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Sample records for al alloy produced

  1. Effect of boron in Fe 70 Al 30 nanostructured alloys produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Rico, M. M.; Pérez Alcázar, G. A.; Greneche, J. M.

    2013-04-01

    The substitution of aluminum by boron in the Fe70Al30 system prepared by high energy ball milling is studied when the B content ranged from 0 up to 20 at. %, and the milling times were 24, 48 and 72 h. X-ray diffraction (XRD) patterns of Fe70Al30 showed a predominant bcc structural phase with a lattice parameter larger than that of α-Fe. A second (tetragonal) phase arose with the addition of boron. It is associated to the existence of (Fe, Al)2B, although the values of the lattice parameters are slightly different from those found in the literature. This phase shows high stability; its lattice parameters and the Mössbauer parameters do not show notable variations, either with milling time or composition. It was also evidenced that an increase of boron content and of milling time produced a decrease of the lattice parameter of the Fe-Al bcc structure. This is in agreement with the small atomic radius of boron in comparison with that of aluminum. This also allows boron to occupy interstitial sites in the lattice, increasing the grain size and giving rise to the ductile character of the alloy. On the other hand, 300 K transmission Mössbauer spectra (TMS) were fitted, for low boron concentrations (<8 at.%), with a hyperfine field distribution (HFD) associated with the bcc phase. For high boron content (≥8 at.%), a magnetic component related to the tetragonal phase is added and its broadened lines are attributed to the disordered character of Fe2B, probably induced by the milling process.

  2. Effect of boron in Fe 70 Al 30 nanostructured alloys produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Rico, M. M.; Pérez Alcázar, G. A.; Greneche, J. M.

    2014-01-01

    The substitution of aluminum by boron in the Fe70Al30 system prepared by high energy ball milling is studied when the B content ranged from 0 up to 20 at. %, and the milling times were 24, 48 and 72 h. X-ray diffraction (XRD) patterns of Fe70Al30 showed a predominant bcc structural phase with a lattice parameter larger than that of α-Fe. A second (tetragonal) phase arose with the addition of boron. It is associated to the existence of (Fe, Al)2B, although the values of the lattice parameters are slightly different from those found in the literature. This phase shows high stability; its lattice parameters and the Mössbauer parameters do not show notable variations, either with milling time or composition. It was also evidenced that an increase of boron content and of milling time produced a decrease of the lattice parameter of the Fe-Al bcc structure. This is in agreement with the small atomic radius of boron in comparison with that of aluminum. This also allows boron to occupy interstitial sites in the lattice, increasing the grain size and giving rise to the ductile character of the alloy. On the other hand, 300 K transmission Mössbauer spectra (TMS) were fitted, for low boron concentrations (<8 at.%), with a hyperfine field distribution (HFD) associated with the bcc phase. For high boron content (≥8 at.%), a magnetic component related to the tetragonal phase is added and its broadened lines are attributed to the disordered character of Fe2B, probably induced by the milling process.

  3. Microstructure and mechanical behaviour of Ti-6Al-7Nb alloy produced by selective laser melting

    SciTech Connect

    Chlebus, Edward; Kuznicka, Bogumila Kurzynowski, Tomasz; Dybala, Bogdan

    2011-05-15

    Selective laser melting (SLM) is an advanced manufacturing technology providing alternative method of producing complex components directly from 3D computer models. The purpose of this work is to determine the influence of the SLM manufacturing strategy on mechanical properties and microstructure of the as-built Ti-Al-Nb alloy. Specimens of Ti-6Al-7Nb were produced in three versions of the specimen axis orientation with respect to its build direction. Mechanical characteristics of the alloy were determined by tensile and compression testing, as well as hardness measurements. Microstructures were characterised utilising optical microscopy, scanning electron microscopy and X-ray diffraction analysis. It was found that the as-built Ti-6Al-7Nb alloy has microstructure of {alpha}' martensite hardened by dispersive precipitates of the second phase, which results in higher tensile and compressive strengths, but lower ductility in comparison to those of an alloy manufactured by conventional methods. The layered microstructure of the material gives it a significant anisotropy of Young's modulus, moderate anisotropy of mechanical properties, but strong anisotropy of sensitivity to the build porosity. The paper develops understanding of the relationships between the strategy of layered manufacturing of the Ti-6Al-7Nb alloy and its microstructural and mechanical characteristics. This is important for future applications of the SLM technology for producing Ti-6Al-7Nb parts, e.g. the custom medical implants. - Research Highlights: {yields} The as-built SLM Ti-6Al-7Nb alloy has a layered microstructure of {alpha}' martensite. {yields} Size and orientation of the {alpha}' plates are determined by the SLM building strategy. {yields} The layered microstructure gives the alloy an anisotropy of Young's modulus. {yields} The building strategy influences anisotropy of material sensitivity to the built porosity.

  4. Al-Fe-Zr alloys for high temperature applications produced by rapid quenching from the melt

    SciTech Connect

    Okazaki, K.; Skinner, D.J.

    1984-09-01

    The melt-spinning technique to produce microstructure for high temperature-high strength Al-Fe-Zr alloys, meeting aerospace structural requirements, is presented, including the investigations for the improvement of the thermal stability of iron aluminide dispersoids by addition of Zr. The alloys containing about 27 to 30 percent volume fraction of dispersoids would be the optimum to meet the requirements from the strength and ductility viewpoint. The thermal stability of the alloys was determined by measuring the microvickers hardness on the isochronally annealed ribbons. 9 references.

  5. Properties of High Volume Fraction Fly Ash/Al Alloy Composites Produced by Infiltration Process

    NASA Astrophysics Data System (ADS)

    Kountouras, D. T.; Stergioudi, F.; Tsouknidas, A.; Vogiatzis, C. A.; Skolianos, S. M.

    2015-09-01

    In the present study, pressure infiltration is employed to synthesize aluminum alloy 7075-fly ash composites. The microstructure and chemical composition of the fly ash and the produced composite material was examined using optical and scanning electron microscopy, as well as x-ray diffraction. Several properties of the produced composite material were examined and evaluated including macro-hardness, wear, thermal expansion, and corrosion behavior. The wear characteristics of the composite, in the as-cast conditions, were studied by dry sliding wear tests. The corrosion behavior of composite material was evaluated by means of potentiodynamic corrosion experiments in a 3.5 wt.% NaCl solution. The composite specimens exhibit a homogeneous distribution of fly ash particles and present enhanced hardness values, compared to the matrix material. The high volume fraction of the fly ash reinforcement (>40%) in the composite material led to increased wear rates, attributed to the fragmentation of the fly ash particles. However, the presence of fly ash particles in the Al alloy matrix considerably decreased the coefficiency of thermal expansion, while resulting in an altered corrosion mechanism of the composite material with respect to the matrix alloy.

  6. Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt

    NASA Astrophysics Data System (ADS)

    El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

    2014-10-01

    The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside α-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of α-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of

  7. Structure and hot hardness of RuAl-based alloys produced by reactive sintering using hot isostatic pressing

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Morozov, A. E.; Padalko, A. G.; Drozdov, A. A.

    2008-04-01

    The structure and hot hardness (at temperatures up to 1100°C) of RuAl-based powder alloys with 1 3 at % Ni, Mo, Re, or Ru are studied. The alloys are produced by the reactive sintering of cold-compacted bars and subsequent threefold isostatic pressing with intermediate annealing at 1500°C performed after the first hot isostatic pressing. The samples have a residual pore content of 1 2.5 vol % and are characterized by a micrononuniform distribution of base and alloying elements. The alloys with refractory metals, such as Re, Mo, or Ru, are found to have the maximum hardness at all temperatures under study. At low temperatures, the effect is more substantial; the hardness of the Re-containing alloys exceeds that of the other alloys by a factor of 1.3 3.6. The increase in the hardness related to solid-solution alloying becomes more substantial owing to the microinhomogeneity of the sintered powder alloys and weakens because of microporosity. Recommendations that allow the uniformity of the distribution of the base and alloying elements to be increased are given.

  8. Effects of Al-5Ti-1B master alloy on the microstructural evaluation of a highly alloyed aluminum alloy produced by SIMA process

    SciTech Connect

    Alipour, M.; Emamy, M.; Azarbarmas, M.; Karamouz, M.

    2010-06-15

    This study was undertaken to investigate the influence of Al-5Ti-1B master alloy on the structural characteristics of Al-12Zn-3 Mg-2.5Cu aluminum alloy. The optimum amount of Ti containing master alloy for proper grain refining was selected as 6 wt.%. A modified strain-induced, melt-activated (SIMA) process for semi-solid processing of alloys was proposed. In order to examine the effectiveness of the modified SIMA process, the recrystallized microstructures of the Al alloy (Al-12Zn-3 Mg-2.5Cu) prepared by the modified SIMA processes were macroscopically. The modified SIMA process employed casting, warm multi-forging, recrystallization and partial melting instead of the conventional process. Reheating condition to obtain a fine globular microstructure was optimized. The microstructure evolution of reheated Al-12Zn-3 Mg-2.5Cu aluminum alloy was characterized by SEM (Scanning electron microscopy) and optical microscopy. In this study the relation between the induced strain with size and shape of grain size has been studied. Results indicated that with the increase of strain sphericity of particles, their size decreases and sphericity takes place in less reahiting time.

  9. Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy

    SciTech Connect

    Tammy J. Harrell; Troy D. Topping; Haiming Wen; Tao Hu; JULIE M. SCHOENUNG; ENRIQUE J. LAVERNIA

    2014-12-01

    Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure (e.g., 100’s nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP’ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 µm apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

  10. Mechanical Strength and Failure Characteristics of Cast Mg-9 pctAl-1 pctZn Alloys Produced by a Heated-Mold Continuous Casting Process: Tensile Properties

    NASA Astrophysics Data System (ADS)

    Okayasu, Mitsuhiro; Takeuchi, Shuhei; Ohfuji, Hiroaki

    2014-11-01

    The mechanical properties and failure characteristics of a cast Mg alloy (AZ91: Mg-Al8.9-Zn0.6-Mn0.2) produced by a heated-mold continuous casting process (HMC) are investigated. In a modification of the original HMC process, the cooling of the liquid alloy by direct water spray is carried out in an atmosphere of high-purity argon gas. The HMC-AZ91 alloy exhibits excellent mechanical properties (high strength and high ductility) that are about twice as high as those for the same alloy produced by conventional gravity casting. The increased material strength and ductility of the HMC sample are attributed to nanoscale and microscale microstructural characteristics. The fine grains and tiny spherical eutectic structures ( e.g., Mg17Al12 and Al6Mn) distributed randomly in the matrix of the HMC alloy result in resistance to dislocation movement, leading to high tensile strength. Basal slip on (0001) planes in the relatively organized crystal orientation of the HMC alloy, as well as grain boundary sliding through tiny spherical eutectic structures, results in high ductility. Details of the failure mechanism under static loading in the HMC alloy are also discussed using failure models.

  11. Effect of milling time and CNT concentration on hardness of CNT/Al{sub 2024} composites produced by mechanical alloying

    SciTech Connect

    Perez-Bustamante, R.; Perez-Bustamante, F.; Estrada-Guel, I.; Licea-Jimenez, L.; Miki-Yoshida, M.; Martinez-Sanchez, R.

    2013-01-15

    Carbon nanotube/2024 aluminum alloy (CNT/Al{sub 2024}) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy confirmed not only the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al{sub 4}C{sub 3}) crystals in the Al matrix. The formation of Al{sub 4}C{sub 3} was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers microhardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al{sub 4}C{sub 3} in the aluminum alloy matrix. - Highlights: Black-Right-Pointing-Pointer The 2024 aluminum alloy was reinforced by CNTs by mechanical alloying process. Black-Right-Pointing-Pointer Composites were microstructural and mechanically evaluated after sintering condition. Black-Right-Pointing-Pointer The greater the CNT concentration, the greater the hardness of the composites. Black-Right-Pointing-Pointer Higher hardness in composites is achieved at 20 h of milling. Black-Right-Pointing-Pointer The formation of Al{sub 4}C{sub 3} does not present a direct relationship with the milling time.

  12. Analysis and Evaluation of Novel Al-Mg-Sc-Zr Aerospace Alloy Strip Produced Using the Horizontal Single Belt Casting (HSBC) Process

    NASA Astrophysics Data System (ADS)

    Ge, Sa; Celikin, Mert; Isac, Mihaiela; Guthrie, Roderick I. L.

    2015-04-01

    Horizontal single belt casting (HSBC) is a near net shape casting process in which molten metal is directly cast into thin strips, at high cooling rates (order of several 100 °C/s), with the potential for high volume, friction free, continuous production of metal strips. This casting process was used in the present work to produce strips of Al-Mg alloys in the AA5000 series, with additions of Sc and Zr. Such aluminum alloys show exceptional potential as a structural material for transportation/aerospace applications. To demonstrate the suitability of the HSBC process to manufacture competitive strip products of Al-Mg-Sc-Zr, the mechanical properties and microstructures of the strips produced using the HSBC process were compared with conventionally cast products. The effects of annealing on the mechanical properties of the strip-cast Al-Mg-Sc-Zr alloys were also investigated.

  13. Mechanical properties of NiAl-Y2O3-based powdered alloys produced by directional recrystallization

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Skachkov, O. A.; Drozdov, A. A.; Morozov, A. E.; Pozharov, S. I.

    2014-03-01

    The mechanical properties of NiAl-Y2O3-based powdered composite alloys (0.5-7.5 vol %), including those with an NiAl intermetallic matrix alloyed with 0.5 wt % Fe and 0.1 wt % La have been studied. Structures with various aspect ratios (AR, the ratio of the grain length to the grain diameter) are formed using deformation and subsequent annealing. A combination of the optimum amount of strengthening phase (2.5 vol % Y2O3) and a quasi-single-crystalline structure with a sharp axial texture with the (100) main orientation and AR ≈ 20-40 provides the maximum short-term strength and life at temperatures up to 1400-1500°C. An NiAl-Y2O3 alloy (2.5 vol %) has the best strength properties among all known nickel superalloys at temperatures higher than 1200°C and can operate under moderate loads at temperatures higher than the working temperatures of nickel superalloys (by 100-400°C) and their melting points. Additional alloying with 10 wt % Co and 2 wt % Nb makes it possible to increase the ultimate tensile strength of an intermetallic NiAl matrix at 1100°C by a factor of 1.3-1.4.

  14. Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications

    NASA Astrophysics Data System (ADS)

    Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.

    2011-01-01

    In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low—temperature glow discharge assisted oxynitriding. The paper describes the surface layer of TiO2+TiN+Ti2N+αTi(N) type produced at temperature 680° C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed. Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.

  15. Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications

    SciTech Connect

    Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.

    2011-01-17

    In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low-temperature glow discharge assisted oxynitriding.The paper describes the surface layer of TiO{sub 2}+TiN+Ti{sub 2}N+{alpha}Ti(N) type produced at temperature 680 deg. C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed.Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.

  16. Microstructure Characteristics and Mechanical Properties of Al-12Si Coatings on AZ31 Magnesium Alloy Produced by Cold Spray Technique

    NASA Astrophysics Data System (ADS)

    Hao, Yi; Wang, Ji-qiang; Cui, Xin-yu; Wu, Jie; Li, Tie-fan; Xiong, Tian-ying

    2016-06-01

    The cold spray technique was to deposit Al-12Si coatings on AZ31 magnesium alloy. The influence of gas pressure and gas temperature on the microstructure of coatings was investigated so as to optimize the process parameters. OM, SEM, and XRD were used to characterize the as-sprayed coatings. Mechanical properties including Vickers microhardness and adhesion strength were measured in order to evaluate coating quality. Test results indicate that the Al-12Si coatings possess the same crystal structure with powders, sufficient thickness, low porosity, high hardness, and excellent adhesion strength under optimal cold spray process parameters.

  17. Microstructure Characteristics and Mechanical Properties of Al-12Si Coatings on AZ31 Magnesium Alloy Produced by Cold Spray Technique

    NASA Astrophysics Data System (ADS)

    Hao, Yi; Wang, Ji-qiang; Cui, Xin-yu; Wu, Jie; Li, Tie-fan; Xiong, Tian-ying

    2016-04-01

    The cold spray technique was to deposit Al-12Si coatings on AZ31 magnesium alloy. The influence of gas pressure and gas temperature on the microstructure of coatings was investigated so as to optimize the process parameters. OM, SEM, and XRD were used to characterize the as-sprayed coatings. Mechanical properties including Vickers microhardness and adhesion strength were measured in order to evaluate coating quality. Test results indicate that the Al-12Si coatings possess the same crystal structure with powders, sufficient thickness, low porosity, high hardness, and excellent adhesion strength under optimal cold spray process parameters.

  18. Microstructure and magnetic properties of nanostructured (Fe0.8Al0.2)100-xSix alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Boukherroub, N.; Guittoum, A.; Laggoun, A.; Hemmous, M.; Martínez-Blanco, D.; Blanco, J. A.; Souami, N.; Gorria, P.; Bourzami, A.; Lenoble, O.

    2015-07-01

    We report on how the microstructure and the silicon content of nanocrystalline ternary (Fe0.8Al0.2)100-xSix powders (x=0, 5, 10, 15 and 20 at%) elaborated by high energy ball milling affect the magnetic properties of these alloys. The formation of a single-phase alloy with body centred cubic (bcc) crystal structure is completed after 72 h of milling time for all the compositions. This bcc phase is in fact a disordered Fe(Al,Si) solid solution with a lattice parameter that reduces its value almost linearly as the Si content is increased, from about 2.9 Å in the binary Fe80Al20 alloy to 2.85 Å in the powder with x=20. The average nanocrystalline grain size also decreases linearly down to 10 nm for x=20, being roughly half of the value for the binary alloy, while the microstrain is somewhat enlarged. Mössbauer spectra show a sextet thus suggesting that the disordered Fe(Al,Si) solid solution is ferromagnetic at room temperature. However, the average hyperfine field diminishes from 27 T (x=0) to 16 T (x=20), and a paramagnetic doublet is observed for the powders with higher Si content. These results together with the evolution of both the saturation magnetization and the coercive field are discussed in terms of intrinsic and extrinsic properties.

  19. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  20. Indium Helps Strengthen Al/Cu/Li Alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B.; Starke, Edgar A., Jr.

    1992-01-01

    Experiments on Al/Cu/Li alloys focus specifically on strengthening effects of minor additions of In and Cd. Indium-bearing alloy combines low density with ability to achieve high strength through heat treatment alone. Tensile tests on peak-aged specimens indicated that alloy achieved yield strength approximately 15 percent higher than baseline alloy. Alloy highly suitable for processing to produce parts of nearly net shape, with particular applications in aircraft and aerospace vehicles.

  1. Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB2 Composites Produced by Direct Metal Laser Sintering (DMLS)

    NASA Astrophysics Data System (ADS)

    Lorusso, Massimo; Aversa, Alberta; Manfredi, Diego; Calignano, Flaviana; Ambrosio, Elisa Paola; Ugues, Daniele; Pavese, Matteo

    2016-06-01

    Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB2 composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB2, 1% wt. of nanosize TiB2. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB2 reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.

  2. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  3. Alloy and method of producing the same

    DOEpatents

    Hufnagel, Todd C.; Ott, Ryan T.; Fan, Cang; Kecskes, Laszlo

    2005-07-19

    In accordance with a preferred embodiment of the invention, an alloy or other composite material is provided formed of a bulk metallic glass matrix with a microstructure of crystalline metal particles. The alloy preferably has a composition of (X.sub.a Ni.sub.b Cu.sub.c).sub.100-d-c Y.sub.d Al.sub.c, wherein the sum of a, b and c equals 100, wherein 40.ltoreq.a.ltoreq.80, 0.ltoreq.b.ltoreq.35, 0.ltoreq.c.ltoreq.40, 4.ltoreq.d.ltoreq.30, and 0.ltoreq.e.ltoreq.20, and wherein preferably X is composed of an early transition metal and preferably Y is composed of a refractory body-centered cubic early transition metal. A preferred embodiment of the invention also provides a method of producing an alloy composed of two or more phases at ambient temperature. The method includes the steps of providing a metastable crystalline phase composed of at least two elements, heating the metastable crystalline phase together with at least one additional element to form a liquid, casting the liquid, and cooling the liquid to form the alloy. In accordance with a preferred embodiment of the invention, the composition and cooling rate of the liquid can be controlled to determine the volume fraction of the crystalline phase and determine the size of the crystalline particles, respectively.

  4. Melting, Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

    NASA Astrophysics Data System (ADS)

    Satya Prasad, V. V.; Khaple, Shivkumar; Baligidad, R. G.

    2014-09-01

    This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.

  5. Development of ODS-Fe{sub 3}Al alloys

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Tortorelli, P.F.; McKamey, C.G.

    1997-12-01

    The overall goal of this program is to develop an oxide dispersion-strengthened (ODS) version of Fe{sub 3}Al that has sufficient creep strength and resistance to oxidation at temperatures in the range 1000 to 1200 C to be suitable for application as heat exchanger tubing in advanced power generation cycles. The main areas being addressed are: (a) alloy processing to achieve the desired alloy grain size and shape, and (b) optimization of the oxidation behavior to provide increased service life compared to semi-commercial ODS-FeCrAl alloys intended for the same applications. The recent studies have focused on mechanically-alloyed powder from a commercial alloy vendor. These starting alloy powders were very clean in terms of oxygen content compared to ORNL-produced powders, but contained similar levels of carbon picked up during the milling process. The specific environment used in milling the powder appears to exert a considerable influence on the post-consolidation recrystallization behavior of the alloy. A milling environment which produced powder particles having a high surface carbon content resulted in a consolidated alloy which readily recrystallized, whereas powder with a low surface carbon level after milling resulted in no recrystallization even at 1380 C. A feature of these alloys was the appearance of voids or porosity after the recrystallization anneal, as had been found with ORNL-produced alloys. Adjustment of the recrystallization parameters did not reveal any range of conditions where recrystallization could be accomplished without the formation of voids. Initial creep tests of specimens of the recrystallized alloys indicated a significant increase in creep strength compared to cast or wrought Fe{sub 3}Al, but the specimens failed prematurely by a mechanism that involved brittle fracture of one of the two grains in the test cross section, followed by ductile fracture of the remaining grain. The reasons for this behavior are not yet understood. The

  6. Alloying and oxidation of in situ produced core-shell Al@Yb nanoalloy particles—An “on-the-fly” study

    SciTech Connect

    Zhang, Chaofan; Andersson, Tomas; Björneholm, Olle; Mikkelä, Mikko-Heikki; Tchaplyguine, Maxim E-mail: zejinliu@vip.sina.com; Mårsell, Erik; Xu, Xiaojun; Liu, Zejin E-mail: zejinliu@vip.sina.com

    2014-08-28

    Core-shell-structured nanoalloy particles with an Al-dominated interior covered by few Yb monolayers have been fabricated using a vapor-aggregation method involving magnetron sputtering. The radially segregated structure of the Yb-Al nanoparticles has been disclosed by “on-the-fly” photoelectron spectroscopy monitoring of the nanoparticle beam in Yb 4f and Al 2p electron binding energy regions. Both, the binding energy values and the electron microscopy images taken on the deposited nanoparticles, allow estimating their dimensions to be in the 5–10 nm range. The photoelectron spectroscopy results suggest that in these nanoparticles no trivalent Yb – the typical case for the macroscopic Yb-Al alloy – is present. The oxidation of preformed Yb-Al nanoparticles was successfully attempted, leading to the appearance of divalent Yb surface oxide – in contrast to the bulk macroscopic Yb which is trivalent in the oxide. Our results suggest that at intermediate oxygen exposures “sandwich-like” nanoparticles of YbO/Yb/Al were synthesized. At higher O{sub 2} exposures, the oxygen seems to penetrate all the way to the Yb-Al interface. The results of the present study have to be considered when photonic applications of Yb-doped garnet nanoparticles are planned.

  7. Alloying and oxidation of in situ produced core-shell Al@Yb nanoalloy particles--an "on-the-fly" study.

    PubMed

    Zhang, Chaofan; Andersson, Tomas; Mikkelä, Mikko-Heikki; Mårsell, Erik; Björneholm, Olle; Xu, Xiaojun; Tchaplyguine, Maxim; Liu, Zejin

    2014-08-28

    Core-shell-structured nanoalloy particles with an Al-dominated interior covered by few Yb monolayers have been fabricated using a vapor-aggregation method involving magnetron sputtering. The radially segregated structure of the Yb-Al nanoparticles has been disclosed by "on-the-fly" photoelectron spectroscopy monitoring of the nanoparticle beam in Yb 4f and Al 2p electron binding energy regions. Both, the binding energy values and the electron microscopy images taken on the deposited nanoparticles, allow estimating their dimensions to be in the 5-10 nm range. The photoelectron spectroscopy results suggest that in these nanoparticles no trivalent Yb--the typical case for the macroscopic Yb-Al alloy--is present. The oxidation of preformed Yb-Al nanoparticles was successfully attempted, leading to the appearance of divalent Yb surface oxide--in contrast to the bulk macroscopic Yb which is trivalent in the oxide. Our results suggest that at intermediate oxygen exposures "sandwich-like" nanoparticles of YbO/Yb/Al were synthesized. At higher O2 exposures, the oxygen seems to penetrate all the way to the Yb-Al interface. The results of the present study have to be considered when photonic applications of Yb-doped garnet nanoparticles are planned. PMID:25173009

  8. Energetic-particle synthesis of nanocomposite Al alloys

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Barbour, J.C.; Myers, S.M.; Dugger, M.T.

    1996-11-26

    Ion implantation of O into Al and growth of Al(O) layers using electro-cyclotron resonance plasma and pulsed laser depositions produce composite alloys with a high density of nanometer-size oxide precipitates in an Al matrix. The precipitates impart high strength to the alloy and reduced adhesion during sliding contact, while electrical conductivity and ductility are retained. Implantation of N into Al produces similar microstructures and mechanical properties. The athermal energies of deposited atoms are a key factor in achieving these properties.

  9. NbAl Intelligent Material Through Mechanical Alloying

    SciTech Connect

    Chinniah, K.; Aikra, K.

    2010-03-11

    An intelligent material of Nb-Al composite, is expected to produce intermetallics phase instantaneously upon collision with hypervelocity space debris to stop the crack propagation. Intermetallics-free MA powder with Nb dispersion in Al matrix is targeted. Nb-Al powders are mechanically alloyed using agate media. Mechanical alloying (MA) with agate media produced fine intermetallics-free powder of Nb dispersion in Al matrix. Intermetallics-free critical MA powder curve for agate media were established. The optimum critical agate MA powder of 200 rpm 132 hours had intelligent properties.

  10. Itinerant antiferromagnetism of TiAl alloys

    NASA Astrophysics Data System (ADS)

    Petrişor, T.; Pop, I.; Giurgiu, A.; Farbaş, N.

    1986-06-01

    Magnetic susceptibility measurements of TiAl alloys are reported. Aluminium, by alloying, acts on the Néel temperature of pure titanium giving rise to a complicated phase diagram. A theoretical model, based on the itinerant antiferromagnetism model of chromium is proposed in order to explain the magnetic phase diagram of TiAl alloys. The experimental and theoretical magnetic phase diagram are in good agreement.

  11. Characteristics of Ti(C, N)/TiB composite layer on Ti-6Al-4V alloy produced by laser surface melting

    NASA Astrophysics Data System (ADS)

    Zeng, Xian; Yamaguchi, Tomiko; Nishio, Kazumasa

    2016-06-01

    A Ti(C, N)/TiB reinforced titanium matrix composite layer was successfully in-situ synthesized by laser melting on Ti-6Al-4V alloy surface with Ti-BN-C mixed powder, aiming at improving the wear resistance. The microstructure, chemical composition, hardness and wear behavior were analyzed. The results showed that, the cross sectional microstructure can be clearly divided into three parts, which were the laser melted layer, heat affected zone and non-affected zone. The reinforcements in laser melted layer consisted of dendritic TiC0.3N0.7 phases and fine-structure TiB phases. The matrix in laser melted layer was in a two-phase structure, being composed of platelet α titanium and intergranular β titanium. The hardness was increased from 320 HV in the substrate to 450-550 HV in the modified layer. The wear resistance was improved that, the wear volume loss of the laser treated sample was approximately half of the as received Ti-6Al-4V alloy after 8 h wear test.

  12. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the

  13. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  14. Effects of Li concentration and a Mg addition on serrated flow in Al-Li alloys

    SciTech Connect

    Zambo, S.J.; Wert, J.A. . Dept. of Materials Science and Engineering)

    1993-12-15

    Serrated flow phenomena have been reported in a variety of precipitation-strengthened aluminum alloys. In the particular case of precipitation-strengthened Al-Li alloys, serrated flow effects of similar character have been reported in binary Al-Li alloys and in commercial-type Al-Li alloys containing multiple alloying elements. Observations of serrated flow in binary Al-Li alloys indicate that the presence of Li alone is sufficient to produce serrated flow. Aging time has been used to probe the mechanisms that cause serrated flow in individual Al-Li alloys, and several investigators have noted that serrated flow disappears when Al-Li alloys are aged to peak strength or overaged. Much of the available experimental evidence supports dislocation-[delta][prime] interactions as the cause of serrated flow in Al-Li alloys, rather than dislocation-solute atom interactions to which serrated flow phenomena are traditionally attributed. Additional support for this conclusion could be provided by comparison of stress-strain curves for a solid solution Al-Li binary alloy of the same composition as the matrix phase of a precipitation-strengthened Al-Li binary alloy. The purpose of the present paper is to show stress--strain curves for Al-1.38Li, Al-1.80Li and Al-1.39Li-1.0Mg alloys, and to interpret the results in terms of the interactions proposed to account for serrated flow in Al-Li alloys.

  15. Method of producing superplastic alloys and superplastic alloys produced by the method

    NASA Technical Reports Server (NTRS)

    Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

    2002-01-01

    A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

  16. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800 C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800 C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700 C. at a low cost

  17. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800.degree. C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800.degree. C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700.degree. C. at a low cost

  18. Taguchi Optimization on the Initial Thickness and Pre-aging of Nano-/Ultrafine-Grained Al-0.2 wt.%Sc Alloy Produced by ARB

    NASA Astrophysics Data System (ADS)

    Yousefieh, Mohammad; Tamizifar, Morteza; Boutorabi, Seyed Mohammad Ali; Borhani, Ehsan

    2016-08-01

    In this study, Taguchi design method with L9 orthogonal array has been used to optimize the initial thickness and pre-aging parameters (temperature and time) for the mechanical properties of Al-0.2 wt.% Sc alloy heavily deformed by accumulative roll bonding (ARB) up to ten cycles. Analysis of variance was performed on the measured data and signal-to-noise ratios. It was found that the pre-aging temperature has the most significant parameter affecting the mechanical properties by percentage contribution of 64.51%. Pre-aging time (19.29%) has the next most significant effect, while initial thickness (5.31%) has statistically less significant effect. In order to confirm experimental conclusions, verification experiments were carried out at optimum working conditions. Under these conditions, the yield strength was 6.51 times higher and toughness was 6.86% lower compared with the starting Al-Sc material. Moreover, mean grain size was decreased to 220 nm by setting the control parameters, which was the lowest value obtained in this study. It was concluded that the Taguchi method was found to be a promising technique to obtain the optimum conditions for such studies. Consequently, by controlling the parameter levels, the high-strength and high-toughness Al-Sc samples were fabricated through pre-aging and subsequent ARB process.

  19. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  20. High temperature creep behaviour of Al-rich Ti-Al alloys

    NASA Astrophysics Data System (ADS)

    Sturm, D.; Heilmaier, M.; Saage, H.; Aguilar, J.; Schmitz, G. J.; Drevermann, A.; Palm, M.; Stein, F.; Engberding, N.; Kelm, K.; Irsen, S.

    2010-07-01

    Compared to Ti-rich γ-TiAl-based alloys Al-rich Ti-Al alloys offer an additional reduction of in density and a better oxidation resistance which are both due to the increased Al content. Polycrystalline material was manufactured by centrifugal casting. Microstructural characterization was carried out employing light-optical, scanning and transmission electron microscopy and XRD analyses. The high temperature creep of two binary alloys, namely Al60Ti40 and Al62Ti38 was comparatively assessed with compression tests at constant true stress in a temperature range between 1173 and 1323 K in air. The alloys were tested in the cast condition (containing various amounts of the metastable phases Al5Ti3 and h-Al2Ti) and after annealing at 1223 K for 200 h which produced (thermodynamically stable) lamellar γ-TiAl + r-Al2Ti microstructures. In general, already the as-cast alloys exhibit a reasonable creep resistance at 1173 K. Compared with Al60Ti40, both, the as-cast and the annealed Al62Ti38 alloy exhibit better creep resistance up to 1323 K which can be rationalized by the reduced lamella spacing. The assessment of creep tests conducted at identical stress levels and varying temperatures yielded apparent activation energies for creep of Q = 430 kJ/mol for the annealed Al60Ti40 alloy and of Q = 383 kJ/mol for the annealed Al62Ti38 material. The latter coincides well with that of Al diffusion in γ-TiAl, whereas the former can be rationalized by the instability of the microstructure containing metastable phases.

  1. Durability Assessment of TiAl Alloys

    NASA Technical Reports Server (NTRS)

    Draper, Susan L.; Lerch, Bradley A.

    2008-01-01

    The durability of TiAl is a prime concern for the implementation of TiAl into aerospace engines. Two durability issues, the effect of high temperature exposure on mechanical properties and impact resistance, have been investigated and the results are summarized in this paper. Exposure to elevated temperatures has been shown to be detrimental to the room temperature ductility of gamma alloys with the most likely mechanisms being the ingress of interstitials from the surface. Fluorine ion implantation has been shown to improve the oxidation resistance of gamma alloys, and ideally it could also improve the environmental embrittlement of high Nb content TiAl alloys. The effect of F ion implantation on the surface oxidation and embrittlement of a third generation, high Nb content TiAl alloy (Ti-45Al-5Nb-B-C) were investigated. Additionally, the ballistic impact resistance of a variety of gamma alloys, including Ti-48Al-2Cr- 2Nb, Ti-47Al-2Cr-2Nb, ABB-2, ABB-23, NCG359E, 95A and Ti-45Al-5Nb-B-C was accessed. Differences in the ballistic impact properties of the various alloys will be discussed, particularly with respect to their manufacturing process, microstructure, and tensile properties.

  2. Alloy development and processing of FeAl: An overview

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Alexander, D.J.; Viswanathan, S.

    1997-03-01

    In the last few years, considerable progress has been made in developing B2-phase FeAl alloys with improved weldability, room-temperature ductility, and high-temperature strength. Controlling the processing-induced microstructure is also important, particularly for minimizing trade-offs in various properties. FeAl alloys have outstanding resistance to high-temperature oxidation, sulfidation, and corrosion in various kinds of molten salts due to formation of protective Al{sub 2}O{sub 3} scales. Recent work shows that FeAl alloys are carburization-resistant as well. Alloys with 36 to 40 at. % Al have the best combination of corrosion resistance and mechanical properties. Minor alloying additions of Mo, Zr, and C, together with microalloying additions of B, produce the best combination of weldability and mechanical behavior. Cast FeAl alloys, with 200 to 400 {mu}m grain size and finely dispersed ZrC, have 2 to 5% tensile ductility in air at room-temperature, and a yield strength > 400 MPa up to about 700 to 750{degrees}C. Extruded ingot metallurgy (I/M) and powder metallurgy (P/M) materials with refined grain sizes ranging from 2 to 50 {mu}m, can have 10 to 15% ductility in air and be much stronger, and can even be quite tough, with Charpy impact energies ranging from 25 to 105 J at room-temperature. This paper highlights progress made in refining the alloy composition and exploring processing effects on FeAl for monolithic applications. It also includes recent progress on developing FeAl weld-overlay technology, and new results on welding of FeAl alloys. It summarizes some of the current industrial testing and interest for applications.

  3. Producing nano-grained and Al-enriched surface microstructure on AZ91 magnesium alloy by high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Hao, Shengzhi; Li, Mincai

    2016-05-01

    Surface treatment of AZ91 magnesium alloy was carried out by high current pulsed electron beam (HCPEB) with accelerating voltage 27 kV and energy density 3 J/cm2. The surface microstructure and phase composition were characterized by using optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The surface microhardness and corrosion resistance were measured. Under HCPEB treatments, the preferential evaporation of Mg element occurred intensively on irradiated surface and the initial large Mg17Al12 phases were dissolved. The nano-grained and Al-enriched surface modified layer was ultimately formed of depth ∼8 μm. According to the testing results, the surface microhardness increased from 63 to 141 HK after 30 pulses of HCPEB treatment, while the best improvement of corrosion resistance was obtained by 15 pulses of HCPEB treatment with a cathodic current density decreased by two orders of magnitude as compared with the initial AZ91 sample.

  4. Modeling of K-shell Al and Mg radiation from compact single, double planar and cylindrical alloyed Al wire array plasmas produced on the 1 MA Zebra generator at UNR

    NASA Astrophysics Data System (ADS)

    Yilmaz, Mehmet F.; Safronova, Alla S.; Kantsyrev, Victor L.; Esaulov, Andrey A.; Williamson, Kenneth M.; Shrestha, Ishor K.; Weller, Michael E.; Osborne, Glenn C.; Shlyaptseva, Veronica V.

    2012-03-01

    Radiative emission from alloyed Al single, double and compact cylindrical wire arrays have been studied using the 1 MA Zebra UNR generator. Single planar wire arrays using ten wires and double planar wire arrays and compact cylindrical wire arrays (CCWA) that both had sixteen wires were utilized. The wire composition is Al-5056 (95% of Al and 5% of Mg). We have observed that implosion of these alloyed Al wire loads generated optically thick Al plasmas that can be diagnosed using K-shell Mg lines. In particular, among the considered loads, the K-shell lines of Al from implosions of the double planar wire arrays have the highest optical depth for He-like Al resonance transitions, which occurred near the stagnation phase. X-ray time-gated and time-integrated spectra and pinhole images as well as photoconductive detectors signals were analyzed to provide information on the plasma parameters; electron temperatures and densities, implosion dynamics features and power and yields of the X-ray radiation. Previously developed non-LTE models were applied to model axially-resolved time-integrated, as well as time-gated spatially-integrated, K-shell spectra from Al and Mg. The derived time-dependent electron temperature, density and axial opacity were studied and compared. In addition, the wire ablation dynamics model (WADM) was used to calculate the kinetic energy of the plasma, which with the aid of a Local Thermal Equilibrium (LTE) magneto-hydrodynamics (MHD) simulation, allowed to estimate the precursor and stagnated z-pinch plasma electron temperatures from implosions of wire array loads.

  5. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

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

    1993-02-01

    Objectives include adequate ductilities ([ge]10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 [plus minus] 2)Al - (0.3 [plus minus] 0.2)Mo - (0.2 [plus minus] 0.15)Zr - (0.3 [plus minus] 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  6. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

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

    1993-02-01

    Objectives include adequate ductilities ({ge}10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 {plus_minus} 2)Al - (0.3 {plus_minus} 0.2)Mo - (0.2 {plus_minus} 0.15)Zr - (0.3 {plus_minus} 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  7. Microstructures and mechanical properties of dispersion-strengthened high-temperature Al-8.5Fe-1.2V-1.7Si alloys produced by atomized melt deposition process

    NASA Astrophysics Data System (ADS)

    Hariprasad, S.; Sastry, S. M. L.; Jerina, K. L.; Lederich, R. J.

    1993-04-01

    Dispersion-strengthened high-temperature Al-8.5 pct Fe-pct Si-pct V alloys were produced by atomized melt deposition (AMD) process. The effects of process parameters on the evolution of microstructures were determined using optical metallography and scanning and transmission electron microscopy. The extent of undercooling and the rate of droplet solidification were correlated with process parameters, such as melt superheat, metal/gas flow rates, and melt stream diameter. The size distribution and morphology of silicide dispersoids were used to estimate the degree of undercooling and the cooling rate as functions of process parameters. The tensile properties at 25 °C to 425 °C and fracture toughness at 25 °C of these alloys produced with wide variations in dispersoids size and grain size were determined. Under optimum conditions, the alloy has ultimate tensile strength of 281 MPa and 9.5 pct ductility in the as-deposited condition. Upon hot-isostatic pressing and extrusion, the ultimate tensile strength increased to 313 MPa and ductility increased to 18 pct.

  8. Microstructural investigations on as-cast and annealed Al-Sc and Al-Sc-Zr alloys

    SciTech Connect

    Lohar, A.K.; Mondal, B.; Rafaja, D.; Klemm, V.; Panigrahi, S.C.

    2009-11-15

    Al-Sc and Al-Sc-Zr alloys containing 0.05, 0.1 and 0.5 wt.% Sc and 0.15 wt.% Zr were investigated using optical microscopy, electron microscopy and X-ray diffraction. The phase composition of the alloys and the morphology of precipitates that developed during solidification in the sand casting process and subsequent thermal treatment of the samples were studied. XRD analysis shows that the weight percentage of the Al{sub 3}Sc/Al{sub 3}(Sc, Zr) precipitates was significantly below 1% in all alloys except for the virgin Al0.5Sc0.15Zr alloy. In this alloy the precipitates were observed as primary dendritic particles. In the binary Al-Sc alloys, ageing at 470 deg. C for 24 h produced precipitates associated with dislocation networks, whereas the precipitates in the annealed Al-Sc-Zr alloys were free of interfacial dislocations except at the lowest content of Sc. Development of large incoherent precipitates during precipitation heat treatment reduced hardness of all the alloys studied. Growth of the Al{sub 3}Sc/Al{sub 3}(Sc, Zr) precipitates after heat treatment was less at low Sc content and in the presence of Zr. Increase in hardness was observed after heat treatment at 300 deg. C in all alloys. There is a small difference in hardness between binary and ternary alloys slow cooled after sand casting.

  9. Microstructure evolution of 7050 Al alloy during age-forming

    SciTech Connect

    Chen, Junfeng; Zou, Linchi; Li, Qiang; Chen, Yulong

    2015-04-15

    The microstructure evolution of the 7050 Al alloy treated by age-forming was studied using a designed device which can simulate the age-forming process. The grain shape, grain boundary misorientation and grain orientation evolution of 7050 Al alloy during age-forming have been quantitatively characterized by electron backscattering diffraction technique. The results show that age-forming produced abundant low-angle boundaries and elongated grains, which attributed to stress induced dislocation movement and grain boundary migration during the age-forming process. On the other side, the stress along rolling direction caused some unstable orientation grains to rotate towards the Brass and S orientations during the age-forming process. Hence, the intensity of the rolling texture orientation in age-formed samples is enhanced. But this effect decays gradually with increasing aging time, since stress decreases and precipitation hardening occurs during the age-forming process. - Highlights: • Quantitative analysis of grain evolution of 7050 Al alloys during age-forming • Stress induces some grain rotation of 7050 Al alloys during age-forming. • Creep leads to elongate grain of 7050 Al alloys during age-forming. • Obtains a trend on texture evolution during age-forming applied stress.

  10. Spark alloying of an AL9 alloy by hard alloys

    NASA Astrophysics Data System (ADS)

    Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.

    2015-08-01

    The phase compositions of spark coatings of Kh12M steel with a VT1-0 (titanium) alloy and T15K6 and T30K4 hard alloys are studied. It is shown that the TiC titanium carbide forms in all cases and tungsten carbide decomposes with the formation of tungsten in a coating. These processes are intensified by increasing time, capacitance, and frequency. The surface hardness, the sample weight, and the white layer thickness increase monotonically.

  11. Modeling of precipitation in Al alloys

    SciTech Connect

    Asta, M.; Foiles, S.M.; Wolfer, W.G.

    1996-10-01

    Objective was the development of a computational model of precipitation from a supersaturated alloy solid solution. The model is based on the formalism of chemical-reaction-rate theory combined with classical descriptions of precipitate thermodynamic properties and a mean-field treatment of diffusion-limited growht and coarsening. For the case of precipitation of Al{sub 3}Sc in supersaturated Al-Sc alloys, it is demonstrated how the model can be used to calculate number densities and size distributions of precipitates as a function of aging time and temperature, including effects of continuous cooling and thermally generated point defects. Application of the model to a specific alloy system requires knowledge of diffusion data, point defect energetics, and thermodynamic properties for bulk phases and interphase interfaces. For interfaces and point defects, thermodynamic data can be difficult to measure and reliable values of defect free energies are often unavailable. For this reason, part of the efforts were devoted to applying semiempirical and first-principles atomistic techniques to the calculation of interfacial and point-defect thermodynamic properties. This report discusses applications for interphase interfaces in the Al-Ag, Al-Sc, and Al-Li alloy systems. We also describe atomistic work aimed at understanding the energetics of vacancy clusters in Al. These clusters serve as sinks for isolated vacancies during aging and their growth can lead to more complex defects, such as dislocation loops, that act as heterogeneous nucleation sites.

  12. Dispersion strengthening of precipitation hardened Al-Cu-Mg alloys prepared by rapid solidification and mechanical alloying

    NASA Technical Reports Server (NTRS)

    Gilman, P. S.; Sankaran, K. K.

    1988-01-01

    Several Al-4Cu-1Mg-1.5Fe-0.75Ce alloys have been processed from either rapidly solidified or mechanically alloyed powder using various vacuum degassing parameters and consolidation techniques. Strengthening by the fine subgrains, grains, and the dispersoids individually or in combination is more effective when the alloys contain shearable precipitates; consequently, the strength of the alloys is higher in the naturally aged rather than the artificially aged condition. The strengths of the mechanically alloyed variants are greater than those produced from prealloyed powder. Properties and microstructural features of these dispersion strengthened alloys are discussed in regards to their processing histories.

  13. Effect of V or Zr addition on the mechanical properties of the mechanically alloyed Al-8wt%Ti alloys

    SciTech Connect

    Moon, I.H.; Lee, J.H.; Lee, K.M. . Dept. of Materials Engineering); Kim, Y.D. . Div. of Metals)

    1995-01-01

    Mechanical alloying (MA) of Al-Ti alloy, being a solid state process, offers the unique advantage of producing homogeneous and fine dispersions of thermally stable Al[sub 3]Ti phase, where the formation of the fine Al[sub 3]Ti phase by the other method is restricted from the thermodynamic viewpoint. The MA Al-Ti alloys show substantially higher strength than the conventional Al alloys at the elevated temperature due to the presence of Al[sub 3]Ti as well as Al[sub 4]C[sub 3] and Al[sub 2]O[sub 3], of which the last two phases were introduced during MA process. The addition of V or Zr to Al-Ti alloy was known to decrease the lattice mismatch between the intermetallic compound and the aluminum matrix, and such decrease in lattice mismatching can influence positively the high temperature mechanical strength of the MA Al-Ti by increasing the resistance to dispersoid coarsening at the elevated temperature. In the present study, therefore, the mechanical behavior of the MA Al-Ti-V and Al-Ti-Zr alloys were investigated in order to evaluate the effect of V or Zr addition on the mechanical properties of the MA Al-8Ti alloy at high temperature.

  14. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  15. Corrosion Studies of 2195 Al-Li Alloy and 2219 Al Alloy with Differing Surface Treatments

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Mendrek, M. J.

    1998-01-01

    Corrosion studies of 2195 Al-Li and 2219 Al alloys have been conducted using the scanning reference electrode technique (SRET) and the polarization resistance (PR) technique. The SRET was used to study corrosion mechanisms, while corrosion rate measurements were studied with the PR technique. Plates of Al203 blasted, soda blasted and conversion coated 2219 Al were coated with Deft primer and the corrosion rates studied with the EIS technique. Results from all of these studies are presented.

