolidation using high-pressure torsion (HPT). For the three compositions, the hardness gradually increases with straining but saturates to the levels as high as 550-920 Hv. In addition to the high hardness, the TiAl material exhibits high yield strength as {approx}3 GPa with good ductility as {approx}23%, when they are examined by micropillar compression tests. X-ray diffraction analysis and high-resolution transmission electron microscopy reveal that the significant increase in hardness and strength is due to the formation of nanograined intermetallics such as Al{sub 3}Ni, Al{sub 3}Ni{sub 2}, TiAl{sub 3}, TiAl{sub 2} and TiAl with average grain sizes of 20-40 nm (author)

  11. Effect of rolling temperature of the magnesium alloy AZ31B formability; Efeito da temperatura de laminacao na deformabilidade da liga de magnesio AZ31B

    Energy Technology Data Exchange (ETDEWEB)

    Catorceno, L.L.C.; Zimmermann, A.J.O.; Padilha, A.F., E-mail: litzy.catorceno@poli.usp.b [Universidade de Sao Paulo (DEMM/EP/USP), SP (Brazil). Escola Politecnica. Dept. de Engenharia Metalurgica e de Materiais

    2010-07-01

    The magnesium alloy AZ31B presents an interesting set of properties, which makes it potential candidate for applications in automotive and aeronautics. The main limitation of magnesium alloys is the low capacity of plastic forming at room temperature. The main motivation of this project is to understand and control the microstructure and crystallographic texture of magnesium alloys, to improve their formability. The effect of rolling temperature on the formability of the alloy was studied in this stage of the project. The alloy in the form of annealed and recrystallized sheets (2 mm thick) was deformed by rolling at four different temperatures: 25, 100, 200 and 250 deg C. The microstructural characterization was achieved using several complementary techniques of microstructural analysis, such as optical microscopy, scanning electron microscopy, X-ray analysis by energy dispersive, X-ray diffraction and microhardness. Results about the effect of rolling temperature on the alloy formability were presented and discussed. (author)

  12. Creep-Fatigue Damage Investigation and Modeling of Alloy 617 at High Temperatures

    Science.gov (United States)

    Tahir, Fraaz

    The Very High Temperature Reactor (VHTR) is one of six conceptual designs proposed for Generation IV nuclear reactors. Alloy 617, a solid solution strengthened Ni-base superalloy, is currently the primary candidate material for the tubing of the Intermediate Heat Exchanger (IHX) in the VHTR design. Steady-state operation of the nuclear power plant at elevated temperatures leads to creep deformation, whereas loading transients including startup and shutdown generate fatigue. A detailed understanding of the creep-fatigue interaction in Alloy 617 is necessary before it can be considered as a material for nuclear construction in ASME Boiler and Pressure Vessel Code. Current design codes for components undergoing creep-fatigue interaction at elevated temperatures require creep-fatigue testing data covering the entire range from fatigue-dominant to creep-dominant loading. Classical strain-controlled tests, which produce stress relaxation during the hold period, show a saturation in cycle life with increasing hold periods due to the rapid stress-relaxation of Alloy 617 at high temperatures. Therefore, applying longer hold time in these tests cannot generate creep-dominated failure. In this study, uniaxial isothermal creep-fatigue tests with non-traditional loading waveforms were designed and performed at 850 and 950°C, with an objective of generating test data in the creep-dominant regime. The new loading waveforms are hybrid strain-controlled and force-controlled testing which avoid stress relaxation during the creep hold. The experimental data showed varying proportions of creep and fatigue damage, and provided evidence for the inadequacy of the widely-used time fraction rule for estimating creep damage under creep-fatigue conditions. Micro-scale damage features in failed test specimens, such as fatigue cracks and creep voids, were quantified using a Scanning Electron Microscope (SEM) to find a correlation between creep and fatigue damage. Quantitative statistical

  13. Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A

    Science.gov (United States)

    Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

    1971-01-01

    Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

  14. Effect of carbon content on elevated temperature stability and tensile properties of Fe-8.5Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baligidad, R.G.; Radhakrishna, A. [Defence Metallurgical Research Lab., Hyderabad (India)

    2000-04-15

    Fe-8.4Al-0.04C, Fe-8.26Al-0.46C and Fe-8.35Al-1.1C alloys were prepared by a combination of air induction melting and electroslag remelting. The low (0.04 wt.%) carbon alloy exhibited microcracks therefore it was not studied further. The ESR ingots of high (0.46 and 1.1 wt.%) carbon alloys exhibited a significant amount of Fe{sub 3}AlC{sub 0.5} precipitation. The cast ESR samples of Fe-8.26Al-0.46C and Fe-8.35Al-1.1 C were placed in a hearth furnace at 873,1073 and 1273 K for 24 h and then furnace cooled. The high carbon alloys do not undergo decarburization and exhibit stable microstructure up to 873 K. Decarburization appears to be a problem only after exposure at temperatures of 1073 K and above. The ESR Fe-8.26Al-0.46C alloy exhibited greater elongation and significantly better elevated temperature strength up to 873 K than those reported for cast VIM low carbon multicomponent alloy with similar Al content. This may be due to the presence of a large volume fraction of stable Fe{sub 3}AlC{sub 0.5} precipitates. All the high carbon alloys exhibit a sharp drop in strength at 873 K regardless of carbon content. These alloys are therefore targeted for potential structural application at or below 873 K. (orig.)