  16. Microalloying ultrafine grained Al alloys with enhanced ductility.

    PubMed

    Jiang, L; Li, J K; Cheng, P M; Liu, G; Wang, R H; Chen, B A; Zhang, J Y; Sun, J; Yang, M X; Yang, G

    2014-01-01

    Bulk ultrafine grained (UFG)/nanocrystal metals possess exceptional strength but normally poor ductility and thermal stability, which hinder their practical applications especially in high-temperature environments. Through microalloying strategy that enables the control of grains and precipitations in nanostructured regime, here we design and successfully produce a highly microstructure-stable UFG Al-Cu-Sc alloy with ~275% increment in ductility and simultaneously ~50% enhancement in yield strength compared with its Sc-free counterpart. Although the precipitations in UFG alloys are usually preferentially occurred at grain boundaries even at room temperature, minor Sc addition into the UFG Al-Cu alloys is found to effectively stabilize the as-processed microstructure, strongly suppress the θ-Al2Cu phase precipitation at grain boundary, and remarkably promote the θ'-Al2Cu nanoparticles dispersed in the grain interior in artificial aging. A similar microalloying strategy is expected to be equally effective for other UFG heat-treatable alloys. PMID:24398915

  17. Microalloying Ultrafine Grained Al Alloys with Enhanced Ductility

    PubMed Central

    Jiang, L.; Li, J. K.; Cheng, P. M.; Liu, G.; Wang, R. H.; Chen, B. A.; Zhang, J. Y.; Sun, J.; Yang, M. X.; Yang, G.

    2014-01-01

    Bulk ultrafine grained (UFG)/nanocrystal metals possess exceptional strength but normally poor ductility and thermal stability, which hinder their practical applications especially in high-temperature environments. Through microalloying strategy that enables the control of grains and precipitations in nanostructured regime, here we design and successfully produce a highly microstructure-stable UFG Al-Cu-Sc alloy with ~275% increment in ductility and simultaneously ~50% enhancement in yield strength compared with its Sc-free counterpart. Although the precipitations in UFG alloys are usually preferentially occurred at grain boundaries even at room temperature, minor Sc addition into the UFG Al-Cu alloys is found to effectively stabilize the as-processed microstructure, strongly suppress the θ-Al2Cu phase precipitation at grain boundary, and remarkably promote the θ′-Al2Cu nanoparticles dispersed in the grain interior in artificial aging. A similar microalloying strategy is expected to be equally effective for other UFG heat-treatable alloys. PMID:24398915

  18. Antiferromagnetic behaviour of Tb2Al alloy

    NASA Astrophysics Data System (ADS)

    Rojas, D. P.; André, G.; Rodríguez Fernández, J.; Sánchez Marcos, J.; Fernández Barquín, L.; Echevarria, C.

    2011-10-01

    The structural, thermal and magnetic properties ol the Tb2Al alloy have been investigated by AC/DC magnetic susceptibility, specific heat, X-ray and neutron diffraction measurements. DC and AC-magnetic susceptibility results are consistent with an AFM order at TN = 52 K. The specific heat data show a lambda anomaly associated to the magnetic transition with a peak at 52 K (cord = 99 J/molTbK). The analysis of thermodiffractograms of neutron diffraction patterns indicates that, below the ordering temperature, the magnetic reflections can be indexed with a commensurate lattice related to the crystallographic cell (Pmna) by a propagation vector k = (1/2, 1/2, 1/2). The results are compared with those reported for other magnetic rare earth alloys of R2Al-type (with R = Nd, Gd and Dy).

  19. Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

    SciTech Connect

    Kingsley, L.M.

    1980-04-01

    Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.

  20. Corrosion Behaviour of Al Alloys in Sea Water

    SciTech Connect

    Kamarudin, S. R. M.; Daud, M.; Muhamad, A.; Sattar, M. S.; Daud, A. R.

    2010-03-11

    The electrochemical behaviour of aluminum (Al) alloys in seawater medium was investigated using potentiodynamic technique, complemented by Scanning Electron Microscopy (SEM) and EDAX. SEM was used to characterize the corroded surface and to observe the extent of corrosion attack on the Al alloys after tested in seawater. EDAX analysis was used to identify elements present on the specimen surface. The results indicate that influences of alloying elements present in the Al alloys play important role in the corrosion of Al alloys in seawater. The behaviour of Al alloys with addition of Zn, Sn, Cu and Si was greatly enhanced in terms of its potential and corrosion behaviour. Potential of Al with alloying elements reached value more negative than -0.9 V{sub SCE} and showed active corrosion behaviour.

  1. Mechanical Properties of High Strength Al-Mg Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Choi, Bong-Jae; Hong, Kyung-Eui; Kim, Young-Jig

    The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

  2. Investigation of slective laser melting of mecanically alloyed metastable Al5Fe2 powder

    NASA Astrophysics Data System (ADS)

    Montiel, Hugo

    Selective Laser Melting (SLM), an Additive Manufacturing (AM) technology, enables the production of complex structured metal products. Aluminum alloys are used in SLM as high-strength lightweight materials for weight reduction in structural components. Previous investigations report high laser powers (300 W) and slow scanning speeds (500 mm/s) to process aluminum alloys under SLM. This research investigates the SLM processing of Al-Fe alloy by utilizing metastable Al5Fe2 powder system produced by mechanical alloying. Metastable systems are thermodynamically activated with internal energy that can generate an energy shortcut when processing under SLM. The optimum laser power, scan speeds and scan distances were investigated by test series experiments. Results indicate that metastable Al5Fe2 alloy can be processed and stabilized under a 200 W laser scanning and a relative high scanning speed of 1000 mm/s. Thus, the internal energy of metastable powder contributes in reducing laser energy for SLM process for Al alloys.

  3. Fabric cutting application of FeAl-based alloys

    SciTech Connect

    Sikka, V.K.; Blue, C.A.; Sklad, S.P.; Deevi, S.C.; Shih, H.R.

    1998-11-01

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

  4. Alloys based on NiAl for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vedula, K. M.; Pathare, V.; Aslanidis, I.; Titran, R. H.

    1984-01-01

    The NiAl alloys for potential high temperature applications were studied. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some ternary alloying additions (Hf, Ta and Nb) were identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. The effects of grain size and stoichiometry in binary alloys are also presented.

  5. Ultrafine-grained structure formation in Ti-6Al-4V alloy via warm swaging

    NASA Astrophysics Data System (ADS)

    Klimova, M.; Boeva, M.; Zherebtsov, S.; Salishchev, G.

    2014-08-01

    The influence of warm swaging on the structure and properties of Ti-6Al-4V alloy was studied. Warm swaging of the alloy in the interval 680-500°C with the total strain of ɛ=2.66 was found to be resulted in the formation of a homogeneous globular microstructure with a grain size of 0.4 μm in both longitudinal and transversal sections. Room temperature tensile strength and tensile elongation of the swaged alloy was 1315MPa and 10.5%, respectively. Ultrafine-grained Ti-6Al-4V alloy produced by swaging exhibited good workability at 600-700 °C.

  6. Recent Developments in Friction Stir Welding of Al-alloys

    NASA Astrophysics Data System (ADS)

    Çam, Gürel; Mistikoglu, Selcuk

    2014-06-01

    The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).

  7. The effect of Si in Al-alloy on electromigration performance in Al filled vias

    NASA Astrophysics Data System (ADS)

    Kageyama, Makiko; Hashimoto, Keiichi; Onoda, Hiroshi

    1998-01-01

    Electromigration performance of vias filled with Al-Si-Cu alloys on Ti glue layers was investigated in comparison with W-stud vias. In Al-Si-Cu filled vias, voids were formed at only a few locations in the test structure, while voids were formed at every via in W-stud via chains. It is supposed that Al moves through the Al-Si-Cu via during electromigration in spite of the existence of a glue layer at the via bottom. This phenomenon was observed only in the vias filled with Al-Si-Cu alloy. Al movement was prohibited in Al-Cu filled vias. In Al-Si-Cu filled vias, an Al-Ti-Si alloy was formed at the via bottom while Al3Ti was formed at Al-Cu filled vias. Al is speculated to move through this Al-Ti-Si alloy during electromigration.

  8. Producing Low-Oxygen Samarium/Cobalt Magnet Alloy

    NASA Technical Reports Server (NTRS)

    Das, Dilip K.; Kumar, Kaplesh; Frost, Robert T.; Chang, C. W.

    1987-01-01

    Experiments aimed at producing SmCo5 alloy with low oxygen contamination described in report. Two methods of alloying by melting without contact with crucible walls tested. Lowest oxygen contamination, 70 parts per million achieved by dc arc melting on water-cooled, tantalum-clad copper hearth in purified quiescent argon atmosphere. Report includes photographs of equipment, photomicrographs of alloy samples, detailed descriptions of procedures tried, and tables of oxygen contamination and intrinsic coercivities of samples produced.

  9. Development of interatomic potentials appropriate for simulation of devitrification of Al90Sm10 alloy

    DOE PAGESBeta

    Mendelev, M. I.; Zhang, F.; Ye, Z.; Sun, Y.; Nguyen, M. C.; Wilson, S. R.; Wang, C. Z.; Ho, K. M.

    2015-04-23

    In this study, a semi-empirical potential for the Al90Sm10 alloy is presented. The potential provides satisfactory reproduction of pure Al properties, the formation energies of a set of Al–Sm crystal phases with Sm content about 10%, and the structure of the liquid Al90Sm10 alloy. During molecular dynamics simulation in which the liquid alloy is cooled at a rate of 1010 K/s, the developed potential produces a glass structure with lower ab initio energy than that produced by ab initio molecular dynamics (AIMD) itself using a typical AIMD cooling rate of 8 ∙1013 K/s. Based on these facts the developed potentialmore » should be suitable for simulations of phase transformations in the Al90Sm10 alloy.« less

  10. Corrosion protection and galvanic corrosion prevention for 7075 Al and Ti-6Al-6V-2Sn alloys. Final report

    SciTech Connect

    Clay, F.A.

    1980-07-01

    Sulfuric-acid-anodized and electroless-nickel-plated 7075 aluminum alloy panels successfully passed 96 hours of salt spray testing when galvanically coupled to duplex-annealed Ti-6Al-6V-2Sn alloy panels. Adherent paint deposits were produced on the titanium alloy and electroless nickel surfaces using a wash primer, an epoxy primer, and a urethane paint coating. A painted part survived 35 cycles of alternating salt spray and hot and freezing environments without blistering. A low chloride cutting fluid was selected for production machining of Ti-6Al-6V-2Sn, based on chemical analysis and stress-corrosion tests. A cleaning process was developed to remove both titanium and aluminum cutting fluids. Modified wedge-opening-loading specimens were used to verify that no stress-corrosion cracking problems occurred with the duplex-annealed Ti-6Al-6V-2Sn alloy because of residual titanium or aluminum cutting fluids.

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

    NASA Technical Reports Server (NTRS)

    Gilman, P. S.

    1984-01-01

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

  12. Low Cost Al-Si Casting Alloy As In-Situ Composite for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

    A new aluminum-silicon (Al-Si) alloy has been successfully developed at NASA- Marshall Space Flight Center (MSFC) that has significant improvement in tensile and fatigue strength at elevated temperatures (500 F-700 F). The alloy offers a number of benefits such as light weight, high hardness, low thermal expansion and high surface wear resistance. In hypereutectic form, this alloy is considered as an in-situ Al-Si composite with tensile strength of about 90% higher than the auto industry 390 alloy at 600 F. This composite is very economically produced by using either conventional permanent steel molds or die casting. The projected material cost is less than $0.90 per pound, and automotive components such as pistons can be cast for high production rate using conventional casting techniques with a low and fully accounted cost. Key Words: Metal matrix composites, In-situ composite, aluminum-silicon alloy, hypereutectic alloy, permanent mold casting, die casting.

  13. Laser Cladding of γ-TiAl Intermetallic Alloy on Titanium Alloy Substrates

    NASA Astrophysics Data System (ADS)

    Maliutina, Iuliia Nikolaevna; Si-Mohand, Hocine; Piolet, Romain; Missemer, Florent; Popelyukh, Albert Igorevich; Belousova, Natalya Sergeevna; Bertrand, Philippe

    2016-01-01

    The enhancement of titanium and titanium alloy's tribological properties is of major interest in many applications such as the aerospace and automotive industry. Therefore, the current research paper investigates the laser cladding of Ti48Al2Cr2Nb powder onto Ti6242 titanium alloy substrates. The work was carried out in two steps. First, the optimal deposition parameters were defined using the so-called "combined parameters," i.e., the specific energy E specific and powder density G. Thus, the results show that those combined parameters have a significant influence on the geometry, microstructure, and microhardness of titanium aluminide-formed tracks. Then, the formation of dense, homogeneous, and defect-free coatings based on optimal parameters has been investigated. Optical and scanning electron microscopy techniques as well as energy-dispersive spectroscopy and X-ray diffraction analyses have shown that a duplex structure consisting of γ-TiAl and α 2-Ti3Al phases was obtained in the coatings during laser cladding. Moreover, it was shown that produced coatings exhibit higher values of microhardness (477 ± 9 Hv0.3) and wear resistance (average friction coefficient is 0.31 and volume of worn material is 5 mm3 after 400 m) compared to those obtained with bare titanium alloy substrates (353 Hv0.3, average friction coefficient is 0.57 and a volume of worn material after 400 m is 35 mm3).

  14. Producing Foils From Direct Cast Titanium Alloy Strip

    NASA Technical Reports Server (NTRS)

    Stuart, T. A.; Gaspar, T. A.; Sukonnik, I. M.; Semiatan, S. L.; Batawi, E.; Peters, J. A.; Fraser, H. L.

    1996-01-01

    This research was undertaken to demonstrate the feasibility of producing high-quality, thin-gage, titanium foil from direct cast titanium strip. Melt Overflow Rapid Solidification Technology (MORST) was used to cast several different titanium alloys into 500 microns thick strip, 10 cm wide and up to 3 m long. The strip was then either ground, hot pack rolled or cold rolled, as appropriate, into foil. Gamma titanium aluminide (TiAl) was cast and ground to approximately 100 microns thick foil and alpha-2 titanium aluminide (Ti3AI) was cast and hot pack rolled to approximately 70 microns thick foil. CP Ti, Ti6Al2Sn4Zr2Mo, and Ti22AI23Nb (Orthorhombic), were successfully cast and cold-rolled into good quality foil (less than 125 microns thick). The foils were generally fully dense with smooth surfaces, had fine, uniform microstructures, and demonstrated mechanical properties equivalent to conventionally produced titanium. By eliminating many manufacturing steps, this technology has the potential to produce thin gage, titanium foil with good engineering properties at significantly reduced cost relative to conventional ingot metallurgy processing.

  15. Elastic moduli of nanocrystalline binary Al alloys with Fe, Co, Ti, Mg and Pb alloying elements

    NASA Astrophysics Data System (ADS)

    Babicheva, Rita I.; Bachurin, Dmitry V.; Dmitriev, Sergey V.; Zhang, Ying; Kok, Shaw Wei; Bai, Lichun; Zhou, Kun

    2016-05-01

    The paper studies the elastic moduli of nanocrystalline (NC) Al and NC binary Al-X alloys (X is Fe, Co, Ti, Mg or Pb) by using molecular dynamics simulations. X atoms in the alloys are either segregated to grain boundaries (GBs) or distributed randomly as in disordered solid solution. At 0 K, the rigidity of the alloys increases with decrease in atomic radii of the alloying elements. An addition of Fe, Co or Ti to the NC Al leads to increase in the Young's E and shear μ moduli, while an alloying with Pb decreases them. The elastic moduli of the alloys depend on a distribution of the alloying elements. The alloys with the random distribution of Fe or Ti demonstrate larger E and μ than those for the corresponding alloys with GB segregations, while the rigidity of the Al-Co alloy is higher for the case of the GB segregations. The moduli E and μ for polycrystalline aggregates of Al and Al-X alloys with randomly distributed X atoms are estimated based on the elastic constants of corresponding single-crystals according to the Voigt-Reuss-Hill approximation, which neglects the contribution of GBs to the rigidity. The results show that GBs in NC materials noticeably reduce their rigidity. Furthermore, the temperature dependence of μ for the NC Al-X alloys is analyzed. Only the Al-Co alloy with GB segregations shows the decrease in μ to the lowest extent in the temperature range of 0-600 K in comparison with the NC pure Al.

  16. Amorphous powders of Al-Hf prepared by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

    1988-01-01

    We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

  17. Microstructure and Aging of Powder-Metallurgy Al Alloys

    NASA Technical Reports Server (NTRS)

    Blackburn, L. B.

    1987-01-01

    Report describes experimental study of thermal responses and aging behaviors of three new aluminum alloys. Alloys produced from rapidly solidified powders and contain 3.20 to 5.15 percent copper, 0.24 to 1.73 percent magnesium, 0.08 to 0.92 percent iron, and smaller amounts of manganese, nickel, titanium, silicon, and zinc. Peak hardness achieved at lower aging temperatures than with standard ingot-metallurgy alloys. Alloys of interest for automobile, aircraft, and aerospace applications.

  18. Effect of thermomechanical processing on mechanical properties of Fe-16 at. % Al alloy

    SciTech Connect

    Sikka, V.K.

    1994-12-31

    An iron-aluminum alloy containing 16 at. % Al, which is essentially free from environmental effect on its ductility, has been developed. This alloy has over 20% elongation at room temperature. This paper presents in detail the effect of vacuum versus air melting on the properties of Fe-16 at. % Al alloy. The comparative results have shown air-induction melting to produce lower room-temperature ductility for the identical processing steps. Additional processing steps required to improve the ductility of air-melted material are also identified.

  19. Effects of Al Contents on Carburization Behavior and Corrosion Resistance of TiAl Alloys

    NASA Astrophysics Data System (ADS)

    Liao, Cui Jiao; He, Yue Hui; Ming, Xing Zu

    2015-10-01

    TiAl alloys with Al contents of 30.7, 37, 46.5, and 54.2 at.% were carburized. Corrosion resistance of the untreated and the carburized TiAl alloys was comparatively analyzed. The phase and microstructure of the carburized TiAl alloys were studied by x-ray diffraction and scanning electron microscopy, respectively. Electrochemical corrosion behavior of the untreated and the carburized TiAl alloys was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Experimental results indicate that different Al contents bring about distinct microstructure of the carburized layers. The lower Al content leads to the formation of the thicker binary carbides and the thinner Ti2AlC phase. Additionally, the lower Al content leads to higher corrosion resistance in the untreated and the carburized states.

  20. Effect of Silicon on the Thixoformability of Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Benati, Davi Munhoz; Zoqui, Eugênio José

    2014-09-01

    The thixoformability of new Al-Si-Cu alloys was evaluated and characterized by their microstructural and rheological behavior. Alloys Al1Si2.6Cu, Al2Si2.6Cu, Al4Si2.6Cu, and Al7Si2.6Cu were produced with the addition of Al5Ti1B grain refiner alloy. The materials were heat treated under two controlled conditions: holding times of 0, 30, 90, and 210 s and solid fraction of 45 and 60%. The evaluation of the microstructure and semisolid behavior was characterized by globule size, shape factor (SF), minimum stress to flow, maximum stress, and apparent viscosity. The heat treatment times promoted the globularization of solid phase particles to achieve better apparent viscosity results for the alloys treated for 210 s. Both 45 and 60% solid fraction showed no significant differences in terms of SF, but the alloys containing lower solid fraction showed better performance for apparent viscosity. Better working ranges for these new Al-Si-Cu alloys were determined reaching average strain of 0.5 MPa and apparent viscosity of 105 Pa s.

  1. Effects of the Al content on pore structures of porous TieAl alloys

    SciTech Connect

    Jaing, Y; He, Y H; Xu, N P; Zou, J; Huang, B; Lui, C T

    2008-01-01

    Porous TieAl alloys with different nominal compositions were fabricated through a reactive synthesis of Ti and Al elemental powders. It has been found that the pore parameters vary with the Al contents, indicating that the nature of the pores can be manipulated through changing the Al contents. In addition, detailed structural characterizations showed that the fabricated porous TieAl alloys can have three crystalline phases (i.e., a2-Ti3Al, g-TiAl, and TiAl3) when using different compositions. The fundamental reasons behind these phenomena have been explored.

  2. Atomistic Modeling of RuAl and (RuNi) Al Alloys

    NASA Technical Reports Server (NTRS)

    Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

  3. Osseointegration of Ti-6Al-4V alloy implants with a titanium nitride coating produced by a PIRAC nitriding technique: a long-term time course study in the rat.

    PubMed

    Sovak, Guy; Gotman, Irena; Weiss, Anna

    2015-02-01

    This study examined bone tissue responses to Ti-6Al-4V alloy implants with a hard TiN coating applied by an original powder immersion reaction-assisted coating (PIRAC) nitriding method. Progression of implant fixation in the distal epiphysis and within the medullary cavity of the rat femur was evaluated between 3 days and 6 months postimplantation by scanning electron microscopy, oxytetracycline incorporation, and histochemistry. After 6 months, successful osseointegration was achieved in both epiphyseal and diaphyseal sites. Throughout, implant portions located within the epiphysis remained in close contact with bone trabeculae that gradually engulfed the implant forming a bone collar continuous with the trabecular network of the epiphysis. In the diaphysis, woven bone was first formed within the marrow cavity around the implant and later was replaced by a shell of compact bone around the implant. In general, higher osseointegration rates were measured for TiN-coated versus the uncoated implants, both in the epiphysis and in the diaphysis. In conclusion, our findings indicate an excellent long-term biocompatibility of TiN coatings applied by the PIRAC nitriding technique and superior osteoinductive ability in comparison with uncoated Ti-6Al-4V alloy. Such coatings can, therefore, be considered for improving the corrosion and wear resistance of titanium-based orthopedic implants. PMID:25482093

  4. Laser ablation of Al-Ni alloys and multilayers

    NASA Astrophysics Data System (ADS)

    Roth, Johannes; Trebin, Hans-Rainer; Kiselev, Alexander; Rapp, Dennis-Michael

    2016-05-01

    Laser ablation of Al-Ni alloys and multilayers has been studied by molecular dynamics simulations. The method was combined with a two-temperature model to describe the interaction between the laser beam, the electrons, and the atoms. As a first step, electronic parameters for the alloys had to be found and the model developed originally for pure metals had to be generalized to multilayers. The modifications were verified by computing melting depths and ablation thresholds for pure Al and Ni. Here known data could be reproduced. The improved model was applied to the alloys Al_3Ni, AlNi and AlNi_3. While melting depths and ablation thresholds for AlNi behave unspectacular, sharp drops at high fluences are observed for Al_3Ni and AlNi_3. In both cases, the reason is a change in ablation mechanism from phase explosion to vaporization. Furthermore, a phase transition occurs in Al_3Ni. Finally, Al layers of various thicknesses on a Ni substrate have been simulated. Above threshold, 8 nm Al films are ablated as a whole while 24 nm Al films are only partially removed. Below threshold, alloying with a mixture gradient has been observed in the thin layer system.

  5. High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

    SciTech Connect

    Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

    2000-05-10

    The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.

  6. Commercialization status of Ni{sub 3}Al-based alloys

    SciTech Connect

    Sikka, V.K.

    1997-12-31

    The Ni{sub 3}Al-based alloys have been under development at the Oak Ridge National Laboratory (ORNL) and other research institutions in the United States and around the world for the last ten years. The incremental developments of composition, melting process, casting methods, property data, corrosion data, weldability development, and prototype component testing under production-like operating conditions have pushed the ORNL-developed Ni{sub 3}Al-based alloys closer to commercialization. This paper will present the highlights of incremental technical developments along with the approach and current status of commercialization. It is concluded that cast components are the primary applications of Ni{sub 3}Al-based alloys, and applications range from heat-treating fixtures of forging dies. It is also concluded that the commercialization process is accelerated when technology is licensed to an organization that can produce the alloy, has component manufacturing capability, and is also a user.

  7. Producing titanium-niobium alloy by high energy beam

    NASA Astrophysics Data System (ADS)

    Sharkeev, Yu. P.; Golkovski, M. G.; Glukhov, I. A.; Eroshenko, A. Yu.; Bataev, V. A.; Fortuna, S. V.

    2016-01-01

    The research is involved in producing a Ti-Nb alloy surface layer on titanium substrate by high energy beam method, as well as in examining their structures and mechanical properties. Applying electron-beam cladding it was possible to produce a Ti-Nb alloy surface layer of several millimeters, where the niobium concentration was up to 40% at. and the structure itself could be related to martensite quenching structure. At the same time, a significant microhardness increase of 3200-3400 MPa was observed, which, in its turn, is connected with the formation of martensite structure. Cladding material of Ti-Nb composition could be the source in producing alloys of homogeneous microhardness and desired concentration of alloying niobium element.

  8. Development of powder metallurgy 2XXX series Al alloys for high temperature aircraft structural applications

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1984-01-01

    The objective of the present investigation was to improve the strength and fracture toughness combination of P/M 2124 Al alloys in accordance with NASA program goals for damage tolerance and fatigue resistance. Two (2) P/M compositions based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.12 and 0.60 wt. pct. Zr were selected for investigation. The rapid solidification rates produced by atomization were observed to prohibit the precipitation of coarse, primary Al3Zr in both alloys. A major portion of the Zr precipitated as finely distributed, coherent Al3Zr phases during vacuum preheating and solution heat treatment. The proper balance between Cu and Mg contents eliminated undissolved, soluble constituents such as Al2CuMg and Al2Cu during atomization. The resultant extruded microstructures produced a unique combination of strength and fracture toughness. An increase in the volume fraction of coherent Al3Zr, unlike incoherent Al20Cu2Mn3 dispersoids, strengthened the P/M Al base alloy either directly by dislocation-precipitate interactions, indirectly by a retardation of recrystallization, or a combination of both mechanisms. Furthermore, coherent Al3Zr does not appear to degrade toughness to the extent that incoherent Al20Cu2Mn3 does. Consequently, the addition of 0.60 wt. pct. Zr to the base alloy, incorporated with a 774K (935 F) solution heat treatment temperature, produces an alloy which exceeds all tensile property and fracture toughness goals for damage tolerant and fatigue resistant applications in the naturally aged condition.

  9. Al-TiH2 Composite Foams Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Prasada Rao, A. K.; Oh, Y. S.; Ain, W. Q.; A, Azhari; Basri, S. N.; Kim, N. J.

    2016-02-01

    The work presented here in describes the synthesis of aluminum based titanium-hydride particulate composite by casting method and its foaming behavior of magnesium alloy. Results obtained indicate that the Al-10TiH2 composite can be synthesized successfully by casting method. Further, results also reveal that closed-cell magnesium alloy foam can be synthesized by using Al-10TiH2 composite as a foaming agent.

  10. Nucleation and Growth of Cu-Al Intermetallics in Al-Modified Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Lead-free solder alloys Sn-Cu (SC) and Sn-Ag-Cu (SAC) are widely used by the microelectronics industry, but enhanced control of the microstructure is needed to improve solder performance. For such control, nucleation and stability of Cu-Al intermetallic compound (IMC) solidification catalysts were investigated by variation of the Cu (0.7-3.0 wt.%) and Al (0.0-0.4 wt.%) content of SC + Al and SAC + Al alloys, and of SAC + Al ball-grid array (BGA) solder joints. All of the Al-modified alloys produced Cu-Al IMC particles with different morphologies and phases (occasionally non-equilibrium phases). A trend of increasing Cu-Al IMC volume fraction with increasing Al content was established. Because of solidification of non-equilibrium phases in wire alloy structures, differential scanning calorimetry (DSC) experiments revealed delayed, non-equilibrium melting at high temperatures related to quenched-in Cu-Al phases; a final liquidus of 960-1200°C was recorded. During cooling from 1200°C, the DSC samples had the solidification behavior expected from thermodynamic equilibrium calculations. Solidification of the ternary alloys commenced with formation of ternary β and Cu-Al δ phases at 450-550°C; this was followed by β-Sn, and, finally, Cu6Sn5 and Cu-Al γ1. Because of the presence of the retained, high-temperature phases in the alloys, particle size and volume fraction of the room temperature Cu-Al IMC phases were observed to increase when the alloy casting temperature was reduced from 1200°C to 800°C, even though both temperatures are above the calculated liquidus temperature of the alloys. Preliminary electron backscatter diffraction results seemed to show Sn grain refinement in the SAC + Al BGA alloy.

  11. An investigation of wear behaviors of different Monel alloys produced by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Esgin, U.; Özyürek, D.; Kaya, H.

    2016-04-01

    In the present study, wear behaviors of Monel 400, Monel 404, Monel R-405 and Monel K-500 alloys produced by Powder Metallurgy (P/M) method were investigated. These compounds prepared from elemental powders were cold-pressed (600 MPa) and then, sintered at 1150°C for 2 hours and cooled down to the room temperature in furnace environment. Monel alloys produced by the P/M method were characterized through scanning electron microscope (SEM+EDS), X-ray diffraction (XRD), hardness and density measurements. In wear tests, standard pin-on-disk type device was used. Specimens produced within four different Monel Alloys were tested under 1ms-1 sliding speed, under three different loads (20N, 30N and 40N) and five different sliding distances (400-2000 m). The results show that Monel Alloys have γ matrix and that Al0,9Ni4,22 intermetallic phase was formed in the structure. Also, the highest hardness value was measured with the Monel K-500 alloy. In wear tests, the maximum weight loss according to the sliding distance, was observed in Monel 400 and Monel 404 alloys while the minimum weight loss was achieved by the Monel K-500 alloy.

  12. Characteristics of heat resistant alloys Ti10Nb45Al and Ti18Nb48Al

    SciTech Connect

    Weijun Zhang; Guoliang Chen; Yandong Wang; Zuqing Sun )

    1993-05-01

    Based on a systematic study of the ternary Ti-Nb-Al system, two attractive heat resistant alloys, Ti10Nb45Al and Ti18Nb48Al, were developed, and the characteristics of these alloys were discussed: (1) After annealing at 1,200 C for 240 h and furnace cooling to room temperature, the Ti10Nb45Al alloy exhibits an [alpha][sub 2] + [gamma] lamellar microstructure, and the Ti18Nb48Al alloy shows a plate-like structure consisting of [alpha][sub 2], [gamma] and [gamma][sub 1] phases. (2) The specific strengths of Ti10Nb45Al and Ti18Nb48Al are much higher than TiAl and superalloys in the temperature range of 800 [approximately] 1,100 C. The compressive yield strengths of these alloys are on the order of 700 MPa at 800 C and 350 MPa at 1,100 C. The density of these alloys is about 4.3 g/cm[sup 3]. (3) The annealed Ti10Nb45Al and Ti18Nb48Al exhibit some ductility at room temperature, with the compressive elongation on the order of 12% and the fracture toughness as high as 16 MPa[radical]m. The ductile-brittle transformation temperatures for Ti10Nb45Al and Ti18Nb48Al are 650 C and 750 C, respectively. (4) The parabolic constant K[sub p] for oxidation of Ti10Nb45Al and Ti18Nb48Al are 0.88 and 0.29 mg[sup 2]cm[sup [minus]4]h[sup [minus]1] respectively, which are two orders of magnitude lower than that of TiAl and Ti[sub 3]Al alloys.

  13. Strain ageing and yield plateau phenomena in {gamma}-TiAl based alloys containing boron

    SciTech Connect

    Cheng, T.T.; Bate, P.S.; Botten, R.R.; Lipsitt, H.A.

    1999-01-08

    There has been considerable interest over the past few years in {gamma}-TiAl based alloys since they offer a combination of low density and useful mechanical properties at temperatures higher than those possible with conventional titanium alloys. However, there are still serious limitations to their use in engineering components due to their limited ductility and fracture toughness. Much of the recent work has been focused on improving the room temperature ductility of these materials, and a significant part of the work has been involved with studying the effects of thermo-mechanical processing (TMP) and alloying. One of the alloying additions which has received much attention is boron. Addition of boron ({ge}0.5 at.%) leads to refined as-cast grain structures and can increase the strength and ductility of these alloys. If boron does segregate to grain boundaries, it would be expected that segregation would also occur at dislocations, which can result in solute locking and yield point phenomena. Nakano and Umakoshi`s results show some signs of this, with regions of distinct upward curvature in stress-strain curves for boron-containing material, although the flow stress was always increasing with strain. Evidence of strain ageing in TiAl alloys containing boron has also been reported by Wheeler et al., and the work reported here also suggests that boron can act to produce solute locking of glide dislocations in a different class of near {gamma}-TiAl alloys.

  14. Development of Ultrafine, Lamellar Structures in Two-Phase {gamma}-TiAl Alloys

    SciTech Connect

    Maziasz, P.J., Liu, C.T.

    1997-12-31

    Processing of two-phase gamma-TiAl alloys (Ti-47Al-2Cr-2Nb or minor modifications thereof) above the alpha-transus temperature (T {sub alpha}) produced unique refined-colony/ultrafine lamellar structures in both powder- and ingot-metallurgy (P/M and I/M, respectively) alloys. These ultrafine lamellar structures consist of fine laths of the gamma and alpha {sub 2} phases, with average interlamellar spacings (lambda {sub Lambda}) of 100-200 nm and alpha {sub 2}-alpha {sub 2} spacings (lambda {sub alpha}) of 200-500 nm, and are dominated by gamma/alpha {sub 2} interfaces. This characteristic microstructure forms by extruding P/M Ti-47Al-2Cr-2Nb alloys above T {sub alpha}, and also forms with finer colony size but slightly coarser fully-lamellar structures by hot-extruding similar I/M alloys. Alloying additions of B and W refine lambda {sub L} and lambda {sub alpha} in both I/M Ti-47Al (cast and heat-treated above T {sub alpha}) or in extruded Ti-47Al-2Cr-2Nb alloys. The ultrafine lamellar structure in the P/M alloy remains stable during heat-treatment at 900 {degrees}C for 2h, but becomes unstable after 4h at 982 {degrees}C; the ultrafine lamellar structure remains relatively stable after aging for {gt}5000 h at 800 {degrees}C. Additions of B+W dramatically improve the coarsening resistance of lambda L and lambda alpha in the I/M Ti-47Al alloys aged for 168 h at 1000{degrees}C. In both the P/M and I/M Ti-47Al-2Cr-2Nb alloys, these refined-colony/ultrafine-lamellar structures correlate with high strength and good ductility at room temperature, and very good strength at high temperatures. While refining the colony size improves the room-temperature ductility, alloys with finer lambda {sub L} are stronger at both room- and high-temperatures. Additions of B+W produce finer as-processed lambda {sub L} and lambda {sub alpha} in I/M TiAl alloys, and stabilize such structures during heat-treatment or aging.

  15. Precipitation Strengthening in Al-Ni-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Huang, Kai; Makhlouf, Makhlouf M.

    2015-12-01

    Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2 to 4 wt pct. manganese is investigated with focus on the effect of the alloys' chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy's yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries.

  16. Ultrafine fully-lamellar structures in two-phase {gamma}-TiAl alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.

    1996-12-31

    Special ultrafine fully lamellar microstructures have been found recently in {gamma}-TiAl alloys with 46-48% Al processed or heat treated above the {alpha}-transus temperature (T{alpha}). Hot extrusion above T{alpha} also produces a refined colony or grain size. Refined-colony/ultrafine-lamellar (RC/UL) microstructures produce an excellent combination of RT ductility and high-temperature strength in Ti-47Al-2Cr-2Nb (at.%) alloys. UL structures also have regularly alternating {gamma} and {alpha}{sub 2} lamellae, such that they are dominated by {gamma}/{alpha}{sub 2} interfaces with relatively few {gamma}/{gamma} twin boundaries. Focus of this study is on how changes in processing parameters or alloy composition affect formation of the UL structure, particularly the {alpha}{sub 2} component.

  17. Supercoducting property of Zr-Cu-Al-Ni-Nb alloys

    NASA Astrophysics Data System (ADS)

    Okai, D.; Motoyama, G.; Kimura, H.; Inoue, A.

    The superconducting property of Zr55Cu(30-X)Al10Ni5NbX alloys prepared by arc melting and liquid quenching methods was investigated by magnetic susceptibility measurements. The crystalline alloys with X = 0∼25 at.% prepared by arc melting method exhibited superconductivity with maximum Tc,on of 10.1 K. The alloys (X = 10∼23 at.%) with crystalline particles embedded in an amorphous structure, which were fabricated by melt spinning method, showed superconductivity with Tc,on of less than 4.0 K. The superconducting property of the Zr-Cu-Al-Ni-Nb alloys was attributed to superconducting phases of Zr2Cu, Zr2Ni, Zr65Al10Nb25 and Zr-Nb contained in the Zr-Cu-Al-Ni-Nb alloys. The melt-spun Zr55Cu(30-X)Al10Ni5NbX (X = 10∼20 at.%) alloys exhibited glass transition at 718∼743 K and were found to be superconducting metallic glasses.

  18. Properties of a new type Al/Pb-0.3%Ag alloy composite anode for zinc electrowinning

    NASA Astrophysics Data System (ADS)

    Yang, Hai-tao; Liu, Huan-rong; Zhang, Yong-chun; Chen, Bu-ming; Guo, Zhong-cheng; Xu, Rui-dong

    2013-10-01

    An Al/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corrosion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) displays a more compact interfacial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of Al/Pb-0.3%Ag alloy (hard anodizing) and Al/Pb-0.3%Ag alloy (plating tin) at 500 A·m-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, Al/Pb-0.3%Ag alloy (hard anodizing), and Al/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 g·m-2·h-1, respectively, in accelerated corrosion test for 8 h at 2000 A·m-2. The anodic oxidation layer of Al/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and Al/Pb-0.3%Ag alloy (plating tin) after the test.

  19. Post-irradiation mechanical properties of an AlMgSi alloy

    NASA Astrophysics Data System (ADS)

    Ismail, Z. H.; Birt, B.

    1995-03-01

    The effect of fast-neutron irradiation on the tensile properties and hardness of the age-hardenable alloy AlMgSi is investigated. Post-irradiation tensile tests are carried out in the temperature range 298 to 628 K. The results show that the degree of irradiation-produced hardening is dependent upon the initial condition of the alloy. The alloy in its soft condition exhibits a higher degree of irradiation hardening compared with that in the hard condition. The implication of the results is discussed in terms of the variation in the microstructures involved and compared with previosly published data.

  20. Nucleation in Al Alloys Processed By MCDC Casting

    NASA Astrophysics Data System (ADS)

    Prasada Rao, A. K.

    2015-06-01

    Present work confines itself to discuss the mechanism responsible for the grain refinement of the melt conditioned direct-chill cast aluminum alloys. It has been found that the Al alloys processed by this process undergo grain refinement irrespective of their chemical composition. The forced convection caused during this process led to dendrite fragmentation which enhances the heterogeneous nucleation and result in grain refinement. It is suggested that owing to their favorable lattice matching with α-Al, these fragments serve as potent nuclei for α-Al grains.

  1. Welding and mechanical properties of cast FAPY (Fe-16 at. % Al-based) alloy slabs

    SciTech Connect

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J.; Howell, C.R.

    1995-08-01

    The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10, and iron = 83.71. The cast ingots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot- worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

  2. Ab initio investigation of grain boundary cohesion in Al alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Shengjun; Kontsevoi, Oleg Y.; Freeman, A. J.; Olson, G. B.

    2010-03-01

    Strength and hardness of aluminum alloys can be substantially increased by alloying with Mg, Zn, Cu, Si, and other elements. The main drawback of Al alloys is their susceptibility to stress corrosion cracking, which is caused by alloying impurities segregated at grain boundaries. We investigated the embrittling and cohesion-enhancing effects of impurities on a σ5(012)[100] grain boundary in Al by means of the full-potential linearized augmented plane-wave (FLAPW) method within the framework of the Rice-Wang thermodynamic model and within the ab initio tensile test approach. We calculated segregation energies, analyzed local atomic configurations, electronic structures and spatial charge density distributions around segregated impurities, and identified the roles of atomic size and the bonding behavior of the impurity with the surrounding Al atoms. The results show that He, H and Na are strong embrittlers, Zn is a weak embrittler, while Sc, B, Cu and Mg are cohesion enhancers. We further evaluated the effect of co-alloying with two or more elements on grain boundary strength. This work provides a fundamental basis for the design of high strength Al alloys.

  3. Influence of RCS on Al-3Mg and Al-3Mg-0.25Sc alloys

    NASA Astrophysics Data System (ADS)

    Bhovi, Prabhakar M.; Venkateswarlu, K.

    2016-02-01

    An influence of repetitive corrugation and straightening (RCS) was studied on Al-3Mg and Al-3Mg-0.25Sc alloys up to eight passes. Each pass consist of a corrugation and followed by straightening. This has resulted in introducing large plastic strain in sample, and thus led to formation of sub-micron grain sizes with high angle grain boundaries. These sub grain formation was eventually resulted in improved mechanical properties. The average grain size of Al-3Mg-0.25Sc alloy after 8 passes yielded to ∼0.6pm. Microhardness, strength properties were evaluated and it suggests that RCS was responsible for high hardness values as compared to the as cast samples. The microhardness values after RCS were 105 HV and 130 HV for Al-3Mg and Al-3Mg-0.25Sc alloys, respectively. Similarly, ∼ 40% improvement in tensile strength from 240 MPa to 370 MPa was observed for Al- 3Mg-0.25Sc alloy after RCS process.Al-3Mg and Al-3Mg-0.25Scalloys exhibited maximum strength of 220 MPa and 370 MPa, respectively. It is concluded that RCS process has a strong influence on Al- 3Mg and Al-3Mg-0.25Sc alloys for obtaining improved mechanical properties and grain refinement. In addition to RCS process and presence of AESc precipitates in Al-3Mg-0.25Sc alloy had a significant role in grain refinement and improved mechanical properties as compared to Al-3Mg alloy.

  4. Energetic-particle synthesis of high-strength Al(O) alloys

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Barbour, J.C.; Myers, S.M.; Dugger, M.T.

    1995-09-28

    High-strength Al(O) alloys, initially discovered by ion implantation, have now been produced with electron-cyclotron resonance plasma deposition and pulsed-laser deposition. The mechanical properties of these deposited alloy layers were examined with nanoindentation, and finite element modeling of the indented layer on Si substrates was used to determine yield stresses for the alloys of {approximately} 1--5 GPa. The key to these high strengths is the high density of nanometer-size {gamma}-Al{sub 2}O{sub 3} precipitates formed when high concentrations (5--30 at.%) of oxygen are introduced into aluminum as individual atoms or molecules. The strongest alloys have precipitates as small as 1 nm, implying that such small precipitates block dislocation motion. Based upon previous studies with oxygen-implanted aluminum, improved tribological properties are expected for layers made by the two new deposition methods.

  5. Tensile properties influencing variables in eutectic Al-Si casting alloys

    SciTech Connect

    Hafiz, M.F. . Dept. of Mechanical Engineering); Kobayashi, Toshiro . Dept. of Production Systems Engineering)

    1994-09-15

    Efforts to identify and characterize the physical properties of aluminum castings alloys are envisaged to lead to a new guideline from which the mechanical behavior of these alloys can be accurately predicted. For aluminum-silicon (Al-Si) casting alloys the tensile properties of a specific composition are observed to vary depending on the production parameters. The difference in the tensile properties appears to be mainly due to the microstructural features concomitant with the imposed production parameters. The present study aims to identify, quantitatively, the tensile properties influencing variables in high purity eutectic Al-Si casting alloy produced under a variety of solidification cooling rate with different strontium (Sr) additions, as a modifying agent. The correlation between the fracture characteristics and the microstructures has also been investigated.

  6. Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2009-01-01

    In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

  7. Tungsten-nickel-cobalt alloy and method of producing same

    DOEpatents

    Dickinson, James M.; Riley, Robert E.

    1977-03-15

    An improved tungsten alloy having a tungsten content of approximately 95 weight percent, a nickel content of about 3 weight percent, and the balance being cobalt of about 2 weight percent is described. A method for producing said tungsten-nickel-cobalt alloy is further described and comprises (a) coating the tungsten particles with a nickel-cobalt alloy, (b) pressing the coated particles into a compact shape, (c) heating said compact in hydrogen to a temperature in the range of 1400.degree. C and holding at this elevated temperature for a period of about 2 hours, (d) increasing this elevated temperature to about 1500.degree. C and holding for 1 hour at this temperature, (e) cooling to about 1200.degree. C and replacing the hydrogen atmosphere with an inert argon atmosphere while maintaining this elevated temperature for a period of about 1/2 hour, and (f) cooling the resulting alloy to room temperature in this argon atmosphere.

  8. Electrochemical method of producing eutectic uranium alloy and apparatus

    DOEpatents

    Horton, James A.; Hayden, H. Wayne

    1995-01-01

    An apparatus and method for continuous production of liquid uranium alloys through the electrolytic reduction of uranium chlorides. The apparatus includes an electrochemical cell formed from an anode shaped to form an electrolyte reservoir, a cathode comprising a metal, such as iron, capable of forming a eutectic uranium alloy having a melting point less than the melting point of pure uranium, and molten electrolyte in the reservoir comprising a chlorine or fluorine containing salt and uranium chloride. The method of the invention produces an eutectic uranium alloy by creating an electrolyte reservoir defined by a container comprising an anode, placing an electrolyte in the reservoir, the electrolyte comprising a chlorine or fluorine containing salt and uranium chloride in molten form, positioning a cathode in the reservoir where the cathode comprises a metal capable of forming an uranium alloy having a melting point less than the melting point of pure uranium, and applying a current between the cathode and the anode.

  9. Effect of surface roughness on the development of protective Al 2O 3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

    NASA Astrophysics Data System (ADS)

    Zhang, Z. G.; Hou, P. Y.; Gesmundo, F.; Niu, Y.

    2006-11-01

    The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al 2O 3 formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al 2O 3 surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al 2O 3-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al 2O 3 layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.

  10. Functionally Graded Al Alloy Matrix In-Situ Composites

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.

    2010-01-01

    In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.

  11. Dendrite coherency of Al-Si-Cu alloys

    NASA Astrophysics Data System (ADS)

    Veldman, Natalia L. M.; Dahle, Arne K.; Stjohn, David H.; Arnberg, Lars

    2001-01-01

    The dendrite coherency point of Al-Si-Cu alloys was determined by thermal analysis and rheological measurement methods by performing parallel measurements at two cooling rates for aluminum alloys across a wide range of silicon and copper contents. Contrary to previous findings, the two methods yield significantly different values for the fraction solid at the dendrite coherency point. This disparity is greatest for alloys of low solute concentration. The results from this study also contradict previously reported trends in the effect of cooling rate on the dendritic coherency point. Consideration of the results shows that thermal analysis is not a valid technique for the measurement of coherency. Analysis of the results from rheological testing indicates that silicon concentration has a dominant effect on grain size and dendritic morphology, independent of cooling rate and copper content, and thus is the factor that determines the fraction solid at dendrite coherency for Al-Si-Cu alloys.

  12. Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

    NASA Astrophysics Data System (ADS)

    Knipling, Keith E.; Dunand, David C.; Seidman, David N.