  15. Microstructure and mechanical properties of Ni3Al intermetallics prepared by directional solidification electromagnetic cold crucible technique

    OpenAIRE

    Hong-sheng Ding; Guo-tian Wang; Rui-run Chen

    2017-01-01

    The present work focused on the Ni3Al-based alloy with a high melting point. The aim of the research is to study the effect of withdrawal rate on the microstructures and mechanical properties of directionally solidified Ni-25Al alloy. Ni3Al intermetallics were prepared at different withdrawal rates by directional solidification (DS) in an electromagnetic cold crucible directional solidification furnace. The DS samples contain Ni3Al and NiAl phases. The primary dendritic spacing (λ) decreases ...

  16. Relations between the modulus of elasticity of binary alloys and their structure

    Science.gov (United States)

    Koster, Werner; Rauscher, Walter

    1951-01-01

    A comprehensive survey of the elastic modulus of binary alloys as a function of the concentration is presented. Alloys that form continuous solid solutions, limited solid solutions, eutectic alloys, and alloys with intermetallic phases are investigated. Systems having the most important structures have been examined to obtain criteria for the relation between lattice structure, type of binding, and elastic behavior.

  17. Simulation of Temperature Distribution in TIG Spot Welds of(Al-Mg) Alloy Using Finite Element Method

    OpenAIRE

    Ahlam Abid Ameer Alkhafajy; Abdul Hussain G. Al-Maliky; Muna K Abbas

    2008-01-01

    This research concern to analyse and simulate the temperature distribution in the spot welding joints using tungsten arc welding shielded with inert gas (TIG Spot) for the aluminum-magnesium alloy type (5052-O). The effect of and the quantity of the heat input that enter the weld zone has been investigated welding current, welding time and arc length on temperature distribution. The finite element method (by utilizing programme ANSYS 5.4) is presented the temperature distribution in a circula...

  18. High temperature mechanical properties of a zirconium-modified, precipitation- strengthened nickel, 30 percent copper alloy

    Science.gov (United States)

    Whittenberger, J. D.

    1974-01-01

    A precipitation-strengthened Monel-type alloy has been developed through minor alloying additions of zirconium to a base Ni-30Cu alloy. The results of this exploratory study indicate that thermomechanical processing of a solution-treated Ni-30Cu-0.2Zr alloy produced a dispersion of precipitates. The precipitates have been tentatively identified as a Ni5Zr compound. A comparison of the mechanical properties, as determined by testing in air, of the zirconium-modified alloy to those of a Ni-30Cu alloy reveals that the precipitation-strengthened alloy has improved tensile properties to 1200 K and improved stress-rupture properties to 1100 K. The oxidation characteristics of the modified alloy appeared to be equivalent to those of the base Ni-30Cu alloy.

  19. Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

    Science.gov (United States)

    Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

    2018-01-01

    The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

  20. Low temperature physical properties of Co-35Ni-20Cr-10Mo alloy MP35N®

    Science.gov (United States)

    Lu, J.; Toplosky, V. J.; Goddard, R. E.; Han, K.

    2017-09-01

    Multiphase Co-35Ni-20Cr-10Mo alloy MP35N® is a high strength alloy with excellent corrosion resistance. Its applications span chemical, medical, and food processing industries. Thanks to its high modulus and high strength, it found applications in reinforcement of ultra-high field pulsed magnets. Recently, it has also been considered for reinforcement in superconducting wires used in ultra-high field superconducting magnets. For these applications, accurate measurement of its physical properties at cryogenic temperatures is very important. In this paper, physical properties including electrical resistivity, specific heat, thermal conductivity, and magnetization of as-received and aged samples are measured from 2 to 300 K. The electrical resistivity of the aged sample is slightly higher than the as-received sample, both showing a weak linear temperature dependence in the entire range of 2-300 K. The measured specific heat Cp of 430 J/kg-K at 295 K agrees with a theoretical prediction, but is significantly smaller than the values in the literature. The thermal conductivity between 2 and 300 K is in good agreement with the literature which is only available above 77 K. Magnetic property of MP35N® changes significantly with aging. The as-received sample exhibits Curie paramagnetism with a Curie constant C = 0.175 K. While the aged sample contains small amounts of a ferromagnetic phase even at room temperature. The measured MP35N® properties will be useful for the engineering design of pulsed magnets and superconducting magnets using MP35N® as reinforcement.