    2007-10-01

    Two conventionally solidified Al-0.2Ti alloys (with 0.18 and 0.22 at. pct Ti) exhibit no hardening after aging up to 3200 hours at 375 °C or 425 °C. This is due to the absence of Al3Ti precipitation, as confirmed by electron microscopy and electrical conductivity measurements. By contrast, an Al-0.2Zr alloy (with 0.19 at. pct Zr) displays strong age hardening at both temperatures due to precipitation of Al3Zr (L12) within Zr-enriched dendritic regions. This discrepancy between the two alloys is explained within the context of the equilibrium phase diagrams: (1) the disparity in solid and liquid solubilities of Ti in α-Al is much greater than that of Zr in α-Al; and (2) the relatively small liquid solubility of Ti in α-Al limits the amount of solute retained in solid solution during solidification, while the comparatively high solid solubility reduces the supersaturation effecting precipitation during post-solidification aging. The lattice parameter mismatch of Al3Ti (L12) with α-Al is also larger than that of Al3Zr (L12), further hindering nucleation of Al3Ti. Classical nucleation theory indicates that the minimum solute supersaturation required to overcome the elastic strain energy of Al3Ti nuclei cannot be obtained during conventional solidification of Al-Ti alloys (unlike for Al-Zr alloys), thus explaining the absence of Al3Ti precipitation and the presence of Al3Zr precipitation.

  13. The structure-property relationships of powder processed Fe-Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Prichard, Paul Dehnhardt

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape PN processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic%). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (Dsb{84} < 32μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 mum. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 mum to 104 mum. Mechanical property testing was conducted on both extruded and sintered material using small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25sp°C to 550sp°C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase alpha + DOsb3 structure. The extruded material developed higher yield strength at temperatures below the DBTT, but the sintered material developed higher strengths above the DBTT. The fracture energy of these

  14. Extrusion textures in Al, 6061 alloy and 6061/SiC{sub p} nanocomposites

    SciTech Connect

    Jiang, X.; Galano, M.; Audebert, F.

    2014-02-15

    The 6061 alloy matrix composites reinforced with 10 wt.% and 15 wt.% of SiC nanoparticles with an average diameter of ∼ 500 nm were hot extruded in strip shape from ball milled powders. The microstructures and textures of the hot extruded nanocomposites have been investigated by means of three dimensional orientation distribution functions and electron backscatter diffraction (EBSD) techniques. Pure Al and 6061 alloy extruded strips from atomised powders have been produced for comparison purposes. The results show that the non-deformable SiC particulates have a strong influence on the formation of extrusion textures in the matrix. Pure Al and 6061 alloy develop a typical β fibre texture after extrusion in strip shape. For 6061/SiC{sub p} nanocomposites, the intensities of major texture components decrease with increasing amount of SiC particles. The total intensities of Brass, Dillamore and S components have decreased by 19% for 6061/10 wt.% SiC{sub p} and 40% for 6061/15 wt.% SiC{sub p} composites when compared with the 6061 alloy. EBSD analysis on local grain orientations shows limited Al grain rotations in SiC rich zones and decreased texture intensities. - Highlights: • The effect of nano-SiCp to the extrusion texture of Al alloy matrix was analysed. • The Intensity of major texture components decreases with increasing amount of SiCp. • Deformation zones with limited Al grain rotations formed in SiCp rich zones.

  15. Fracture toughness of stoichiometric, non-stoichiometric and ternary-alloyed Al{sub 2}Ti

    SciTech Connect

    Ma, J.C.; Lukitsch, M.J.; Ambrow, C.E.; Benci, J.E.

    1997-12-31

    Polycrystalline stoichiometric Al{sub 2}Ti was produced via casting or powder metallurgy and further processed yielding material in six conditions. The fracture toughness of the six material conditions was determined from the critical load to initiate cracks with a Vickers indenter. The results show a strong dependence on material condition. Powder processed Al{sub 2}Ti exhibits the highest fracture toughness value among the material conditions studied. Polycrystalline non-stoichiometric Al{sub 2{+-}y}Ti{sub 1{+-}y} and ternary-alloyed Al{sub 2}Ti + X were prepared in as-cast and cast and annealed conditions. Each material condition exhibited a multiphase microstructure. The composition of the phases present in each alloy was analyzed with SEM/EDS. Fracture toughness values of cast and annealed stoichiometric and non-stoichiometric binary alloys are 20--30% greater than as-cast stoichiometric Al{sub 2}Ti. For the ternary alloys, the fracture toughness values show a strong dependence on the ternary element used and heat treatment condition. The fracture toughness values of three hot forged ternary alloys were also determined.

  16. New Powder Metallurgical Approach to Achieve High Fatigue Strength in Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.; Kumar, Pankaj; Sun, Pei; Zak Fang, Z.; Koopman, Mark

    2016-05-01

    Recently, manufacturing of titanium by sintering and dehydrogenation of hydride powders has generated a great deal of interest. An overarching concern regarding powder metallurgy (PM) titanium is that critical mechanical properties, especially the high-cycle fatigue strength, are lower than those of wrought titanium alloys. It is demonstrated here that PM Ti-6Al-4V alloy with mechanical properties comparable (in fatigue strength) and exceeding (in tensile properties) those of wrought Ti-6Al-4V can be produced from titanium hydride powder, through the hydrogen sintering and phase transformation process. Tensile and fatigue behavior, as well as fatigue fracture mechanisms, have been investigated under three processing conditions. It is shown that a reduction in the size of extreme-sized pores by changing the hydride particle size distribution can lead to improved fatigue strength. Further densification by pneumatic isostatic forging leads to a fatigue strength of ~550 MPa, comparable to the best of PM Ti-6Al-4V alloys prepared by other methods and approaching the fatigue strengths of wrought Ti-6Al-4V alloys. The microstructural factors that limit fatigue strength in PM titanium have been investigated, and pathways to achieve greater fatigue strengths in PM Ti-6Al-4V alloys have been identified.

  17. Precipitation during infiltration of A201 aluminum alloy into Al-Fe-V-Si preform

    SciTech Connect

    Yang, C.C.; Chen, Y.C.; Chang, E.

    1996-04-01

    The newly developed Al-Fe-V-Si aluminum alloy, produced by melt spinning into ribbons, comminution of ribbon to particles, and then consolidation of particles by extrusion and forging, is being considered for high temperature applications due to the material`s characteristics of high elevated temperature strength, low density, good toughness and thermal stability. In order to extend the near-net shaping capability of the material, the authors have proposed a new process that Al-Fe-V-Si aluminum alloy particles can be consolidated by casting, in which the liquid aluminum alloy was infiltrated around the Al-Fe-V-Si particles to form a FVS1212/A201 composite material. Preliminary study of the Al-Fe-V-Si particle reinforced A201 aluminum alloy composite demonstrated that the compression strength at 300 C can be twice as high as A201 aluminum alloy. This work constitutes a continuation of the previous efforts to understand the microstructural evolution sequences, particularly the precipitation events during infiltration of the liquid aluminum into Al-Fe-V-Si preform.

  18. Local Structures of Mechanically Alloyed Al70Cu20Fe10 Nanocomposites Studied by XRD and XAFS

    SciTech Connect

    Yin Shilong; Qian Liying; He Bo; Zou Shaobo; Wei Shiqiang; Bian Qing

    2007-02-02

    Ternary Al70Cu20Fe10 alloy nano-composites prepared by mechanical alloying are characterized by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results indicate that after milled for 10 hours, the coordination environment around Cu atoms is changed largely and becomes disordered, but the local structure of Fe atoms still remains as that of {alpha}-Fe. This indicates the forming of inter-metallic compound Al2Cu with body center cubic structure. Even if the milling time is extended to 40 hours, only small amount of {alpha}-Fe can be alloyed to produce Al-Fe-Cu alloy. However, the annealing treatment at 700 deg. C can drive the {alpha}-Fe to incorporate into the Al2Cu compound to form an icosahedral alloy phase.

  19. Multi-step wrought processing of TiAl-based alloys

    SciTech Connect

    Fuchs, G.E.

    1997-04-01

    Wrought processing will likely be needed for fabrication of a variety of TiAl-based alloy structural components. Laboratory and development work has usually relied on one-step forging to produce test material. Attempts to scale-up TiAl-based alloy processing has indicated that multi-step wrought processing is necessary. The purpose of this study was to examine potential multi-step processing routes, such as two-step isothermal forging and extrusion + isothermal forging. The effects of processing (I/M versus P/M), intermediate recrystallization heat treatments and processing route on the tensile and creep properties of Ti-48Al-2Nb-2Cr alloys were examined. The results of the testing were then compared to samples from the same heats of materials processed by one-step routes. Finally, by evaluating the effect of processing on microstructure and properties, optimized and potentially lower cost processing routes could be identified.

  20. Enhanced superplasticity and strength in modified Ti-6Al-4V alloys

    SciTech Connect

    Wert, J.A.; Paton, N.E.

    1983-12-01

    Beta-stabilizing elements were added Ti-6Al-4V alloy with a view to lowering its optimum superplastic forming temperature. The alloys modified with 2 wt pct Fe, Co, and Ni produced values of flow stress, strain rate sensitivity, and total elongation at 1088 K approaching those of the base Ti-6Al-4V alloy at its standard superplastic forming temperature of 1200 K. In addition to lowering the superplastic forming temperature, the beta-stabilizing elements also increased room temperature strength levels above those normally found for Ti-6Al-4V. The addition of beta-stabilizing elements raised resistance to deformation at room temperature, while lowering it at elevated temperatures. This result is explained by considering the effects of high-diffusivity beta stabilizers on deformation processes at room and elevated temperatures. 23 references.

  1. Thermo-mechanical processing (TMP) of Ti-48Al-2Nb-2Cr based alloys

    SciTech Connect

    Fuchs, G.E.

    1995-02-01

    The effects of heat treatment and deformation processing on the microstructures and properties of {gamma}-TiAl based alloys produced by ingot metallurgy (I/M) and powder metallurgy (P/M) techniques were examined. The alloy selected for this work is the second generation {gamma}-TiAl based alloy -- Ti-48Al-2Nb-2Cr (at %). Homogenization of I/M samples was performed at a variety of temperatures, followed by hot working by isothermal forging. P/M samples were prepared from gas atomized powders, consolidated by both HIP and extrusion and some of the HIPed material was then hot worked by isothermal forging. The effects of processing, heat treatment and hot working on the microstructures and properties will be discussed.

  2. Effect of initial texture on texture evolution in 1050 Al alloys under simple shear

    NASA Astrophysics Data System (ADS)

    Han, Jun-Hyun; Oh, Kyu Hwana; Lee, Jae-Chul

    2003-08-01

    The effect of the initial textures prior to dissimilar channel angular pressing (DCAP) on the texture evolution of the 1050 Al alloy sheets, processed by the continuous confined strip shearing (C2S2) process, were studied. The four different specimens, i.e., cold rolled, heat treated, warm rolled, and as-cast 1050 Al alloy sheets, having various initial textures were prepared using different thermomechanical routes. Although the major texture types were significantly affected by the initial textures prior to DCAP, DCAP always promoted both the <111>//normal direction (ND) textures and the {001}<110> rotated cube texture regardless of the initial texture status. Effects of the texture evolutions due to equal channel angular pressing (ECAP) on deep drawbility and planar anisotropy were analyzed based on the -r value and the Δ r value determined from the measured pole figures. A feasibility for producing the 1050 Al alloy sheets having high deep drawbility and low planar anisotropy was demonstrated.

  3. Simulation of aluminothermic smelting of Al-Zr and Al-Zr-Mo-Sn alloys

    NASA Astrophysics Data System (ADS)

    Larionov, A. V.; Chumarev, V. M.; Udoeva, L. Yu.; Mansurova, A. N.; Rylov, A. N.; Raikov, A. Yu.; Aleshin, A. P.; Trubachev, M. V.

    2013-09-01

    Aluminothermic smelting of Al-Zr and Al-Zr-Mo-Sn alloys has been simulated in terms of thermodynamics. The thermodynamic properties of molybdenum and zirconium intermetallic compounds are calculated. It is demonstrated that, with consideration for their formation, the calculated compositions of aluminothermic blends and the forecasted extraction of target metals into an alloy are in good agreement with the data obtained during pilot tests.

  4. POWDER METALLURGY TiAl ALLOYS: MICROSTRUCTURES AND PROPERTIES

    SciTech Connect

    Hsiung, L

    2006-12-11

    The microstructures and properties of powder metallurgy TiAl alloys fabricated by hot extrusion of gas-atomized powder at different elevated temperatures were investigated. Microstructure of the alloy fabricated at 1150 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains and coarse ordered B2 grains. Particles of ordered hexagonal {omega} phase were also observed in some B2 grains. The alloy containing B2 grains displayed a low-temperature superplastic behavior: a tensile elongation of 310% was measured when the alloy was tested at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. Microstructure of the alloy fabricated at 1250 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains, coarse {alpha}{sub 2} grains, and lamellar ({gamma} + {alpha}{sub 2}) colonies. An observation of stacking faults associated with fine {gamma} lamellae in {alpha}{sub 2} grains reveals that the stacking fault of {alpha}{sub 2} phase plays an important role in the formation of lamellar ({gamma} + {alpha}{sub 2}) colonies. Unlike the alloy fabricated at 1150{sup o}, the alloy fabricated at 1250{sup o} displayed no low-temperature superplasticity, but a tensile elongation of 260% at 1000 C was measured. Microstructure of the alloy fabricated at 1400 C consisted of fully lamellar ({gamma} + {alpha}{sub 2}) colonies with the colony size ranging between 50 {micro}m and 100 {micro}m, in which the width of {gamma} lamella is in a range between 100 nm and 350 nm, and the width of {alpha}{sub 2} lamella is in a range between 10 nm and 50 nm. Creep behavior of the ultrafine lamellar alloy and the effects of alloying addition on the creep resistance of the fully lamellar alloy are also investigated.

  5. Al-Li Alloy 1441 for Fuselage Applications

    NASA Technical Reports Server (NTRS)

    Bird, R. K.; Dicus, D. L.; Fridlyander, J. N.; Sandler, V. S.

    2000-01-01

    A cooperative investigation was conducted to evaluate Al-Cu-Mg-Li alloy 1441 for long service life fuselage applications. Alloy 1441 is currently being used for fuselage applications on the Russian Be-103 amphibious aircraft, and is expected to be used for fuselage skin on a new Tupolev business class aircraft. Alloy 1441 is cold-rollable and has several attributes that make it attractive for fuselage skin applications. These attributes include lower density and higher specific modulus with similar strength as compared to conventional Al-Cu-Mg alloys. Cold-rolled 1441 Al-Li sheet specimens were tested at NASA Langley Research Center (LaRC) and at the All-Russia Institute of Aviation Materials (VIAM) in Russia to evaluate tensile properties, fracture toughness, impact resistance, fatigue life and fatigue crack growth rate. In addition, fuselage panels were fabricated by Tupolev Design Bureau (TDB) using 1441 skins and Al-Zn-Mg-Cu alloy stiffeners. The panels were subjected to cyclic pressurization fatigue tests at TDB and at LaRC to simulate fuselage pressurization/depressurization during aircraft service. This paper discusses the results from this investigation.

  6. Recovery of Li from alloys of Al- Li and Li- Al using engineered scavenger compounds

    DOEpatents

    Riley, W. D.; Jong, B. W.; Collins, W. K.; Gerdemann, S. J.

    1994-01-01

    A method of producing lithium of high purity from lithium aluminum alloys using an engineered scavenger compound, comprising: I) preparing an engineered scavenger compound by: a) mixing and heating compounds of TiO2 and Li2CO3 at a temperature sufficient to dry the compounds and convert Li.sub.2 CO.sub.3 to Li.sub.2 O; and b) mixing and heating the compounds at a temperature sufficient to produce a scavenger Li.sub.2 O.3TiO.sub.2 compound; II) loading the scavenger into one of two electrode baskets in a three electrode cell reactor and placing an Al-Li alloy in a second electrode basket of the three electrode cell reactor; III) heating the cell to a temperature sufficient to enable a mixture of KCl-LiCl contained in a crucible in the cell to reach its melting point and become a molten bath; IV) immersing the baskets in the bath until an electrical connection is made between the baskets to charge the scavenger compound with Li until there is an initial current and voltage followed by a fall off ending current and voltage; and V) making a connection between the basket electrode containing engineered scavenger compound and a steel rod electrode disposed between the basket electrodes and applying a current to cause Li to leave the scavenger compound and become electrodeposited on the steel rod electrode.

  7. Development of Ti-6Al-4V and Ti-1Al-8V-5Fe Alloys Using Low-Cost TiH2 Powder Feedstock

    SciTech Connect

    Joshi, Vineet V.; Lavender, Curt; Moxon, Vladimir; Duz, Vlad; Nyberg, Eric; Weil, K. Scott

    2012-09-25

    Thermo-mechanical processing was performed on two titanium alloy billets, a beta-titanium alloy (Ti1Al8V5Fe) and an alpha-beta titanium alloy (Ti6Al4V), which had been produced using a novel low-cost powder metallurgy process that relies on the use of TiH2 powder as a feedstock material. The thermomechanical processing was performed in the beta region of the respective alloys to form 16-mm diameter bars. The hot working followed by the heat treatment processes not only eliminated the porosity within the materials but also developed the preferred microstructures. Tensile testing and rotating beam fatigue tests were conducted on the as-rolled and heat-treated materials to evaluate their mechanical properties. The mechanical properties of these alloys matched well with those produced by the conventional ingot processing route.

  8. The immiscibility of InAlN ternary alloy.

    PubMed

    Zhao, Guijuan; Xu, Xiaoqing; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Ji, Zesheng; Meng, Yulin; Wang, Lianshan; Yang, Shaoyan

    2016-01-01

    We have used two models based on the valence force field and the regular solution model to study the immiscibility of InAlN ternary alloy, and have got the spinodal and binodal curves of InAlN. Analyzing the spinodal decomposition curves, we obtain the appropriate concentration region for the epitaxial growth of the InN-AlN pseudobinary alloy. At a temperature most common for the epitaxial growth of InAlN (1000 K), the solubility of InN is about 10%. Then we introduce the mismatch strain item into the Gibbs free energy, and the effect of different substrates is taken into consideration. Considering Si, Al2O3, InN, GaN, AlN as a substrate respectively, it is found that all the five systems are stabilized with the upper critical solution temperature largely reduced. Finally, InN and GaN are potential substrates for In-rich InAlN, while AlN and GaN substrates are recommended in the Al-rich region. Si and Al2O3 may be ideal substrates for thin InAlN film. PMID:27221345

  9. The immiscibility of InAlN ternary alloy

    PubMed Central

    Zhao, Guijuan; Xu, Xiaoqing; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Ji, Zesheng; Meng, Yulin; Wang, Lianshan; Yang, Shaoyan

    2016-01-01

    We have used two models based on the valence force field and the regular solution model to study the immiscibility of InAlN ternary alloy, and have got the spinodal and binodal curves of InAlN. Analyzing the spinodal decomposition curves, we obtain the appropriate concentration region for the epitaxial growth of the InN-AlN pseudobinary alloy. At a temperature most common for the epitaxial growth of InAlN (1000 K), the solubility of InN is about 10%. Then we introduce the mismatch strain item into the Gibbs free energy, and the effect of different substrates is taken into consideration. Considering Si, Al2O3, InN, GaN, AlN as a substrate respectively, it is found that all the five systems are stabilized with the upper critical solution temperature largely reduced. Finally, InN and GaN are potential substrates for In-rich InAlN, while AlN and GaN substrates are recommended in the Al-rich region. Si and Al2O3 may be ideal substrates for thin InAlN film. PMID:27221345

  10. The immiscibility of InAlN ternary alloy

    NASA Astrophysics Data System (ADS)

    Zhao, Guijuan; Xu, Xiaoqing; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Ji, Zesheng; Meng, Yulin; Wang, Lianshan; Yang, Shaoyan

    2016-05-01

    We have used two models based on the valence force field and the regular solution model to study the immiscibility of InAlN ternary alloy, and have got the spinodal and binodal curves of InAlN. Analyzing the spinodal decomposition curves, we obtain the appropriate concentration region for the epitaxial growth of the InN-AlN pseudobinary alloy. At a temperature most common for the epitaxial growth of InAlN (1000 K), the solubility of InN is about 10%. Then we introduce the mismatch strain item into the Gibbs free energy, and the effect of different substrates is taken into consideration. Considering Si, Al2O3, InN, GaN, AlN as a substrate respectively, it is found that all the five systems are stabilized with the upper critical solution temperature largely reduced. Finally, InN and GaN are potential substrates for In-rich InAlN, while AlN and GaN substrates are recommended in the Al-rich region. Si and Al2O3 may be ideal substrates for thin InAlN film.

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

    NASA Astrophysics Data System (ADS)

    Watanabe, Goro; Yogo, Yasuhiro; Takao, Hisaaki

    2014-08-01

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

  12. Processing-property-microstructure relationships in TiAl-based alloys

    SciTech Connect

    Loretto, M.H.; Hu, D.; Godfrey, A.

    1997-12-31

    A range of Ti-Al-based alloys have been produced by plasma melting either small buttons (1kg samples) or ingots (up to 50kg). Some of the ingots have been atomized. The influence of thermomechanical processing on the microstructure of these materials has been assessed using optical and electron microscopy and the room temperature mechanical properties and creep strengths determined. It has been found that either through appropriate processing and/or through alloy development, it is possible to obtain alloys with room temperature strengths up to 1,000 MPa. Elongations of about 1% at room temperature have been obtained for alloys with this strength and this is coupled with significant improvements in creep strength over the reference alloy, Ti-48Al-2Mn-2Nb. The influence of the difficulty of slip transfer between gamma and alpha 2 has been assessed as one of the factors limiting ductility. Regions which are low in aluminum, which are present in the atomized powders initiate fracture at very low strains. These results are discussed in terms of the factors that control the strength and fracture behavior of TiAl-based alloys.

  13. The structure-property relationships of powder processed Fe-Al-Si alloys

    SciTech Connect

    Prichard, P.D.

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D{sub 84} < 32 {micro}m). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 {micro}m. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 {micro}m to 104 {micro}m. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase {alpha} + DO{sub 3} structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  14. Investigation of Carbon incorporation into Al 6061 alloys

    NASA Astrophysics Data System (ADS)

    Ge, Xiaoxiao; Riba, Lourdes Salamanca; Wuttig, Manfred; Covetics Collaboration

    The incorporation of carbon nanostructures into aluminum alloys, such as Al6061 and Al7075, has the potential to further improve the mechanical, electrical and anti-corrosion properties of these alloys. We report on a novel method to incorporate up to 10.0 wt% carbon into the crystal structure of Al 6061 alloys to form a new material ``Al Covetics''. In this method, a DC current is applied to molten Al metal containing activated carbon particles. The current facilitates ionization of the carbon atoms and their bonding to each other, forming graphic chains and layers along preferential directions of the Al lattice. Raman mapping of the G and D peaks of graphitic carbon was used to confirm the role of the current in ensuring that the carbons remain in the metal by electro-static force and spread into the metal matrix evenly. Sp2 bonding of carbon was found all over the surface in the Covetics. Carbon signals were also observed everywhere in Covetics with Energy Dispersive X-ray Spectroscopy. However, localized carbon signals were detected in samples made with activated carbon but without applying any current. The dependence of the mechanical, electrical and structural properties of Al Covetics on C content from 3 to 10 wt. % will be presented.

  15. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G. |; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  16. Recent advances in alloy design of Ni{sub 3}Al alloys for structural use

    SciTech Connect

    Liu, C.T.; George, E.P.

    1996-12-31

    This is a comprehensive review of recent advances in R&D of Ni{sub 3}Al-based alloys for structural use at elevated temperatures in hostile environments. Recent studies indicate that polycrystalline Ni{sub 3}Al is intrinsically quite ductile at ambient temperatures, and its poor tensile ductility and brittle grain-boundary fracture are caused mainly by moisture-induced hydrogen embrittlement when the aluminide is tested in moisture- or hydrogen-containing environments. Tensile ductility is improved by alloying with substitutional and interstitial elements. Among these additives, B is most effective in suppressing environmental embrittlement and enhancing grain-boundary cohesion, resulting in a dramatic increase of tensile ductility at room temperature. Both B-doped and B-free Ni{sub 3}Al alloys exhibit brittle intergranular fracture and low ductility at intermediate temperatures (300-850 C) because of oxygen-induced embrittlement in oxidizing environments. Cr is found to be most effective in alleviating elevated-temperature embrittlement. Parallel efforts on alloy development using physical metallurgy principles have led to development of several Ni{sub 3}Al alloys for industrial use. The unique properties of these alloys are briefly discussed. 56 refs, 15 figs, 3 tabs.

  17. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K.; Wilkening, D.; Liebetrau, J.; Mackey, B.

    1998-11-01

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{trademark} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

  18. Eutectic nucleation in hypoeutectic Al-Si alloys

    SciTech Connect

    Nafisi, S. Ghomashchi, R.; Vali, H.

    2008-10-15

    The nucleation mechanism of eutectic grains in hypoeutectic Al-Si foundry alloys has been investigated by examining deep etched specimens in high-resolution field emission gun scanning electron microscope (FEG-SEM) and by using in-situ Focused Ion Beam (FIB) milling and microscopy. Both unmodified and Sr-modified alloys were studied to characterize the nucleation mechanism of eutectic silicon flakes and fibers. It is proposed that following nucleation of eutectic Al on the primary {alpha}-Al dendrites, fine Si particles form at the solidification front upon which the eutectic Si flakes and fibers could develop. The formation of small Si particles is attributed to Si enrichment of the remaining melt due to the formation of eutectic Al (aluminum spikes) at the eutectic temperature. A hypothesis is then proposed to explain the mechanism of eutectic grains formation with main emphasis on the eutectic Si phase.

  19. Laves phase in Ti-42Al-10Mn alloy

    SciTech Connect

    Chen, Z.; Jones, I.P.; Small, C.J.

    1996-07-01

    Mn is one of the most effective alloying additions to {gamma}-TiAl titanium aluminide for improving room temperature ductility. The purpose of this investigation as a whole is to study phase relationships in the Mn addition alloys over a wide range of temperatures and to determine the solubilities of Mn in the {gamma} and {alpha}{sub 2} phases in order to explore the potential of Mn additions to {gamma}-TiAl. The aim of this specific paper, however, is to confirm the identify of the ternary Ti{sub 3}Al{sub 3}Mn{sub 2} phase in the Ti-Al-Mn system and to show how to remove it.

  20. Composite droplets: evolution of InGa and AlGa alloys on GaAs(100).

    PubMed

    Sablon, K A; Wang, Zh M; Salamo, G J

    2008-03-26

    We present a comparative study for the evolution of utilizing indium gallium (InGa) and aluminum gallium (AlGa) alloys fabricated on GaAs(100) by means of simultaneous and sequential droplet formation. The composite alloys reported using the sequential approach lack the ability to precisely determine the final alloy composition as well as consistency in the density of the droplets. Further, the composition of the InGa alloy is not uniform, as seen by the size distribution using an atomic force microscope (AFM). Although this approach may be acceptable for materials with similar surface kinetics, as in the case of AlGa, it is not acceptable for InGa. This investigation reveals that the simultaneous approach for fabricating composite alloys is the optimum approach for producing InGa alloys with better control on composition for plasmonic applications such as plasmonic waveguides. PMID:21817741

  1. /Al-4Cu Composite Material Produced by Squeeze Casting Method

    NASA Astrophysics Data System (ADS)

    Ficici, Ferit

    2014-05-01

    The wear behavior of a weight fraction of particles with up to 30 wt.% in situ AlB2 flakes reinforced in Al-4Cu matrix alloy composites and fabricated by a squeeze casting method was investigated in a pin-on-disk abrasion test instrument against different SiC abrasives at room conditions. Wear tests were performed under the load of 10 N against SiC abrasive papers of 80, 100, and 120 mesh grits. The effects of sliding speed, AlB2 flake content, and abrasive grit sizes on the abrasive wear properties of the matrix alloy and composites have been evaluated. The main wear mechanisms were identified using an optical microscope. The results showed that in situ AlB2 flake reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding speed and the abrasive grit size. The wear resistances of the composites were considerably bigger than those of the matrix alloy and increased with increases in in situ AlB2 flake contents.

  2. Efficient Utilization of Nickel Laterite to Produce Master Alloy

    NASA Astrophysics Data System (ADS)

    Ma, Xiaodong; Cui, Zhixiang; Zhao, Baojun

    2016-07-01

    To lower the smelting temperature associated with the carbothermic reduction processing of laterite, the optimization of slag and alloy systems was investigated to enable the reduction of laterite ore in the molten state at 1723 K. The master Fe-Ni-Mo alloy was successfully produced at a lower temperature (1723 K). The liquidus of the slag decreased with the addition of oxide flux (Fe2O3 and CaO) and that of the ferronickel alloy decreased with the addition of Mo/MoO3. More effective metal-slag separation was achieved at 1723 K, which reduces the smelting temperature by 100 K compared with the current electric furnace process. A small addition of Mo/MoO3 not only decreased the melting point of ferronickel alloys but also served as a collector to aggregate the ferronickel sponges allowing them to grow larger. The FeO concentration in the slag and the nickel grade of the alloy decreased with increasing graphite reductant addition.

  3. 99. 99% Al/ 6063 Alloy Co-extruded beam chamber

    SciTech Connect

    Ishimaru, H.; Narushima, K.; Kanazawa, K.

    1988-09-30

    In an electron storage ring, synchrotron radiation causes stimulated gas desorption from the vacuum chamber wall. It raises the operating pressure far above the ultrahigh vacuum range needed for long beam lifetimes. In order to determine an ideal material for low dynamic gas desorption we have studied the properties of co-extruded 99.99%Al/ 6063 alloy. (AIP)

  4. Characterization of Continuous Cast AA2037 Al Alloy

    SciTech Connect

    Kenik, Edward A; Zeng, Qiang; Zhai, Tongguang

    2009-01-01

    The microstructure of a contiuous cast Al alloy was characterized with transmission and scanning transmission electron microscopy, as well as x-ray microanalysis. Several precipitate phases were identified as a function of prior thermomechanical treatment in order to understand the improvement of fatigue properties resulting from those treatments.

  5. High strain rate superplasticity in a friction stir processed 7075 Al alloy

    SciTech Connect

    Mishra, R.S.; Mahoney, M.W.; McFaden, S.X.; Mara, N.A.; Mukherjee, A.K.

    1999-12-31

    In this paper, the authors report the first results using friction stir processing (FSP). In the last ten years, a new technique of Friction Stir Welding (FSW) has emerged as an exciting solid state joining technique for aluminum alloys. This technique, developed by The Welding Institute (TWI), involves traversing a rotating tool that produces intense plastic deformation through a stirring action. The localized heating is produced by friction between the tool shoulder and the sheet top surface, as well as plastic deformation of the material in contact with the tool. This results in a stirred zone with a very fine grain size in a single pass. Mahoney et al. observed a grain size of 3 {micro}m in a 7075 Al alloy. This process can be easily adopted as a processing technique to obtain fine grain size. FSP of a commercial 7075 Al alloy resulted in significant enhancement of superplastic properties. The optimum superplastic strain rate was 10{sup {minus}2}s{sup {minus}1} at 490 C in the FSP 7075 Al alloy, an improvement of more than an order of magnitude in strain rate. The present results suggest an exciting possibility to use a simple FSP technique to enhance grain size dependent properties.

  6. Interfacial reactions and oxidation behavior of Al 2O 3 and Al 2O 3/Al coatings on an orthorhombic Ti 2AlNb alloy

    NASA Astrophysics Data System (ADS)

    Li, H. Q.; Wang, Q. M.; Gong, J.; Sun, C.

    2011-02-01

    The uniform and dense Al2O3 and Al2O3/Al coatings were deposited on an orthorhombic Ti2AlNb alloy by filtered arc ion plating. The interfacial reactions of the Al2O3/Ti2AlNb and Al2O3/Al/Ti2AlNb specimens after vacuum annealing at 750 °C were studied. In the Al2O3/Ti2AlNb specimens, the Al2O3 coating decomposed significantly due to reaction between the Al2O3 coating and the O-Ti2AlNb substrate. In the Al2O3/Al/Ti2AlNb specimens, a γ-TiAl layer and an Nb-rich zone came into being by interdiffusion between the Al layer and the O-Ti2AlNb substrate. The γ-TiAl layer is chemically compatible with Al2O3, with no decomposition of Al2O3 being detected. No internal oxidation or oxygen and nitrogen dissolution zone was observed in the O-Ti2AlNb alloy. The Al2O3/Al/Ti2AlNb specimens exhibited excellent oxidation resistance at 750 °C.

  7. Comparison of the transformation temperature, microstructure and magnetic properties of Co-Ni-Al and Co-Ni-Al-Cr shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dağdelen, Fethi; Malkoç, Türkan; Kök, Mediha; Ercan, Ercan

    2016-06-01

    In this study, two-phase Co-Ni-Al shape memory alloys that have drawn attention recently due to their technological applications were investigated. Co-Ni-Al and Co-Ni-Al-Cr alloys were produced by melting method in an arc-melter furnace and physical properties between alloys were compared. At the end of experimental measurements it was observed that chromium addition did not change the crystal structure of the Co-Ni-Al alloy, but decreased the martensitic transformation temperature, the most significant property of shape memory alloys. Moreover, there was no significant change in the microstructure of the Co-Ni-Al alloy with chromium addition, and the presence of the two phases determined by X-ray analysis was also determined by optical microscopy. There was no significant change in micro hardness values of the alloys, while important changes in the magnetic properties were determined. It was observed that the Curie temperature decreased by approximately 500 {}^{circ}C with chromium addition and a considerable decrease in the magnetic saturation value was also determined.

  8. Comparison of the transformation temperature, microstructure and magnetic properties of Co-Ni-Al and Co-Ni-Al-Cr shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dağdelen, Fethi; Malkoç, Türkan; Kök, Mediha; Ercan, Ercan

    2016-06-01

    In this study, two-phase Co-Ni-Al shape memory alloys that have drawn attention recently due to their technological applications were investigated. Co-Ni-Al and Co-Ni-Al-Cr alloys were produced by melting method in an arc-melter furnace and physical properties between alloys were compared. At the end of experimental measurements it was observed that chromium addition did not change the crystal structure of the Co-Ni-Al alloy, but decreased the martensitic transformation temperature, the most significant property of shape memory alloys. Moreover, there was no significant change in the microstructure of the Co-Ni-Al alloy with chromium addition, and the presence of the two phases determined by X-ray analysis was also determined by optical microscopy. There was no significant change in micro hardness values of the alloys, while important changes in the magnetic properties were determined. It was observed that the Curie temperature decreased by approximately 500°C with chromium addition and a considerable decrease in the magnetic saturation value was also determined.

  9. Characterization of Al-Cu-Mg-Ag Alloy RX226-T8 Plate

    NASA Technical Reports Server (NTRS)

    Lach, Cynthia L.; Domack, Marcia S.

    2003-01-01

    aircraft wing and fuselage skin materials through the addition of silver to Al-Cu-Mg alloys based on Al 2519 chemistry [2]. Thermal stability of the resulting Al-Cu-Mg-Ag alloys, C415-T8 and C416-T8, was due to co-precipitation of the thermally stable . (AlCu) and ' (Al2Cu) strengthening phases [1-4]. The strength and toughness behavior was investigated for these alloys produced as 0.090-inch thick rolled sheet in the T8 condition and after various thermal exposures. The mechanical properties were shown to be competitive with conventional aircraft alloys, 2519-T8 and 2618-T8 [2]. During the Integral Airframe Structure (IAS) program, advanced aluminum alloys were examined for use in an integrally stiffened airframe structure where the skin and stiffeners would be machined from plate and extruded frames would be mechanically attached (see Figure 1) [5]. Advantages of integrally stiffened structure include reduced part count, and reduced assembly times compared to conventional built-up airframe structure. The near-surface properties of a thick plate are of significance for a machined integrally stiffened airframe structure since this represents the skin location. Properties measured at the mid-plane of the plate are more representative of the stiffener web. RX226 was developed to exploit strength-toughness improvements and thermal stability benefits of Al-Cu-Mg-Ag alloys in plate gages. This study evaluated the microstructure and properties of three gages of plate produced in the T8 condition.

  10. Structural and Thermal Study of Nanocrystalline Fe-Al-B Alloy Prepared by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Gharsallah, Hana Ibn; Sekri, Abderrahmen; Azabou, Myriam; Escoda, Luiza; Suñol, Joan Josep; Khitouni, Mohamed

    2015-08-01

    Nanostructured iron-aluminum alloy of Fe-25 at. pct Al composition doped with 0.2 at. pct B was prepared by mechanical alloying. The phase transformations and structural changes occurring in the studied material during mechanical alloying and during subsequent heating were investigated by SEM, XRD, and DSC techniques. The patterns so obtained were analyzed using the Rietveld program. The alloyed powders were disordered Fe(Al) solid solutions and Fe2B boride phase. The Fe2B boride phase is formed after 4 hours of milling. The crystallite size reduction to the nanometer scale (5 to 8 nm) is accompanied by an increase in lattice strains. The powder milled for 40 hours was annealed at temperatures of 523 K, 823 K, 883 K, and 973 K (250 °C, 550 °C, 610 °C, and 700 °C) for 2 hours. Low temperatures annealing are responsible for the relaxation of the disordered structure, while high temperatures annealing enabled supersaturated Fe(Al) solid solutions to precipitate out fines Fe3Al, Fe2Al5, and Fe4Al13 intermetallics and, also the recrystallization and the grain growth phenomena.

  11. Microscopic Properties of Long-Period Ordering in Al-Rich TiAl Alloys

    NASA Astrophysics Data System (ADS)

    Hata, S.; Nakano, T.; Kuwano, N.; Itakura, M.; Matsumura, S.; Umakoshi, Y.

    2008-07-01

    The ordering mechanism of long-period superstructures (LPSs) in Al-rich TiAl alloys has been investigated by high-resolution transmission electron microscopy (HRTEM). The LPSs are classified in terms of arrangements of base clusters with different shapes and compositions formed in Ti-rich (002) layers of L10-TiAl matrix: square Ti4Al, fat rhombus Ti3Al, and lean rhombus Ti2Al type clusters. The HRTEM observations revealed that antiphase boundaries of long-range-ordered LPS domains and short-range-ordered microdomains are constructed by various space-filling arrangements of the base clusters. Such a microscopic property characterized by the base clusters and their arrangements is markedly analogous to that of the {left< {{text{1,1/2,0}}} rightrangle } * special-point ordering alloys such as Ni-Mo.

  12. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  13. Development and commercialization status of Fe{sub 3}Al-based intermetallic alloys

    SciTech Connect

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

    1993-06-01

    The Fe{sub 3}Al-based intermetallic alloys offer unique benefits of excellent oxidation and sulfidation resistance, limited by poor room-temperature (RT) ductility and low high-temperature strength. Recent understanding of environmental effects on RT ductility of these alloys has led to progress toward taking commercial advantage of Fe{sub 3}Al-based materials. Cause of low ductility appears to be related to hydrogen formed from reaction with moisture. The environmental effect has been reduced in these intermetallic alloys by two methods. The first deals with producing a more hydrogen-resistant microstructure through thermomechanical processing, and the second dealed with compositional modification. The alloys showing reduced environmental effect have been melted and processed by many different methods. Laboratory and commercial heats have been characterized. Tests have been conducted in both air and controlled environments to quantify environmental effects on these properties. These materials were also tested for aqueous corrosion and resistance to stress corrosion cracking. Oxidation and sulfidation data were generated and effects of minor alloying elements on were also investigated. Several applications have been identified for the newly developed iron aluminides. Commercialization status of these alloys is described.

  14. Investigation of superplastic behavior of NiAl and Ni{sub 3}Al duplex alloy

    SciTech Connect

    Liu Zhenyun; Lin Dongliang; Gu Yuefeng; Shan Aidang

    1997-12-31

    The superplastic behavior of a NiAl and Ni{sub 3}Al duplex alloy was investigated. It was found that the alloy exhibits superplastic behavior over a narrow temperature range, from 975 C to 1,025 C at the strain rate of 1.52 {times} 10{sup {minus}4}s{sup {minus}1}. A maximum tensile elongation of 149% was obtained at 1,000 C with the strain rate sensitivity up to 0.375. The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: {dot {var_epsilon}} = Ao{sup 2.67} exp({minus}303,000/RT). Optical microstructure and TEM observation show that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation.

  15. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  16. Mercury embrittlement of Cu-Al alloys under cyclic loading

    NASA Technical Reports Server (NTRS)

    Regan, T. M.; Stoloff, N. S.

    1977-01-01

    The effect of mercury on the room temperature, high cycle fatigue properties of three alloys: Cu-5.5 pct Al, Cu-7.3 pct Al, and Cu-6.3 pct Al-2.5 pct Fe has been determined. Severe embrittlement under cyclic loading in mercury is associated with rapid crack propagation in the presence of the liquid metal. A pronounced grain size effect is noted under mercury, while fatigue properties in air are insensitive to grain size. The fatigue results are discussed in relation to theories of adsorption-induced liquid metal embrittlement.

  17. Special Features of the Mechanical Characteristics of Al-Al2O3 Composites Produced By Explosive Compaction of Powders Under Shock-Wave Deformation

    NASA Astrophysics Data System (ADS)

    Zhukov, I. A.; Garkushin, G. V.; Vorozhtsov, S. A.; Khrustalyov, A. P.; Razorenov, S. V.; Kvetinskaya, A. V.; Promakhov, V. V.; Zhukov, A. S.

    2016-01-01

    The results obtained from investigations into the special features inherent in the mechanical characteristics (Hugoniot elastic limit and spall strength) observed under shock-wave loading of Al-Al2O3 composite samples produced by an explosive powder compaction technique are presented. Embedding 10 wt.% of aluminum oxide in the aluminum matrix has been found to increase the Hugoniot elastic limit as opposed to the commercialgrade AD1(Al 1013) aluminum alloy.

  18. Divorced Eutectic Solidification of Mg-Al Alloys

    NASA Astrophysics Data System (ADS)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  19. Microstructure and mechanical properties of Ni sub 3 Al-based alloys reinforced with particulates

    SciTech Connect

    McKamey, C.G.; Carmichael, C.A.

    1990-01-01

    Hot-extrusion was used to produce Ni{sub 3}Al-based alloys to which 10 vol % TiN, NbC, HfO{sub 2}, or HfN was added for reinforcement. The TiN, NbC, and HfO{sub 2} particulates produced Ni{sub 3}Al-matrix composites in which no reaction was noted at the particle-matrix interface. However, the addition of HfN resulted in extensive reaction in which the hafnium appeared to diffuse into the matrix. Microstructures of this alloy showed a complex array of phases and voids where the HfN particles are presumed to have been originally. Hot hardness, compression, and compression creep tests were preformed on specimens cut from the extruded bar of each alloy. No significant strengthening was observed for the alloys containing TiN, NbC, or HfO{sub 2}. However the HfN-containing alloy did show significant strengthening in simple compression and compression creep. This presentation will include microstructures and the results of the mechanical properties tests. 26 refs., 5 figs.

  20. Microstructural Investigations On Ni-Ta-Al Ternary Alloys

    SciTech Connect

    Negache, M.; Souami, N.

    2010-01-05

    The Ni-Al-Ta ternary alloys in the Ni-rich part present complex microstructures. They are composed of multiple phases that are formed according to the nominal composition of the alloy, primary Ni(gamma), Ni{sub 3}Al(gamma'), Ni{sub 6}AlTa(tau{sub 3}), Ni{sub 3}Ta(delta) or in equilibrium: two solid phases (gamma'-tau{sub 3}), (tau{sub 3}-delta), (tau{sub 3}-gamma), (gamma-delta) or three solid phases (gamma'-tau{sub 3}-delta). The nature and the volume fraction of these phases give these alloys very interesting properties at high temperature, and this makes them attractive for specific applications. We have developed a series of ternary alloys in electric arc furnace, determining their solidification sequences using Differential Thermal Analysis (DTA), characterized by SEM-EDS, X-ray diffraction and by a microhardness tests. The follow-up results made it possible to make a correlation between the nature of the formed phases and their solidifying way into the Ni{sub 75}Al{sub x}Ta{sub y} (x+y = 25at.%) system, which are varied and complex. In addition to the solid solution Ni (gamma), the formed intermetallics compounds (gamma', tau{sub 3} and delta) has been identified and correlated with a complex balance between phases.We noticed that the hardness increases with the tantalum which has a hardening effect and though the compound Ni{sub 3}Ta(delta) is the hardest. The below results provide a better understanding of the complex microstructure of these alloys.

  1. An evaluation of the benefits of utilizing rapid solidification for development of 2XXX (Al-Cu-Mg) alloys

    NASA Technical Reports Server (NTRS)

    Paris, H. G.; Chellman, D. J.

    1986-01-01

    The advantages of rapid solidification processing over ingot metallurgy processing in the development of 2XXX aluminum alloy compositions were evaluated using a similarly processed ingot metallurgy (IM) control alloy. The powder metallurgy (PM) alloy extrusions showed a reduced age-hardening response in comparison with similar IM compositions, with higher tensile properties for naturally aged extrusions but lower properties for artificially aged ones. However, the tensile properties of naturally and artificially aged PM alloy extrusions based on a version of IM 2034 alloy, but containing 0.6 weight percent zirconium, were comparable to those of the IM control extrusions and had significantly superior combinations of strength and toughness. The tensile properties of this PM alloy showed even greater advantage in 6.4-mm (0.25-in.) and 1.8-mm (0.070-in.) plate and sheet, the yield strength being about 68 MPa (10 ksi) greater than reported values for the IM 2034 alloy sheet. An artificially aged PM alloy based on 2219 alloy also showed a strength and strength-toughness combination comparable to those of the PM Al-Cu-Mg-Zr alloy, substantially outperforming the IM 2219 alloy. These results show that rapid solidification offers the flexibility needed to modify conventional IM compositions to produce new alloy compositions with superior mechanical properties.

  2. Al-Cu-Li and Al-Mg-Li alloys: Phase composition, texture, and anisotropy of mechanical properties (Review)

    NASA Astrophysics Data System (ADS)

    Betsofen, S. Ya.; Antipov, V. V.; Knyazev, M. I.

    2016-04-01

    The results of studying the phase transformations, the texture formation, and the anisotropy of the mechanical properties in Al-Cu-Li and Al-Mg-Li alloys are generalized. A technique and equations are developed to calculate the amounts of the S1 (Al2MgLi), T1 (Al2CuLi), and δ' (Al3Li) phases. The fraction of the δ' phase in Al-Cu-Li alloys is shown to be significantly higher than in Al-Mg-Li alloys. Therefore, the role of the T1 phase in the hardening of Al-Cu-Li alloys is thought to be overestimated, especially in alloys with more than 1.5% Li. A new model is proposed to describe the hardening of Al-Cu-Li alloys upon aging, and the results obtained with this model agree well with the experimental data. A texture, which is analogous to that in aluminum alloys, is shown to form in sheets semiproducts made of Al-Cu-Li and Al-Mg-Li alloys. The more pronounced anisotropy of the properties of lithium-containing aluminum alloys is caused by a significant fraction of the ordered coherent δ' phase, the deformation mechanism in which differs radically from that in the solid solution.

  3. Electrochemical method of producing eutectic uranium alloy and apparatus

    DOEpatents

    Horton, J.A.; Hayden, H.W.

    1995-01-10

    An apparatus and method are disclosed for continuous production of liquid uranium alloys through the electrolytic reduction of uranium chlorides. The apparatus includes an electrochemical cell formed from an anode shaped to form an electrolyte reservoir, a cathode comprising a metal, such as iron, capable of forming a eutectic uranium alloy having a melting point less than the melting point of pure uranium, and molten electrolyte in the reservoir comprising a chlorine or fluorine containing salt and uranium chloride. The method of the invention produces an eutectic uranium alloy by creating an electrolyte reservoir defined by a container comprising an anode, placing an electrolyte in the reservoir, the electrolyte comprising a chlorine or fluorine containing salt and uranium chloride in molten form, positioning a cathode in the reservoir where the cathode comprises a metal capable of forming an uranium alloy having a melting point less than the melting point of pure uranium, and applying a current between the cathode and the anode. 2 figures.

  4. Microstructure of laser clad Ni- Cr- Al- Hf alloy on a γ' strengthened ni- base superalloy

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Mazumder, J.

    1988-08-01

    Alloys and coatings for alloys for improved high temperature service life under aggressive atmo-spheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-AI-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable in-crease in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of γ' (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-AI-Hf alloy.

  5. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  6. The properties of aluminum alloys containing nickel, produced using powder metallurgy method

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Jamaludin Shamsul, B.; Ahmad, Khairel R.; Hussein, Wan M. H.

    2015-05-01

    In this paper, the effects of nickel on the microstructure and mechanical properties of experimental an Al-Zn-Mg-Cu PM alloys under the impacts of the retrogression and re-aging treatment was investigated. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered samples subjected to the homogenizing condition at 470°C for 1.5 hours then aging at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Characterization's results indicate that the microstructures of an Al-Zn-Mg-Cu-Ni PM alloys presented an intermetallics compound in the aluminum's matrix, identified as the AlNi and Al3Ni2 phases besides the MgZn and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloys.

  7. Grain Refinement of an Al-2 wt%Cu Alloy by Al3Ti1B Master Alloy and Ultrasonic Treatment

    NASA Astrophysics Data System (ADS)

    Wang, E. Q.; Wang, G.; Dargusch, M. S.; Qian, M.; Eskin, D. G.; StJohn, D. H.

    2016-03-01

    Both inoculation by AlTiB master alloys and Ultrasonic Treatment (UT) are effective methods of refining the grain size of aluminium alloys. The present study investigates the influence of UT on the grain refinement of an Al-2 wt% Cu alloy with a range of Al3TilB master alloy additions. When the alloy contains the smallest amount of added master alloy, UT caused significant additional grain refinement compared with that provided by the master alloy only. However, the influence of UT on grain size reduces with increasing addition of the master alloy. Plotting the grain size data versus the inverse of the growth restriction factor (Q) reveals that the application of UT causes both an increase in the number of potentially active nuclei and a decrease in the size of the nucleation free zone due to a reduction in the temperature gradient throughout the melt. Both these factors promote the formation of a fine equiaxed grain structure.

  8. Deformation characteristics of the rapidly solidified Al-8. 5% Fe-1. 2% V-1. 7% Si alloy

    SciTech Connect

    Hariprasad, S.; Sastry, S.M.L.; Jerina, K.L. )

    1993-08-15

    Dispersion strengthened Al-8.5% Fe-1.2% V-1.7% Si (8009) alloy containing 40-80 nm diameter dispersoids and exhibiting attractive elevated temperature strengths can be successfully produced by rapid solidification techniques such as Planar Flow Casting (PFC) and Atomized Melt Deposition (AMD). The grain sizes of alloys produced by PFC and AMD are typically O.5 to 1.0 [mu]m. Fine grain sized aluminum alloys have been found to exhibit plastic instabilities such as yield drop, formation of Lueder's bands and positive deviation from Hall-Petch relationship. The stress-strain behavior at room and elevated temperature of the fine grained dispersion strengthened Al-8.5% Fe-1.2% V-1.7% Si alloy produced by PFC and the AMD processes was determined with the objective of delineating the effect of fine grain size on the deformation behavior.

  9. Characteristics of laser welded wrought Mg-Al-Mn alloy

    SciTech Connect

    Quan Yajie Chen Zhenhua; Yu Zhaohui; Gong Xiaosan; Li Mei

    2008-12-15

    Magnesium alloys have gained increased attention in recent years as a structural metal because of their property merits, which necessitates the development of welding techniques qualified for applications in the aeronautic and automotive industries. Laser welding is known to be an excellent method for joining metals. In this paper, a 3 kW CO{sub 2} laser beam was used to weld the wrought Mg-Al-Mn alloy. The characteristics of the microstructure and the mechanical properties of the joints were analyzed by optical microscopy (OM), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), tensile testing and hardness testing. The experimental results show that the wrought Mg-Al-Mn alloy can be joined successfully using optimized welding conditions. The results of tensile testing show that the highest ultimate tensile strength (UTS) of the joints is up to 94% of that of the base metal. The base metal consists of a typical rolled structure, the narrow heat affected zone (HAZ) has no obvious grain coarsening, and the fusion zone consists of fine grains with a high density of {gamma}-Mg{sub 17}Al{sub 12} precipitates. The hardness test results indicate that the microhardness in the fusion zone is higher than that of the base metal. The elemental analysis reveals that the Mg content in the weld is lower than that of the base metal, but the Al content is slightly higher.

  10. NiAl alloys for high-temperature structural applications

    NASA Astrophysics Data System (ADS)

    Darolia, Ram

    1991-03-01

    If their properties can be improved, nickel aluminide alloys offer significant payoffs in gas turbine engine applications. For these materials, excellent progress has been made toward understanding their mechanical behavior as well as improving their low-temperature ductility and high-temperature strength. For example, recent work shows that room-temperature ductility can be improved dramatically by microalloying with iron, gallium or molybdenum. The next challenge is to develop an alloy which has the required balance of ductility, toughness and strength. Development of design and test methodologies for components made out of low-ductility, anisotropic materials will also be required. While significant challenges remain, the continuing developments suggest that the prognosis for using NiAl alloys as high-temperature structural materials is good.

  11. Effect of Al-3Nb-1B Master Alloy on the Grain Refinement of AZ91D Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhou, Wei; Hu, Penghe; Zhou, Quan

    2016-06-01

    An Al-3Nb-1B master alloy has been prepared using a melt reaction method. The microstructure of the master alloy and its refinement performance on AZ91D magnesium alloy were investigated. Experimental results showed that the Al-3Nb-1B master alloy was mainly composed of α-Al and NbB2 phases. With the increase of the addition amount of Al-3Nb-1B master alloy, the primary α-Mg grains of AZ91D magnesium alloy were further refined. Upon adding 0.5 wt pct Al-3Nb-1B master alloy, the average grain size of the primary α-Mg decreased from 240 to 52 μm. The present results indicated that NbB2 can act as effective heterogeneous nucleus of the primary α-Mg, which accounted for the good grain refining performance on AZ91D magnesium alloy. Compared with the unrefined alloy, the yield strength, ultimate tensile strength, and elongation of AZ91D magnesium alloy refined by 0.5 wt pct Al-3Nb-1B master alloy were increased by 18.4, 15.7, and 27.3 pct, respectively due to the grain refinement effect.

  12. Electrical Transport Properties of Liquid Al-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

    2010-06-01

    Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

  13. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  14. Oxidation characteristics of Ti-14Al-21Nb ingot alloy

    NASA Technical Reports Server (NTRS)

    Sankaran, Sankara N.; Clark, Ronald K.; Unnam, Jalaiah; Wiedemann, Karl E.

    1990-01-01

    Static oxidation kinetics of Ti14Al21Nb (wt pct) ingot alloy were studied in air over the temperature interval of 649 to 1093 C in a thermogravimetric apparatus. The oxidation products were characterized by x ray diffraction, electron microprobe analysis, energy dispersive x ray analysis, and Auger electron spectroscopy. Cross-sections of the oxidized samples were also examined using light and scanning electron microscopy. The oxidation rate was substantially lower than the conventional alloys of titanium, but the kinetics displayed a complex behavior involving two or more oxidation rates depending on the temperature and duration of exposure. The primary oxide formed was TiO2, but this oxide was doped with Nb. Small amounts of Al2O3 and TiN were also present in the scale. Diffusion of oxygen into the alloy was observed and the diffusivity seemed to be dependent on the microstructure of the metal. A model was presented to explain the oxidation behavior of the alloy in terms of the reduction in the oxygen diffusivity in the oxide caused by the modification of the defect structure of TiO2 by Nb ions.

  15. Fatigue crack growth behavior of Al-Li alloy 1441

    SciTech Connect

    Prakash, R.V.; Parida, B.K.

    1995-12-31

    Fatigue crack growth behavior of Al-Li alloy 1441 having a marginally lower lithium content, compared to 80xx and 20xx series Al-Li alloys is presented in this paper. This investigation was conducted on single edge tension--SE(T)--specimens, under constant amplitude as well as under MiniLCA flight spectrum loading with the specific objective of determining the effects of stress ratio, orientation, thickness and cladding. Three thicknesses were considered: 1.2 mm(clad and unclad), 2.0 mm(clad and unclad) and 8.0 mm unclad. Constant amplitude fatigue tests were conducted at stress ratios of {minus}0.3, 0.1 and 0.7. Testing was performed under ambient conditions and along three orientations, namely L-T, T-L and L+45 degrees. Crack growth characteristics of this alloy are compared with that of BS:L73 (2014-T4 equivalent) for assessing the possibility of replacing BS:L73. Significant effect of stress ratio on crack growth rate was observed in all thicknesses. However, in case of 1.2 and 2.0 mm thick sheets, the effect was minimal at intermediate-crack growth regime. The orientation of the specimen does not adversely affect the fatigue crack growth behavior of 8.0 mm and 2.0 mm thick specimens. However, for 1.2 mm unclad sheet crack growth resistance in L-T direction was found to be superior to that along T-L direction. In majority of test cases considered, no significant effect was observed on crack growth rate due to thickness or cladding. Crack growth characteristics of Al-Li alloy 1441 and Al-Cu alloy BS:L73 under constant amplitude as well as MiniLCA spectrum loading are similar in the low and intermediate-crack growth rate regime. Based on these observations, it is felt that this Al-Li alloy has the potential for future aerospace applications.

  16. Microstructure selection maps for Al-Fe alloys

    SciTech Connect

    Gilgien, P.; Zryd, A.; Kurz, W.

    1995-09-01

    The solidification microstructures for Al-0.5-4 at.% Fe alloys under constrained growth conditions have been calculated using analytical models of the growth kinetics of dendritic, eutectic and plane front interface morphologies of stable and metastable phases. Laser remelting experiments are carried out on an Al-4 at.% Fe alloy with low beam velocity (10 mm/s) in order to complete previous experimental results on the solidification microstructures obtained at intermediate growth rates by Bridgman experiments and at a high growth rates by rapid laser resolidification. Comparison of predicted with experimentally determined solidification microstructure maps shows satisfactory agreement in view of the limited knowledge of the thermophysical properties of this system. These maps are useful for the interpretation of microstructures and phases forming under medium to high solidification rates and for the understanding and development of rapid solidification processing. Further the modeling is useful for improving available phase diagram information.

  17. High temperature embrittlement caused by traces of calcium or strontium in an Al-5.5 mol% Mg alloy

    SciTech Connect

    Horikawa, Keitaro; Kuramoto, Shigeru; Kanno, Motohiro

    1998-09-04

    Al-5--10mol%Mg alloys are now being developed for automotive parts since they have good formability. However, an alloy containing magnesium of more than 5mol% has poor hot rolling characteristics. It has been reported that an Al-5.5mol%Mg alloy shows high temperature embrittlement (HTE) based on intergranular fracture at around 300 C depending on strain rate. This embrittlement is considered to be closely related to the unfavorable hot rolling characteristics of the Al-Mg alloy. One of the present authors reported recently that this embrittlement is caused by a trace amount of sodium of only of only 0.6mass ppm (0.7mol ppm) in a coarse-grained Al-5.5mol%Mg alloy produced using high purity ingots. Although numerous studies have been made on the effect of sodium, little is known about the effect of alkali and alkaline-earth elements other than sodium. However, unusual impurities may inevitably creep in the recycling process in future. For example, it is reported that the Al-Mg alloy is contaminated by calcium through the ceramic tube filter using during melting and casting, and strontium is used commercially as an additional element in Al-Si alloys. Hence, aluminum alloys made using recycled stock may be contaminated at least by calcium and strontium. The purpose of this study is to determine the effect of traces of calcium or strontium on hot ductility of an Al-5.5mol%Mg alloy.

  18. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  19. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  20. Effect of Al on the Wetting Behavior Between TiC x and Molten Ti-Al Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Xuyang; Lv, Xuewei; Dong, Hongbiao; Li, Chunxin; Bai, Chenguang

    2015-10-01

    The wetting behavior and the interfacial reactions between TiC x substrate and molten Ti-Al alloys with different Al contents were studied using the Sessile Drop method at 1758 K (1485 °C) in argon atmosphere. It is found that the wettability and interface reaction products depend on Al content in the molten alloy. The initial contact angles between the molten Ti-Al alloy and TiC0.78 surface reduces from 110 to 80 deg when Al content in the alloy changes from 40 to 80 wt pct. The reduction in the initial contact angle is due to the decrease of surface tension of the molten Ti-Al alloys with increasing Al contents. The segregation of Al atoms to the surface occurred at all bulk concentrations of Ti-Al alloys. Al with lower surface tension tends to segregate on the surface of liquid Ti-Al alloy. In the spreading stage, the interfacial reaction led to the decrease in the contact angle. The adhesion in Ti-Al/TiC x system can be interpreted in terms of strong chemical interactions, which is greatly affected by the diffusion of C. The equilibrium contact angle was measured less than 10 deg. Finally, the reaction sequence at the Ti-Al melt and TiC x substrate interface is proposed.

  1. High temperature, oxidation resistant noble metal-Al alloy thermocouple

    NASA Technical Reports Server (NTRS)

    Smialek, James L. (Inventor); Gedwill, Michael G. (Inventor)

    1994-01-01

    A thermocouple is disclosed. The thermocouple is comprised of an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600 - 1300 C) in inert, oxidizing or reducing environments, gases, or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.

  2. Tensile properties of Fe-16 at. % Al alloys

    SciTech Connect

    Sikka, V.K.

    1995-02-01

    A newly developed melting method for Fe-16 at. % Al alloy (FAPY) is described. Tensile data on the air-induction-melted (AIM) and vacuum-induction-melted (VIM) heats of FAPY after identical processing are presented. Optical, scanning electron micrographs (SEM), and microprobe analysis were carried out to explain the lower room-temperature ductility and more scatter in the data for the AIM material as opposed to the VIM material.

  3. Refinement performance and mechanism of an Al-50Si alloy

    SciTech Connect

    Dai, H.S.; Liu, X.F.

    2008-11-15

    The microstructure and melt structure of primary silicon particles in an Al-50%Si (wt.%) alloy have been investigated by optical microscopy, scanning electron microscopy, electron probe micro-analysis and a high temperature X-ray diffractometer. The results show that the Al-50Si alloy can be effectively refined by a newly developed Si-20P master alloy, and the melting temperature is crucial to the refinement process. The minimal overheating degree {delta}T{sub min} ({delta}T{sub min} is the difference between the minimal overheating temperature T{sub min} and the liquidus temperature T{sub L}) for good refinement is about 260 deg. C. Primary silicon particles can be refined after adding 0.2 wt.% phosphorus amount at sufficient temperature, and their average size transforms from 2-4 mm to about 30 {mu}m. The X-ray diffraction data of the Al-50Si melt demonstrate that structural change occurs when the melting temperature varies from 1100 deg. C to 1300 deg. C. Additionally, the relationship between the refinement mechanism and the melt structure is discussed.

  4. Rapid-solidification processing and powder metallurgy of al alloys. Final technical report, 15 April 1982-15 April 1985

    SciTech Connect

    Fraser, H.L.

    1986-10-29

    Regarding work on the development of microstructure during rapid solidification, three areas were addressed. The first of these involved a determination of the mechanism of formation of the so-called zones A and B in hypereutectic Al-transition metal alloys. The second area of work involving the development of microstructure concerns submerged phase transformations. In a study of Al-Be hypereutectic alloys, it was determined that solidification proceeded by a set of phase transformations that may be described by a monotectic reaction. The third area of study concerning microstructural development involves quasi-crystalline Al alloys. In fact, work done in this program has concentrated on the potentially beneficial aspects of quasi-crystalline phases in the microstructure of Al alloys. Work on the consolidation of particulate was concentrated on the use of conventional techniques (.e. extrusion) and novel processes (i.e. dynamic compaction). An estimate of the mechanical properties of rapidly solidified Al alloys was obtained. As explained above, the effect of extrusion is to cause decomposition of the rapidly solidified microstructure. A comparison was made, using the alloy Al-8Fe-2Mo, between the tensile properties of the decomposed microstructure (.e. extruded) and subscale test specimens produced by laser surface melting, consisting entirely of zone A.

  5. Transverse-Weld Tensile Properties of a New Al-4Cu-2Si Alloy as Filler Metal

    NASA Astrophysics Data System (ADS)

    Sampath, K.

    2009-12-01

    AA2195, an Al-Cu-Li alloy in the T8P4 age-hardened condition, is a candidate aluminum armor for future combat vehicles, as this material offers higher static strength and ballistic protection than current aluminum armor alloys. However, certification of AA2195 alloy for armor applications requires initial qualification based on the ballistic performance of welded panels in the as-welded condition. Currently, combat vehicle manufacturers primarily use gas metal arc welding (GMAW) process to meet their fabrication needs. Unfortunately, a matching GMAW consumable electrode is currently not commercially available to allow effective joining of AA2195 alloy. This initial effort focused on an innovative, low-cost, low-risk approach to identify an alloy composition suitable for effective joining of AA2195 alloy, and evaluated transverse-weld tensile properties of groove butt joints produced using the identified alloy. Selected commercial off-the-shelf (COTS) aluminum alloy filler wires were twisted to form candidate twisted filler rods. Representative test weldments were produced using AA2195 alloy, candidate twisted filler rods and gas tungsten arc welding (GTAW) process. Selected GTA weldments produced using Al-4wt.%Cu-2wt.%Si alloy as filler metal consistently provided transverse-weld tensile properties in excess of 275 MPa (40 ksi) UTS and 8% El (over 25 mm gage length), thereby showing potential for acceptable ballistic performance of as-welded panels. Further developmental work is required to evaluate in detail GMAW consumable wire electrodes based on the Al-Cu-Si system containing 4.2-5.0 wt.% Cu and 1.6-2.0 wt.% Si.

  6. Correlation of texture and intergranular corrosion in Al-Mg 5xxx series alloys

    NASA Astrophysics Data System (ADS)

    Engler, O.; Hentschel, T.; Brinkman, H.-J.

    2015-04-01

    Aluminium-alloys of the AA 5xxx series with Mg contents in excess of 3% may suffer from intergranular corrosion (IGC) when exposed to temperatures in the range 60 to 200°C. At these temperatures Al-Mg alloys are rendered susceptible to IGC by precipitation of β-Al8Mg5 phases along the grain boundaries. Accordingly, susceptibility to IGC will depend on grain size as well as type and orientation of the grain boundaries present in the material, that is, on the crystallographic texture of the material at final gauge. Therefore, it is of great interest to study the correlation of texture and precipitation of β-AlMg phases and, therewith, susceptibility to IGC. For this purpose, different AA 5182 samples were processed so as to produce different crystallographic textures and characterized with respect to microstructure and resistance against IGC. EBSD local texture analysis was applied to provide information about the grain boundary character distribution. Eventually, this may enable Al industry to reduce the susceptibility of Al-Mg alloys to IGC by proper control of the final gauge texture, such that higher Mg-contents may be used in IGC-critical applications.

  7. Electron-ion plasma modification of Al-based alloys

    NASA Astrophysics Data System (ADS)

    Ivanov, Yurii; Rygina, Mariya; Petrikova, Elizaveta; Krysina, Olga; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina

    2016-01-01

    The paper reports on the study where we analyzed the surface structure and strength properties of coated Al alloys modified by electron-ion plasma treatment. The Al alloys were deposited with a thin (≈0.5 μm) TiCu film coating (TiCu-Al system) and with a hard TiCuN coating (TiCuN-AlSi system) on a TRIO vacuum setup in the plasma of low-pressure arc discharges. The temperature fields and phase transformations in the film-substrate system were estimated by numerical simulation in a wide range of electron energy densities (5-30 J/cm2) and pulse durations (50-200 μs). The calculations allowed us to determine the threshold energy density and pulse duration at which the surface structure of the irradiated Al-based systems is transformed in a single-phase state (solid or liquid) and in a two-phase state (solid plus liquid). The elemental composition, defect structure, phase state, and lattice state in the modified surface layers were examined by optical, scanning, and transmission electron microscopy, and by X-ray diffraction analysis. The mechanical characteristics of the modified layers were studied by measuring the hardness and Young's modulus. The tribological properties of the modified layers were analyzed by measuring the wear resistance and friction coefficient. It is shown that melting and subsequent high-rate crystallization of the TiCu-Al system makes possible a multiphase Al-based surface structure with the following characteristics: crystallite size ranging within micrometer, microhardness of more than 3 times that in the specimen bulk, and wear resistance ≈1.8 times higher compared to the initial material. Electron beam irradiation of the TiCuN-AlSi system allows fusion of the coating into the substrate, thus increasing the wear resistance of the material ≈2.2 times at a surface hardness of ˜14 GPa.

  8. Microstructure analysis of Al-Si-Cu alloys prepared by gradient solidification technique

    NASA Astrophysics Data System (ADS)

    Borkar, Hemant; Seifeddine, Salem; Jarfors, Anders E. W.

    2015-03-01

    Al-Si-Cu alloys were cast with the unique gradient solidification technique to produce alloys with two cooling rates corresponding to secondary dendrite arm spacing (SDAS) of 9 and 27 μm covering the microstructural fineness of common die cast components. The microstructure was studied with optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The alloy with higher cooling rate, lower SDAS, has a more homogeneous microstructure with well distributed network of eutectic and intermetallic phases. The results indicate the presence of Al-Fe-Si phases, Al-Cu phases and eutectic Si particles but their type, distribution and amount varies in the two alloys with different SDAS. EBSD analysis was also performed to study the crystallographic orientation relationships in the microstructure. One of the major highlights of this study is the understanding of the eutectic formation mechanism achieved by studying the orientation relationships of the aluminum in the eutectic to the surrounding primary aluminum dendrites.

  9. Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication

    SciTech Connect

    Yamamoto, Y.; Yang, Y.; Field, K. G.; Terrani, K.; Pint, B. A.; Snead, L. L.

    2014-06-10

    Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very fine sub-grain structure with the sub-grain size of 1-3μm which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.

  10. Surface modification of Al-20Si alloy by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Gao, B.; Tu, G. F.; Li, S. W.; Hao, S. Z.; Dong, C.

    2011-02-01

    Hypereutectic Al-20Si (Si 20 wt.%, Al balance)alloy surface was treated with high current pulsed electron beam (HCPEB) under different pulse numbers. The results indicate that HCPEB irradiation induces the formation of metastable structures on the treated surface. The coarse primary Si particle melts, producing a "halo" microstructure with primary Si as the center on the melted surface. A supersaturated solid solution of Al is formed in the melted layer caused by Si atoms dissolving into the Al matrix. Cross-section structure analysis shows that a 4 μm remelted layer is formed underneath the top surface of the HCEPB-treated sample. Compared with the matrix, the Al and Si elements in the remelted layer are distributed uniformly. In addition, the grains of the Al-20Si alloy surface are refined after HCPEB treatment, as shown by TEM observation. Nano-silicon particles are dispersed on the surface of remelted layer. Polygonal subgrains, approximately 50-100 nm in size, are formed in the Al matrix. The hardness test results show that the microhardness of the α(Al) and eutectic structure is increased with increasing pulse number. The hardness of the "halo" microstructure presents a gradient change after 15 pulse treatment due to the diffusion of Si atoms. Furthermore, hardness tests of the cross-section at different depths show that the microhardness of the remelted layer is higher than that of the matrix. Therefore, HCPEB technology is a good surface modification method for enhancing the surface hardness of hypereutectic Al-20Si alloy.

  11. Anomalous temperature dependence of flow stress in a Fe{sub 3}Al alloy

    SciTech Connect

    Song, J.H.; Ha, T.K.; Chang, Y.W.

    2000-01-01

    Iron aluminides have attracted much interest since 1930s when the excellent corrosion resistance was noted in alloys with the composition of more than about 18 at.% Al. These alloys have relatively low material cost, due to the reduced usage of strategic elements like Cr, Mo and Ni, and a lower density than stainless steels. Their tensile strength is also comparable to those of ferritic and austenitic steels. These advantages have led the iron aluminide alloys being considered for many applications in industries needing sulfidation and oxidation resistance (1). However, the poor ductility at ambient temperatures and an abrupt drop in strength above 600 C have limited these alloys for structural applications. In the past years, extensive efforts have been devoted to understanding and improving the metallurgical properties of iron aluminides with the aim of producing more strong, ductile, and corrosion-resistant materials for structural applications. These studies have resulted in significant contributions to the understanding of the fabrication and mechanical properties of iron aluminides. Deformation behavior in iron aluminides is now known to depend on composition, temperature, and the presence or absence of ordered structures. Recent studies have demonstrated that improved engineering ductility of 10--15% can be achieved in wrought Fe{sub 3}Al-based iron aluminide alloys, through the control of composition and microstructure. The effect of strain rate on the deformation behavior of Fe{sub 3}Al alloys, especially on the anomalous temperature dependence of strength is of interest recently and more systematic investigation is now necessitated. Load relaxation test has been generally regarded as a very effective technique to measure the strain rate sensitivity over a wider range of strain rates with very little microstructural changes and has been applied to the plasticity of various rate-sensitive materials. In the present study, the iron aluminide alloys with 27

  12. Erosion behavior of Fe-Al intermetallic alloys

    SciTech Connect

    Kim, Y.S.; Song, J.H.; Chang, Y.W.

    1997-04-01

    The Fe-rich Fe-Al intermetallics have generated some interest, especially during the last decade, due to their excellent resistance for oxidation and sulfidation, high specific strength, and low material cost. The aluminide is therefore considered as one of the promising candidates for high-temperature structural materials in a corrosive atmosphere. Research effort has been focused mainly on process, development, and enhancement of room-temperature ductility together with the characterization of physical properties such as mechanical properties, oxidation, corrosion, and abrasive wear behavior. However, there have been only a few works reported to date in regard to the erosion characteristics of the alloy, one of the most important material property of this ordered intermetallic alloy for the use in a fossil-fuel plant. In this study, the solid-particle erosion behavior of the Fe-Al intermetallic alloys containing the various aluminum contents ranging from 25 to 30 at.% has been investigated to clarify the effect of aluminum content and different ordered structures, viz. DO{sub 3} and B2, on the erosion behavior. An attempt has been made to correlate the erosion behavior of these intermetallics to their mechanical properties by carrying out tensile tests together with SEM observation of the eroded surfaces.

  13. The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Titran, R. H.

    1992-01-01

    The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

  14. Microstructure evolution and properties of Al/Al-Mg-Si alloy clad wire during heat treatment

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Guan, Ren-guo; Zhang, Yang; Su, Ning; Ji, Lian-ze; Li, Yuan-dong; Chen, Ti-jun

    2016-06-01

    In this paper, heat treatment was carried out on Al/Al-Mg-Si alloy clad wire, and microstructure evolution and properties of Al/Al-Mg-Si alloy clad wire during heat treatment were investigated. During solution, contents of Mg and Si in inner matrix increased due to dissolution of primary Mg2Si, and they also increased in outer matrix because Mg and Si diffused across the interface. Tensile strength of the clad wire increased firstly and then decreased, and elongation continuously increased, while conductivity continuously decreased with the increase in solution time. In aging process, Mg2Si precipitated in both inner core and outer layer, and the content and average diameter of the precipitate increased with the increase in aging time. The content of precipitate was higher, and the average diameter was bigger in inner core. Tensile strength of the clad wire increased firstly and then decreased with the increase in aging time, and the elongation continuously decreased, while the conductivity continuously increased. The peak tensile strength of 202 MPa occurred at 8 h, when the corresponding elongation was 20 % and the conductivity reached 56.07 %IACS. Even tensile strength of the prepared clad wire approximately equaled to that of Al-0.5Mg-0.35Si alloy 203 MPa, the conductivity was obviously improved from 54.2 to 56.07 %IACS.

  15. Effects of Si Addition and Heating Ar on the Electromigration Performance of Al-Alloy Interconnects

    NASA Astrophysics Data System (ADS)

    Lee, Dok Won; Lee, Byung-Zu; Jeong, Jong Yeul; Park, Hyun; Shim, Kyu Cheol; Kim, Jong Seok; Park, Young Bae; Woo, Sun-Woong; Lee, Jeong-gun

    2002-02-01

    The electromigration (EM) performance of Ti/Al-alloy multilayered metallization with one-step sputtered Al-alloy has been studied. The Al-alloys investigated included Al-1.0%Si-0.5%Cu and Al-0.5%Cu, and the Al-alloy films were prepared with and without heating Ar. The package-level EM test results indicate that the EM resistance of the Al-Si-Cu stack is nearly identical to that of the Al-Cu stack. Si addition was found to degrade the microstructure of the Al-alloy film, while it had the retarding effect on the Ti/Al reaction, which suggests that there exists a trade-off between the film microstructure and the formation of TiAl3 intermetallic compound. The EM performance of the one-step sputtered Al-alloy stack was enhanced by the use of heating Ar during the deposition of Al-alloy film, which has been attributed to the improved microstructure of the Al-alloy film by the use of heating Ar.

  16. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  17. Investigation of new type Cu-Hf-Al bulk glassy alloys

    NASA Astrophysics Data System (ADS)

    Nagy, E.; Rontó, V.; Sólyom, J.; Roósz, A.

    2009-01-01

    In the last years new type Cu-Hf-Al ternary alloys were developed with high glass forming ability and ductility. The addition of Al to Cu-Hf alloys results in improvements in glass formation, thermal stability and mechanical properties of these alloys. We have investigated new Cu-based bulk amorphous alloys in Cu-Hf-Al ternary system. The alloys with Cu49Hf42Al9, Cu46Hf45Al9, Cu50Hf42.5Al7.5 and Cu50Hf45Al5 compositions were prepared by arc melting. The samples were made by centrifugal casting and were investigated by X-ray diffraction method. Thermodynamic properties were examined by differential scanning calorimetry and the structure of the crystallising phases by scanning electron microscopy. The determination of liquidus temperatures of alloys were measured by differential thermal analysis.

  18. Modeling creep deformation of a two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure

    SciTech Connect

    Bartholomeusz, M.F. ); Wert, J.A. . Dept. of Materials Science and Engineering)

    1994-10-01

    A two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti[sub 3]Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti[sub 3]Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti[sub 3]Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti[sub 3]Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar microstructure. Application of the model yields a very good correlation between the predicted an experimentally observed minimum creep rates over moderate stress and temperature ranges.

  19. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  20. Effect of scandium doping on the oxidation resistance of Zn5Al and Zn55Al alloys

    NASA Astrophysics Data System (ADS)

    Obidov, Z. R.; Amonova, A. V.; Ganiev, I. N.

    2013-04-01

    The influence of scandium on the oxidation kinetics of Zn5Al and Zn55Al alloys is studied. It is observed that small additions (0.005-0.05 wt %) of Sc substantially improve the oxidation resistance of zincaluminium alloys.

  1. Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy

    SciTech Connect

    G.A. Young; J.R. Scully

    2001-09-12

    It is well established that Al-Zn-Mg-(Cu) aluminum alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are commonly used to increase HEAC resistance at the expense of strength. Overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). When freshly bared coupons of AA 7050 are exposed to 90 C, 90% RH air, hydrogen ingress follows inverse-logarithmic-type kinetics and is equivalent for underaged (HEAC susceptible) and overaged (HEAC resistant) tempers. However, when the native oxide is allowed to form (24 hrs in 25 C, 40% RH lab air) prior to exposure to 90 C, 90% RH air, underaged alloy shows significantly greater hydrogen ingress than the overaged alloy. Humid air is a very aggressive environment producing local ({approx}1{micro}m) hydrogen concentrations in excess of 10,000 wt. ppm at 90 C. In the copper bearing alloy, overaging also effects the apparent diffusivity of hydrogen. As AA 7050 is aged from underaged {yields} peak aged {yields} overaged, the activation energy for hydrogen diffusion increases and the apparent diffusivity for hydrogen decreases, In the low copper alloy, overaging has little effect on hydrogen diffusion. Comparison of the apparent activation energies for hydrogen diffusion and for K independent (stage II) crack growth

  2. Model for nonprotective oxidation of Al-Mg alloys

    SciTech Connect

    Zayan, M.H. )

    1990-12-01

    The oxidation of Al-5Mg alloy has been studied at 550 C in dry air. Morphological details of the MgO layers which develop on this alloy during high-temperature oxidation have been studied by scanning electron microscopy (SEM). A localized detachment of the protective, adherent MgO layer was found, which is caused by voids formed by vacancy condensation at the metal-oxide interface. The source of these vacancies was the outward diffusion of Mg though the oxide layer. Continuing growth of these voids was responsible for cracking of oxide ridges and nodules, as well as the growth of new MgO having a cauliflower morphology. A model describing the process of the outward diffusion is given.

  3. Solidification behavior and structure of Al-Cu alloy welds

    SciTech Connect

    Brooks, J.A.; Li, M.; Yang, N.C.Y.

    1997-09-01

    The microsegregation behavior of electron beam (EB) and gas tungsten arc (GTA) welds of Al-Cu alloys covering a range from 0.19 to 7.74 wt% Cu were characterized for dendrite core concentrations and fraction eutectic solidification. Although a single weld speed of 12.7 mm/sec was used, some differences were observed in the segregation behavior of the two weld types. The microsegregation behavior was also modeled using a finite differences technique considering dendrite tip and eutectic undercooling and solid state diffusion. Fairly good agreement was observed between measured and calculated segregation behavior although differences between the two weld types could not be completely accounted for. The concept of dendrite tip undercooling was used to explain the formation of a single through thickness centerline grain in the higher alloy content GTA welds.

  4. Tensile behavior of Fe-40Al alloys with B and Zr additions

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Nathal, M. V.

    1986-01-01

    Both Fe-40Al and Fe-40Al-0.1Zr with and without B were produced by the hot extrusion of powdered metal. Tensile properties were determined from room temperature to 1100 K in air. All of the materials possessed some ductility at room temperature, and addition of B caused an increase in ductility and a change in fracture mode from intergranular to transgranular cleavage. At high temperatures, failure was caused primarily by the formation of grain boundary cavities in all of the alloys. The effect of Zr addition was unclear because of the complexity of the various microstructures. Comparison of air and vacuum testing at high temperatures revealed that an apparent oxidation assisted mechanism reduced high temperature ductility in these alloys, especially at 900 K.

  5. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  6. B2 structure of high-entropy alloys with addition of Al

    SciTech Connect

    Li, C.; Zhao, M.; Li, J. C.; Jiang, Q.

    2008-12-01

    A series of AlCrCoNiFe based alloys with equal percentage of principal components (high-entropy alloys or HE alloys) is fabricated. The related crystalline structures of the alloys are measured and calculated. Results show that the formed bcc phase is a compound based B2 structure where there is partial ionic bonding between Al and other transition metals. Thus, the bcc structure of the alloys should be a B2 instead of an A2 due to the large difference in electronegativities among the components consisting of the HE alloys.

  7. Effects of rhenium alloying on the microstructures and mechanical properties of directionally solidified NiAl-Mo eutectic alloy

    SciTech Connect

    Misra, A.; Wu, Z.L.; Gibala, R.

    1997-12-31

    Low ductility of the reinforcing bcc metal phase at room temperature and weak interfaces can limit the intrinsic toughness and ductility of NiAl-bcc metal eutectic composites. The potential of rhenium (Re) addition, which is known to solid solution soften and lower the ductile-to-brittle transition temperature of various bcc metals, to enhance the ductility and toughness of a directionally solidified NiAl-9 at.% Mo eutectic alloy was investigated. Re partitioned to the bcc metal phase and formed a substitutional solid solution. The interface morphology was changed from a faceted to a non-faceted one. Re alloying caused softening of the Mo fibers, and as a result NiAl-Mo(Re) alloys were softer in compression and flexure and had {approximately}20% higher fracture toughness values as compared to the transverse orientation toughness of NiAl-9Mo alloy. The toughness of the NiAl-Mo(Re) alloys was lower than the longitudinal orientation toughness of the NiAl-9Mo alloy due to the poor alignment of the Mo(Re) phase with the growth direction. The toughening mechanisms have been evaluated and schemes for processing NiAl-Mo(Re) alloys for higher toughness in the longitudinal orientation are suggested. The role of the residual interstitial impurities and partitioning of Ni and Al to Mo fibers on the mechanical properties are highlighted.

  8. Structural and dynamical properties of liquid Al-Au alloys

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Voigtmann, Th.; Kolland, G.; Kobatake, H.; Brillo, J.

    2015-11-01

    We investigate temperature- and composition-dependent structural and dynamical properties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au-Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the concentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

  9. Conditions for CET in a gamma TiAl alloy

    NASA Astrophysics Data System (ADS)

    Mooney, R. P.; Lapin, J.; Klimová, A.; McFadden, S.

    2015-06-01

    The solidification of gamma TiAl alloys is of interest to the aerospace and automotive industries. A gamma TiAl multicomponent alloy: Ti-45.5Al-4.7Nb-0.2C-0.2B (at. %) has been the focus of a study to investigate the solidification conditions that led to a Columnar to Equiaxed Transition (CET) in a directional solidification experiment where traditional Bridgman solidification was combined in series with the power down method. In this paper, a numerical modelling result (a locus plot of columnar growth rate and temperature gradient) from this experiment is superimposed onto CET maps generated using an established analytical model for CET from the literature. A parametric study is carried out over suitable ranges of nucleation undercooling and nuclei density values. The predicted CET positions are compared with the experimentally measured CET position. Reasonable agreement is found at low levels of nuclei density. The paper concludes with estimates for the solidification conditions (nuclei density and nucleation undercooling) that led to the CET.

  10. Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode

    NASA Astrophysics Data System (ADS)

    Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.

    2006-11-01

    Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5μs duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.

  11. Hydrogen peroxide treatment on Ti-6Al-4V alloy: A promising surface modification technique for orthopaedic application

    NASA Astrophysics Data System (ADS)

    Karthega, M.; Rajendran, N.

    2010-01-01

    Ti-6Al-4V alloy was treated with various concentrations (5 wt.%, 15 wt.% and 25 wt.%) of hydrogen peroxide (H 2O 2) and then heat treated to produce an anatase titania layer. The surface modified substrates were immersed in simulated body fluid (SBF) solution for the growth of an apatite layer on the surface and the formed apatite layer was characterized using various surface characterization techniques. The results revealed that titania layer with anatase nature was observed for all H 2O 2 treated Ti-6Al-4V alloy, irrespective of the H 2O 2 concentrations. Ti-6Al-4V alloy treated with 15 wt.% and 25 wt.% of H 2O 2 induced apatite formation, however 5 wt.% of H 2O 2 treated Ti-6Al-4V failed to form apatite layer on the surface. The electrochemical behaviour of H 2O 2 treated specimens in SBF solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy. Ti-6Al-4V alloy treated with 25 wt.% of H 2O 2 solution exhibited low current density and high charge transfer resistance values compared to specimens treated with other concentrations of H 2O 2 and untreated Ti-6Al-4V alloy.

  12. Texture evolution in Al-Li 2195 alloy during net shape roll forging

    SciTech Connect

    Kalu, P.N.; Zhang, Lan

    1998-06-12

    The quest to manufacture low-cost, large complex structures with minimum material wastage has instigated research into near-net shape (NNS) technologies. In this paper, the microstructural and texture evolution in Al-Li 2195 alloy resulting from a specific NNS processing called roll forging was evaluated. The processing consists of five stages and combines conventional ingot conversion (stages I and II), back extrusion (stage III) and ring rolling to produce hollow cylinder (stage IV). Considerable potential exists for the property enhancement of the components produced by this processing method if a better understanding of the evolution of microstructure and texture is developed.

  13. Soft mode behavior in Ni--Al alloys

    SciTech Connect

    Shapiro, S.M.; Yang, B.X.; Shirane, G.; Larese, J.Z.; Tanner, L.E.; Moss, S.C.

    1988-06-01

    Inelastic neutron scattering experiments performed on carefully prepared single crystals of Ni/sub x/Al/sub 1/minus/x/ (x /equals/ 50, 58, 62.5 at. percent) reveal an anomaly in the //zeta//zeta/0)-TA mode whose position in /zeta/ depends linearly on x. The temperature dependent studies of the 62.5/percent/ alloy show marked softening of the phonon energy at /zeta/ /equals/ 1/6. At the same temperatures, an elastic central peak develops. At T/sub M/ /equals/ 80K a new structure develops which exhibits a modulation at nearly, but not exactly, /zeta/ /equals/ 1/7. 11 refs., 2 figs.

  14. Zener Relaxation Peak in an Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Cun; Cheng, He-Fa; Gong, Chen-Li; Wei, Jian-Ning; Han, Fu-Sheng

    2002-11-01

    We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt%)Cr-(5 wt%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction versus temperature plot at about 550°C. The peak is of a stable relaxation and is reversible, which occurs not only during heating but also during cooling. Its activation energy is 2.5 (+/- 0.15) eV in terms of the Arrhenius relation. In addition, the peak is not obvious in specimens with a smaller grain size. It is suggested that the peak originates from Zener relaxation.

  15. Ratcheting fatigue behaviour of Al-7075 T6 alloy: Influence of stress parameters

    NASA Astrophysics Data System (ADS)

    Amarnath, Lala; Bhattacharjee, Antara; Dutta, K.

    2016-02-01

    The use of aluminium and aluminium based alloys are increasing rapidly on account of its high formability, good thermal and electrical conductivity, high strength and lightness. Aluminium alloys are extensively used in aerospace, automobile, marine and space research industries and are also put into structural applications where chances of fatigue damage cannot be ruled out. In the current work, it is intended to study the ratcheting fatigue behavior of 7075-T6 aluminium alloy at room temperature. This Al alloy is potentially used in aviation, marine and automotive components as well as in bicycle parts, rock mounting equipment and parts of ammunition where there is every chance of failure of the parts due to deformation caused by ratcheting. Ratcheting is the process of accruement of plastic stain produced when a component is subjected to asymmetric cyclic loading under the influence of low cycle fatigue. To accomplish the requirements of the projected research, stress-controlled cyclic loading experiments were done using a ±250 kN servo-hydraulic universal testing machine (Instron: 8800R). The effect of stress parameters such as mean stress and stress amplitude were investigated on the ratcheting behavior of the selected aluminium alloy. It was observed that, ratcheting strain increased with increase in the value of stress amplitude at any constant mean stress while a saturation in strain accumulation attained in the investigated material after around 10-20 cycles, under all test conditions. The analyses of hysteresis loop generated during cyclic loading indicate that the material exhibits cyclic hardening in the initial fifty cycles which gets softened in further loading up to about 70-80 cycles and finally attains a steady state. The increase in the ratcheting strain value with stress parameters happens owing to increased deformation domain during cycling. The cyclic hardening accompanied by softening is correlated with characteristic precipitation features of

  16. Structure of molten Al and eutectic Al-Si alloy studied by neutron diffraction

    SciTech Connect

    Dahlborg, U.; Kramer, Matthew J.; Besser, M.; Morris, J. R.; Calvo-Dahlborg, M.

    2012-11-24

    The structure of molten eutectic Al87.8Si12.2 alloy has been studied by neutron diffraction during a temperature cycle. For comparison measurements were performed on pure molten Al. The measurements show that the alloy after heating above the liquidus contains particles of two kinds, aluminum-rich and silicon-rich. The silicon-rich particles are partly dissolved after a further heating. Earlier published data obtained by the γ-ray absorption technique of the density of the molten eutectic Al–Si alloy had demonstrated the existence of two temperatures above the liquidus temperature: A dissolution temperature Td, at which the microstructure of the melt inherited from the ingot starts to dissolve and a branching temperature, Tb, at which the melt reaches a fully mixed state. The highest temperature that was possible to reach during the neutron experiments lies between Td and Tb. The obtained results support these conclusions that molten alloys after melting are inhomogeneous up to a temperature well above the liquidus. Moreover, the difference in shape between the static structure factors measured by neutron and X-ray diffraction on molten aluminum is observed and is found to be more accentuated and to extend to larger wavevectors than in earlier works.

  17. Relationship between microstructure and texture in Fe-25%Cr-5%Al ribbons produced by planar flow casting

    SciTech Connect

    Jimenez, J.A.; Frommeyer, G.; Torralba, M.; Ruano, O.A.

    1995-10-01

    The automotive industry has used for many years exhaust gas catalytic supports based on heat resistant Fe-Cr-Al ferritic stainless steels. The Fe-Cr-Al alloys are usually cast and then rolled into a foil of desired thickness. Planar flow casting (PFC) represents a cheaper alternative route for production of thick ribbons of about 100 {micro}m directly from the melt. On the other hand, it is well established that a solidification rate as high as 10{sup 5} K s{sup {minus}1} can be reached by means of PFC. This rapid solidification rate determines better properties of the alloy associated with the fine and homogeneous microstructure developed. The aim of the present work is to study the relationship between the microstructure and the texture in ribbons of a Fe-25% Cr-5% Al alloy produced by PFC with a thickness ranging from 40--180 {micro}m. All composition are given in weight percent.

  18. Viscosities of aluminum-rich Al-Cu liquid alloys

    NASA Astrophysics Data System (ADS)

    Ganesan, S.; Speiser, R.; Poirier, D. R.

    1987-06-01

    Viscosity data for Al-Cu liquid alloys in the ranges of 0≤ C L≤33.1 wt pct Cu and 1173≤ T ≤973 K are reviewed. It was found that Andrade's equation can be used to represent the variation of viscosity with temperature for a given composition, but that each of the two parameters in Andrade's equation shows no systematic variation with composition of the liquid-alloys. Consequently, arithmetic averages of the parameters were used and assumed to apply to all compositions in the range 0≤ C L ≤33.1 wt pct Cu. Such a procedure implies that the viscosity happens to vary with composition solely because the specific volume varies with composition. In order to establish the predictability of extrapolating such simple behavior, a more complex model was considered. The latter model was recently presented by Kucharski and relates viscosity to the structure and thermodynamics of liquid alloys. Viscosities obtained by interpolating Andrade's equation and Kucharski's model compare closely; furthermore, values obtained by extrapolations to lower temperatures also compare favorably. Finally the simpler model was used to calculate the viscosity of the interdendritic liquid during solidification.

  19. Quantification of Microsegregation in Cast Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Ganesan, M.; Thuinet, L.; Dye, D.; Lee, P. D.

    2007-08-01

    The random sampling approach offers an elegant yet accurate way of validating microsegregation models. However, both instrumental errors and interference from secondary phases complicate the treatment of randomly sampled microprobe data. This study demonstrates that the normal procedure of sorting the data for each element independently can lead to inaccurate estimation of segregation profiles within multicomponent, multiphase, aluminum alloys. A recently proposed alloy-independent approach is shown to more reliably isolate these interferences, allowing more accurate validation of microsegregation models. Application of this approach to examine solidification segregation of a 319-type alloy demonstrated that, for these slowly cooled castings, neither Sr or TiB2 additions significantly affected coring of Cu within the primary α-Al dendrites. Comparison against predictions of CALPHAD-type Gulliver-Scheil models was less satisfactory. Consideration of back-diffusion and morphology effects through a one-dimensional (1-D) numerical model do not improve the agreement. Possible reasons for the lack of agreement are hypothesized.

  20. Radial macrosegregation and dendrite clustering in directionally solidified Al-7Si and Al-19Cu alloys

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2016-05-01

    Hypoeutectic Al-7 wt% Si and Al-19 wt% Cu alloys were directionally solidified upward in a Bridgman furnace through a range of constant growth speeds and thermal gradients. Though processing is thermo-solutally stable, flow initiated by gravity-independent advection at, slightly leading, central dendrites moves rejected solute out ahead and across the advancing interface. Here any lagging dendrites are further suppressed which promotes a curved solid-liquid interface and the eventual dendrite "clustering" seen in transverse sections (dendrite "steepling" in longitudinal orientations) as well as extensive radial macrosegregation. Both aluminum alloys showed considerable macrosegregation at the low growth speeds (10 and 30 μm s-1) but not at higher speed (72 μm s-1). Distribution of the fraction eutectic-constituent on transverse sections was determined in order to quantitatively describe radial macrosegregation. The convective mechanisms leading to dendrite-steepling were elucidated with numerical simulations, and their results compared with the experimental observations.

  1. Modulus measurements in ordered Co-Al, Fe-Al, and Ni-Al alloys

    NASA Technical Reports Server (NTRS)

    Harmouche, M. R.; Wolfenden, A.

    1985-01-01

    The composition and/or temperature dependence of the dynamic Young's modulus for the ordered B2 Co-Al, Fe-Al, and Ni-Al aluminides has been investigated using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The modulus has been measured in the composition interval 48.49 to 52.58 at. pct Co, 50.87 to 60.2 at. pct Fe, and 49.22 to 55.95 at. pct Ni for Co-Al, Fe-Al, and Ni-Al, respectively. The measured values for Co-Al are in the temperature interval 300 to 1300 K, while those for the other systems are for ambient temperature only. The data points show that Co-Al is stiffer than Fe-Al, which is stiffer than Ni-Al. The data points for Fe-Al and Ni-Al are slightly higher than those reported in the literature.

  2. Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

    NASA Astrophysics Data System (ADS)

    Yan, F.; McKay, B. J.; Fan, Z.; Chen, M. F.

    2012-01-01

    An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg2Si particles evenly distributed throughout an α-Al matrix with a β-Al3Mg2 fully divorced eutectic phase observed in interdendritic regions. The Mg2Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg2Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al3Mg2 eutectic phase with no evidence of any effect on the primary Mg2Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

  3. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  4. Wetting and reaction promoted by ultrasound between sapphire and liquid Al-12Si alloy.

    PubMed

    Cui, Wei; Wang, Changwen; Yan, Jiuchun; Wang, Zhipeng; Wei, Daqing

    2013-01-01

    Ultrasonic-assisted wetting between sapphire bulks and liquid Al-12Si alloy in an atmospheric environment at 620 °C is carried out in this study. Complete, rather than partial, wetting and joining can be achieved with the aid of ultrasound. Growth of epitaxial alumina on sapphire bulks is promoted dramatically during ultrasonic-assisted wetting comparing to that during hot-dipping without ultrasound. XRD results show that the epitaxial alumina is non-crystalline. This indicates that the temperature on the surface of the sapphire substrate is not more than 1200 °C even though the collapse of acoustic cavitation bubbles could theoretically produce extremely high temperature. The bonding force at the interface between the Al-Si alloy and sapphire is strengthened because of the epitaxial alumina. The interfacial shear strength of sapphire/Al-Si alloy can reach as high as 60-65 MPa. The fracture morphology shows that cracks initiated at the interface between Si grains and the epitaxial alumina on sapphire. This result is especially useful for the joining of metals and ceramics. PMID:22929927

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

    SciTech Connect

    Kad, B.K.

    1999-07-01

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

  6. Grain Refinement of a Large-Scale Al Alloy Casting by Introducing the Multiple Ultrasonic Generators During Solidification

    NASA Astrophysics Data System (ADS)

    Li, Ruiqing; Liu, Zhilin; Dong, Fang; Li, Xiaoqian; Chen, Pinghu

    2016-05-01

    Based on the multiple ultrasonic generators, a new technique was reported to produce the large-scale Al alloy castings for downstream deformation processing. The effects of different configurations of ultrasonic generators on the degree and homogeneity of grain refinement were investigated during solidification. Experimental results show that a grain-refined structure with reduced macrosegregation was obtained in the large-scale cylindrical Al alloy ingot (650 mm in diameter, 4800 mm in length). Meanwhile, the role of ultrasonic treatment in the production of large-scale castings was discussed. Additionally, these results raise some new questions regarding the relationship between ultrasonic physics and grain refinement, which require further studies.

  7. Grain Refinement of a Large-Scale Al Alloy Casting by Introducing the Multiple Ultrasonic Generators During Solidification

    NASA Astrophysics Data System (ADS)

    Li, Ruiqing; Liu, Zhilin; Dong, Fang; Li, Xiaoqian; Chen, Pinghu

    2016-08-01

    Based on the multiple ultrasonic generators, a new technique was reported to produce the large-scale Al alloy castings for downstream deformation processing. The effects of different configurations of ultrasonic generators on the degree and homogeneity of grain refinement were investigated during solidification. Experimental results show that a grain-refined structure with reduced macrosegregation was obtained in the large-scale cylindrical Al alloy ingot (650 mm in diameter, 4800 mm in length). Meanwhile, the role of ultrasonic treatment in the production of large-scale castings was discussed. Additionally, these results raise some new questions regarding the relationship between ultrasonic physics and grain refinement, which require further studies.

  8. Development of high-emittance scales on thoriated nickel-chromium-aluminum-base alloys. [produced by high temperature oxidation

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, I. G.; Wilcox, B. A.

    1973-01-01

    The surface regions of a DSNiCrAl alloy have been doped, by a pack diffusion process, with small amounts of Mn, Fe, or Co, and the effect of these dopants on the total normal emissivity of the scales produced by subsequent high temperature oxidation has been measured. While all three elements lead to a modest increase in emissivity, (up to 23% greater than the undoped alloy) only the change caused by manganese is thermally stable. However, this increased emissivity is within 85 percent of that of TDNiCr oxidized to form a chromia scale. The maganese-doped alloy is some 50 percent weaker than undoped DSNiCrAl after the doping treatment, and approximately 30 percent weaker after oxidation.

  9. Drilling of intermetallic alloys gamma TiAl

    SciTech Connect

    Beranoagirre, A.; Olvera, D.; Lopez de Lacalle, L. N.; Urbicain, G.

    2011-01-17

    Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice for the high mechanical/thermal demands in the vicinity of the combustion chamber of aircraft engines. There are assembled parts such as cases, disks or blisks; in the manufacturing of these components the last drilling operation could jeopardize the full work integrity adding new costs to the just very expensive parts. Therefore drilling is a high-added value step in the complete sequence. The present work is framed within the study of hole making in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results from milling tests on three types of gamma TiAl alloys (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters, which will contribute to open the increase in use of these special alloys. Drilling tools made of integral hard metal were used, applying different feeds and cutting speeds. The influence of cutting speed and feed is discussed.

  10. The Behaviour of Bifilm Defects in Cast Al-7Si-Mg Alloy.

    PubMed

    El-Sayed, Mahmoud Ahmed

    2016-01-01

    Double oxide films (bifilms) are significant defects in the casting of light alloys, and have been shown to decrease tensile and fatigue properties, and also to increase their scatter, making casting properties unreproducible and unreliable. A bifilm consists of doubled-over oxide films containing a gas-filled crevice and is formed due to surface turbulence of the liquid metal during handling and/or pouring. Previous studies has shown that the nature of oxide film defects may change with time, as the atmosphere inside the bifilm could be consumed by reaction with the surrounding melt, which may enhance the mechanical properties of Al alloy castings. As a proxy for a bifilm, an air bubble was trapped within an Al-7wt.%Si-0.3wt.%Mg (2L99) alloy melt, subjected to stirring. The effect of different parameters such as the holding time, stirring velocity and melt temperature on the change in gas composition of the bubble was investigated, using a design of experiments (DoE) approach. Also, the solid species inside the bubbles solidified in the melt were examined using SEM. The results suggested that both oxygen and nitrogen inside the bifilm would be consumed by reaction with the surrounding melt producing MgAl2O4 and AlN, respectively. Also, hydrogen was suggested to consistently diffuse into the defect. The reaction rates and the rate of H diffusion were shown to increase upon increasing the holding time and temperature, and stirring velocity. Such significant effect of the process parameters studied on the gaseous content of the bubble suggesting that a careful control of such parameters might lead to the deactivation of bifilm defects, or at least elimination of their deteriorous effect in light alloy castings. PMID:27529350

  11. The Behaviour of Bifilm Defects in Cast Al-7Si-Mg Alloy

    PubMed Central

    2016-01-01

    Double oxide films (bifilms) are significant defects in the casting of light alloys, and have been shown to decrease tensile and fatigue properties, and also to increase their scatter, making casting properties unreproducible and unreliable. A bifilm consists of doubled-over oxide films containing a gas-filled crevice and is formed due to surface turbulence of the liquid metal during handling and/or pouring. Previous studies has shown that the nature of oxide film defects may change with time, as the atmosphere inside the bifilm could be consumed by reaction with the surrounding melt, which may enhance the mechanical properties of Al alloy castings. As a proxy for a bifilm, an air bubble was trapped within an Al-7wt.%Si-0.3wt.%Mg (2L99) alloy melt, subjected to stirring. The effect of different parameters such as the holding time, stirring velocity and melt temperature on the change in gas composition of the bubble was investigated, using a design of experiments (DoE) approach. Also, the solid species inside the bubbles solidified in the melt were examined using SEM. The results suggested that both oxygen and nitrogen inside the bifilm would be consumed by reaction with the surrounding melt producing MgAl2O4 and AlN, respectively. Also, hydrogen was suggested to consistently diffuse into the defect. The reaction rates and the rate of H diffusion were shown to increase upon increasing the holding time and temperature, and stirring velocity. Such significant effect of the process parameters studied on the gaseous content of the bubble suggesting that a careful control of such parameters might lead to the deactivation of bifilm defects, or at least elimination of their deteriorous effect in light alloy castings. PMID:27529350

  12. Microstructure and tribological behaviors of Ti6Al4V alloy treated by plasma Ni alloying

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxia; He, Zhiyong; Wang, Yingqin; Liu, Xiaoping; Tang, Bin

    2011-09-01

    Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique. Surface morphology, micro-structure, composition distribution, phase structure, and microhardness of the Ni modified layer were analyzed. Tribological performance of the Ni modified layer and Ti6Al4V substrate was investigated by using pin-on-disc tribometer. The results indicate that roughness of the Ni modified layer was increased due to formation of the micro-convex on the modified surface. The concentration of Ni gradually decreased from the surface to interior. The maximum content of Ni atoms was nearly 90%. The modified layer was composed of TiNi, Ti2Ni and Ti phases. The maximum microhardness of the Ni modified layer was about 677 HV0.025 which was increased about two-fold of microhardness of the control Ti6Al4V substrate. Wear resistance of the Ni modified layer was improved obviously, and showed micro-abrasion wearing. The strengthened mechanism of the as-treated Ti6Al4V alloy is discussed.

  13. Influence cobalt on microstructural and hardness property of Al-Zn-Mg-Cu-Fe-Cr-Ni P/ M alloys

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Rahmat, Azim; Bashirom, Nurhuda

    2015-05-01

    In this study, influence cobalt additives on the microstructural and hardness properties of an Al-Zn-Mg-Cu-Fe-Cr-Ni PM alloy undergone the retrogression and re-aging treatment were carried out. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered compacts subjected to a homogenizing treated at 470°C for 1.5 hours then aged at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Microstructural results of the Al-Zn-Mg-Cu-Fe-Cr-Ni-Co alloys introduced an intermetallics compound in the matrix of alloy, identified as the Al5Co2, Al70Co20Ni10 and Al4Ni3 phases besides to the MgZn2 and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloy. The highest Vickers hardness of aluminum alloy containing cobalt was gotten after applying the retrogression and re-aging treatment.

  14. The effect of quaternary element on the thermodynamic parameters and structure of CuAlMn shape memory alloys

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Karagoz, Z.

    2013-10-01

    In this study, the Cu-based shape memory alloys were produced by arc melting. We have investigated the effects of the alloying elements on the characteristic transformation temperatures, enthalpy, entropy values, and the structure of Cu-Al-Mn ternary system. The evolution of the transformation temperatures was studied by the differential scanning calorimetry. The characteristic transformation temperatures can be controlled by the variations in the aluminum and manganese content. Additionally, the effect of magnesium and iron on the transformation temperatures and thermodynamic parameters was investigated in the Cu-Al-Mn ternary system. The addition of the magnesium decreases the characteristic transformation temperatures of the Cu-Al-Mn system, but that of the iron increases. The structural changes of the samples were studied by X-ray diffraction measurements and optical microscope observations. Due to the low solubility of the magnesium, the magnesium addition into the Cu-Al-Mn system forms precipitates in the matrix. It is evaluated that the transformation parameters of the CuAlMn shape memory alloys can be controlled by the change of the alloying elements and the weight percentages of alloying elements.

  15. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-07-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1-x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1-x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1-x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1-x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  16. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  17. Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Hsu, Jen-Hwa; Vinod, V. T. P.; Černík, Miroslav; Kamat, S. V.

    2015-11-01

    We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

  18. Phase Composition and Microstructure of Ti-Nb Alloy Produced by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Sharkeev, Yu P.; Eroshenko, A. Yu; Kovalevskaya, Zh G.; Saprykin, A. A.; Ibragimov, E. A.; Glukhov, I. A.; Chimich, M. A.; Uvarkin, P. V.; Babakova, E. V.

    2016-07-01

    The phase composition and microstructure of Ti-Nb alloy produced from composite titanium and niobium powder by selective laser melting (SLM) was studied. Produced monolayered Ti-Nb alloy enhanced the formation of fine-grained and medium-grained zones with homogeneous element composition of 36-38% Nb mass interval. Alloy phase composition responded to β-alloy substrate phase (grain size was 5-7 pm) and non-equilibrium martensite α"- phase (grain size was 0.1-0.7 µm). α"-phase grains were found along β-phase grain boundaries and inside grains, including decreased niobium content. Alloy microhardness varied within 4200-5500 MPa.

  19. The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles

    SciTech Connect

    Fei Tang

    2004-12-19

    Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two important aspects, including improving the properties of MMCs and finding more economical techniques to produce MMCs. Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. Microstructures and tensile properties of AYAl-Cu-Fe composites were characterized. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of

  20. Infiltration of Saffil alumina fiber with AlCu and AlSi alloys

    SciTech Connect

    Garbellini, O.; Morando, C.; Biloni, H.; Palacio, H. . Inst. de Fisica de Materiales)

    1999-06-18

    Currently there is a considerable scientific and technological interest in the composite materials, which a strong ceramic reinforcement is incorporated into a metal matrix (MMC) to tailor its properties for specific applications. Among the various techniques for fabricating MMC, the liquid metal infiltration process by means of a pressurized gas is an attractive fabrication route for near net shaped metal matrix composite and has been successfully used to fabricate Al, Mg and more recently, Ni and Ni aluminide matrix composites, which can be reinforced by SiC or Al[sub 2]O[sub 3] particles, whiskers, or short fibers. This paper describes the experimental technique used and presents an experimental investigation of the effects of the process parameters employed, such as the preform and melt temperatures, the volume fraction of fibers in the preform and the applied pressure upon the infiltration length of a chopped preform during a unidirectional infiltration aided by gas pressure casting. The experiments of the present work were conducted to provide kinetic data with a view to optimizing the selection of the process initial conditions for infiltration which have an effect on the infiltration length of the molten matrix alloy into a preform and it is a first step in investigating the correlation between the infiltration length (fluidity) of AlCuSi matrix alloys and the microstructure of the composites fabricated by pressure casting. For this purpose, this paper focuses on AlCu and AlSi matrix alloys reinforced by short-fibers [delta]-alumina SAFFIL. The experiments reported here were performed with the fibers initially at a temperature significantly below the metal melting point. This is the case of practical interest for the fabrication of many fiber-reinforced metal components.

  1. Ni3Al-based alloys for die and tool application

    DOEpatents

    Liu, Chain T.; Bloom, Everett E.

    2001-01-01

    A novel Ni.sub.3 Al-based alloy exhibits strengths and hardness in excess of the standard base alloy IC-221M at temperatures of up to about 1000.degree. C. The alloy is useful in tool and die applications requiring such temperatures, and for structural elements in engineering systems exposed to such temperatures.

  2. Effects of Li content on precipitation in Al-Cu-(Li)-Mg-Ag-Zr alloys

    SciTech Connect

    Huang, B.P.; Zheng, Z.Q.

    1998-01-06

    Although much attention has been paid to Al-Cu-Li-Mg-Ag-Zr alloys, there are sparse reports about the influence of Li on precipitation in these alloys. The aim of the present study is to determine the effects of Li on modifying precipitation in a baseline aluminum alloy 2195 and the accompanying variants with 0--1.6 wt.% Li.

  3. Long range order and vacancy properties in Al-rich Fe{sub 3}Al and Fe{sub 3}Al(Cr) alloys

    SciTech Connect

    Kim, S.M.; Morris, D.G.

    1998-05-01

    Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analyzed to obtain information about the temperature dependence of the DO{sub 3} and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO{sub 3} and B2 ordered Al-rich Fe{sub 3}Al is shown to be consistent with considerations of interatomic bond energies.

  4. Producing Ti-6Al-4V plate from single-melt EBCHM ingot

    NASA Astrophysics Data System (ADS)

    Wood, J. R.

    2002-02-01

    The study reviewed in this paper was initiated to produce low-cost, aerospace-quality Ti-6Al-4V alloy plate directly from single melt, electron beam cold hearth melted slab ingots. This study is one of the programs of the Metals Affordability Initiative Consortium under the direction of the U.S. Air Force Research Laboratory’s Materials and Manufacturing Directorate. The main objective of this program is to achieve significant cost savings for titanium plate production while accelerating the implementation time. This article discusses the progress to date in this multi-year program.

  5. Microstructure-property relationships in low-density Al-Li-Mg alloys

    SciTech Connect

    Buchheit, T.E.; Wert, J.A. )

    1993-04-01

    The present article describes an investigation of the microstructure and tensile properties of cast Al-Li-Mg alloys with very low densities, in the range 2.3 to 2.4 Mg/m[sup 3]. Low density is achieved by adding Li and Mg in excess of the solubility limit, which prevents subsequent dissolution of the Al[sub 2]LiMg particles that form during solidification. A simple model developed during the course of this research allows prediction of the volume fraction of Al[sub 2]LiMg and alloy density from alloy composition. The model was used to select two alloy compositions for detailed investigation: Al12Li6Mg and Al16Li8Mg. The microstructures of the cast alloys consist of coarse Al[sub 2]LiMg particles embedded in an Al matrix containing Al[sub 3]Li particles. Both alloys exhibit low tensile elongation in the as-cast condition. Additional processing steps were used to modify the microstructural characteristics thought to be responsible for the low tensile elongation of the as-cast alloys. The Al16Li8Mg alloy, with an Al[sub 2]LiMg volume fraction of 0.25, does not exhibit increased tensile elongation as a result of processing, and the brittle nature of this material is attributed to the high volume fraction of the Al[sub 2]LiMg phase. The Al12Li6Mg alloy, with an Al[sub 2]LiMg volume fraction of 0.13, exhibits a remarkable increase in tensile elongation after extrusion, an effect attributed to fragmentation and dispersal of a three-dimensional (3-D) network of the intermetallic phase in the as-cast alloy.

  6. Hf dopants in γ'-Ni3Al alloy

    NASA Astrophysics Data System (ADS)

    Ivanovski, V. N.; Cekić, B.; Umićević, A.; Belošević-Čavor, J.; Schumacher, G.; Koteski, V.; Barudzija, T.

    2013-08-01

    The Time Differential Perturbed Angular (TDPAC) measurements of nuclear quadrupole interactions (NQIs) at 181Ta ion probe in the polycrystalline intermetallic alloy γ'-Ni3Al doped with 0.2 at. % Hf were performed in the temperature range 78-1230 K, in order to determine the lattice location of Hf atoms in the ordered γ'-Ni3Al structure. The two NQIs obtained are discussed within the present L12 cubic structure and a tetragonal distortion of L12 to another two DO22 and L60 type structures. The first low frequency NQI at the site of the 181Ta ion-probe after substitution of aluminum for hafnium in DO22 at ambient temperature, is vQ1(300 K) = 39(1) MHz with η1 = 0. The corresponding high frequency value on the second crystallographic site in L60, is vQ2(300 K) = 204(14) MHz with η2 = 0.47(11). These two NQI's have different temperature behavior. The presence of both DO22 and L60 tetragonal distortions of the parent cubic L12 lattice, detected after adding 0.2 at. % Hf, are with modulations to the lattice constant (a) with a ratio (c/a), 2.04 and 0.87, respectively. Ab initio calculations of electronic and structural properties and hyperfine parameters at the 181Ta ion probe of the γ'-Ni3Al-0.2 at. % Hf alloy were performed using the full potential augmented plane wave plus local-orbital (APW+lo) method as implemented in the WIEN2k code. The accuracy of the calculations and comparison with the experimental results enabled us to identify the observed hyperfine interactions and to infer the EFG sign that cannot be measured in conventional TDPAC measurements.

  7. A new phase in rapidly solidified Ti[sub 3]Al-based alloys

    SciTech Connect

    Xu Rui; Xu Daming; Li Qingchun . Dept. of Materials Science and Engineering); Li Dong; Cui Yuyou; Hu Zhuangqi . State Key Lab. for RSA)

    1995-01-15

    Rapid solidification processing has been developed to improve the properties of alloys through refining microstructures, disordering and forming metastable phases. The as-melt spun Ti[sub 3]Al-based alloy with Nb additions above 5-at%, which consist of [alpha][sub 2] and [beta][sub 0] phases in a normal condition, exhibited as single [beta][sub 0] structure. Jackson et al have carried out a comparative study of I/M and RS Ti[sub 3]Al-1 Zr(at%) alloy. Their study revealed that considerable refinement of grains and anti-phase domains was achieved in the rapidly solidified material prepared by the pendant drop melt extraction process (PDME). It is suggested that rapid solidification processing can reduce the ordering of the Ti[sub 3]Al-based alloy. In the past years, it was found that the Ti[sub 3]Al-based alloy with alloying additions (mainly Nb) has been studied extensively, and some new phases such as T and O have been observed in the alloys, but less attention has been given to alloys with low Nb additions. The RS Ti[sub 3]Al-base alloys with Nb below 5-at% have been investigated systematically and a new metastable phase, ordering martensite [alpha][double prime][sub 0] (orthogonal), has been observed in these alloys.

  8. Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

    SciTech Connect

    Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

    2015-10-01

    Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

  9. An Introduction to the BFS Method and Its Use to Model Binary NiAl Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, J.; Amador, C.

    1998-01-01

    We introduce the Bozzolo-Ferrante-Smith (BFS) method for alloys as a computationally efficient tool for aiding in the process of alloy design. An intuitive description of the BFS method is provided, followed by a formal discussion of its implementation. The method is applied to the study of the defect structure of NiAl binary alloys. The groundwork is laid for a detailed progression to higher order NiAl-based alloys linking theoretical calculations and computer simulations based on the BFS method and experimental work validating each step of the alloy design process.

  10. On the electrochemical formation of Pu-Al alloys in molten LiCl-KCl

    NASA Astrophysics Data System (ADS)

    Mendes, E.; Malmbeck, R.; Nourry, C.; Souček, P.; Glatz, J.-P.

    2012-01-01

    Properties of Pu-Al alloys were investigated in connection with development of pyrochemical methods for reprocessing of spent nuclear fuel. Electroseparation techniques in molten LiCl-KCl are being developed in ITU to group-selectively recover actinides from the mixture with fission products. In the process, actinides are electrochemically reduced on solid aluminium cathodes, forming solid actinide-aluminium alloys. This article is focused on electro-chemical characterisation of Pu-Al alloys in molten LiCl-KCl, on electrodeposition of Pu on solid Al electrodes and on determination of chemical composition and structure of the formed alloys. Cyclic voltammetry and chronopotentiometry were used to study Pu-Al alloys in the temperature range 400-550 °C. Pu is reduced to metal in one reduction step Pu 3+/Pu 0 on an inert W electrode. On a reactive Al electrode, the reduction of Pu 3+ to Pu 0 occurs at a more positive potential due to formation of Pu-Al alloys. The open circuit potential technique was used to identify the alloys formed. Stable deposits were obtained by potentiostatic electrolyses of LiCl-KCl-PuCl 3 melts on Al plates. XRD and SEM-EDX analyses were used to characterise the alloys, which were composed mainly of PuAl 4 with some PuAl 3. In addition, the preparation of PuCl 3 containing salt by carbochlorination of PuO 2 is described.

  11. Effect of Grain Refinement and Cooling Rate on the Microstructure and Mechanical Properties of Secondary Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Timelli, Giulio; Camicia, Giordano; Ferraro, Stefano

    2013-10-01

    The effect of AlTi5B1 grain refinement and different solidification rates on metallurgical and mechanical properties of a secondary AlSi7Cu3Mg alloy is reported. While the Ti content ranges from 0.04 up to 0.225 wt.%, the cooling rate varies between 0.1 and 5.5 °C/s. Metallographic and thermal analysis techniques have been used to quantitatively examine the macro- and microstructural changes occurring with grain refiner addition at various cooling rates. The results indicate that a small AlTi5B1 addition produces the greatest refinement, while no significant reduction of grain size is obtained with a great amount of grain refiner. On increasing the cooling rate, a lower amount of AlTi5B1 master alloy is necessary to produce a uniform grain size throughout the casting. The combined addition of AlTi5B1 and Sr does not produce any reciprocal interaction or effect on primary α-Al and eutectic solidification. The grain refinement improves the plastic behavior of the alloy and increases the reliability of castings, as evidenced by the Weibull statistics.

  12. Phase transformations during deformation of Fe-Ni and Fe-Mn alloys produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Cherdyntsev, V. V.; Pustov, L. Yu.; Kaloshkin, S. D.; Tomilin, I. A.; Shelekhov, E. V.; Laptev, A. I.; Baldokhin, Yu. V.; Estrin, E. I.

    2007-10-01

    Compositions of Fe(100 - x)Mn x ( x = 10 and 12 at. %) and Fe(100 - y)Ni y ( y = 18 and 20 at. %) were produced by combined mechanical alloying of pure-metal powders and annealed in the austenitic field. After annealing and cooling to room temperature, the alloys had a single-phase austenitic structure. During deformation, the γ phase partially transforms into the α 2 phase (and/or ɛ phase in Fe-Mn alloys). The phase composition of the alloys after deformation depends on the amount of alloying elements and the predeformation annealing regime. The amount of martensite in the structure of a bulk alloy obtained by powder compacting grows proportionally to the degree of deformation of the sample.

  13. Processing, properties, and applications of Ni{sub 3}Al-based alloys

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Liu, C.T.

    1997-06-01

    The Ni{sub 3}Al-based alloys represent a quantum jump in advanced alloys for structural applications at elevated temperatures. These alloys offer benefits of oxidation, carburization, and chlorination resistance, and significantly higher strength than many commercially used alloys. The commercial applications of the Ni{sub 3}Al-based alloys have begun to occur because of their comprehensive development This paper is to provide a review of. (1) alloy development, (2) melting, casting, and processing of alloys, (3) property data, (4) welding process and weldment properties, and (5) case histories of current applications. It is concluded that the cast alloy IC-221M is on its way to commercialization. 22 refs., 8 figs., 2 tabs.

  14. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  15. Development of interatomic potentials appropriate for simulation of devitrification of Al90Sm10 alloy

    SciTech Connect

    Mendelev, M. I.; Zhang, F.; Ye, Z.; Sun, Y.; Nguyen, M. C.; Wilson, S. R.; Wang, C. Z.; Ho, K. M.

    2015-04-23

    In this study, a semi-empirical potential for the Al90Sm10 alloy is presented. The potential provides satisfactory reproduction of pure Al properties, the formation energies of a set of Al–Sm crystal phases with Sm content about 10%, and the structure of the liquid Al90Sm10 alloy. During molecular dynamics simulation in which the liquid alloy is cooled at a rate of 1010 K/s, the developed potential produces a glass structure with lower ab initio energy than that produced by ab initio molecular dynamics (AIMD) itself using a typical AIMD cooling rate of 8 ∙1013 K/s. Based on these facts the developed potential should be suitable for simulations of phase transformations in the Al90Sm10 alloy.

  16. CVD Diamond Coating on Al-Interlayered FeCoNi Alloy Substrate: An Interfacial Study

    NASA Astrophysics Data System (ADS)

    Li, Y. S.; Sun, X. Y.; Yang, L. Z.; Kurmaev, E. Z.; Yang, Q.

    2015-12-01

    In this study, an Al thin film interlayer of 80 nm thick has been applied on FeCoNi alloy substrate which possesses a low coefficient of thermal expansion, to enhance the interfacial adhesion of diamond films produced by microwave plasma-enhanced chemical vapor deposition. Characterization of the top deposit, interlayer and the underlying substrate was performed by Raman spectroscopy, energy dispersive X-ray analysis, X-ray photoelectronic spectroscopy, X-scanning electron microscopy and X-ray diffraction. The Al interlayer has effectively inhibited the formation of graphitic carbon and markedly enhanced the nucleation, growth and adhesion of diamond films. The beneficial role Al plays is primarily attributed to the formation of an alumina barrier layer on the substrate surface, as verified by interfacial analysis.

  17. Effect of scandium on the microstructure and ageing behaviour of cast Al-6Mg alloy

    SciTech Connect

    Kaiser, M.S.; Datta, S.; Roychowdhury, A. Banerjee, M.K.

    2008-11-15

    Microstructural modification and grain refinement due to addition of scandium in Al-6Mg alloy has been studied. Transmission electron microscopy is used to understand the microstructure and precipitation behaviour in Al-6Mg alloy doped with scandium. It is seen from the microstructure that the dendrites of the cast Al-6Mg alloy have been refined significantly due to addition of scandium. Increasing amount of scandium leads to a greater dendrite refinement. The age hardening effect in scandium added Al-6Mg alloys has been studied by subjecting the alloys containing varying amount of scandium ranging from 0.2 wt.% to 0.6 wt.% to isochronal and isothermal ageing at various temperatures for different times. It is observed that significant hardening takes place in the aged alloys due to the precipitation of scandium aluminides.

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Experimental study on directional solidification of Al-Si alloys under the influence of electric currents

    NASA Astrophysics Data System (ADS)

    Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.

    2016-07-01

    The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.

  20. The Charpy impact behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 at % Mn alloys

    SciTech Connect

    Liu, J.N.; Yan, W.; Ma, J.L.; Wu, K.H.

    1997-12-31

    A series of experiments were conducted to investigate the impact fracture behavior of Fe{sub 3}Al and Fe{sub 3}Al-20 Mn alloys. The results of this study indicated that: (i) The addition of Mn introduces an ordered L1{sub 2}-type phase in the Fe{sub 3}Al-based alloys. On the other hand, the addition of Mn decreases the order parameter of the DO{sub 3} {alpha} phase. (ii) The total-impact energy of an Fe{sub 3}Al alloy increases with the temperature at the low-temperature range (<600 C), then drops around 700 C, and finally increases again as the temperature further elevates. (iii) The trend of the variation of the impact energy of Fe{sub 3}Al-20 at % Mn alloy with temperature is the same as that of the Fe{sub 3}Al alloy. (iv) And the addition of Mn significantly improves the impact energy of the Fe{sub 3}Al-based alloy, and changes the variation of the crack-growth energy with the testing temperature when the temperature is above 700 C.

  1. Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Liang, Shuhua; Yang, Qing; Wang, Xianhui

    2016-11-01

    Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is <110>, and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

  2. Influence of SiC Particles Distribution and Their Weight Percentage on 7075 Al Alloy

    NASA Astrophysics Data System (ADS)

    Bhushan, Rajesh Kumar; Kumar, Sudhir

    2011-03-01

    The stir casting method was used for fabrication of 7075 aluminum alloy with 10 wt.% SiC particles of size 20-40 μm. The research objective of this paper are to achieve uniform distribution of SiC particles in the 7075 aluminum alloy matrix, characterization, and analysis of mechanical properties of composite formed. Experiments were carried out at stirring speeds of 500, 650, 750 rpm, and stirring period of 10 min. Microstructures of aluminum alloy and composites with 5, 10 wt.% SiC reinforcements were examined. The results reveal that composite produced at stirring speed of 650 rpm and stirring time of 10 min has uniform distribution of SiC particles. XRD and EDAX analysis were carried out for 7075 Al alloy and composite with 10 wt.% SiC reinforcement. No adverse reaction was observed in XRD and EDAX of composite with 10 wt.% SiC reinforcement. Tensile strength and hardness increased by 12.74% and 10.48%, respectively, with the increase in percentage of SiC reinforcement from 5 to 15 wt.%.

  3. Surface Analysis of sp2 Carbon in Ag and Al Covetic Alloys*

    NASA Astrophysics Data System (ADS)

    Jaim, H. M. Iftekhar; Cole, Daniel P.; Salamanca-Riba, Lourdes G.

    Ag, Al-6061 and Al-7075 were doped with carbon by an electrocharging assisted process where high electric current is applied to the molten metal containing particles of activated carbon. This process gives rise to epitaxial growth of graphene nanoribbons (GNR) and carbon nanostructures within the metal matrix. Alloys produced with such technique are named Covetics. Al-6061 and Al-7075 covetics have shown superior mechanical, electrical and anti-corrosion properties. The nanostructured carbon incorporation has been confirmed by XPS, Raman, and TEM studies. Here, we present detailed surface characterization of the carbon nanostructures in these new alloys. Raman and EELS mapping of carbon nanostructure were carried out to identify the nature of bonding, strain and defect characteristics. Mostly, crystalline GNR or graphene sheets were found to create networks with sp2 character, under compressive strain with high concentration of defects. AFM and KPFM showed contrast in phases and potentials for ribbon like features. Incorporation of sp2 carbon in metals is an initial step for the integration of carbon nanostructures for future applications requiring high strength and conductivity.

  4. Effect of strain path change on precipitation behaviour of Al-Cu-Mg-Si alloy

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Kulkarni, K.; Gurao, N. P.

    2015-04-01

    The effect of strain path change on precipitation behaviour of Al- Cu-Mg-Si alloy was investigated. Two different types of crystallographic textures were produced by changing the strain path during rolling. The deformed samples were subjected to a short recrystallization treatment and ageing to identify the effect of strain path change manifested in terms of crystallographic texture on precipitation behaviour. Preliminary characterization indicates that ageing kinetics as well as precipitate morphology vary depending upon the mode of rolling. The coherency strains associated with a coherent interface is relieved in a unlike manner for differently rolled samples.

  5. Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

    PubMed

    Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

    2016-08-13

    This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402936

  6. Microstructural evolution and mechanical properties of cryomilled nanograined near Al-5083 alloy following deformation processing

    NASA Astrophysics Data System (ADS)

    Kaisar, Khan Hasib

    , iii) elongated larger grains with lengths in the range 3 to 7 μm that were observed using EBSD. Room temperature tensile tests with small tensile samples indicated that ultimate strengths in the range 740-760 MPa and elongation to failure better than 2.5%. These data could be produced reproducibly following extrusion at 400 C at an average strain rate of 0.05/sec, and fractography revealed a rough topography with large pull out regions that consisted of typical ductile dimple void growth at the 200-500 nm scale, while in other regions the dimples were very shallow that would suggest failure with little energy loss likely in regions of nanograins less than 100 nm. The combination of strength and ductility in the material are some of the best that have been reported for Al-5083 alloys, and likely a result of the multi-scale microstructure resulting from processing through the cryomilling and extrusion plus annealing procedures.

  7. Influence of homogenization and artificial aging heat treatments on corrosion behavior of Mg-Al alloys

    SciTech Connect

    Beldjoudi, T.; Fiaud, C.; Robbiola, L. . Lab. d'Etudes de la Corrosion)

    1993-09-01

    The influence of heat treatment on corrosion behavior of magnesium-aluminum (Mg-9Al) alloys was investigated by studying the electrochemical properties of Mg-9Al in the solution-treated (T4) and artificially aged (T6) conditions. The alloys' properties were compared to those of pure Mg, the intermetallic Mg[sub 17]Al[sub 12] phase, and different Mg-Al-based alloys (Mg-3Al, AZ91). The Mg-9Al alloy exhibited better corrosion resistance in the T6 condition than in the T4 condition because of the intermetallic Mg[sub 17]Al[sub 12] precipitates present n the T6 alloy. The mechanism responsible for this behavior was attributed to a more protective porous film on the T6 matrix alloy than on the T4 alloy. Addition of zinc did not modify these results. Localized corrosion testing showed the Mg-Al alloys were attacked preferentially in relation to magnesium silicide (Mg[sub 2]Si) precipitates which were characterized clearly using metallurgical examinations.

  8. Metal science and engineering aspects of TiAl-based binary alloys investigations

    SciTech Connect

    Bondarev, B.I.; Elagin, D.V.; Molotkov, A.V.; Notkin, A.B.

    1995-12-31

    This paper covers structure and mechanical properties of TiAl-based alloys depending on the process of material production as well as on working and heat treatment conditions. TiAl-based binary alloys were studied. The basic types of structures which can be observed in this alloy were revealed.These structures were examined and methods of their formation were determined.The processes for manufacturing components for gas turbine and car engine applications are discussed.

  9. Microstructure Evolution of Cold-Sprayed Al-Si Alloy Coatings on γ-TiAl During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2015-08-01

    This paper investigated the influence of heat treatment on the microstructure of Al-Si alloy coatings on γ-TiAl alloy. The coatings were prepared by cold spraying with Al-12Si and Al-20Si alloy powders as the feedstock, and then the as-sprayed coatings were subjected to heat treatment. The microstructure, chemical composition, and phase transformation of the coatings were studied by SEM, XRD, and EPMA. The diffusing behavior of Al and Si during heat treatment was investigated. The results showed that a silicon-aluminizing coating was formed through the inward diffusion of Al/Si elements into the substrate. The obtained kinetics curve of the formation of silicon-aluminizing coating at 580 °C similarly followed parabolic law.

  10. Solidification of hypermonotectic Al-In alloys under microgravity conditions

    NASA Technical Reports Server (NTRS)

    Potard, C.

    1982-01-01

    Four samples of the Al-In system having monotectic and hypermonotectic compositions that were solidified under microgravity during the NASA-SPAR IX flight of January 20, 1981, are considered. The experimental thermal and physicochemical conditions that were actually achieved are analyzed. Radiographic and metallographic observations of the samples reveal a nonregular dispersed primary phase inside the monotectic matrix. These observations are discussed in relation to capillarity and solidification aspects. A key finding is the preservation of a certain degree of dispersion of the indium primary phase. This result differs fundamentally from the results obtained under microgravity conditions on the same system and compositions (Gelles and Markworth, 1980; Alborn and Loehberg, 1979). The results are seen as clearly establishing that the space environment can be used to obtain dispersed structures from hypermonotectic alloys.

  11. Fracture toughness of an Al-Li-Cu-In alloy

    SciTech Connect

    Wagner, J.A.; Gangloff, R.P. Virginia, University, Charlottesville )

    1992-06-01

    The crack initiation and growth fracture toughness of select AL-Li-Cu alloy variants are characterized and elucidated. Conventionally processed plates form large DC cast ingots are investigated to eliminate the variation in microstructure associated with laboratory scale and SPF-processed material. Fracture resistance is characterized using the J-integral method to establish crack initiation and growth behavior at 25 and -185 C. It is shown that state-of-the-art 2090-T81 has superior toughness compared to 2090 + In-T6 at both test temperatures, with the low toughness of 2090 + In-T6 associated with intersubgranular fracture attributed to a high density of subboundary precipitates. 21 refs.

  12. Fracture toughness of an Al-Li-Cu-In alloy

    NASA Technical Reports Server (NTRS)

    Wagner, John A.; Gangloff, Richard P.

    1992-01-01

    The crack initiation and growth fracture toughness of select AL-Li-Cu alloy variants are characterized and elucidated. Conventionally processed plates form large DC cast ingots are investigated to eliminate the variation in microstructure associated with laboratory scale and SPF-processed material. Fracture resistance is characterized using the J-integral method to establish crack initiation and growth behavior at 25 and -185 C. It is shown that state-of-the-art 2090-T81 has superior toughness compared to 2090 + In-T6 at both test temperatures, with the low toughness of 2090 + In-T6 associated with intersubgranular fracture attributed to a high density of subboundary precipitates.

  13. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  14. Optimization of an oxide dispersion strengthened Ni-Cr-Al alloy for gas turbine engine vanes

    NASA Technical Reports Server (NTRS)

    Klarstrom, D. L.; Grierson, R.

    1975-01-01

    The investigation was carried out to determine the optimum alloy within the Ni-16Cr-Al-Y2O3 system for use as a vane material in advanced aircraft gas turbine engines. Six alloys containing nominally 4%, 5% and 6% Al with Y2O3 levels of 0.8% and 1.2% were prepared by mechanical attrition. Six small-scale, rectangular extrusions were produced from each powder lot for property evaluation. The approximate temperatures for incipient melting were found to be 1658 K (2525 F), 1644 K (2500 F) and 1630 K (2475 F) for the 4%, 5% and 6% aluminum levels, respectively. With the exception of longitudinal crystallographic texture, the eight extrusions selected for extensive evaluation either exceeded or were close to mechanical property goals. Major differences between the alloys became apparent during dynamic oxidation testing, and in particular during the 1366 K (2000 F)/500 hour Mach 1 tests carried out by NASA-Lewis. An aluminum level of 4.75% was subsequently judged to be optimum based on considerations of dynamic oxidation resistance, susceptibility to thermal fatigue cracking and melting point.

  15. Hot Corrosion of Single-Crystal NiAl-X Alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1998-01-01

    Several single-crystal NiAl-X alloys (X=Hf, Ti, Cr, Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at 900 deg. C for 300 1-hr cycles. The surface morphology after testing consisted of either mounds or an inward, uniform-type of attack which preserved surface features. It was observed that the surface morphology was affected by the surface preparation treatments. Microstructurally, the hot corrosion attack initiated as pits but evolved to a rampant attack consisting of the rapid inward growth of Al2O3. Electropolishing and chemical milling produced many pits and grooves on the surface. However, the presence of pits and grooves did not appear to strongly influence the hot corrosion response. Attack on many samples was strongly localized which was attributed to compositional inhomogeneity within the samples. It was found that increasing the Ti content from 1% to 5 % degraded the hot corrosion response of these alloys. In contrast, the addition of 1-2% Cr reduced the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the 4-5% Ti addition.

  16. In situ investigation of spinodal decomposition in hypermonotectic Al Bi and Al Bi Zn alloys

    NASA Astrophysics Data System (ADS)

    Schaffer, P. L.; Mathiesen, R. H.; Arnberg, L.; Di Sabatino, M.; Snigirev, A.

    2008-05-01

    Spinodal decomposition of hypermonotectic Al-6 wt.%Bi, Al-8 wt.%Bi and Al-6 wt.%Bi-8 wt.%Zn alloys has been investigated using synchrotron radiography. In the case of the 6 and 8 wt.%Bi binary alloys undercoolings of 70 and 110 K, respectively, were required to initiate the L→L1+L2 reaction, which appeared to occur very close to the monotectic reaction temperature. The nucleated L2 droplets were set in collective size-dependent motion by forces coupled to external fields (gravity and imposed temperature gradient) as well as forces arising due to internal fluctuations of the system. With experimental conditions similar to those realized during strip casting of the same materials, it was found that the size-dependant droplet velocity field combined with Stokes drag at the L1-L2 interfaces as well as attractive and repulsive diffusion-coupling between adjacent L2 droplets, yield complex meso- to microscale hydrodynamics. The hydrodynamics are the dominating mechanisms for L2 droplet coagulation, and are accordingly decisive for the final size distribution and geometrical dispersion of the soft Bi-rich component in the cast material. A different decomposition mode was observed in the Al-6 wt.%Bi-8 wt.%Zn ternary alloy, with the L2 droplets undergoing an immiscible-miscible-immiscible transition. In contrast to what was found for the binaries, L2 domains formed at relatively small undercoolings, and very little droplet motion was observed, as all L2 domains nucleated and remained on the crucible walls until they encroached on the monotectic front. At small distances from the monotectic front a Zn-rich solute boundary layer preceding the α-Al, caused the L2 domains to dissolve as Bi-Zn-Al regains complete miscibility upon reaching a critical Zn-concentration. In the shallow mush region behind the monotectic reaction, a high Zn solid solubility and a relatively fast diffusion of Zn in α-Al combine to cause a rapid diminishing Zn concentration in the mush liquid

  17. Study on improved tribological properties by alloying copper to CP-Ti and Ti-6Al-4V alloy.

    PubMed

    Wang, Song; Ma, Zheng; Liao, Zhenhua; Song, Jian; Yang, Ke; Liu, Weiqiang

    2015-12-01

    Copper alloying to titanium and its alloys is believed to show an antibacterial performance. However, the tribological properties of Cu alloyed titanium alloys were seldom studied. Ti-5Cu and Ti-6Al-4V-5Cu alloys were fabricated in the present study in order to further study the friction and wear properties of titanium alloys with Cu additive. The microstructure, composition and hardness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and hardness tester. The tribological behaviors were tested with ZrO2 counterface in 25% bovine serum using a ball-on-disc tribo-tester. The results revealed that precipitations of Ti2Cu intermetallic compounds appeared in both Ti-5Cu and Ti-6Al-4V-5Cu alloys. The tribological results showed an improvement in friction and wear resistance for both Ti-5Cu and Ti-6Al-4V-5Cu alloys due to the precipitation of Ti2Cu. The results also indicated that both CP-Ti and Ti-5Cu behaved better wear resistance than Ti-6Al-4V and Ti-6Al-4V-5Cu due to different wear mechanisms when articulated with hard zirconia. Both CP-Ti and Ti-5Cu revealed dominant adhesive wear with secondary abrasive wear mechanism while both Ti-6Al-4V and Ti-6Al-4V-5Cu showed severe abrasive wear and cracks with secondary adhesive wear mechanism due to different surface hardness integrated by their microstructures and material types. PMID:26354247

  18. THORIUM-BERYLLIUM ALLOYS AND METHOD OF PRODUCING SAME

    DOEpatents

    Spedding, F.H.; Wilhelm, H.A.; Keller, W.H.

    1959-09-01

    >The preparation is described of thorium-berylium alloys from halides of the metals by stmultaneously reducing thorium fluoride and beryllium fluoride with calcium at approximately 650 deg C and maintaining the temperature until the thorium-beryhltum alloy separates from the slag.

  19. Effect of iron content on the structure and mechanical properties of Al25Ti25Ni25Cu25 and (AlTi)60-xNi20Cu20Fex (x=15, 20) high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Fazakas, É.; Zadorozhnyy, V.; Louzguine-Luzgin, D. V.

    2015-12-01

    In this work, we investigated the microstructure and mechanical properties of Al25Ti25Ni25Cu25 Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 high entropy alloys, produced by arc melting and casting in an inert atmosphere. The structure of these alloys was studied by X-ray diffractometry and scanning electron microscopy. The as-cast alloys were heat treated at 773, 973 and 1173 K for 1800 s to investigate the effects of aging on the plasticity, hardness and elastic properties. Compared to the conventional high-entropy alloys the Al25Ti25Ni25Cu25, Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 alloys are relatively hard and ductile. Being heat treated at 973 K the Al22.5Ti22.5Ni20Cu20Fe15 alloy shows considerably high strength and relatively homogeneous deformation under compression. The plasticity, hardness and elastic properties of the studied alloys depend on the fraction and intrinsic properties of the constituent phases. Significant hardening effect by the annealing is found.

  20. Synthesis and Characterization of W80Ni10Mo10 alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Patra, A.; Karak, S. K.; Pal, S.

    2015-02-01

    The present study aims at synthesis and characterization of nanostructured W80Ni10Mo10 (wt. %) alloy produced by mechanical alloying (MA). Elemental powders of tungsten (W), nickel (Ni), molybdenum (Mo) were subjected to mechanical attrition in a high energy planetary ball-mill using chrome steel as grinding media and toluene as a process control agent. The crystallite size and lattice strain of the nanostructured powders at different stages of milling (0 h to 20h) was calculated from the X-ray diffraction patterns (XRD). The crystallite size of W in W80Ni10Mo10 powder was reduced from 100 μm to 55 nm at 10 h and farther reduction to 40 nm at 20 h of milling with increase in lattice strain of 0.25% at 20 h of milling. The lattice parameter of tungsten showed initial expansion upto 0.03% at 10 h of milling and then contraction upto 0.04% at 20 h of milling. The scanning electron microscopy (SEM) also showed mixed morphology of W80Ni10Mo10 powders consisting spherical and elongated particles after 20 h of milling. SEM analysis also revealed that particle size reduced from 100 μm to 2 μm with an increase in the milling time from 0 to 20 hours. The dark-field Transmission Electron Microscopy (TEM) observations revealed that the crystallite size of W in milled W80Ni10Mo10 alloy is in good agreement with calculated crystallite size from XRD.

  1. (Fe,Si,Al)-based nanocrystalline soft magnetic alloys for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Daniil, Maria; Osofsky, Michael S.; Gubser, Donald U.; Willard, Matthew A.

    2010-04-01

    In this work Al and Si are substituted for Fe in a (Fe,Si,Al)-Nb-B-Cu alloy with the goal of improving its magnetic properties at 77 K. The x-ray diffraction patterns for a series of five alloys annealed at 823 K shows a Fe3(Si,Al) ordered phase with some residual amorphous phase. The lowest coercivity at room temperature was observed for the alloy with composition Fe68Si15.5Al3.5Nb3B9Cu1. At cryogenic temperatures, the saturation magnetization of 99.3 A m2/kg, coercivity of 0.45 A/m, and resistivity of 122 μΩ cm for the Fe63Si17.5Al6Nb3B9Cu1 alloy, compare favorably to commercial alloys at 77 K.

  2. Effect of delayed aging on mechanical properties of an Al-Cu-Mg alloy

    SciTech Connect

    Ravindranathan, S.P.; Kashyap, K.T.; Kumar, S.R.; Ramachandra, C.; Chatterji, B.

    2000-02-01

    The effect of delayed aging on mechanical properties is characteristically found in Al-Mg-Si alloys. Delayed aging refers to the time elapsed between solutionizing and artificial aging. Delayed aging leads to inferior properties. This effect was investigated in an Al-Cu-Mg alloy (AU2GN) of nominal composition Al-2Cu-1.5Mg-1Fe-1Ni as a function of delay. This alloy also showed a drop in mechanical properties with delay. The results are explained on the basis of Pashley's kinetic model to qualitatively explain the evolution of a coarse precipitate structure with delay. It is found that all the results of delayed aging in the Al-Cu-Mg alloys are similar to those found in Al-Mg-Si alloys.

  3. Precipitation Hardening and Statistical Modeling of the Aging Parameters and Alloy Compositions in Al-Cu-Mg-Ag Alloys

    NASA Astrophysics Data System (ADS)

    Al-Obaisi, A. M.; El-Danaf, E. A.; Ragab, A. E.; Soliman, M. S.

    2016-04-01

    The addition of Ag to Al-Cu-Mg systems has been proposed to replace the existing high-strength 2xxx and 7xxx Al alloys. The aged Al-Cu-Mg-Ag alloys exhibited promising properties, due to special type of precipitates named Ω, which cooperate with other precipitates to enhance the mechanical properties significantly. In the present investigation, the effect of changing percentages of alloying elements, aging time, and aging temperature on the hardness values was studied based on a factorial design. According to this design of experiments (DOE)—23 factorial design, eight alloys were cast and hot rolled, where (Cu, Mg, and Ag) were added to aluminum with two different levels for each alloying element. These alloys were aged at different temperatures (160, 190, and 220 °C) over a wide range of time intervals from 10 min. to 64 h. The resulting hardness data were used as an input for Minitab software to model and relate the process variables with hardness through a regression analysis. Modifying the alloying elements' weight percentages to the high level enhanced the hardness of the alloy with about 40% as compared to the alloy containing the low level of all alloying elements. Through analysis of variance (ANOVA), it was figured out that altering the fraction of Cu had the greatest effect on the hardness values with a contribution of about 49%. Also, second-level interaction terms had about 21% of impact on the hardness values. Aging time, quadratic terms, and third-level interaction terms had almost the same level of influence on hardness values (about 10% contribution). Furthermore, the results have shown that small addition of Mg and Ag was enough to improve the mechanical properties of the alloy significantly. The statistical model formulated interpreted about 80% of the variation in hardness values.

  4. Precipitation Hardening and Statistical Modeling of the Aging Parameters and Alloy Compositions in Al-Cu-Mg-Ag Alloys

    NASA Astrophysics Data System (ADS)

    Al-Obaisi, A. M.; El-Danaf, E. A.; Ragab, A. E.; Soliman, M. S.

    2016-06-01

    The addition of Ag to Al-Cu-Mg systems has been proposed to replace the existing high-strength 2xxx and 7xxx Al alloys. The aged Al-Cu-Mg-Ag alloys exhibited promising properties, due to special type of precipitates named Ω, which cooperate with other precipitates to enhance the mechanical properties significantly. In the present investigation, the effect of changing percentages of alloying elements, aging time, and aging temperature on the hardness values was studied based on a factorial design. According to this design of experiments (DOE)—23 factorial design, eight alloys were cast and hot rolled, where (Cu, Mg, and Ag) were added to aluminum with two different levels for each alloying element. These alloys were aged at different temperatures (160, 190, and 220 °C) over a wide range of time intervals from 10 min. to 64 h. The resulting hardness data were used as an input for Minitab software to model and relate the process variables with hardness through a regression analysis. Modifying the alloying elements' weight percentages to the high level enhanced the hardness of the alloy with about 40% as compared to the alloy containing the low level of all alloying elements. Through analysis of variance (ANOVA), it was figured out that altering the fraction of Cu had the greatest effect on the hardness values with a contribution of about 49%. Also, second-level interaction terms had about 21% of impact on the hardness values. Aging time, quadratic terms, and third-level interaction terms had almost the same level of influence on hardness values (about 10% contribution). Furthermore, the results have shown that small addition of Mg and Ag was enough to improve the mechanical properties of the alloy significantly. The statistical model formulated interpreted about 80% of the variation in hardness values.

  5. The effect of Ti addition on oxidation behavior of FeAl intermetallic alloy

    SciTech Connect

    Li, D.; Lin, D.

    1997-12-31

    The influence of Ti addition on the high temperature oxidation behaviors of FeAl intermetallic alloys in air at 1,000 C and 1,100 C have been investigated. The oxidation kinetics of FeAl alloys were examined by the weight gain method and oxide products were examined by XRD, SEM, EDS and EPMA. The results showed that the oxidation kinetic curves of both Ti-doped and binary Fe-36.5Al alloys were described as different parabolas followed the formula: ({Delta}W/S){sup 2} = K{sub p}t. The parabolic rate constant, K{sub p} values are about 2.4 and 3.3 mg{sup 2}cm{sup {minus}4}h{sup {minus}1} for Fe-36.5Al alloy and about 1.3 and 2.0 mg{sup 2}cm{sup {minus}4}h{sup {minus}1} for Fe-36.5Al-2Ti alloy when oxidizing at 1,000 C and 1,100 C respectively. The difference between Fe-36.5Al and Fe-36.5Al-2Ti alloy is not only in the surface morphology but also in the phase components. In the surface there is only {alpha}-Al{sub 2}O{sub 3} oxide for the Fe-36.5Al alloy while there are {alpha}-Al{sub 2}O{sub 3} and TiO oxide for the Fe-36.5Al-2Ti alloy. The effects of Ti addition on the oxidation resistance of FeAl alloy were discussed based on the microstructural evidence.

  6. Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

    SciTech Connect

    Kalay, Yunus Eren

    2009-01-01

    Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occurs under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 {micro}m with a Peclet number of ~0.2, JH and TMK deviate from

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

    NASA Technical Reports Server (NTRS)

    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

  8. Validated thermodynamic prediction of AlP and eutectic (Si) solidification sequence in Al-Si cast alloys

    NASA Astrophysics Data System (ADS)

    Liang, S. M.; Schmid-Fetzer, R.

    2016-03-01

    The eutectic microstructure in hypoeutectic Al-Si cast alloys is strongly influenced by AlP particles which are potent nuclei for the eutectic (Si) phase. The solidification sequence of AlP and (Si) phases is, thus, crucial for the nucleation of eutectic silicon with marked impact on its morphology. This study presents this interdependence between Si- and P-compositions, relevant for Al-Si cast alloys, on the solidification sequence of AlP and (Si). These data are predicted from a series of thermodynamic calculations. The predictions are based on a self-consistent thermodynamic description of the Al-Si-P ternary alloy system developed recently. They are validated by independent experimental studies on microstructure and undercooling in hypoeutectic Al-Si alloys. A constrained Scheil solidification simulation technique is applied to predict the undercooling under clean heterogeneous nucleation conditions, validated by dedicated experimental observations on entrained droplets. These specific undercooling values may be very large and their quantitative dependence on Si and P content of the Al alloy is presented.

  9. Fatigue crack propagation behaviour of unidirectionally solidified gamma/gamma-prime-delta eutectic alloys. [Ni-Nb-Al alloys

    NASA Technical Reports Server (NTRS)

    Bretz, P. E.; Hertzberg, R. W.

    1979-01-01

    Fatigue crack propagation studies were carried out on unidirectionally solidified gamma/gamma-prime-delta (Ni-Nb-Al) alloys over an aluminum content range of 1.5-2.5% by weight. The variation of Al content of as-grown alloys did not significantly affect the crack growth behavior of these eutectic composites. The results indicate that the addition of Al to the eutectic dramatically improved the FCP behavior. The gamma/gamma-prime-delta alloy exhibited crack growth rates for a given stress intensity range that are an order of magnitude lower than those for the gamma-delta alloy. It is suggested that this difference in FCP behavior can be explained on the basis of stacking fault energy considerations. Extensive delaminations at the crack tip were also revealed, which contributed to the superior fatigue response. Delamination was predominantly intergranular in nature.

  10. Influence of alloying elements on the oxidation behavior of NbAl3

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Stephens, J. R.; Smialek, J. L.; Barrett, C. A.; Fox, D. S.

    1988-01-01

    NbAL3 is one candidate material for advanced aeropropulsion systems because of its high melting point, low density, and good oxidation resistance. Although NbAl3 has the lowest oxidation rate among the binary Nb-Al alloys, it does not form exclusive layers of protective Al2O3 scales. Recently Perkin et al., have shown the feasibility of forming alumina scales on Nb-Al alloys at greatly reduced Al contents. However, the objective was to maintain the high Al content, and hence low density, while achieving the capability of growing protective alumina scales. Alloy development followed approaches similar to those used successfully for superalloys and oxidation resistant MCrAlY coatings. Among the three elements examined (Ti, Si, and Cr) as ternary additions to Nb-Al3, Cr was the most effective in favoring the selective oxidation of Al. Nb-41Al-8Cr formed exclusive layers of alumina and had a k sub p value of 0.22 mg squared/cm (sup 4)/hr at 1200 C. The addition of 1 wt percent Y to this alloy was also beneficial, resulting in nearly an order of magnitude decrease in K sub p at 1200 C. Further improvements were achieved by adding about 1 wt percent Si to the quaternary alloy. The k sub p value of 0.012 mg squared/cm (sup 4)/hr for Nb-40Al-8Cr-1Y-1Si at 1200 C was identical to the best NiAl + Zr alloys. These NbAl3 alloys also exhibited excellent cyclic oxidation resistance for 100 hr at 1200 C, being nearly equivalent to NiAl + Zr.

  11. Interdiffusion behavior of Pt-modified γ-Ni + γ'-Ni3Al alloys coupled to Ni-Al-based alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenari; Wang, Wen; Sordelet, Daniel J.; Gleeson, Brian

    2005-07-01

    The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ'-Ni3Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched γ'-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ' alloys. For a given diffusion couple end member, the thickening kinetics of the γ' layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ' alloy. The γ'-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ' coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate.

  12. Mechanical properties of submicron-grained TiAl alloys prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Oehring, M.; Appel, F.; Pfullmann, Th.; Bormann, R.

    1995-02-01

    Ti-48 at. % Al powders of the metastable hexagonal-closed-packed solid solution with a grain size of 15 nm were prepared by mechanical alloying. The powders were consolidated to a density of greater than 99.5% by hot isostatic pressing (HIP) at 800 °C. After HIP the material exhibits a globular microstructure of the equilibrium phases α2 and γ with a mean grain size of 150 nm. Microhardness measurements show a Hall-Petch type [E. O. Hall, Proc. Phys. Soc. B 64, 747 (1951); N. J. Petch, J. Iron Steel Inst. 174, 25 (1953)] dependence on grain size. Room temperature compression tests reveal low ductility, but high fracture strengths ≥1800 MPa. On increasing the test temperature the yield strength drops sharply in the temperature range 600-800 °C to very low values. The results indicate that submicron-grained TiAl alloys can be deformed at much lower temperatures than coarse-grained material, making them suitable as precursors for net shaping, in particular if high deformation ratios are required.

  13. Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

  14. Microstructure and Mechanical Properties of the Ti-45Al-5Fe Intermetallic Alloy

    NASA Astrophysics Data System (ADS)

    Nazarova, T. I.; Imayev, V. M.; Imayev, R. M.

    2015-10-01

    Microstructure including changes in the phase composition and mechanical compression properties of the Ti-45Al-5Fe (at.%) intermetallic alloy manufactured by casting and subjected to homogenization annealing are investigated as functions of the temperature. The initial alloy has a homogeneous predominantly lamellar structure with relatively small size of colonies of three intermetallic phases: γ(TiAl), τ2(Al2FeTi), and α2(Ti3Al) in the approximate volume ratio 75:20:5. Compression tests have revealed the enhanced strength at room temperature and the improved hot workability at 800°C compared to those of TNM alloys of last generation.

  15. Simulation of the aluminothermic smelting of Mo-Ti-Al and Mo-Ti-V-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Udoeva, L. Yu.; Chumarev, V. M.; Larionov, A. V.; Rylov, A. N.; Trubachev, M. V.

    2013-08-01

    Thermodynamic simulation is performed to estimate the parameters and indicators of the aluminothermic melting of Mo-Ti-Al and Mo-Ti-V-Cr-Al master alloys intended for the alloying of titanium. The simulation is carried out with the HSC 6.1 Chemistry software package and is based on approximate calculations of the thermodynamic properties of Mo, Cr, and V aluminides, which are unavailable in handbooks. A comparison of the calculated and experimental data on the compositions of the forming alloys demonstrates that the developed models are adequate to technological processes and can be applied to optimize the parameters and to predict the compositions of smelting products.

  16. Utilizing various test methods to study the stress corrosion behavior of Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1984-01-01

    Recently, much attention has been given to aluminum-lithium alloys because of rather substantial specific-strength and specific-stiffness advantages offered over commercial 2000and 7000-series aluminum alloys. An obstacle to Al-Li alloy development has been inherent limited ductility. In order to obtain a more refined microstructure, powder metallurgy (P/M) has been employed in alloy development programs. As stress corrosion (SC) of high-strength aluminum alloys has been a major problem in the aircraft industry, the possibility of an employment of Al-Li alloys has been considered, taking into account a use of Al-Li-Cu alloys. Attention is given to a research program concerned with the evaluation of the relative SC resistance of two P/M processed Al-Li-Cu alloys. The behavior of the alloys, with and without an addition of magnesium, was studied with the aid of three test methods. The susceptibility to SC was found to depend on the microstructure of the alloys.

  17. Formation of a metastable ferromagnetic tau phase during containerless melt processing and rapid quenching in Mn-Al-C alloys

    NASA Technical Reports Server (NTRS)

    Kim, Y. J.; Perepezko, J. H.

    1992-01-01

    Solidification of selected Mn-Al-C alloys during containerless levitation and rapid quenching has yielded the first report for a ferromagnetic metastable tau phase formed directly from the melt. Complete solidification to tau phase was interrupted by the competitive evolution of an equilibrium epsilon phase during recalescence. The amount of undercooling required to produce the metastable ferromagnetic tau phase in a Mn(0.55)Al(0.433)C(0.017) alloy during solidification was estimated as approximately 470 K based on differential thermal analysis results. When the alloy carbon content was increased to 3.4 at. pct, transition in structure development occurred so that the samples exhibited gamma 2 phase formation as well as tau and epsilon phases.

  18. The corrosion behaviors and mechanism of 1420 Al-Li alloy

    SciTech Connect

    Cui Yusheng; Zhu Ziyong; Liu Sue; Ke Wei; Zhang Yun; Zhang Wanming

    1996-03-01

    Aluminum-lithium alloys are attractive materials for aircraft components and aerospace applications due to their reduced density and increased stiffness as compared with conventional aluminum alloys. Although many behaviors of Al-Li alloys have been and are being studied, it is necessary to understand their stress corrosion cracking (SCC) characteristics and mechanism because of the high SCC susceptibility of other high-strength aluminum alloys. The purpose of the investigation is to look for the best combination of strength, ductility, and SCC resistance and to understand the mechanism of SCC for Al-Li alloys. In the present paper the SCC behavior of 1420 Al-Li has been studied. The intermetallic compounds in the alloy were synthesized for investigating their electrochemical behaviors.

  19. Microstructure-property relationships in low-density Al-Li-Mg alloys

    NASA Astrophysics Data System (ADS)

    Buchheit, T. E.; Wert, J. A.

    1993-04-01

    The present article describes an investigation of the microstructure and tensile properties of cast Al-Li-Mg alloys with very low densities, in the range 2.3 to 2.4 Mg/m3. Low density is achieved by adding Li and Mg in excess of the solubility limit, which prevents subsequent dissolution of the Al2LiMg particles that form during solidification. A simple model developed during the course of this research allows prediction of the volume fraction of Al2LiMg and alloy density from alloy composition. The model was used to select two alloy compositions for detailed investigation: A112Li6Mg and A116Li8Mg. The microstructures of the cast alloys consist of coarse Al2LiMg particles embedded in an Al matrix containing Al3Li particles. Both alloys exhibit low tensile elongation in the as-cast condition. Additional processing steps were used to modify the microstructural characteristics thought to be responsible for the low tensile elongation of the ascast alloys. The A116Li8Mg alloy, with an Al2LiMg volume fraction of 0.25, does not exhibit increased tensile elongation as a result of processing, and the brittle nature of this material is attributed to the high volume fraction of the Al2LiMg phase. The A112Li6Mg alloy, with an Al2LiMg volume fraction of 0.13, exhibits a remarkable increase in tensile elongation after extrusion, an effect attributed to fragmentation and dispersal of a three-dimensional (3-D) network of the intermetallic phase in the as-cast alloy.

  20. Impact behavior of FeAl alloy FA-350

    SciTech Connect

    Alexander, D.J.

    1994-09-01

    The tensile properties and impact behavior of the iron aluminide FeAl-type alloy FA-350 [Fe-35.8Al-0.05Zr-0.24B (at. %)] have been studied over the temperature range of {minus}100 to 800C. Half-size Charpy specimens were either oil quenched from 700C or furnace cooled. The energy absorbed during the impact test showed a maximum value at 100 to 200C, with decreasing energy as the temperature was increased, for both heat treatments. The furnace-cooled material had greater energy absorption than the oil-quenched material. The tensile tests showed increasing ductility (as measured by total elongation) with increasing temperature. The furnace-cooled material had lower strength and higher ductility than the oil-quenched material. Fractographic examination of the oil-quenched impact specimens revealed that several different fracture modes operated, depending on the test temperature. Fracture occurred by intergranular and quasicleavage fracture at low temperatures, predominantly quasicleavage at intermediate temperatures, and intergranular fracture at 800C. For the furnace-cooled material fracture was predominantly quasicleavage at all temperatures. The higher ductility and energy absorption for the furnace-cooled material is believed to be the result of softening due to a decrease in the retained vacancy concentration.

  1. Interstitial precipitation in Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Spear, W. S.; Polonis, D. H.

    1994-06-01

    Two separate stages of precipitation have been identified during the aging of ternary Fel8Cr3Al and Fel8Cr5Al alloys at temperatures in the vicinity of 475 °C. The first stage involves the formation of interstitial precipitates resulting from C and N impurities; the second and slower stage is the formation of the Cr-rich α' phase. Transmission electron microscopy (TEM) results show that carbonitride precipitation occurs preferentially at dislocations, stacking faults, and grain boundaries, and also uniformly through the matrix. Aging for times in excess of 400 hours at 475 °C promotes coarsening of the heterogeneous precipitates and dissolution of the uniformly distributed matrix particles. A resistometric analysis shows that the kinetics of the initial stages of precipitation can be described by a (time)2/3 relation. This kinetic behavior is explained in terms of stress-assisted diffusion in the highly stressed matrix resulting from coherency strains accompanying carbonitride precipitation. Experimental values of the activation energy for the first stage reaction correlate closely with those reported for the interstitial diffusion of C and N in alpha iron.

  2. Hydrogen isotope trapping in Al-Cu binary alloys

    DOE PAGESBeta

    Chao, Paul; Karnesky, Richard A.

    2016-01-01

    In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol–1 (0.19 ± 0.03 eV). Typical occupancy of this trap is high;more » for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D2 for 68 days, there is ca. there is 3.15×10–7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.« less

  3. Hydrogen isotope trapping in Al-Cu binary alloys

    SciTech Connect

    Chao, Paul; Karnesky, Richard A.

    2016-01-01

    In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol–1 (0.19 ± 0.03 eV). Typical occupancy of this trap is high; for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D2 for 68 days, there is ca. there is 3.15×10–7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.

  4. Novel high-strength ternary Zr-Al-Sn alloys with martensite structure for nuclear applications

    NASA Astrophysics Data System (ADS)

    Nie, Li; Zhan, Yongzhong; Hu, Tong; Chen, Xiaoxian; Wang, Chenghui

    2013-11-01

    High strength is essential for the practical application of Zr alloys as structural materials. In this work, Zr-5Al-xSn (x = 2, 3, 4, 5 and 6) alloys have been designed and fabricated through arc melting in order to effectively improve the strength while retaining good ductility. Phase analysis results show that all the samples consist of single phase α-Zr. The variation trend of lattice constants as a function of Sn content has been analyzed. The microstructural analysis indicates that the Zr-5Al-xSn alloys mainly contain martensite structure. Mechanical tests show that these Zr-5Al-xSn alloys exhibit high compressive strength (1250-1450 MPa), high yield stress (800-1000 MPa), and favorable plastic strain of 18-23%. The fracture mode has been experimentally analyzed. Finally, both Zr-5Al-3Sn and Zr-5Al-5Sn are subjected to heat treatments for further study on the roles of Sn element and controlled heat treatment on the microstructure and mechanical properties of Zr alloys. Sn is found to promote the formation of ZrAl in the Zr-5Al-xSn alloys. Moreover, the martensite laths are observed to evolve into larger strip grains and fine equiaxed grains after heat treatment at 900 °C for 2 h. These factors strengthen the Zr-5Al-xSn alloys.

  5. Influence of alloying elements on the oxidation behavior of NbAl3

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Stephens, J. R.; Smialek, J. L.; Barrett, C. A.; Fox, D. S.

    1989-01-01

    NbAl3 is one candidate material for advanced aeropropulsion systems because of its high melting point, low density, and good oxidation resistance. Although NbAl3 has the lowest oxidation rate among the binary Nb-Al alloys, it does not form exclusive layers of protective Al203 scales. Recently Perkin et al., have shown the feasibility of forming alumina scales on Nb-Al alloys at greatly reduced Al contents. However, the objective was to maintain the high Al content, and hence low density, while achieving the capability of growing protective alumina scales. Alloy development followed approaches similar to those used successfully for superalloys and oxidation resistant MCrAly coatings. Among the three elements examined (Ti, Si, and Cr) as ternary additions to Nb-Al3, Cr was the most effective in favoring the selective oxidation of Al. Nb-41Al-8Cr formed exclusive layers of alumina and had a k sub p value of 0.22 mg squared/cm (sup 4)/hr at 1200 C. The addition of 1 wt percent Y to this alloy was also beneficial, resulting in nearly an order of magnitude decrease in K sub p at 1200 C. Further improvements were achieved by adding about 1 wt percent Si to the quaternary alloy. The k sub p value of 0.012 mg squared/cm (sup 4)/hr for Nb-40Al-8Cr-1Y-1Si at 1200 C was identical to the best NiAl + Zr alloys. These NbAl3 alloys also exhibited excellent cyclic oxidation resistance for 100 hr at 1200 C, being nearly equivalent to NiAl + Zr.

  6. Mechanical properties of Al-Cu alloy-SiC composites

    SciTech Connect

    Anggara, B. S.; Handoko, E.; Soegijono, B.

    2014-09-25

    The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

  7. Kinetic Study of the Solid-State Transformation of Vacuum-Plasma-Sprayed Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Salimijazi, H. R.; Mousavi, Z. A.; Golozar, M. A.; Mostaghimi, J.; Coyle, T.

    2014-01-01

    Because of the nature of the plasma spraying process, the physical and mechanical properties of vacuum-plasma-sprayed structures of Ti-6Al-4V alloy are completely different from those of conventionally manufactured alloys such as bulk materials from casting and forging. To obtain desired mechanical and physical properties, vacancy and internal defects must be reduced, splat boundaries must be eliminated, and optimal phase compositions should be obtained through postdeposition heat treatments. To determine appropriate heat treatment processes, one needs to study the kinetic behavior of the as-sprayed microstructure at elevated temperatures. In the current study, the kinetics of the solid transformations found in Ti-6Al-4V alloys produced during the vacuum plasma spraying process was studied based on the Johnson-Mehl-Avrami theory. For the kinetic behavior of this alloy, the nonconstant temperature dependence of the transformation rate constant exhibits an irregularity at 900 °C, marking a change in the transformation mechanism. For the lower-temperature (<900 °C) curves, the constant gradient indicates a lack of change in the transformation mechanism, including homogeneous nucleation, with growth of α phase. For higher temperatures (>900 °C), a gradient change indicates a change in the transformation mechanism. The first mechanism was the formation of α-phase grain boundary, and the second mechanism was α-plate nucleation and growth from grain boundaries. The value of the transformation rate constant in the kinetics study of as-sprayed Ti-6Al-4V alloy was much higher than for material produced by the casting method. Using the results obtained from the kinetics of the phase transformation at different constant temperatures, a time-temperature-transformation (TTT) diagram for as-sprayed Ti-6Al-4V alloy was developed.

  8. Third element effect in the surface zone of Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Airiskallio, E.; Nurmi, E.; Heinonen, M. H.; Väyrynen, I. J.; Kokko, K.; Ropo, M.; Punkkinen, M. P. J.; Pitkänen, H.; Alatalo, M.; Kollár, J.; Johansson, B.; Vitos, L.

    2010-01-01

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  9. Structure of liquid Al and Al67Mg33 alloy: comparison between experiment and simulation

    NASA Astrophysics Data System (ADS)

    Kramer, M. J.; Mendelev, M. I.; Asta, M.

    2014-06-01

    We report data on the structure of liquid Al and an Al67Mg33 alloy obtained from state-of-the-art X-ray diffraction experiments and ab initio molecular dynamics (AIMD) simulations. To facilitate a direct comparison between these data, we develop a method to elongate the AIMD pair correlation function in order to obtain reliable AIMD structure factors. The comparison reveals an appreciable level of discrepancy between experimental and AIMD liquid structures, with the latter being consistently more ordered than the former at the same temperature. The discrepancy noted in this study is estimated to have significant implications for simulation-based calculations of liquid transport properties and solid-liquid interface kinetic properties.

  10. Properties Evaluation and Studying Production Mechanism of Nanocrystalline NiAl Intermetallic Compound by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Khajesarvi, Ali; Akbari, Golamhossein

    2016-04-01

    Ni50Al50 intermetallic compound was synthesized by mechanical alloying (MA) of elemental mixtures of Ni and Al powders in a planetary ball mill. After 16 hours of milling and obtaining crystallites with a critical size, the initial NiAl compound was formed along with the combustive reaction after opening the vial lid. In the time interval of 16 to 128 hours, the reaction from combustive state reached the explosive state. Finally, after 128 hours of milling, the initial powders were wholly transformed into NiAl before completion of the milling time. Structural changes of powder particles during MA were studied by X-ray diffractometry and scanning electron microscopy. The crystallite size measurements revealed that the grain size of the NiAl phase decreased from 155 to 26 nm with increasing MA time from 8 to 128 hours. Microhardness for nanocrystalline Ni50Al50 intermetallic compound produced after 128 hours of milling was measured as about 350 Hv.

  11. The influence of microstructure on blistering and bubble formation by He ion irradiation in Al alloys

    NASA Astrophysics Data System (ADS)

    Soria, S. R.; Tolley, A.; Sánchez, E. A.

    2015-12-01

    The influence of microstructure and composition on the effects of ion irradiation in Al alloys was studied combining Atomic Force Microscopy, Scanning Electron Microscopy and Transmission Electron Microscopy. For this purpose, irradiation experiments with 20 keV He+ ions at room temperature were carried out in Al, an Al-4Cu (wt%) supersaturated solid solution, and an Al-5.6Cu-0.5Si-0.5Ge (wt.%) alloy with a very high density of precipitates, and the results were compared. In Al and Al-4Cu, He bubbles were found with an average size in between 1 nm and 2 nm that was independent of fluence. The critical fluence for bubble formation was higher in Al-4Cu than in Al. He bubbles were also observed below the critical fluence after post irradiation annealing in Al-4Cu. The incoherent interfaces between the equilibrium θ phase and the Al matrix were found to be favorable sites for the formation of He bubbles. Instead, no bubbles were observed in the precipitate rich Al-5.6Cu-0.5Si-0.5Ge alloy. In all alloys, blistering was observed, leading to surface erosion by exfoliation. The blistering effects were more severe in the Al-5.6Cu-0.5Si-0.5Ge alloy, and they were enhanced by increasing the fluence rate.

  12. Alloying effects on mechanical and metallurgical properties of NiAl

    SciTech Connect

    Liu, C.T.; Horton, J.A.; Lee, E.H.; George, E.P.

    1993-06-01

    Alloying effects were investigated in near-stoichiometric NiAl for improving its mechanical and metallurgical properties. Ternary additions of 19 elements at levels up to 10 at. % were added to NiAl; among them, molybdenum is found to be most effective in improving the room-temperature ductility and high-temperature strength. Alloying with 1.0 {plus_minus} 0.6% molybdenum almost doubles the room-temperature tensile ductility of NiAl and triples its yield strength at 1000C. The creep properties of molybdenum-modified NiAl alloys can be dramatically improved by alloying with up to 1% of niobium or tantalum. Because of the low solubilities of molybdenum and niobium in NiAl, the beneficial effects mainly come from precipitation hardening. Fine and coarse precipitates are revealed by both transmission electron microscopy (TEM) and electron microprobe analyses. Molybdenum-containing alloys possess excellent oxidation resistance and can be fabricated into rod stock by hot extrusion at 900 to 1050C. This study of alloying effects provides a critical input for the alloy design of ductile and strong NiAl aluminide alloys for high-temperature structural applications.

  13. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys

    PubMed Central

    Li, Jiehua; Hage, Fredrik S.; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-01-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP ‘patch’ dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption. PMID:27120994

  14. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys.

    PubMed

    Li, Jiehua; Hage, Fredrik S; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-01-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP 'patch' dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption. PMID:27120994

  15. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Li, Jiehua; Hage, Fredrik S.; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-04-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP ‘patch’ dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption.

  16. Geometric and Chemical Composition Effects on Healing Kinetics of Voids in Mg-bearing Al Alloys

    NASA Astrophysics Data System (ADS)

    Song, Miao; Du, Kui; Wang, Chunyang; Wen, Shengping; Huang, Hui; Nie, Zuoren; Ye, Hengqiang

    2016-05-01

    The healing kinetics of nanometer-scale voids in Al-Mg-Er and Al-Mg-Zn-Er alloy systems were investigated with a combination of in situ transmission electron microscopy and electron tomography at different temperatures. Mg was observed completely healing the voids, which were then rejuvenated to the alloy composition with further aging, in the Al-Mg-Er alloy. On the contrary, Mg51Zn20 intermetallic compound was formed in voids in the Al-Mg-Zn-Er alloy, which leads to complete filling of the voids but not rejuvenation for the material. For voids with different geometrical aspects, different evolution processes were observed, which are related to the competition between bulk and surface diffusion of the alloys. For voids with a large size difference in their two ends, a viscous flow of surface atoms can be directly observed with in situ electron microscopy, when the size of one end becomes less than tens of nanometers.

  17. Mechanical properties and corrosion resistance of Ti-6Al-7Nb alloy dental castings.

    PubMed

    Kobayashi, E; Wang, T J; Doi, H; Yoneyama, T; Hamanaka, H

    1998-10-01

    With the aim of applying a novel titanium alloy, Ti-6Al-7Nb, to a dental casting material, a comprehensive research work was carried out on its characteristics, such as castability, mechanical properties and corrosion resistance in the present study. As a result, Ti-6Al-7Nb alloy exhibited sufficient castability by a dental casting method for titanium alloys and enough mechanical properties for dental application. It is also showed excellent corrosion resistance through an immersion test in 1.0% lactic acid and an anodic polarization test in 0.9% NaCl solution. From these results, it is concluded that this Ti-6Al-7Nb alloy is applicable as a dental material in place of Ti-6Al-4V alloy, which includes cytotoxic vanadium. PMID:15348689

  18. Numerical Simulation of Residual Stress in an Al-Cu Alloy Block During Quenching and Aging

    NASA Astrophysics Data System (ADS)

    Dong, Ya-Bo; Shao, Wen-Zhu; Lu, Liang-Xing; Jiang, Jian-Tang; Zhen, Liang

    2015-12-01

    In this study, residual stresses after different quenching and aging processes of Al-Cu forged blocks were investigated by numerical simulation method and experimental measurements. An iterative zone-based heat transfer calculation was coupled with the hyperbolic sine-type constitutive model to simulate the residual stress during quenching process. The simulation results were compared with experiment data using both x-ray diffraction and crack compliance methods. The simulation results were in good agreement with the experimental measurements with around 9-13% deviation at the largest. Residual stress reduction can be achieved by decreasing the cooling rate during quenching. Quenching in water with different temperatures of 60, 80, and 100 °C resulted in the maximum compressive residual stress reduction of approximately 28.2, 75.7, and 88.9%, respectively, in Al-Cu alloy samples. When quenched in 10, 20, and 30% PAG solution, the reduction of maximum compressive residual stress in Al-Cu alloy samples was approximately 35.1, 47.8, and 53.2%, respectively. In addition, in order to study the amount of residual stress relief after aging treatments, aging treatments at 140 and 170 °C for different times were also studied. Aging treatment used to obtain the peak-aged (T6) and overaged (T7) condition produces only about 22.5 to 34.7% reduction in residual stresses.

  19. Probing the defect state of individual precipitates grown in an Al-Mg-Si alloy

    SciTech Connect

    Klobes, Benedikt; Korff, Bjoern; Balarisi, Osman; Eich, Patrick; Haaks, Matz; Maier, Karl; Sottong, Reinhard; Huehne, Sven-Martin; Mader, Werner; Staab, Torsten E. M.

    2010-08-01

    Precipitates forming in decomposable aluminum alloys such as Al-Mg-Si evolve toward the corresponding intermetallic phase, which is {beta} (Mg{sub 2}Si) in this case, depending on heat-treatment conditions. Individual {beta} precipitates were produced in an Al-1.11 at. % Mg-0.77 at. % Si alloy and identified using optical as well as electron microscopy. The individual {beta} precipitates could be investigated with regard to their intrinsic crystal defects using a finely focused positron microbeam provided by the Bonn Positron Microprobe. Comparison with theoretical calculations of the Doppler broadening of annihilation radiation reveals that {beta} precipitates most likely do not contain vacancies in either sublattice and that 0.16 is the upper bound of the fraction of trapped positrons. The usage of different enhancement factors had only little influence on the calculations whereas the general gradient approximation affected the contribution of Si orbitals, in particular. Additional measurements of the Doppler broadening based on the radioactive source {sup 68}Ge, which emits high-energy positrons probing bulk regions of the sample, were carried out. These measurements show that {beta} precipitates are sparsely distributed in the Al matrix.

  20. Probing the defect state of individual precipitates grown in an Al-Mg-Si alloy

    NASA Astrophysics Data System (ADS)

    Klobes, Benedikt; Korff, Björn; Balarisi, Osman; Eich, Patrick; Haaks, Matz; Maier, Karl; Sottong, Reinhard; Hühne, Sven-Martin; Mader, Werner; Staab, Torsten E. M.

    2010-08-01

    Precipitates forming in decomposable aluminum alloys such as Al-Mg-Si evolve toward the corresponding intermetallic phase, which is β (Mg2Si) in this case, depending on heat-treatment conditions. Individual β precipitates were produced in an Al- 1.11at.% Mg- 0.77at.% Si alloy and identified using optical as well as electron microscopy. The individual β precipitates could be investigated with regard to their intrinsic crystal defects using a finely focused positron microbeam provided by the Bonn Positron Microprobe. Comparison with theoretical calculations of the Doppler broadening of annihilation radiation reveals that β precipitates most likely do not contain vacancies in either sublattice and that 0.16 is the upper bound of the fraction of trapped positrons. The usage of different enhancement factors had only little influence on the calculations whereas the general gradient approximation affected the contribution of Si orbitals, in particular. Additional measurements of the Doppler broadening based on the radioactive source G68e , which emits high-energy positrons probing bulk regions of the sample, were carried out. These measurements show that β precipitates are sparsely distributed in the Al matrix.

  1. Microstructure and properties of welds between 5754 Al alloys and AZ31 Mg alloys using a Yb:YAG laser

    NASA Astrophysics Data System (ADS)

    Bannour, Sana; Autric, Michel; Masse, Jean-Eric; Mattei, Simone; Mhiri, Hatem

    2015-02-01

    Dissimilar laser beam welding between A5754 Al alloys and AZ31 Mg alloys with the plate thickness of 2 mm was investigated. Complex flow pattern characterized by a large volume of intermetallic compounds Al12Mg17 and Al3Mg2 is formed in the fusion zone. Microhardness measurement of the dissimilar welds presents an uneven distribution due to the complicated microstructure of the weld, and the maximum value of microhardness in the fusion zone is much higher than of the base materials.

  2. TEM microstructural characterization of melt-spun aged Al-6Si-3Cu-xMg alloys

    SciTech Connect

    Lopez, Ismeli Alfonso . E-mail: post18@jupiter.umich.mx; Zepeda, Cuauhtemoc Maldonado; Gonzalez Reyes, Jose Gonzalo; Flores, Ariosto Medina; Rodriguez, Juan Serrato; Gomez, Luis Bejar

    2007-06-15

    Three Al-6Si-3Cu-xMg alloys (x = 0.59, 3.80 and 6.78 wt.%) were produced using melt-spinning. As-melt-spun ribbons were aged at 150, 180 and 210 deg. C for times between 0.05 and 100 h. Microstructural changes were examined using transmission electron microscopy (TEM) and microhardness was measured. TEM analysis of the as-melt-spun alloys revealed 5 nm nanoparticles and larger particles (50 nm) composed of Al{sub 2}Cu ({theta}) for the 0.59% Mg alloy and Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) for 3.80% and 6.78% Mg alloys. Silicon solid solubility was extended to 9.0 at.% and Mg in solid solution reached 6.7 at.%. After aging treatments the 6.78% Mg alloy exhibited the most significant increase in microhardness, reaching 260 kg/mm{sup 2}. TEM analysis of aged specimens also showed {theta} and Q phase (5-20 nm nanoparticles and 35-40 nm particles). The combination of the volume fraction and size of the particles plays an important role in microhardness variation.

  3. A systematic ALCHEMI study of Fe-doped NiAl alloys

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-06-01

    ALCHEMI site-occupation studies of alloying additions to ordered aluminide intermetallic alloys have been performed with varying degrees of success, depending on the ionization delocalization correction. This study examines the variation in the site-occupancy of Fe in B2-ordered NiAl vs solute concentration and alloy stoichiometry. The fraction of Fe on the `Ni` site is plotted vs Fe concentration. The good separation among the data from alloys of the three stoichiometries shows that the site occupancy of iron depends on the relative concentrations of the Ni and Al host elements; however a preference for the `Ni` site is clearly indicated.

  4. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  5. Improved Stress Corrosion Cracking Resistance and Strength of a Two-Step Aged Al-Zn-Mg-Cu Alloy Using Taguchi Method

    NASA Astrophysics Data System (ADS)

    Lin, Lianghua; Liu, Zhiyi; Ying, Puyou; Liu, Meng

    2015-12-01

    Multi-step heat treatment effectively enhances the stress corrosion cracking (SCC) resistance but usually degrades the mechanical properties of Al-Zn-Mg-Cu alloys. With the aim to enhance SCC resistance as well as strength of Al-Zn-Mg-Cu alloys, we have optimized the process parameters during two-step aging of Al-6.1Zn-2.8Mg-1.9Cu alloy by Taguchi's L9 orthogonal array. In this work, analysis of variance (ANOVA) was performed to find out the significant heat treatment parameters. The slow strain rate testing combined with scanning electron microscope and transmission electron microscope was employed to study the SCC behaviors of Al-Zn-Mg-Cu alloy. Results showed that the contour map produced by ANOVA offered a reliable reference for selection of optimum heat treatment parameters. By using this method, a desired combination of mechanical performances and SCC resistance was obtained.

  6. Undercooling and solidification behavior of melts of the quasicrystal-forming alloys Al-Cu-Fe and Al-Cu-Co

    SciTech Connect

    Holland-Moritz, D.; Schroers, J.; Herlach, D.M.; Grushko, B.; Urban, K.

    1998-03-02

    Al-Cu-Fe, Al-Fe and Al-Cu-Co melts of different compositions were undercooled by containerless processing in an electromagnetic levitation facility. The phase selection during solidification from the undercooled melt was determined by direct measurements of the temperature changes during recalescence. Complimentarily, the phase selection and microstructure development was studied by scanning- and transmission electron microscopy (SEM, TEM) and X-ray diffraction (XRD) on the as-solidified samples with the undercooling and the alloy composition as experimental parameters. For comparison, rapidly quenched samples of the same alloys were produced by splat-cooling and investigated by TEM and XRD. The undercooling results were analyzed within the framework of classical nucleation theory. The activation threshold for the nucleation was found to be small for the icosahedral quasicrystalline phase in Al-Cu-Fe, medium for the decagonal D-phase in Al-Cu-Co and crystalline phases with polytetrahedral symmetry elements (Al{sub 13}Fe{sub 4} and Al{sub 5}Fe{sub 2}), but large for the cubic phase of Al{sub 50}(CuCo){sub 50} with non-polytetrahedral crystalline symmetry. These results are explained assuming of an icosahedral short-range order that prevails in the undercooled melt and gives rise to an interfacial energy decreasing with increasing degree of polytetrahedral order in the solid nucleus.

  7. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

    Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

    1986-01-01

    Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

  8. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

    Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

    1987-01-01

    Alloys based on FeAl are attractive alternative materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

  9. Evaluation of tribological behavior of Al-Co-Cr-Fe-Ni high entropy alloy using molecular dynamics simulation.

    PubMed

    Huang, Jen-Ching

    2012-01-01

    High-entropy alloys have been studied extensively for their excellent properties and performance, including outstanding strength and resistance to oxidation at high temperatures. This study employed molecular dynamics simulation to produce a high-entropy alloy containing an equal molar ratio of Al, Co, Cr, Fe, and Ni and investigated the tribological behavior of the material using a diamond tool in a vacuum environment. We also simulated a AlCoCrFeNi high-entropy alloy cooled from a high temperature molten state to 300 K in a high-speed quenching process to produce an amorphous microstructure. In a simulation of nanoscratching, the cutting force-distance curve of high-entropy alloys was used to evaluate work hardening and stick-slip. An increase in temperature was shown to reduce the scratching force and scratching resistance. Nanoscratching the high-entropy alloy at elevated temperatures provided evidence of work hardening; however, the degree of work hardening decreased with an increase in temperature. And it can also be found that when the temperature is higher, the fluctuation of the cutting force curve is greater. PMID:22549875

  10. Microstructure And Oxidation Properties Of Laser Clad Ni70AL20Cr7Hf3 Alloys With Extended Solid Solution Of Hf

    NASA Astrophysics Data System (ADS)

    Mazumder, J.; Sircar, S.; Ribaudo, C.; Kar, A.,

    1989-01-01

    Alloys coatings for superalloys for improved higher temperature (1200°C) service life under aggressive atmospheres are of great interest at present. There is a general consensus that addition of rare earths such as hafnium (Hf) to these alloys has a pronounced effect on the oxidation resistance properties at high temperatures. In situ laser cladding technique was used to produce Ni-Al-Cr-Hf alloys with extended solid solution of Hf in a near stoichiometric Ni3Al matrix. A 10 kW CW CO2 laser was used in conjunction with a screw-feed powder dispenser to perform the in situ cladding process.

  11. Li overlayer formation, oxidation and sputtering characteristics of Al-Li alloys and W/Al-Li composites for fusion applications

    SciTech Connect

    Krauss, A.R. ); DeWald, A.B.; Scott, P.; Savage, H. )

    1990-01-01

    The next generation of long pulse fusion devices will impose severe requirements on the properties of plasma-facing materials. In devices such as ITER, a divertor design is being considered, using a divertor plate which would be either tungsten or a low-Z material such as graphite or beryllium. Strongly segregating lithium alloys have been proposed as a means of producing a self-sustaining low-Z overlayer which lowers plasma Z{sub eff} and resists self-sputtering. Aluminum-lithium alloys are among the better-characterized lithium-bearing alloys, and it has been demonstrated that lithium segregates strongly in aluminum. However, aluminum has a relatively low melting point, and for low lithium concentrations, the lithium diffusion rate is too slow to replenish lithium at the rate at which it is eroded by the incoming plasma. It has been suggested previously that the superionic {beta} phase Al-Li alloy (48--54 at. % Li) should have high enough diffusivity to be able to replenish surface lithium, and that incorporation of the {beta}-phase AlLi in a composite with tungsten would provide high temperature strength and melt layer stability, along with significantly better thermal conductivity than pure tungsten. Such a composite has been fabricated, as well as a variation containing titanium as a means of controlling oxidation at grain boundaries. The Li overlayer formation, erosion, and replenishment are characterized for the {beta}-phase LiAl alloy, and W-AlLi and W-Ti-AlLi composites. It is found that if there is no oxide layer to inhibit the Li segregation, Li diffusion is extremely rapid, and an oxygen-free Li overlayer is formed which is stable under continuous ion beam sputtering. 21 refs., 7 figs.

  12. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  13. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-03-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δχ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  14. Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

    SciTech Connect

    Osborne, M.G.

    1998-02-23

    A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100--1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings.

  15. Burner Rig Hot Corrosion of a Single Crystal Ni-48Al-Ti-Hf-Ga Alloy

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Darolia, Ram; Cuy, Michael D.

    1998-01-01

    The hot corrosion resistance of a single crystal Ni-48Al-1Ti-0.5Hf-0.2Ga alloy was examined in a Mach 0.3 burner rig at 900 C for 300 hours. The combustion chamber was doped with 2 ppmw synthetic sea salt. The hot corrosion attack produced a random mound morphology on the surface. Microstructurally, the hot corrosion attack appeared to initiate with oxide-filled pits which were often broad and shallow. At an intermediate stage, the pits increased in size to incorporate unoxidized Ni islands in the corrosion product. The rampant attack stage, which was observed only at sharp sample corners, was characterized by rapid inward growth of alumina in finger-like protrusions incorporating significant amounts of Al-depleted Ni islands. Aluminum consumption in the oxide fingers resulted in the growth of a gamma' layer ahead of the advancing oxide fingers.

  16. Structure and properties during aging of an ultra-high strength Al-Cu-Li-Ag-Mg alloy

    NASA Technical Reports Server (NTRS)

    Gayle, Frank W.; Heubaum, Frank H.; Pickens, Joseph R.

    1990-01-01

    The structure and properties of the strengthening phases formed during aging in an Al-Cu-Li-Ag-Mg alloy (Weldalite 049) were elulcidated, by following the development of the microstructure by means of TEM. The results of observations showed that the Weldalite 049 alloy has a series of unusual and technologically useful combinations of mechanical properties in different aging conditions, such as natural aging without prior cold work to produce high strengths, a reversion temper of lower yield strength and unusually high ductility, a room temperature reaging of the reversion temper eventually leading to the original T4 hardness, and ultrahigh-strength T6 properties.

  17. Creep Strength and Microstructure of Al20-25+Nb Alloy Sheets and Foils for Advanced Microturbine Recurperators

    SciTech Connect

    Maziasz, Philip J; Shingledecker, John P; Evans, Neal D; Yamamoto, Yukinori; More, Karren Leslie; Trejo, Rosa M; Lara-Curzio, Edgar

    2007-01-01

    The Oak Ridge National Laboratory (ORNL) and ATI Allegheny Ludlum worked together on a collaborative program for about two years to produce a wide range of commercial sheets and foils of the new AL20-25+Nb{trademark} (AL20-25+Nb) stainless alloy for advanced microturbine recuperator applications. There is a need for cost-effective sheets/foils with more performance and reliability at 650-750 C than 347 stainless steel, particularly for larger 200-250 kW microturbines. Phase 1 of this collaborative program produced the sheets and foils needed for manufacturing brazed plated-fin air cells, while Phase 2 provided foils for primary surface air cells, and did experiments on modified processing designed to change the microstructure of sheets and foils for improved creep-resistance. Phase 1 sheets and foils of AL20-25+Nb have much more creep-resistance than 347 steel at 700-750 C, and those foils are slightly stronger than HR120 and HR230. Results for Phase 2 showed nearly double the creep-rupture life of sheets at 750 C/100 MPa, and similar improvements in foils. Creep data show that Phase 2 foils of AL20-25+Nb alloy have creep resistance approaching that of alloy 625 foils. Testing at about 750 C in flowing turbine exhaust gas for 500 h in the ORNL Recuperator Test Facility shows that foils of AL20-25+Nb alloy have oxidation-resistance similar to HR120 alloy, and much better than 347 steel.

  18. Mechanical properties of cast Ti-6Al-4V-XCu alloys.

    PubMed

    Aoki, T; Okafor, I C I; Watanabe, I; Hattori, M; Oda, Y; Okabe, T

    2004-11-01

    The mechanical properties of Ti-6Al-4V-XCu (1, 4 and 10 wt% Cu) alloys were examined. The castings for each alloy were made in a centrifugal titanium casting machine. Two shapes of specimens were used: a dumbbell (20 mm gauge length x 2.8 mm diameter) for mechanical property studies, and a flat slab (2 mm x 10 mm x 10 mm) for metallography, microhardness determination and X-ray diffractometry. Tensile strength, yield strength, modulus of elasticity, elongation and microhardness were evaluated. After tensile testing, the fracture surfaces were observed using scanning electron microscopy. The tensile strengths of the quaternary alloys decreased from 1016 MPa for the 1% Cu alloy to 387 MPa for the 10% Cu alloy. Elongation decreased with an increase in the copper content. The 1% Cu alloy exhibited elongation similar to Ti-6Al-4V without copper (3.0%). The results also indicated that the copper additions increased the bulk hardness of the quaternary alloy. In particular, the 10% Cu alloy had the highest hardness and underwent the most brittle fracture. The mechanical properties of cast Ti-6Al-4V alloy with 1 and 4% Cu were well within the values for existing dental casting non-precious alloys. PMID:15525390

  19. An overview of the welding of Ni{sub 3}Al and Fe{sub 3}Al alloys

    SciTech Connect

    Santella, M.L.

    1996-12-31

    Weldability (degree to which defect formation is resisted when an alloy is welded) is an issue in fabrication of Ni{sub 3}Al and Fe{sub 3}Al. Work to define and improve welding of Ni{sub 3}Al and Fe{sub 3}Al alloys is reviewed and progress illustrated by examples of current activities. The cast Ni{sub 3}Al alloys currently under development, IC221M and IC396M, have low resistance to solidification cracking and hence difficult to weld. Modifications to the composition of both base alloys and weld deposits,however, increase their resistance to cracking. Crack-free, full-penetration welds were made in centrifugally cast tubes of IC221M. Tensile and stress- rupture properties of the weldments compare favorably with base metal properties. Weldability issues have limited the use of Fe{sub 3}Al alloys to weld overlay applications. Filler metal compositions suitable for weld overlay cladding were developed, and the preheat and postweld heat treatment needed to avoid cracking, were determined experimentally.

  20. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  1. Transformation to Ni5Al3 in a 63.0 at. pct Ni-Al alloy

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Locci, I. E.; Vedula, K.; Michal, G. M.

    1993-01-01

    Microstructures of 63 at. pct P/M Ni-Al alloys with a composition close to the stoichiometry of the Ni5Al3 phase were investigated using homogenized and quenched specimens aged at low temperatures for various times. Results of analyses of XRD data and electron microscopy observations were used for quantitative phase analysis, performed to calculate the (NiAl + Ni5Al3)/Ni5Al3 phase boundary locations. The measured lattice parameters of Ni5Al3 phase formed at 823, 873, and 923 K indicated an increase in tetragonality of the phase with increasing nickel content.

  2. Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

    SciTech Connect

    Pereira, J.C.; Zambrano, J.C.; Afonso, C.R.M.; Amigó, V.

    2015-03-15

    Nickel-based superalloys such as NiCoCrAlY are widely used in high-temperature applications, such as gas turbine components in the energy and aerospace industries, due to their strength, high elastic modulus, and high-temperature oxidation resistance. However, the processing of these alloys is complex and costly, and the alloys are currently used as a bond coat in thermal barrier coatings. In this work, the effect of cold press and sintering processing parameters on the microstructure and mechanical properties of NiCoCrAlY alloy were studied using the powder metallurgy route as a new way to obtain NiCoCrAlYTa samples from a gas atomized prealloyed powder feedstock. High mechanical strength and adequate densification up to 98% were achieved. The most suitable compaction pressure and sintering temperature were determined for NiCoCrAlYTa alloy through microstructure characterization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy microanalysis (EDS) were performed to confirm the expected γ-Ni matrix and β-NiAl phase distribution. Additionally, the results demonstrated the unexpected presence of carbides and Ni–Y-rich zones in the microstructure due to the powder metallurgy processing parameters used. Thus, microhardness, nanoindentation and uniaxial compression tests were conducted to correlate the microstructure of the alloy samples with their mechanical properties under the different studied conditions. The results show that the compaction pressure did not significantly affect the mechanical properties of the alloy samples. In this work, the compaction pressures of 400, 700 and 1000 MPa were used. The sintering temperature of 1200 °C for NiCoCrAlYTa alloy was preferred; above this temperature, the improvement in mechanical properties is not significant due to grain coarsening, whereas a lower temperature produces a decrease in mechanical properties due to high porosity and

  3. Correlating Hardness Retention and Phase Transformations of Al and Mg Cast Alloys for Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Kasprzak, W.; Czerwinski, F.; Niewczas, M.; Chen, D. L.

    2015-03-01

    The methodology based on correlating hardness and phase transformations was developed and applied to determine the maximum temperature of hardness retention of selected Al-based and Mg-based alloys for aerospace applications. The Al alloys: A356, F357, and C355 experienced 34-66% reduction of the initial hardness, in comparison to 4-22% hardness reduction observed in Mg alloys: QE22A, EV31A, ZE41A, and WE43B after the same annealing to 450 °C. For Al alloys the hardness reduction showed a steep transition between 220 and 238 °C. In contrast, Mg alloys showed a gradual hardness decrease occurring at somewhat higher temperatures between 238 and 250 °C. The hardness data were correlated with corresponding phase transformation kinetics examined by dilatometer and electrical resistivity measurements. Although Mg alloys preserved hardness to higher temperatures, their room temperature tensile strength and hardness were lower than Al alloys. The experimental methodology used in the present studies appears to be very useful in evaluating the softening temperature of commercial Al- and Mg-based alloys, permitting to assess their suitability for high-temperature applications.

  4. Assessing the elastic properties and ductility of Fe-Cr-Al alloys from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Nurmi, E.; Wang, G.; Kokko, K.; Vitos, L.

    2016-01-01

    Fe-Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we use ab initio calculations based on density functional theory to study the elastic properties of Fe?Cr?Al? alloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe-Cr-Al alloys.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  6. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    SciTech Connect

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-08-01

    Iron-aluminide coatings were prepared by gas tungsten arc and gas metal arc weld-overlay techniques. All the weld overlays showed good oxidation/sulfidation behavior under isothermal conditions, including a gas metal arc deposit with only 21 at.% Al. A rapid degradation in corrosion resistance was observed under thermal cycling conditions when the initially grown scales spalled and the subsequent rate of reaction was not controlled by the formation of slowly growing aluminum oxides. Higher starting aluminum concentrations (>{approximately}25 at.%) are needed to assure adequate oxidation/sulfidation lifetimes of the weld overlays. A variety of stable oxides was added to a base Fe-28 at.% Al-2 % Cr alloy to assess the effect of these dopants on the oxidation behavior at 1200{degrees}C. A Y{sub 2}O{sub 3} dispersion improved the scale adhesion relative to a Zr alloy addition, but wasn`t as effective as it is in other alumina-forming alloys. Preliminary data for powder-processed Fe-28 at.% Al-2% Cr exposed to the H{sub 2}S-H{sub 2}-H{sub 2}O-Ar gas at 800{degrees}C showed that the oxidation/sulfidation rate was similar to that of many Fe{sub 3}Al alloys produced by ingot metallurgy routes.

  7. Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation

    SciTech Connect

    Catalini, David; Kaoumi, Djamel; Reynolds, Anthony; Grant, Glenn J.

    2015-07-09

    INCOLOY® MA956 is a ferritic Oxide Dispersion Strengthened (ODS) alloy. Three different oxides, Y4Al2O9, YAlO3 and Y3Al5O12, have been observed in this alloy. The oxide particle sizes range from just a few up to hundreds of nm and these particles are responsible of the high temperature mechanical strength of this alloy. Mechanically alloyed MA956 powder was consolidated via Friction Consolidation using three different processing conditions. As a result, three small compacts of low porosity were produced. The compacts exhibited a refined equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion.YAlO3 and Y3Al5O12 were identified in the compacts by Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of Y3Al5O12 precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS showing an aluminum enrichment trend as precipitates grow in size.

  8. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  9. Twin Roll Casting of Al-Mg Alloy with High Added Impurity Content

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Hari Babu, N.; Scamans, G. M.; Fan, Z.; O'Reilly, K. A. Q.

    2014-06-01

    The microstructural evolution during twin roll casting (TRC) and downstream processing of AA5754 Al alloy with high added impurity content have been investigated. Strip casts with a high impurity content resulted in coarse α-Al grains and complex secondary phases. The grain size and centerline segregation reduced significantly on the addition of Al-Ti-B grain refiner (GR). Coarse-dendrite arm spacing (DAS) "floating" grains are observed in the impure alloy (IA) with higher volume in the GR strips. Two-dimensional (2D) metallographic analysis of the as-cast strip suggests that secondary phases (Fe-bearing intermetallics and Mg2Si) are discrete and located at the α-Al cell/grain boundaries, while three-dimensional (3D) analysis of extracted particles revealed that they were intact, well interconnected, and located in interdendritic regions. Homogenizing heat treatment of the cast strip breaks the interconnective networks and modifies the secondary phases to a more equiaxed morphology. During rolling, the equiaxed secondary phases align along the rolling direction. X-ray diffraction (XRD) analysis suggests that α-Al(FeMn)Si and Mg2Si are the predominant secondary phases that are formed during casting and remain throughout the downstream processing of the GR-IA. The high-impurity sheet processed from TRC resulted in superior strength and ductility over the sheet processed from small book mold ingot casting. The current study has shown that the TRC process can tolerate higher impurity levels and produce formable sheets from the recycled aluminum for structural applications.

  10. Laser cladding of quasi-crystal-forming Al-Cu-Fe-Bi on an Al-Si alloy substrate

    NASA Astrophysics Data System (ADS)

    Biswas, Krishanu; Chattopadhyay, Kamanio; Galun, Rolf; Mordike, Barry L.

    2005-07-01

    We report here the results of an investigation aimed at producing coatings containing phases closely related to the quasi-crystalline phase with dispersions of soft Bi particles using an Al-Cu-Fe-Bi elemental powder mixture on Al-10.5 at. pct Si substrates. A two-step process of cladding followed by remelting is used to fine-tune the alloying, phase distribution, and microstructure. A powder mix of Al64Cu22.3Fe11.7Bi2 has been used to form the clads. The basic reason for choosing Bi lies in the fact that it is immiscible with each of the constituent elements. Therefore, it is expected that Bi will solidify in the form of dispersoids during the rapid solidification. A detailed microstructural analysis has been carried out by using the backscattered imaging mode in a scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructural features are described in terms of layers of different phases. Contrary to our expectation, the quasi-crystalline phase could not form on the Al-Si substrate. The bottom of the clad and remelted layers shows the regrowth of aluminum. The formation of phases such as blocky hexagonal Al-Fe-Si and a ternary eutectic (Al + CuAl2 + Si) have been found in this layer. The middle layer shows the formation of long plate-shaped Al13Fe4 along with hexagonal Al-Fe-Si phase growing at the periphery of the former. The formation of metastable Al-Al6Fe eutectic has also been found in this layer. The top layer, in the case of the as-clad track, shows the presence of plate-shaped Al13Fe4 along with a 1/1 cubic rational approximant of a quasi-crystal. The top layer of the remelted track shows the presence of a significant amount of a 1/1 cubic rational approximant. In addition, the as-clad and remelted microstructures show a fine-scale dispersion of Bi particles of different sizes formed during monotectic solidification. The remelting is found to have a strong effect on the size and distribution of Bi particles. The dry

  11. Precipitation and fracture behaviour of Fe-Mn-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Lee, Hu-Chul

    2013-12-01

    The effects of Al addition on the precipitation and fracture behaviour of Fe-Mn-Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L10 θ-MnNi to B2 Ni2MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α‧-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni2MnAl precipitates in the alloy containing 4.2 wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe-Mn-Ni-Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.

  12. Microstructural stability and creep properties of die casting Mg-4Al-4RE magnesium alloy

    SciTech Connect

    Rzychon, Tomasz; Kielbus, Andrzej; Cwajna, Jan; Mizera, Jaroslaw

    2009-10-15

    The AE44 (Mg-4Al-4RE) alloy was prepared by a hot-chamber die casting method. The microstructure, microstructural stability and creep properties at 175 deg. C were investigated. The microstructure was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and the Rietveld method. The results show that die cast AE44 magnesium alloy consists of {alpha}-Mg, Al{sub 11}RE{sub 3}, Al{sub 2}RE and Al{sub 2.12}RE{sub 0.88} phases. The Al{sub 11}RE{sub 3} phase is thermally stable at 175 deg. C whereas the metastable Al{sub 2.12}RE{sub 0.88} phase undergoes a transition into the equilibrium Al{sub 2}RE phase. The alloy investigated is characterized by good creep properties at temperatures of 175 deg. C and 200 {sup o}C.

  13. Superplastic formability of Al-Cu-Li alloy Weldalite (TM) 049

    NASA Technical Reports Server (NTRS)

    Ma, Bao-Tong; Pickens, Joseph R.

    1991-01-01

    Extensive research during the past decade shows that several aluminum lithium alloys can be processed to attain a microstructure that enables superplasticity. The high tensile stress of Al-Cu-Li alloy Weldalite (TM) 049 in the T4 and T6 tempers offers tremendous potential for attaining exceptional post-SPF (superplastic formability) properties. The used SPF material is Weldalite, which was shown to induce SPF behavior in other Al-Cu-Li alloys. The superplastic behavior and resulting post-SPF mechanical properties of this alloy, which was designed to be the next major structural alloy for space applications, were evaluated. The results indicate that Weldalite alloy does indeed exhibit excellent superplasticity over a wide range of temperatures and strain rates and excellent post-SPF tensile strength at various potential service temperatures.

  14. Wear characteristics of Al-AlN composites produced in-situ by nitrogenation

    NASA Astrophysics Data System (ADS)

    Pradhan, S.; Jena, S. K.; Patnaik, S. C.; Swain, P. K.; Majhi, J.

    2015-02-01

    In the present scenario most of the parts used in automobile and aerospace industries are made of composites. Aluminium metal has a very high strength to weight ratio. Al-AlN metal matrix composites have excellent mechanical properties like good wear resistance, high hardness and high strength to weight ratio which are obtained from low density of aluminium and high hardness and wear resistance of AlN. Therefore, use of Al-AlN MMC leads to advantages in automobile industries as it reduces fuel consumption and gives better structural strength. The composites can be produced ex-situ by introducing AlN as reinforcement into the metal matrix and in- situ by nitrogenation process. In the present process Al-AlN composites were fabricated by treating molten aluminium with a mixture of CaO and NH4Cl and held at temperature range at 750-930°C and then cast into a metal mould. Addition of CaO to NH4Cl is found to have a more pronounced effect as a nitrogenation agent in comparison with NH4Cl in the molten aluminium in the temperature range of 700- 1000°C. Castings of aluminium and Al-AlN composites were prepared by mixing different ratios of aluminium and NH4Cl, at different casting temperatures and holding time. Wear resistance and hardness of the samples were determined, and microstructure studies were carried out. The composite formed using higher amount of NH4Cl had higher hardness and wear resistance.

  15. Heterogeneous nucleation of the primary phase in the rapid solidification of Al-4.5wt%Cu alloy droplet

    NASA Astrophysics Data System (ADS)

    Maitre, A.; Bogno, A.-A.; Bedel, M.; Reinhart, G.; Henein, H.

    2015-06-01

    This paper reports on rapid solidification of Al-Cu alloys. A heterogeneous nucleation/growth model coupled with a thermal model of a falling droplet through a stagnant gas was developed. The primary undercooling as well as the number of nucleation points was compared with Al-Cu alloy droplets produced by Impulse Atomization (IA). Based on experimental results from Neutron Diffraction, secondary (eutectic) phases were obtained. Then, primary and secondary undercoolings were estimated using the metastable extensions of solidus and liquidus lines calculated by Thermo-Calc. Moreover, Synchrotron X-ray microtomography has been performed on Al-4.5wt%Cu droplets. The undercoolings are in good agreement. Results also evidence the presence of one nucleation point and are in agreement with the experimental observations.

  16. Structure, phase composition, and strengthening of cast Al-Ca-Mg-Sc alloys

    NASA Astrophysics Data System (ADS)

    Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Alekseeva, E. V.

    2016-02-01

    The structure and phase composition of Al-Ca-Mg-Sc alloys containing 0.3 wt % Sc, up to 10 wt % Ca, and up to 10 wt % Mg have been investigated in the cast state and state after heat treatment. It has been shown that only binary phases Al4Ca, Al3Sc, and Al3Mg2 can be in equilibrium with the aluminum solid solution. It has been found that the maximum strengthening effect caused by the precipitation of Al3Sc nanoparticles for all investigated alloys is attained after annealing at 300-350°C.

  17. Prediction of novel alloy phases of Al with Sc or Ta.

    PubMed

    Bilić, Ante; Gale, Julian D; Gibson, Mark A; Wilson, Nick; McGregor, Kathie

    2015-01-01

    Using the evolutionary optimization algorithm, as implemented in the USPEX crystal predictor program, and first principles total energy calculations, the compositional phase diagrams for Al-Sc and Al-Ta alloy systems at zero temperature and pressure have been calculated. In addition to the known binary intermetallic phases, new potentially stable alloys, AlSc3 and AlTa7, have been identified in the Al-poor region of the phase diagram. The dynamic and thermal stability of their lattices has been confirmed from the calculated vibrational normal mode spectra in the harmonic approximation. PMID:25950915

  18. Prediction of novel alloy phases of Al with Sc or Ta

    PubMed Central

    Bilić, Ante; Gale, Julian D.; Gibson, Mark A.; Wilson, Nick; McGregor, Kathie

    2015-01-01

    Using the evolutionary optimization algorithm, as implemented in the USPEX crystal predictor program, and first principles total energy calculations, the compositional phase diagrams for Al-Sc and Al-Ta alloy systems at zero temperature and pressure have been calculated. In addition to the known binary intermetallic phases, new potentially stable alloys, AlSc3 and AlTa7, have been identified in the Al-poor region of the phase diagram. The dynamic and thermal stability of their lattices has been confirmed from the calculated vibrational normal mode spectra in the harmonic approximation. PMID:25950915

  19. Synthesis of metastable phases in Al-Nb powders by mechanical alloying

    SciTech Connect

    Peng, Z.; Suryanarayana, C.; Froes, F.H. )

    1992-08-15

    Recently there have been many investigations on the synthesis and properties of transition metal trialuminides based on titanium, zirconium, vanadium, niobium and tantalum for use as structural materials in an elevated temperature environment. This interest is due to their high strength-to-density ratios, high melting points and excellent oxidation resistance. Amongst these, niobium trialuminide (NbAl{sub 3}) has a high melting point (1605{degrees} C), possesses adequate oxidation resistance (a result of the formation of a protective alumina over-layer and a density (4.54 g/cc) which is lower than that of advanced Ni{sub 3}Al-based compounds (7.6 g/cc). However, NbAl{sub 3} melts congruently and since it has an extremely limited homogeneity range, it is difficult to ensure that the chemistry falls in this desired narrow range. Further, due to the intrinsic brittleness, niobium aluminide ingots crack during solidification. Some of these problems can be overcome by producing the NbAl{sub 3} compound through the powder metallurgy route. This paper reports on the successful synthesis of homogeneous NbAl{sub 3} and amorphous phases by mechanical alloying starting from elemental powders.

  20. Selected fretting-wear-resistant coatings for Ti-6 pct Al-4 pct V alloy

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1985-01-01

    The ability of several wear-resistant coatings to reduce fretting in the Ti-6Al-4V alloy is investigated. The experimental apparatus and procedures for evaluating fretting in uncoated Ti-6Al-4V alloy and in the alloy with plasma-sprayed coatings, polymer-bonded coating, and surface treatments are described. The wear volume and wear rate for the alloys are measured and compared. It is concluded that Al2O3 with 13 percent TiO2, preoxidation and nitride surface treatments, and MoS2 sputtering result in wear-resistant surfaces; however, the polyimide coating is the most wear resistant coating in both dry and moist air, and it causes the least wear to the uncoated alloy surface.

  1. Directional solidification studies in Ni-Al alloys

    SciTech Connect

    Lee, Je-hyun

    1993-05-01

    Three solid phases are involved in the phase equilibria of the intermetallic compound Ni{sub 3}Al near its melting point, {beta}, {gamma}{prime}(Ni{sub 3}Al), and {gamma}. The generally-accepted phase diagram involves a eutectic reaction between {beta}{prime} and {gamma}, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the {beta} and {gamma}{prime} phases. The phase equilibria near Ni{sub 3}Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures tonned at the solidification front, and using diffusion couple experiments. These experiments show that eutectic forms between {beta} and {gamma}{prime} phases, as in the Schramm diagram. Growth and phase transformations of these three phases are also studied in the directional solidification experiments. Microstructure analysis shows that etching of Ni{sub 3}Al({gamma}{prime}) is very sensitive to small composition variations and crystallographic orientation changes. The eutectic solidification study confirms that the equilibrium eutectic is {gamma}{prime}+{beta}, and that the metastable {gamma}+{beta} eutectic might be also produced in this system according to the impurities, solidification rates, and composition variations.

  2. The effect of alloying additions on the high temperature deformation characteristics of Ti-48Al (at%) alloys

    SciTech Connect

    Sabinash, C.M.; Sastry, S.M.L.; Jerina, K.L.

    1995-05-01

    Addition of ternary and quaternary alloying elements at levels between one and three atomic percent increase the room temperature ductility of Ti-48Al (at%) based titanium aluminides. In this investigation the deformation characteristics of Ti-48Al-2X (X = Cr, Mn) alloys at temperatures of 1,200 C to 1,300 C and strain rates of 10{sup {minus}3}s{sup {minus}1} to 10{sup {minus}1}s{sup {minus}1} were studied and compared with the deformation characteristics of Ti-48Al using the same conditions. Three titanium aluminide alloys with target compositions of Ti-48Al, Ti-48Al-2Cr, and Ti-48Al-2Mn (at%) were induction skull melted and cast into 69.85 mm. diameter ingots. The cast ingots were hot isostatically pressed (HIPed) at 103.5 MPa, 1,177 C for 4 hours to close casting porosity and homogenize the alloy microstructure and composition. Cylindrical test specimens 10 mm dia by 15 mm height were excised by EDM from the ingot and were subjected to isothermal compression testing in air at 1,200--1,300 C and the effective strain rates of 10{sup {minus}3}--10{sup {minus}1}s{sup {minus}1}.

  3. New Fe-Co-Ni-Cu-Al-Ti Alloy for Single-Crystal Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Belyaev, I. V.; Bazhenov, V. E.; Moiseev, A. V.; Kireev, A. V.

    2016-03-01

    A new alloy intended for single-crystal permanent magnets has been suggested. The new alloy has been designed based on the well-known Fe-Co-Ni-Cu-Al-Ti system and contains to 1 wt % Hf. The alloy demonstrates an enhanced potential ability for single-crystal forming in the course of unidirectional solidification of ingot. Single-crystal permanent magnets manufactured from this alloy are characterized by a high level of magnetic properties. When designing the new alloy, computer simulation of the phase composition and calculations of solidification parameters of complex metallic systems have been performed using the Thermo-Calc software and calculation and experimental procedures based on quantitative metallographic analysis of quenched structures. After the corresponding heat treatment, the content of high-magnetic phase in the alloy is 10% higher than that in available analogous alloys.

  4. Spark plasma sintering of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy

    NASA Astrophysics Data System (ADS)

    Zúñiga, Alejandro; Ajdelsztajn, Leonardo; Lavernia, Enrique J.

    2006-04-01

    The microstructure and aging behavior of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy was studied. The nanocrystalline powders were produced by milling at liquid nitrogen temperature and then consolidated using spark plasma sintering (SPS). The microstructure after SPS consisted of a bimodal aluminum grain structure (coarse-grained and fine-grained regions), along with Al9FeNi and Al2CuMg particles dispersed throughout. The microstructure observed in the as-consolidated sample is rationalized on the basis of high current densities that are generated during sintering. Solution treatment and aging of the SPS Al-Cu-Mg-Fe-Ni-Sc sample resulted in softening instead of hardening. This observation can be explained by the reduced amount of Cu, Mg, and Si in solid solution available to form S' Al2CuMg due to the precipitation of Al7FeCu2 and Si-rich particles, and by the fact that rodlike S' Al2CuMg particles could only precipitate out in the coarse-grained regions, greatly decreasing their influence on the hardness. This lack of precipitation in the fine-grained region is argued to represent a new physical observation and is rationalized on the basis of physical and thermodynamic effects. The nanocrystalline SPS Al-Cu-Mg-Fe-Ni-Sc sample was also extremely thermally stable, retaining a fine-grained structure even after solution treatment at 530°C for 5 h. The observed thermal stability is rationalized on the basis of solute drag and Zener pinning caused by the impurities introduced during the cryomilling process.

  5. Consolidation and Forging Methods for a Cryomilled Al Alloy

    NASA Astrophysics Data System (ADS)

    Newbery, A. P.; Ahn, B.; Hayes, R. W.; Pao, P. S.; Nutt, S. R.; Lavernia, E. J.

    2008-09-01

    The method used to consolidate a cryogenically ball-milled powder is critical to the retention of superior strength along with acceptable tensile ductility in the bulk product. In this study, gas-atomized Al 5083 powder was cryomilled, hot vacuum degassed, and consolidated by hot isostatic pressing (HIP) or by quasi-isostatic (QI) forging to produce low-porosity billets. The billets were then forged, either at high strain rate (without a die) or quasi-isostatically, and subsequently hot rolled to produce three 6.5-mm-thick plates. Despite extended periods at elevated temperatures and differences between the consolidation/deformation methods, a similar predominantly ultrafine grain microstructure was obtained in all three plates. The plates possessed similar ultimate tensile strengths, about 50 pct greater than standard work-hardened Al 5083. However, in terms of fracture toughness, there were significant differences between the plates. Debonding at prior cryomilled powder particle surfaces was an important fracture mechanism for “HIPped” material, leading to low toughness for crack surfaces in the plane of the plate. This effect was minimized by the implementation of double QI forging, producing plate with good isotropic fracture toughness. The type of particle boundary deformation during forging and the influence of impurities appeared to be more important in determining fracture toughness than the presence of ˜10 vol pct coarser micron-sized grains.

  6. X-ray imaging and controlled solidification of Al-Cu alloys toward microstructures by design

    DOE PAGESBeta

    Clarke, Amy J.; Tourret, Damien; Imhoff, Seth D.; Gibbs, Paul J.; Fezzaa, Kamel; Cooley, Jason C.; Lee, Wah -Keat; Deriy, Alex; Patterson, Brian M.; Papin, Pallas A.; et al

    2015-01-30

    X-ray imaging, which permits the microscopic visualization of metal alloy solidification dynamics, can be coupled with controlled solidification to create microstructures by design. This x-ray image shows a process-derived composite microstructure being made from a eutectic Al-17.1 at.%Cu alloy by successive solidification and remelting steps.

  7. Fabrication and heat treatment of high strength Al-Cu-Mg alloy processed using selective laser melting

    NASA Astrophysics Data System (ADS)

    Zhang, Hu; Zhu, Haihong; Nie, Xiaojia; Qi, Ting; Hu, Zhiheng; Zeng, Xiaoyan

    2016-04-01

    The proposed paper illustrates the fabrication and heat treatment of high strength Al-Cu-Mg alloy produced by selective laser melting (SLM) process. Al-Cu-Mg alloy is one of the heat treatable aluminum alloys regarded as difficult to fusion weld. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers with a focused laser beam. The process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling. In this research, 3D Al-Cu-Mg parts with relative high density of 99.8% are produced by SLM from gas atomized powders. Room temperature tensile tests reveal a remarkable mechanical behavior: the samples show yield and tensile strengths of about 276 MPa and 402 MPa, respectively, along with fracture strain of 6%. The effect of solution treatment on microstructure and related tensile properties is examined and the results demonstrate that the mechanical behavior of the SLMed Al-Cu-Mg samples can be greatly enhanced through proper heat treatment. After T4 solution treatment at 540°C, under the effect of precipitation strengthening, the tensile strength and the yield strength increase to 532 MPa and 338 MPa, respectively, and the elongation increases to 13%.

  8. Nonequilibrium synthesis of NbAl3 and Nb-Al-V alloys by laser cladding. II - Oxidation behavior

    NASA Technical Reports Server (NTRS)

    Haasch, R. T.; Tewari, S. K.; Sircar, S.; Loxton, C. M.; Mazumder, J.

    1992-01-01

    Isothermal oxidation behaviors of NbAl3 alloy synthesized by laser cladding were investigated at temperatures between 800 and 1400 C, and the effect of vanadium microalloying on the oxidation of the laser-clad alloy was examined. The oxidation kinetics of the two alloys were monitored using thermal gravimetric weight gain data, and the bulk and surface chemistries were analyzed using XRD and XPS, respectively. It was found that NbAl3 did not form an exclusive layer of protective Al2O3. The oxidation products at 800 C were found to be a mixture of Nb2O5 and Al2O3. At 1200 C, a mixture of NbAlO4, Nb2O5, and Al2O3 formed; and at 1400 C, a mixture of NbAlO4, Al2O3, NbO2, NbO(2.432), and Nb2O5 formed. The addition of V led to a dramatic increase of the oxidation rate, which may be related to the formation of (Nb, V)2O5 and VO2, which grows in preference to protective Al2O3.

  9. High-strength, creep-resistant molybdenum alloy and process for producing the same

    DOEpatents

    Bianco, Robert; Buckman, Jr., R. William; Geller, Clint B.

    1999-01-01

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2-4% by volume (.about.1-4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T.sub.m of molybdenum.

  10. High-strength, creep-resistant molybdenum alloy and process for producing the same

    SciTech Connect

    Bianco, Robert; Buckman, Jr. William R.; Geller, Clint B.

    1997-12-01

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2--4% by volume ({approximately}1--4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T{sub m} of molybdenum.

  11. High-strength, creep-resistant molybdenum alloy and process for producing the same

    DOEpatents

    Bianco, R.; Buckman, R.W. Jr.; Geller, C.B.

    1999-02-09

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2--4% by volume (ca. 1--4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T{sub m} of molybdenum. 10 figs.

  12. Effect of Al Addition on ω Precipitation and Age Hardening of Ti-Al-Mo-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Li, Chenglin; Lee, Dong-Geun; Mi, Xujun; Ye, Wenjun; Hui, Songxiao; Lee, Yongtai

    2016-05-01

    The effect of Al addition on ω precipitation and age-hardening behavior of Ti-9.2Mo-2Fe and Ti-2Al-9.2Mo-2Fe alloy during aging treatment was investigated. The results showed that athermal and isothermal ω phase formation in Ti-2Al-9.2Mo-2Fe alloy was suppressed to a certain extent due to Al addition. In addition, a small amount of athermal ω phase was observed in the β matrix with a size of about ~5 nm during water quenching from above the β transus temperature for both alloys. Isothermal ω formation was also found during aging at temperatures ranging from 573 K to 773 K (300 °C to 500 °C) in both alloys, although it had a limited time of stability at 773 K (500 °C). The hardening due to isothermal ω precipitation exhibited no over-aging as long as ω phase existed in both alloys, and ω phase played a more important role in hardening than α phase. And the ω phase in 50 to 100 nm size exhibited the best hardening effect in Ti-9.2Mo-2Fe alloy. Similarly, α phase with 100 to 200 nm in length showed better hardening effects in Ti-2Al-9.2Mo-2Fe alloy. Both the alloys showed stronger age hardening at an intermediate temperature of 673 K (400 °C) and in the first aging stage at a higher temperature of 773 K (500 °C) due to the sufficiently fine size (50 nm), while they exhibited weaker age hardening at a lower temperature of 573 K (300 °C) and long period aging at a higher temperature of 773 K (500 °C) due to incomplete ω formation and/or coarsening of α phase. No over or peak aging stage was found at 573 K and 673 K (300 °C and 400 °C) during the aging for 72 hours, while the peak hardness values of both alloys aged at 773 K (500 °C) were obtained in the first stage of aging. The hardness of the alloys was very sensitive to size and volume fraction of ω phase, which depends on aging temperature, time, and composition of the involved alloys.

  13. Surface integrity after pickling and anodization of Ti-6Al-4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Vermesse, Eric; Mabru, Catherine; Arurault, Laurent

    2013-11-01

    The surface integrity of Ti-6Al-4V titanium alloy was studied at different stages of surface treatments, especially pickling and compact anodization, through surface characteristics potentially worsening fatigue resistance.

  14. Intergranular fracture in an Al-Li-Cu-Mg-Zr alloy

    SciTech Connect

    Wert, J.A.; Lumsden, J.B.

    1985-02-01

    The intergranular fracture characteristics of the Al-Li-Cu-Mg-Zr alloy is studied for underaged (170 C/4 hr) and overaged (230 C/4 hr) conditions. In addition, extensive intergranular fracture parallel to the tensile axis (delamination) in longitudinal tensile specimens is found together with equal concentration of K on all intergranular fracture surfaces independent of aging treatment. K is believed to promote intergranular fracture in Al-Li alloys similarly to a Na presence. 7 references.

  15. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  16. Some Experimental Results in the Rolling of Ni3Al Alloy

    NASA Technical Reports Server (NTRS)

    Shih, Hui-Ru; Sikka, Vinod K.

    1996-01-01

    This study examines several issues to understand the cold rollability of Ni3Al alloy. It finds that the cold rolling response of Ni3Al alloy (IC50) is very sensitive to the starting thickness. The segregation of elements is worse for the thicker casting as opposed to the thinner section. This is exemplified by the point that cast plus annealed pieces showed cracking at much larger reduction as opposed to the as-cast piece.

  17. Interdiffusion and Reaction between Zr and Al Alloys from 425 degrees to 625 degrees C

    SciTech Connect

    J. Dickson; L. Zhou; A. Ewh; M. Fu; D. D. Keiser, Jr.; Y. H. Sohn; A. Paz y Puente

    2014-06-01

    Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo nuclear fuels and Al cladding alloys. Interdiffusion and reactions between Zr and Al, Al-2 wt.% Si, Al-5 wt.% Si or AA6061 were investigated using solid-to-solid diffusion couples annealed in the temperature range of 425 degrees to 625 degrees C. In the binary Al and Zr system, the Al3Zr and Al2Zr phases were identified, and the activation energy for the growth of the Al3Zr phase was determined to be 347 kJ/mol. Negligible diffusional interactions were observed for diffusion couples between Zr vs. Al-2 wt.% Si, Al-5 wt.% Si and AA6061 annealed at or below 475 degrees C. In diffusion couples with the binary Al–Si alloys at 560 degrees C, a significant variation in the development of the phase constituents was observed including the thick t1 (Al5SiZr2) with Si content up to 12 at.%, and thin layers of (Si,Al)2Zr, (Al,Si)3Zr, Al3SiZr2 and Al2Zr phases. The use of AA6061 as a terminal alloy resulted in the development of both T1 (Al5SiZr2) and (Al,Si)3Zr phases with a very thin layer of (Al,Si)2Zr. At 560 degrees C, with increasing Si content in the Al–Si alloy, an increase in the overall rate of diffusional interaction was observed; however, the diffusional interaction of Zr in contact with multicomponent AA6061 with 0.4–0.8 wt.% Si was most rapid.

  18. Oxidation Behavior of Al2O3 Coating on Ti-25Al-12.5Nb Alloy

    NASA Astrophysics Data System (ADS)

    Małecka, J.

    2016-07-01

    The oxidation behavior of Al2O3 coating deposited on Ti-25Al-12.5Nb alloy by sol-gel method was investigated at 700 and 800 °C under isothermal oxidation conditions in air. At both temperatures, the coated samples exhibited reduced mass gain compared to uncoated alloy; at 700 °C rather insignificant differences were observed; however, at the temperature of 800 °C, the deposited coating strongly limits the mass gain of the test material. As a consequence of the isothermal oxidation a scale forms containing mainly TiO2 on the alloy surface of the uncoated alloy, while during the oxidation of the coated alloy the surface coating of Al2O3 dissociated and the initially compact Al2O3 coating dissolved and its place was taken by a porous scale. These coated samples displayed good resistance to oxidation in set conditions and no zones of dissolved oxygen and nitrogen were recorded. No spallation of the coated samples was observed.

  19. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  20. Durability Assessment of Various Gamma TiAl Alloys

    NASA Technical Reports Server (NTRS)

    Lerch, Brad; Draper, Sue; Pereira, Mike; Zhuang, Wyman

    2003-01-01

    Seven cast and one wrought gamma-alloys were ballistically impacted and tested under high cycle fatigue. The fatigue strength of each alloy was characterized as a function of initial flaw size and modeled using a threshold-based fracture mechanics approach.

  1. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-07-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  2. Dilute-As AlNAs Alloy for Deep-Ultraviolet Emitter

    PubMed Central

    Tan, Chee-Keong; Borovac, Damir; Sun, Wei; Tansu, Nelson

    2016-01-01

    The band structures of dilute-As AlNAs alloys with As composition ranging from 0% up to 12.5% are studied by using First-Principle Density Functional Theory (DFT) calculation. The energy band gap shows remarkable reduction from 6.19 eV to 3.87 eV with small amount of As content in the AlNAs alloy, which covers the deep ultraviolet (UV) spectral regime. A giant bowing parameter of 30.5 eV ± 0.5 eV for AlNAs alloy is obtained. In addition, our analysis shows that the crossover between crystal field split-off (CH) band and heavy hole (HH) bands occurs in the dilute-As AlNAs alloy with As-content of ~1.5%. This result implies the possibility of dominant transverse electric (TE)-polarized emission by using AlNAs alloy with dilute amount of As-content. Our findings indicate the potential of dilute-As AlNAs alloy as the new active region material for TE-polarized III-Nitride-based deep UV light emitters. PMID:26905060

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

    NASA Technical Reports Server (NTRS)

    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.

  4. Thermodynamic analysis of compatibility of several reinforcement materials with beta phase NiAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with beta phase NiAl alloys within the concentration range 40 to 50 at. percent Al have been analyzed from thermodynamic considerations at 1373 and 1573 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, beryllides, and silicides. Thermodynamic data for NiAl alloys have been reviewed and activity of Ni and Al in the beta phase have been derived at 1373 and 1573 K. Criteria for chemical compatibility between the reinforcement material and the matrix have been defined and several chemically compatible reinforcement materials have been defined.

  5. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  6. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  7. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  8. Permanent mold casting of titanium alloy Ti-6Al-4V

    SciTech Connect

    Sadayappan, M.; Sahoo, M.; Lavender, C.; paul.jablonski, P.D.

    2008-01-01

    A literature review indicated that data on the effect of various casting defects, such as inclusions and porosity, on the properties of titanium alloy castings were not readily available. This information is required to reduce the cost of fabricating titanium castings for potential automotive applications. To this end, a research project was initiated to develop data on the as-cast properties of titanium alloy Ti-6Al-4V (Ti64). Step plate castings with 3.2, 6.3, 13, and 25 mm thick steps were produced in a high-density graphite mold following melting in an induction furnace with water-cooled copper hearth. The mechanical properties were determined in the as-cast condition and were found to be close to the values reported in standards. Few casting defects such as inclusions and porosity were observed, and the loss of strength due to these defects is not significant. It is shown that titanium castings with good mechanical properties can be produced in high-density graphite molds.

  9. Characteristics of Friction Welding Between Solid Bar of 6061 Al Alloy and Pipe of Al-Si12CuNi Al Cast Alloy

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Sakaguchi, H.; Kusaka, M.; Kaizu, K.; Takahashi, T.

    2015-11-01

    This paper describes the characteristics of friction welding between a solid bar of 6061 Al alloy and a pipe of Al-Si12CuNi (AC8A) Al cast alloy. When the joint was made by a continuous drive friction welding machine (conventional method), the AC8A portion of the joint showed heavy deformation and the AA6061 showed minimal deformation. In particular, the joint could not be successfully made with following conditions, because AC8A pipe side crushed due to insufficient friction heat or high pressure: a short friction time such as 0.3 s, high friction pressure such as 100 MPa, or high forge pressure such as 150 MPa. The heavy deformation of AC8A side was caused by increasing friction torque during braking. To prevent braking deformation until rotation stops, a joint was made by a continuous drive friction welding machine that has an electromagnetic clutch. When the clutch was released, the relative speed between both specimens simultaneously decreased to zero. When the joint was made with friction pressure of 25 MPa, friction time of 0.3 s, and forge pressure of 125 MPa, the joining could be successfully achieved and that had approximately 16% efficiency. In addition, when the joint was made with friction pressure of 25 MPa, friction time of 0.7 s, and forge pressure of 125 MPa, it had approximately 54% efficiency. However, all joints showed the fracture between the traveled weld interface and the AC8A side, because the weld interface traveled in the longitudinal direction of AC8A side from the first contacted position of both weld faying surfaces. Hence, it was clarified that the friction welding between a solid bar of AA6061 and a cast pipe of AC8A was not desirable since the traveling phenomena of the weld interface were caused by the combination of the shapes of the friction welding specimens.

  10. Age hardening characteristics and mechanical behavior of Al-Cu-Li-Zr-In alloys

    NASA Technical Reports Server (NTRS)

    Wagner, John A.

    1989-01-01

    An investigation was conducted to determine the age-hardening response and cryogenic mechanical properties of superplastic Al-Cu-Li-Zr-In alloys. Two alloys with compositions Al-2.65Cu-2.17Li-O.13Zr (baseline) and Al-2.60Cu-2.34Li-0.16Zr-0.17In were scaled-up from 30 lb permanent mold ingots to 350 lb DC (direct chill) ingots and thermomechanically processed to 3.2 mm thick sheet. The microstructure of material which contained the indium addition was partially recrystallized compared to the baseline suggesting that indium may influence recrystallization behavior. The indium-modified alloy exhibited superior hardness and strength compared to the baseline alloy when solution-heat-treated at 555 C and aged at 160 C or 190 C. For each alloy, strength increased and toughness was unchanged or decreased when tested at - 185 C compared to ambient temperature. By using optimized heat treatments, the indium-modified alloy exhibited strength levels approaching those of the baseline alloy without deformation prior to aging. The increase in strength of these alloys in the T6 condition make them particularly attractive for superplastic forming applications where post-SPF parts cannot be cold deformed to increase strength.

  11. Analysis of heat-affected zone cracking in Ni/sub 3/Al alloys

    SciTech Connect

    Santella, M.L.; Maguire, M.C.; David, S.A.

    1986-01-01

    A key issue in the development of Ni/sub 3/Al for engineering applications is their weldability. Detailed welding studies have been done which show that iron-containing nickel aluminides are prone to heat-affected zone (HAZ) cracking. Hot ductility testing of these alloys has suggested that grain boundary cohesive strength controls high temperature ductility and the resistance to HAZ cracking. This analysis cannot, however, be used to explain the behavior of other aluminide alloys. The intention of this work is to more fully characterize the relationship between mechanical behavior and HAZ cracking susceptibility for Ni/sub 3/Al alloys.

  12. A surface analytical examination of Stringer particles in Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Larson, L. A.; Avalos-Borja, M.; Pizzo, P. P.

    1983-01-01

    A surface analytical examination of powder metallurgy processed Al-Li-Cu alloys was conducted. The oxide stringer particles often found in these alloys was characterized. Particle characterization is important to more fully understand their impact on the stress corrosion and fracture properties of the alloy. The techniques used were SIMS (Secondary Ion Mass Spectroscopy) and SAM (Scanning Auger Microscopy). The results indicate that the oxide stringer particles contain both Al and Li with relatively high Li content and the Li compounds may be associated with the stringer particles, thereby locally depleting the adjacent matrix of Li solute.

  13. Mechanical Responses of Superlight β-Based Mg-Li-Al-Zn Wrought Alloys under Resonance

    NASA Astrophysics Data System (ADS)

    Song, Jenn-Ming; Lin, Yi-Hua; Su, Chien-Wei; Wang, Jian-Yih

    2009-05-01

    To extend the application of lightweight Mg alloys in the automotive industry, this study suggests a β-based Mg-Li alloy (LAZ1110) with superior vibration fracture resistance by means of material design. In the cold-rolled state, a strengthened β matrix by the additions of Al and Zn, as well as intergranular platelike α precipitates, which are able to stunt the crack growth, contributes to a comparable vibration life with commercial Mg-Al-Zn alloys under a similar strain condition.

  14. Cryogenic mechanical properties of low density superplastically formable Al-Li alloys

    NASA Technical Reports Server (NTRS)

    Verzasconi, S. L.; Morris, J. W., Jr.

    1989-01-01

    The aerospace industry is considering the use of low density, superplastically formable (SPF) materials, such as Al-Li alloys in cryogenic tankage. SPF modifications of alloys 8090, 2090, and 2090+In were tested for strength and Kahn tear toughness. The results were compared to those of similar tests of 2219-T87, an alloy currently used in cryogenic tankage, and 2090-T81, a recently studied Al-Li alloy with exceptional cryogenic properties (1-9). With decreasing temperature, all materials showed an increase in strength, while most materials showed an increase in elongation and decrease in Kahn toughness. The indium addition to 2090 increased alloy strength, but did not improve the strength-toughness combination. The fracture mode was predominantly intergranular along small, recrystallized grains, with some transgranular fracture, some ductile rupture, and some delamination on large, unrecrystallized grains.

  15. Effect of Ca addition on the corrosion behavior of Mg-Al-Mn alloy

    NASA Astrophysics Data System (ADS)

    Yang, Jiang; Peng, Jian; Nyberg, Eric A.; Pan, Fu-sheng

    2016-04-01

    The microstructures and corrosion resistance of magnesium-5 wt% aluminum-0.3 wt% manganese alloys (Mg-Al-Mn) with different Ca additions (0.2-4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.

  16. Creep deformation of a two-phase TiAl/Ti[sub 3]Al lamellar alloy and the individual TiAl and Ti[sub 3]Al constituent phases

    SciTech Connect

    Bartholomeusz, M.F.; Wert, J.A. ); Qibin Yang )

    1993-08-01

    Two-phase TiAl/Ti[sub 3]Al alloys in which the constituent phases form a lamellar microstructure are reported to possess good combinations of low-temperature fracture toughness, tensile strength and fatigue resistance. However, information about the high-temperature creep properties of the two-phase TiAl/Ti[sub 3]Al alloys with lamellar microstructures (referred to as lamellar alloys in the remainder of the paper) is limited. Based on a simple rule of mixtures model of strength, it would be expected that the creep rates of the lamellar alloy would be between the creep rates of TiAl and Ti[sub 3]Al. In contrast to composite model predictions of strength, Polvani and coworkers found that the minimum creep rates of two duplex alloys, a [gamma]/[gamma][prime] nickel-base superalloy and NiAl/Ni[sub 2]AlTi, were significantly lower than the minimum creep rates of either of the constituent phases. They also reported that most dislocations in the two-phase NiAl/Ni[sub 2]AlTi alloy were contained within the semi-coherent interfacial dislocation networks between the two phases. Based on this observation they proposed that the creep rate is controlled by the rate at which dislocations moving through both phases are emitted and absorbed by the interphase dislocation networks. The greater strain hardening rate of the lamellar TiAl/Ti[sub 3]Al alloy suggests that it may exhibit lower steady-state creep rates that the individual constituent phases. The objective of the present study is to evaluate the creep properties of a TiAl/ Ti[sub 3]Al lamellar alloy and of the individual constituent phases. In this paper, the results of this investigation will be presented and compared with previously published results for this alloy system.

  17. Corrosion behavior of cast Ti-6Al-4V alloyed with Cu.

    PubMed

    Koike, Marie; Cai, Zhuo; Oda, Yutaka; Hattori, Masayuki; Fujii, Hiroyuki; Okabe, Toru

    2005-05-01

    It has recently been found that alloying with copper improved the inherently poor grindability and wear resistance of titanium. This study characterized the corrosion behavior of cast Ti-6Al-4V alloyed with copper. Alloys (0.9 or 3.5 mass % Cu) were cast with the use of a magnesia-based investment in a centrifugal casting machine. Three specimen surfaces were tested: ground, sandblasted, and as cast. Commercially pure titanium and Ti-6Al-4V served as controls. Open-circuit potential measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air + 10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was conducted in the same medium deaerated by N(2) + 10% CO(2). Polarization resistance (R(p)), Tafel slopes, and corrosion current density (I(corr)) were determined. A passive region occurred for the alloy specimens with ground and sandblasted surfaces, as for CP Ti. However, no passivation was observed on the as-cast alloys or on CP Ti. There were significant differences among all metals tested for R(p) and I(corr) and significantly higher R(p) and lower I(corr) values for CP Ti compared to Ti-6Al-4V or the alloys with Cu. Alloying up to 3.5 mass % Cu to Ti-6Al-4V did not change the corrosion behavior. Specimens with ground or sandblasted surfaces were superior to specimens with as-cast surfaces. PMID:15744719

  18. Synthesis and characterization of quasicrystals in an Al-Fe-W alloy

    SciTech Connect

    Mukhopadhyay, N.K.; Weatherly, G.C.; Embury, J.D. ); Lloyd, D.J. )

    1992-07-01

    After the discovery of quasicrystals (QC) in an al-14% Mn alloy, many attempts have been made to find alloy systems which form quasicrystals. Much effort has been devoted to the study of the Al-Fe system and its modification by Cu and other elements such as Mn, Cr, Mo and Ta to improve the ease of forming icosahedral quasicrystals (IQC). Although the Al-Fe system does not form IQC, the formation of a decagonal quasicrystal (DQC) being favored, these elements promote the IQC phase. This paper considers the Al-Fe system and its modification by W and demonstrates the existence of IQC in an Al-Fe-W ternary alloy.

  19. Long-term superelastic cycling at nano-scale in Cu-Al-Ni shape memory alloy micropillars

    SciTech Connect

    San Juan, J. Gómez-Cortés, J. F.

    2014-01-06

    Superelastic behavior at nano-scale has been studied along cycling in Cu-Al-Ni shape memory alloy micropillars. Arrays of square micropillars were produced by focused ion beam milling, on slides of [001] oriented Cu-Al-Ni single crystals. Superelastic behavior of micropillars, due to the stress-induced martensitic transformation, has been studied by nano-compression tests during thousand cycles, and its evolution has been followed along cycling. Each pillar has undergone more than thousand cycles without any detrimental evolution. Moreover, we demonstrate that after thousand cycles they exhibit a perfectly reproducible and completely recoverable superelastic behavior.

  20. Local formation of a Heusler structure in CoFe-Al alloys

    NASA Astrophysics Data System (ADS)

    Wurmehl, S.; Jacobs, P. J.; Kohlhepp, J. T.; Swagten, H. J. M.; Koopmans, B.; Maat, S.; Carey, M. J.; Childress, J. R.

    2011-01-01

    We systematically study the changes in the local atomic environments of Co in CoFe-Al alloys as a function of Al content by means of nuclear magnetic resonance. We find that a Co2FeAl Heusler type structure is formed on a local scale. The observed formation of a highly spin-polarized Heusler compound may explain the improved magnetotransport properties in CoFe-Al based current-perpendicular-to-the-plane spin-valves.

  1. Effect of composition on antiphase boundary energy in Ni3Al based alloys: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gorbatov, O. I.; Lomaev, I. L.; Gornostyrev, Yu. N.; Ruban, A. V.; Furrer, D.; Venkatesh, V.; Novikov, D. L.; Burlatsky, S. F.

    2016-06-01

    The effect of composition on the antiphase boundary (APB) energy of Ni-based L 12-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric γ' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3 d row. The elements from the left side of the 3 d row increase the APB energy of the Ni-based L 12-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed.

  2. An oxide dispersion strengthened Ni-W-Al alloy with superior high temperature strength

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1976-01-01

    An experimental oxide dispersion strengthened (ODS) alloy, WAZ-D, derived from the WAZ-20 composition was produced by the mechanical alloying process. Cast WAZ-20 is strengthened by both a high refractory metal content, and 70 volume percent of gamma prime. The ODS alloy WAZ-D was responsive to variables of alloy content, of attritor processing, of consolidation by extrusion, and of heat treatment. The best material produced had large highly elongated grains. It exhibited tensile strengths generally superior to a comparable cast alloy. The ODS alloy exhibited high temperature stress rupture life considerably superior to any known cast superalloy. Tensile and rupture ductility were low, as was intermediate temperature rupture life. Very low creep rates were noted and some specimens failed with essentially no third stage creep. Also the benefit derived from the oxide dispersion, far out-weighed that from the elongated microstructure alone.

  3. Microstructural stability of Fe-Cr-Al alloys at 450-550 °C

    NASA Astrophysics Data System (ADS)

    Ejenstam, Jesper; Thuvander, Mattias; Olsson, Pär; Rave, Fernando; Szakalos, Peter

    2015-02-01

    Iron-Chromium-Aluminium (Fe-Cr-Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe-Cr-Al alloys suffer from α-α‧ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe-Cr-Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe-10Cr-(4-8)Al alloys and a Fe-21Cr-5Al were thermally aged in the temperature interval of 450-550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe-Cr-Al system was developed. No phase separation was observed in the Fe-10Cr-(4-8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  4. Laser Weldability of High-Strength Al-Zn Alloys and Its Improvement by the Use of an Appropriate Filler Material

    NASA Astrophysics Data System (ADS)

    Enz, Josephin; Riekehr, Stefan; Ventzke, Volker; Huber, Norbert; Kashaev, Nikolai

    2016-06-01

    Heat-treatable Al-Zn alloys are promising candidates for use as structural lightweight materials in automotive and aircraft applications. This is mainly due to their high strength-to-density ratio in comparison to conventionally employed Al alloys. Laser beam welding is an efficient method for producing joints with high weld quality and has been established in the industry for many years. However, it is well known that aluminum alloys with a high Zn content or, more precisely, with a high (Zn + Mg + Cu) content are difficult to fusion weld due to the formation of porosity and hot cracks. The present study concerns the laser weldability of these hard-to-weld Al-Zn alloys. In order to improve weldability, it was first necessary to understand the reasons for weldability problems and to identify crucial influencing factors. Based on this knowledge, it was finally possible to develop an appropriate approach. For this purpose, vanadium was selected as additional filler material. Vanadium exhibits favorable thermophysical properties and, thereby, can improve the weldability of Al-Zn alloys. The effectiveness of the approach was verified by its application to several Al-Zn alloys with differing amounts of (Zn + Mg + Cu).

  5. Laser Weldability of High-Strength Al-Zn Alloys and Its Improvement by the Use of an Appropriate Filler Material

    NASA Astrophysics Data System (ADS)

    Enz, Josephin; Riekehr, Stefan; Ventzke, Volker; Huber, Norbert; Kashaev, Nikolai

    2016-04-01

    Heat-treatable Al-Zn alloys are promising candidates for use as structural lightweight materials in automotive and aircraft applications. This is mainly due to their high strength-to-density ratio in comparison to conventionally employed Al alloys. Laser beam welding is an efficient method for producing joints with high weld quality and has been established in the industry for many years. However, it is well known that aluminum alloys with a high Zn content or, more precisely, with a high (Zn + Mg + Cu) content are difficult to fusion weld due to the formation of porosity and hot cracks. The present study concerns the laser weldability of these hard-to-weld Al-Zn alloys. In order to improve weldability, it was first necessary to understand the reasons for weldability problems and to identify crucial influencing factors. Based on this knowledge, it was finally possible to develop an appropriate approach. For this purpose, vanadium was selected as additional filler material. Vanadium exhibits favorable thermophysical properties and, thereby, can improve the weldability of Al-Zn alloys. The effectiveness of the approach was verified by its application to several Al-Zn alloys with differing amounts of (Zn + Mg + Cu).

  6. Comparison of Tophet-A and Evanohm-R alloys for producing thin film nichrome resistors. Final report

    SciTech Connect

    Egert, C.M.; Boatman, J.

    1995-02-28

    The purported advantages of the Evanohm alloy were not observed in this preliminary study. Under the deposition conditions, the Evanohm alloy produced a greater variation in resistance of the as-deposited thin films than the Tophet alloy currently in use for producing resistors. A broader screening experiment for optimum operating conditions for the Evanohm wire is recommended.

  7. The effect of Zn on precipitation in Al-Mg-Si alloys

    NASA Astrophysics Data System (ADS)

    Saito, Takeshi; Wenner, Sigurd; Osmundsen, Elisa; Marioara, Calin D.; Andersen, Sigmund J.; Røyset, Jostein; Lefebvre, Williams; Holmestad, Randi

    2014-07-01

    Effects of addition of Zn (up to 1 wt%) on microstructure, precipitate structure and intergranular corrosion (IGC) in an Al-Mg-Si alloys were investigated. During ageing at 185 °C, the alloys showed modest increases in hardness as function of Zn content, corresponding to increased number densities of needle-shaped precipitates in the Al-Mg-Si alloy system. No precipitates of the Al-Zn-Mg alloy system were found. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the Zn atoms were incorporated in the precipitate structures at different atomic sites with various atomic column occupancies. Zn atoms segregated along grain boundaries, forming continuous film. It correlates to high IGC susceptibility when Zn concentration is ~1wt% and the materials in peak-aged condition.

  8. Blanch Resistant and Thermal Barrier NiAl Coating Systems for Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

    A method of forming an environmental resistant thermal barrier coating on a copper alloy is disclosed. The steps include cleansing a surface of a copper alloy, depositing a bond coat on the cleansed surface of the copper alloy, depositing a NiAl top coat on the bond coat and consolidating the bond coat and the NiAl top coat to form the thermal barrier coating. The bond coat may be a nickel layer or a layer composed of at least one of copper and chromium-copper alloy and either the bond coat or the NiAl top coat or both may be deposited using a low pressure or vacuum plasma spray.

  9. Porous Ti6Al4V alloys with enhanced normalized fatigue strength for biomedical applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Zhou, Lian

    2016-03-01

    In this paper, porous Ti6Al4V alloys for biomedical applications were fabricated by diffusion bonding of alloy meshes. The compression-compression fatigue behavior was studied. It results that porous Ti6Al4V alloys show enhanced normalized fatigue strength which is in the range of 0.5-0.55 at 10(6)cycles. The porosity has some effect on the absolute S-N curves but minor effect on the normalized S-N curves. The relationship between strain per cycle and number of cycles shows three distinct stages and the value of strain per cycle is constant in stage II. The reasons for the higher normalized fatigue strength of porous Ti6Al4V alloys are discussed based on the fatigue crack initiation and propagation. PMID:26706555

  10. An important factor powerfully influencing the Al Ni-based alloys' glass-forming ability

    NASA Astrophysics Data System (ADS)

    Bo, Zhang; Xiufang, Bian; Chunxia, Fu; Na, Han; Jiankun, Zhou; Weimin, Wang

    2005-12-01

    In order to get better glass-forming abilities (GFAs), Ni atoms are partially replaced by Cu and Co atoms in Al84Ni12Zr4 alloys. Thermal analysis shows that the reduced crystallization temperature Trx has no direct correlation with the GFA of the alloys. However, it is notable that prepeaks have been found in the total structure factors of the amorphous Al84Ni(12-x)Zr4Cux and Al84Ni(12-x)Zr4Cox alloys. In addition, the results prove that the intensity of the prepeaks influences the GFA powerfully. The amorphous alloys with larger intensity of the prepeak show better GFA. The influence of prepeaks on the GFA can be explained by the atomic configuration difference among the liquid, crystal and glass states.

  11. Solidification Behavior of gamma'-Ni3Al Containing Alloys in the Ni-Al-O System

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2007-01-01

    The chemical activities of Al and Ni in gamma(prime)-Ni3Al-containing systems were measured using the multi-cell Knudsen effusion-cell mass spectrometry technique (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K. From these measurements a better understanding of the equilibrium solidification behaviour of gamma(prime)-Ni3Al-containing alloys in the Ni-Al-O system was established. Specifically, these measurements revealed that (1) gamma(prime)-Ni3Al forms via the peritectiod reaction, gamma + Beta (+ A12O3) = gamma (prime) (+ Al2O3), at 1633 +/- 1 K, (2) the {gamma + Beta + Al2O3} phase field is stable over the temperature range 1633 through 1640 K, and (3) equilibrium solidification occurs by the eutectic reaction, L (+ Al2O3) = gamma + Beta (+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%Al (at an unknown oxygen content). When projected onto the Ni-Al binary, this behaviour is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(prime)-Ni3Al phase field.

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

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2007-01-01

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

  13. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  14. Improve sensitization and corrosion resistance of an Al-Mg alloy by optimization of grain boundaries.

    PubMed

    Yan, Jianfeng; Heckman, Nathan M; Velasco, Leonardo; Hodge, Andrea M

    2016-01-01

    The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Understanding sensitization requires the review of grain boundary character on the precipitation process which can assist in developing and designing alloys with improved corrosion resistance. This study shows that the degree of precipitation in Al-Mg alloy is dependent on grain boundary misorientation angle, adjacent grain boundary planes and grain boundary types. The results show that the misorientation angle is the most important factor influencing precipitation in grain boundaries of the Al-Mg alloy. Low angle grain boundaries (≤15°) have better immunity to precipitation and grain boundary acid attack. High angle grain boundaries (>15°) are vulnerable to grain boundary acid attack. Grain boundaries with adjacent plane orientations near to {100} have potential for immunity to precipitation and grain boundary acid attack. This work shows that low Σ (Σ ≤ 29) coincident site lattice (CSL) grain boundaries have thinner β precipitates. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced. This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering. PMID:27230299

  15. Improve sensitization and corrosion resistance of an Al-Mg alloy by optimization of grain boundaries

    PubMed Central

    Yan, Jianfeng; Heckman, Nathan M.; Velasco, Leonardo; Hodge, Andrea M.

    2016-01-01

    The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Understanding sensitization requires the review of grain boundary character on the precipitation process which can assist in developing and designing alloys with improved corrosion resistance. This study shows that the degree of precipitation in Al-Mg alloy is dependent on grain boundary misorientation angle, adjacent grain boundary planes and grain boundary types. The results show that the misorientation angle is the most important factor influencing precipitation in grain boundaries of the Al-Mg alloy. Low angle grain boundaries (≤15°) have better immunity to precipitation and grain boundary acid attack. High angle grain boundaries (>15°) are vulnerable to grain boundary acid attack. Grain boundaries with adjacent plane orientations near to {100} have potential for immunity to precipitation and grain boundary acid attack. This work shows that low Σ (Σ ≤ 29) coincident site lattice (CSL) grain boundaries have thinner β precipitates. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced. This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering. PMID:27230299

  16. Improve sensitization and corrosion resistance of an Al-Mg alloy by optimization of grain boundaries

    NASA Astrophysics Data System (ADS)

    Yan, Jianfeng; Heckman, Nathan M.; Velasco, Leonardo; Hodge, Andrea M.

    2016-05-01

    The sensitization and subsequent intergranular corrosion of Al-5.3 wt.% Mg alloy has been shown to be an important factor in stress corrosion cracking of Al-Mg alloys. Understanding sensitization requires the review of grain boundary character on the precipitation process which can assist in developing and designing alloys with improved corrosion resistance. This study shows that the degree of precipitation in Al-Mg alloy is dependent on grain boundary misorientation angle, adjacent grain boundary planes and grain boundary types. The results show that the misorientation angle is the most important factor influencing precipitation in grain boundaries of the Al-Mg alloy. Low angle grain boundaries (≤15°) have better immunity to precipitation and grain boundary acid attack. High angle grain boundaries (>15°) are vulnerable to grain boundary acid attack. Grain boundaries with adjacent plane orientations near to {100} have potential for immunity to precipitation and grain boundary acid attack. This work shows that low Σ (Σ ≤ 29) coincident site lattice (CSL) grain boundaries have thinner β precipitates. Modified nitric acid mass loss test and polarization test demonstrated that the global corrosion resistance of sputtered Al-Mg alloy is enhanced. This may be attributed to the increased fractions of low Σ (Σ ≤ 29) CSL grain boundaries after sputtering.

  17. Influence of testing environment on the room temperature ductility of FeAl alloys

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Nathal, M. V.

    1990-01-01

    The effects of testing atmospheres (air, O2, N2, and vacuum) on the room-temperature ductility of Fe-40Al, Fe-40Al-0.5B, and Fe-50Al alloys were investigated. The results confirmed the decrease in room-temperature ductility of Fe-rich FeAl alloys by the interaction of the aluminide with water vapor, reported previously by Liu et al. (1989). The highest ductilities were measured in the atmosphere with the lowest moisture levels, i.e., in vacuum. It was found that significant ductility is still restricted to Fe-rich alloys (Fe-40Al), as the Fe-50Al alloy remained brittle under all testing conditions. It was also found that slow cooling after annealing was beneficial, and the effect was additive to the environmental effect. The highest ductility measurements in this study were 9 percent elongation in furnace-cooled Fe-40Al and in Fe-40Al-0.5B, when tested in vacuum.

  18. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  19. Grain Refinement of Freeform Fabricated Ti-6Al-4V Alloy Using Beam/Arc Modulation

    NASA Technical Reports Server (NTRS)

    Mitzner, Scott; Liu, Stephen; Domack, Marcia S.; Hafley, Robert A.

    2012-01-01

    Grain refinement can significantly improve the mechanical properties of freeform-fabricated Ti-6Al-4V alloy, promoting increased strength and enhanced isotropy compared with coarser grained material. Large beta-grains can lead to a segregated microstructure, in regard to both alpha-phase morphology and alpha-lath orientation. Beam modulation, which has been used in conventional fusion welding to promote grain refinement, is explored in this study for use in additive manufacturing processes including electron beam freeform fabrication (EBF(sup 3)) and gas-tungsten arc (GTA) deposition to alter solidification behavior and produce a refined microstructure. The dynamic molten pool size induced by beam modulation causes rapid heat flow variance and results in a more competitive grain growth environment, reducing grain size. Consequently, improved isotropy and strength can be achieved with relatively small adjustments to deposition parameters.

  20. REVERSIBLE AND IRREVERSIBLE PASSIVATION OF A LA-NI-AL ALLOY

    SciTech Connect

    Shanahan, K.; Klein, J.

    2009-06-25

    This paper seeks to explore some of the effects of passivating a LaNi{sub 4.25}Al{sub 0.75} sample by air oxidation under controlled conditions. Passivation of this metal hydride alloy seems to have two distinct regimes. The first occurs with air oxidation at 80 C and 20 C. It is characterized by complete reversibility upon hydrogen readsorption, although said readsorption is hindered substantially at room temperature, requiring the material to be heated to produce the reactivation. The second regime is illustrated by 130 C air oxidation and is characterized by irreversible loss of hydrogen absorption capacity. This passivation does not hinder hydrogen readsorption into the remaining hydride material.

  1. Effect of La2O3 Nanoparticles on the Brazeability, Microstructure, and Mechanical Properties of Al-11Si-20Cu Alloy

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Roh, Myung Hwan; Jung, Jae Pil

    2016-06-01

    The Al-11Si-20Cu brazing alloy and its ex situ composite with the content ranging from 0.01 to 0.05 wt.% of La2O3 are produced by electromagnetic induction-cum-casting route. The brazeability of the alloy and composite samples are tested using the spreading technique according to JIS Z-3197 standard. The mechanical properties such as filler microhardness, tensile shear strength, and elongation of the brazed joints are evaluated in the as-brazed condition. It is reported that incorporation of an optimal amount of 0.05 wt.% of hard La2O3 nanoparticles in the Al-Si-Cu matrix inhibits the growth of the large CuAl2 intermetallic compounds (IMCs) and Si particles. As a consequence, the composite filler brazeability, microhardness, joint tensile shear strength, and elongation are improved significantly compared to those of monolithic Al-11Si-20Cu alloy.

  2. Apatite deposition and collagen coating effects in Ti-Al-V and Ti-Al-Nb alloys

    NASA Astrophysics Data System (ADS)

    Choi, Y.; Hong, S. I.

    2014-12-01

    The biomimetic deposition rate of apatite for Ti-6Al-4V was found to be greater than that for Ti-6Al-7Nb in regular 1 × Modified SBF. The coating of collagen was found to enhance the biomimetic deposition of apatite on Ti-6Al-4V and Ti-6Al-7Nb. The nucleation and growth of the apatite deposition layer was faster on collagen coated Ti alloys. An interesting observation is that the granular structure became less clear and the nodular boundary became obscure in apatite deposited on the collagen-coated Ti alloys. The ill-defined granular structure may be associated with the presence of more amorphous calcium phosphate. The morphology of apatite nodules was found to be modified by collagen coating and collagen addition.

  3. Preparation and properties of Al-alloy coconut shell char particulate composites

    NASA Astrophysics Data System (ADS)

    Murali, T. P.; Surappa, M. K.; Rohatgi, P. K.

    1982-09-01

    A technique to produce cast Al-11.8 pct Si alloy composites containing up to 40 vol pct (15 pct by weight) dispersions of 125 μm size coconut shell char particles is described. The technique consists of stirring shell char particles into the vortex created by mechanical stirring of melts and subsequent casting of composite melts in suitable molds. The composite melts were also pressure die cast at a pressure of 100 MPa into cylindrical castings. The incorporation of large volume fraction of shell char particles is aided by (a) preheating of the particles to about 500 ° to 600 ° for two hours before introduction into the melts, and (b) alloying of Al-11.8 pct Si melts with 3 to 6 pct Mg. Electron Probe Micro Analysis (EPMA) analysis indicated an Mg enriched region around dispersed char particles in the composite indicating that prealloying with Mg probably improves wetting between char particles and the melt. Dispersions of 15 pct wt of char particles lead to decreases in hardness (from 85 BHN to 55 BHN), compression strength (from 542.30 MPa to 218.68 MPa), U. T. S., (from 164.16 MPa to 63.75 MPa), and electrical conductivity (from 27.8 pct IACS to 11 pct IACS). However, since these decreases are accompanied by a decrease in density, specific strength values of Al-11.8 pct-shell char composites are adequate for a variety of applications. Adhesive wear rates and friction coefficient values at low sliding speeds (0.56 m per second, and at loads of 10 N and 60 N) decrease with increase in wt pct of char particles under dry conditions.

  4. Preparation and properties of Al-alloy coconut shell char particulate composites

    NASA Astrophysics Data System (ADS)

    Murali, T. P.; Surappa, M. K.; Rohatgi, P. K.

    1991-12-01

    A technique to produce cast Al-11.8 pct Si alloy composites containing up to 40 vol pct (15 pct by weight) dispersions of 125 µm size coconut shell char particles is described. The technique consists of stirring shell char particles into the vortex created by mechanical stirring of melts and subsequent casting of composite melts in suitable molds. The composite melts were also pressure die cast at a pressure of 100 MPa into cylindrical castings. The incorporation of large volume fraction of shell char particles is aided by (a) preheating of the particles to about 500 ‡C to 600 ‡C for two hours before introduction into the melts, and (b) alloying of Al-11.8 pct Si melts with 3 to 6 pct Mg. Electron Probe Micro Analysis (EPMA) analysis indicated an Mg enriched region around dispersed char particles in the composite indicating that prealloying with Mg probably improves wetting between char particles and the melt. Dispersions of 15 pct wt of char particles lead to decreases in hardness (from 85 BHN to 55 BHN), compression strength (from 542.30 MPa to 218.68 MPa), U. T. S., (from 164.16 MPa to 63.75 MPa), and electrical conductivity (from 27.8 pct I ACS to 11 pct I ACS). However, since these decreases are accompanied by a decrease in density, specific strength values of Al-11.8 pct-shell char composites are adequate for a variety of applications. Adhesive wear rates and friction coefficient values at low sliding speeds (0.56 m per second, and at loads of 10 N and 60 N) decrease with increase in wt pct of char particles under dry conditions.

  5. Magnetic properties of ultrasoft-nanocomposite FeAlSiBNbCu alloys

    NASA Astrophysics Data System (ADS)

    Todd, I.; Tate, B. J.; Davies, H. A.; Gibbs, M. R. J.; Kendall, D.; Major, R. V.

    2000-06-01

    The effects of up to 10 at% substitution of Fe by Al on the microstructure and DC and AC magnetic properties of nanocrystalline FeSiBCuNb alloy ribbon are summarised and analysed. The minimum DC H c developed during annealing decreases by 40% for 2 at% Al (to 0.3 A/m) and remains roughly constant for larger Al contents. The largest peak value of μ 0.4 at 50 Hz also corresponds to 2 at% Al. The best frequency response for μ 0.4 occurs for 6 at% Al while there was no improvement in AC power loss behaviour over the 0% Al alloy. The improvements in DC H c and AC μ 0.4 are ascribed to a reduction in K 1 of the Fe-Si-based nanocrystallites by the introduction of Al.

  6. Recovery of Li from alloys of Al-Li and Li-Al using engineered scavenger compounds

    SciTech Connect

    Riley, W.D.; Jong, B.W.; Collins, W.K.; Gerdemann, S.J.

    1992-01-01

    The invention relates to a process for obtaining Li metal selectively recovered from Li-Al or Al-Li alloy scrap by: (1) removing Li from aluminum-lithium alloys at temperatures between about 400 C-750 C in a molten salt bath of KC1-LiCl using lithium titanate (Li2O.3TiO2) as an engineered scavenger compound (ESC); and (2) electrodepositing of Li from the loaded ESC to a stainless steel electrode. By use of the second step, the ESC is prepared for reuse. A molten salt bath is required in the invention because of the inability of molten aluminum alloys to wet the ESC.

  7. Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.; Alexander, D.J.

    1997-04-01

    A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductility and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.

  8. Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Grant, P. S.; O'Reilly, K. A. Q.

    2016-04-01

    The evolution of iron (Fe) bearing intermetallics (Fe-IMCs) during direct chill casting and homogenization of a grain-refined 6063 aluminum-magnesium-silicon (Al-Mg-Si) alloy has been studied. The as-cast and homogenized microstructure contained Fe-IMCs at the grain boundaries and within Al grains. The primary α-Al grain size, α-Al dendritic arm spacing, IMC particle size, and IMC three-dimensional (3D) inter-connectivity increased from the edge to the center of the as-cast billet; both α c-AlFeSi and β-AlFeSi Fe-IMCs were identified, and overall α c-AlFeSi was predominant. For the first time in industrial billets, the different Fe-rich IMCs have been characterized into types based on their 3D chemistry and morphology. Additionally, the role of β-AlFeSi in nucleating Mg2Si particles has been identified. After homogenization, α c-AlFeSi predominated across the entire billet cross section, with marked changes in the 3D morphology and strong reductions in inter-connectivity, both supporting a recovery in alloy ductility.

  9. Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Grant, P. S.; O'Reilly, K. A. Q.

    2016-06-01

    The evolution of iron (Fe) bearing intermetallics (Fe-IMCs) during direct chill casting and homogenization of a grain-refined 6063 aluminum-magnesium-silicon (Al-Mg-Si) alloy has been studied. The as-cast and homogenized microstructure contained Fe-IMCs at the grain boundaries and within Al grains. The primary α-Al grain size, α-Al dendritic arm spacing, IMC particle size, and IMC three-dimensional (3D) inter-connectivity increased from the edge to the center of the as-cast billet; both α c-AlFeSi and β-AlFeSi Fe-IMCs were identified, and overall α c-AlFeSi was predominant. For the first time in industrial billets, the different Fe-rich IMCs have been characterized into types based on their 3D chemistry and morphology. Additionally, the role of β-AlFeSi in nucleating Mg2Si particles has been identified. After homogenization, α c-AlFeSi predominated across the entire billet cross section, with marked changes in the 3D morphology and strong reductions in inter-connectivity, both supporting a recovery in alloy ductility.

  10. Corrosion performance of Fe-Cr-Al and Fe aluminide alloys in complex gas environments

    SciTech Connect

    Natesan, K.; Johnson, R.N.

    1995-05-01

    Alumina-forming structural alloys can offer superior resistance to corrosion in the presence of sulfur-containing environments, which are prevalent in coal-fired fossil energy systems. Further, Fe aluminides are being developed for use as structural materials and/or cladding alloys in these systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. In addition, surface coatings of Fe aluminide are being developed to impart corrosion resistance to structural alloys. This paper describes results from an ongoing program that is evaluating the corrosion performance of alumina-forming structural alloys, Fe-Al and Fe aluminide bulk alloys, and Fe aluminide coatings in environments typical of coal-gasification and combustion atmospheres. Experiments were conducted at 650-1000{degrees}C in simulated oxygen/sulfur gas mixtures. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HCl-containing gases. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales and to determine the modes of corrosion degradation that occur in the materials when they are exposed to S/Cl-containing gaseous environments.

  11. Effects of small amount of additional elements on control of interstitial impurities and mechanical properties of V?4Cr?4Ti?Si?Al?Y alloys

    NASA Astrophysics Data System (ADS)

    Chuto, Toshinori; Satou, Manabu; Hasegawa, Akira; Abe, Katsunori; Muroga, Takeo; Yamamoto, Norikazu

    2004-03-01

    In order to improve the mechanical properties of low activation vanadium alloys for fusion structural applications, effects of small addition of Si, Al and Y on the control of interstitial impurities (O, C and N) during the fabrication process were examined for several V-4Cr-4Ti-Si-Al-Y alloys produced by the levitation melting method. Charpy impact tests and tensile tests were carried out for five kinds of V-4Cr-4Ti-Si-Al-Y alloys using miniaturized specimens for the purpose of evaluating the effects of these elements on mechanical properties. Oxygen concentration decreased almost linearly with increasing loss of yttrium during melting. This oxygen reduction with yttrium loss during the melting process may have been achieved by two types of mechanisms, they are, (i) suppression of oxygen penetration into the molten materials from the environment and (ii) getting of oxygen from the matrix by forming Y 2O 3, which floats to the surface during the melting. There was no effect of Si and Al addition to control the concentration of interstitial impurities. V-4Cr-4Ti-0.1Si-0.1Al-0.1Y alloy showed the best impact properties out of the alloys investigated. Upper-shelf energy of the alloys decreased with increasing yttrium content. High number density of coarse inclusions containing yttrium could cause the degradation of impact properties, though they hardly affect tensile properties of the alloys. Even at higher yttrium contents, V-4Cr-4Ti-Y alloys without addition of Si and Al showed relatively high upper-shelf energy.

  12. Wear and Friction Characteristics of AlN/Diamond-Like Carbon Hybrid Coatings on Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Nakamura, Masashi; Kubota, Sadayuki; Suzuki, Hideto; Haraguchi, Tadao

    2015-10-01

    The use of diamond-like carbon (DLC) coatings has the potential to greatly improve the wear resistance and friction of aluminum alloys, but practical application has so far been limited by poor adhesion due to large difference in hardness and elasticity between the two materials. This study investigates the deposition of DLC onto an Al-alloy using an intermediate AlN layer with a graded hardness to create a hybrid coating. By controlling the hardness of the AlN film, it was found that the wear life of the DLC film could be improved 80-fold compared to a DLC film deposited directly onto Al-alloy. Furthermore, it was demonstrated through finite element simulation that creating a hardness gradient in the AlN intermediate layer reduces the distribution of stress in the DLC film, while also increasing the force of adhesion between the DLC and AlN layers. Given that both the DLC and AlN films were deposited using the same unbalanced magnetron sputtering method, this process is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components commonly used within the aerospace and automotive industries.

  13. Recovery and recrystallisation in mechanically alloyed and annealed, legacy, FeCrAlY ODS alloy precursor powders

    NASA Astrophysics Data System (ADS)

    Dawson, K.; Rao, A.; Tatlock, G. J.; Jones, A. R.

    2015-08-01

    This study presents findings related to the recrystallisation behaviour in Mechanically Alloyed (MA) and annealed powders of legacy commercial Oxide Dispersion Strengthened (ODS) FeCrAl alloys PM2000, MA956 and ODM751. Annealing of as-MA ODS alloy powders at temperatures ≥ 800 °C induced primary recrystallisation. The volume fraction (Vf) recrystallised increased with higher annealing temperatures in the range studied (∼800-1050 °C). However, low temperature (650 °C) recovery reduced the subsequent kinetics of recrystallisation in PM2000 alloy. Transmission Electron Microscopy (TEM) analysis of annealed PM2000 and MA956 alloy powders indicates that precipitation of nano-particulate Y-Al-O phases begins at temperatures as low as 650 °C and microstructural changes during annealing of ODS powders involved interactions between nano-particle formation and recovery/recrystallisation processes. High number densities (NV > 1023 m-3) of coherent nano-precipitates were identified in both recovered and recrystallised regions of powder particles. These formed over a range of temperatures used in the consolidation processing of ODS alloys. The orientation relationship between nano-particles and the matrix was identical in both recovered and recrystallised grains, indicating that particles were dissolved at recrystallising interfaces and subsequently reprecipitated. Examination and comparison of as-MA and annealed powder specimens suggests that nuances in the manufacturing of these three, nominally similar, alloys leads to differences in recovery/recrystallisation behaviour, which may influence microstructure and, ultimately, properties in the final product form.

  14. The oxidation behavior of Ni-Cr-Al-2ThO2 alloys at 1093 and 1204 C.

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wilcox, B. A.; Stringer, J.

    1972-01-01

    A pack diffusion process has been developed which permits the introduction of nearly 6 wt % Al into solid solution in the near surface region of TDNiCr (Ni-20 wt % Cr-2 vol % ThO2) and Ni-20Cr. Alumina scales, adherent under cyclic heating and cooling conditions, were produced on TDNiCr-5.86Al upon exposure to an environment of 1330 N/sq m (10 torr) or 101,000 N/sq m (760 torr) air at temperatures of 1093 and 1204 C. While the same oxidation kinetics were observed in isothermal tests for Ni-14.6Cr-5.86Al as were obtained for the TDNiCr-5.86Al, the dispersion-strengthened alloy exhibited superior oxide scale adhesion during cyclic testing. At 1204 C, continuous weight gains were observed under all test conditions for TDNiCr-5.86Al, in contrast to the weight loss with time which occurred several hours after exposure of TDNiCr to an oxidizing environment. TDNiCr with an initial aluminum surface concentration of 4.95 wt % has nearly comparable oxidation resistance to the TDNiCr-5.86Al alloy.

  15. Understanding the Origins of Intergranular Corrosion in Copper-Containing Al-Mg-Si Alloys

    NASA Astrophysics Data System (ADS)

    Kairy, Shravan K.; Alam, Talukder; Rometsch, Paul A.; Davies, Chris H. J.; Banerjee, Raj; Birbilis, Nick

    2016-03-01

    A definitive understanding of the mechanism of intergranular corrosion (IGC) in under-aged (UA) Cu-containing Al-Mg-Si alloys has not been clear to date. The grain boundary microstructure and chemistry in an UA Cu-containing Al-Mg-Si alloy were characterized by coupling atom probe tomography and scanning transmission electron microscopy. The rapid formation of an ultra-thin wetting Cu layer and discrete Q-phase (Al4Cu2Mg8Si7) precipitates along the grain boundaries, and a precipitate-free zone adjacent to the grain boundaries in the UA condition contribute to IGC.

  16. Microstructure and wear resistance of Al-SiC composites coatings on ZE41 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Rodrigo, P.; Campo, M.; Torres, B.; Escalera, M. D.; Otero, E.; Rams, J.

    2009-08-01

    Al and Al-SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesium alloy substrates. Coatings with controlled reinforcement rate of up to 23 vol.% were obtained by spraying mixtures containing aluminium powder with up to 50 vol.% SiC particles. The coatings were sprayed on the magnesium alloy with minor degradation of its microstructure or mechanical properties. The coatings were compacted to improve their microstructure and protective behaviour. The wear behaviour of these coatings has been tested using the pin-on-disk technique and the reinforced coatings provided 85% more wear resistance than uncoated ZE41 and 400% more than pure Al coatings.

  17. Electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys for biomedical applications.

    PubMed

    Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu

    2016-05-01

    The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials. PMID:26952395

  18. Mechanical properties of Al-60 Pct SiC p composites alloyed with Mg

    NASA Astrophysics Data System (ADS)

    Ahlatci, H.; Çimenoğlu, H.; Candan, E.

    2004-07-01

    In the present work, the effect of an Mg addition on the mechanical properties of the Al-60 vol pct SiC p composites were investigated by uniaxial compression, three-point bending, impact and wear tests (composite-metal and composite-abrasive types). The composites were produced by the pressure-infiltration technique. The composition of the Al matrix was varied between 0 and 8 pct Mg. The mean diameter of the SiC particles was 23 µm. Upon addition of Mg, Mg2Si precipitated in the matrix and the amount of the porosity dramatically decreased. Mg-alloyed-matrix composites exhibited higher strength, lower toughness, and higher wear resistance than pure-Al-matrix composites. During composite-metal wear testing, wear progressed in two sequential periods (running-in and steady state). Weight loss during wear testing decreased with increasing Mg content of the matrix. The degree of improvement of abrasive resistance depended on the abrasive-grain size. Above 200 °C, the composite-abrasive wear resistance decreased with increasing test temperature for all materials.

  19. Investigation of the Microstructure of Joints of Aluminum Alloys Produced by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Kolubaev, E. A.

    2015-02-01

    Special features of the microstructure of joints of aluminum-magnesium and aluminum-copper alloys produced by friction stir welding are analyzed. It is demonstrated that a layered structure with ultradisperse grains is produced by friction stir welding at the center of the weld joint. An analogy is drawn between the microstructures of joints produced by friction stir welding and surface layer produced by sliding friction.

  20. Research of Mechanical Property Gradient Distribution of Al-Cu Alloy in Centrifugal Casting

    NASA Astrophysics Data System (ADS)

    Sun, Zhi; Sui, Yanwei; Liu, Aihui; Li, Bangsheng; Guo, Jingjie

    Al-Cu alloy castings are obtained using centrifugal casting. The regularity of mechanical property gradient distribution of Al-Cu alloy castings with the same centrifugal radius at different positions is investigated. The result shows that the tensile strength, yield strength, elongation and microscope hardness exhibit the following gradient distribution characteristic — high on both sides and low on the center. The trend of mechanical property gradient distribution of Al-Cu alloy increases with the increase in the rotation speed. Moreover, the mechanical properties of casting centerline two sides have asymmetry. The reason is that the grain size of casting centerline two sides and Al2Cu phase and Cu content change correspondingly.

  1. Microstructural evolution in Al-Zn-Mg-Cu-Sc-Zr alloys during short-time homogenization

    NASA Astrophysics Data System (ADS)

    Liu, Tao; He, Chun-nian; Li, Gen; Meng, Xin; Shi, Chun-sheng; Zhao, Nai-qin

    2015-05-01

    Microstructural evolution in a new kind of aluminum (Al) alloy with the chemical composition of Al-8.82Zn-2.08Mg-0.80Cu-0.31Sc-0.3Zr was investigated. It is found that the secondary phase MgZn2 is completely dissolved into the matrix during a short homogenization treatment (470°C, 1 h), while the primary phase Al3(Sc,Zr) remains stable. This is due to Sc and Zr additions into the Al alloy, high Zn/Mg mass ratio, and low Cu content. The experimental findings fit well with the results calculated by the homogenization diffusion kinetics equation. The alloy shows an excellent mechanical performance after the short homogenization process followed by hot-extrusion and T6 treatment. Consequently, a good combination of low energy consumption and favorable mechanical properties is obtained.

  2. Brazeability of a 3003 Aluminum alloy with Al-Si-Cu-based filler metals

    NASA Astrophysics Data System (ADS)

    Tsao, L. C.; Weng, W. P.; Cheng, M. D.; Tsao, C. W.; Chuang, T. H.

    2002-08-01

    Al-Si-Cu-based filler metals have been used successfully for brazing 6061 aluminum alloy as reported in the authors’ previous studies. For application in heat exchangers during manufacturing, the brazeability of 3003 aluminum alloy with these filler metals is herein further evaluated. Experimental results show that even at such a low temperature as 550 °C, the 3003 alloys can be brazed with the Al-Si-Cu fillers and display bonding strengths that are higher than 77 MPa as well. An optimized 3003 joint is attained in the brazements with the innovative Al-7Si-20Cu-2Sn-1Mg filler metal at 575 °C for 30 min, which reveals a bonding strength capping the 3003 Al matrix.

  3. Designing Gamma TiAl Alloys (K5 Based) for Use at 840 C and Above

    NASA Technical Reports Server (NTRS)

    Kim, Young-Won; Kim, Sang-Lan

    2002-01-01

    The objective of this program was to investigate how carbon additions and Al content variation affects RT tensile properties and creep performance in gamma TiAl alloys. On the basis of the results from the work four alloys were selected within the composition range of Ti-(44.7-47.0) Al-(1.0-1.7)Cr-3.0Nb-0.2W-0.2B-(0.23-0.43)C-(0, 0.2)Si. Through extensive annealing/aging experiments, detailed observations of microstructure evolution, property measurements and analyses, comprehensive understanding was made in the carbide formation process. It was found that creep properties depend on the distribution of carbide particles, which is controlled not only by the aging process but also the amount ratio fo Al and carbon. From the results and analysis, new creep-resistant alloy compositions are suggested for further development.

  4. Corrosion Performance Based on the Microstructural Array of Al-Based Monotectic Alloys in a NaCl Solution

    NASA Astrophysics Data System (ADS)

    Osório, Wislei R.; Freitas, Emmanuelle S.; Garcia, Amauri

    2014-01-01

    The aim of this study is to compare the electrochemical behavior of three monotectic Al-based alloys (Al-Pb, Al-Bi, and Al-In) in a 0.5 M NaCl solution at room temperature. Two distinct microstructure arrays were experimentally obtained for each Al monotectic alloy by using a water-cooled unidirectional solidification system. Results of electrochemical impedance spectroscopy (EIS) plots, potentiodynamic polarization curves, and impedance parameters obtained by an equivalent circuit analysis are discussed. It was found that the Al-Pb alloy has lower corrosion current density, higher polarization resistance, lower relative weight, and cost than the corresponding values of Al-Bi and Al-In alloys. It is also shown that the electrochemical behavior of the three alloys examined are intimately correlated with the scale of the corresponding microstructure, with smaller droplets and spacings (i.e., cell and interphase spacings) being associated with a decrease in the corrosion resistance.

  5. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  6. The fracture resistance of 1420 and 1421 Al-Mg-Li alloys

    NASA Technical Reports Server (NTRS)

    Birt, M. J.; Hafley, R. A.; Wagner, J. A.; Lisagor, W. B.

    1993-01-01

    The resistance to stable crack growth in 1420-T6 (Al-5Mg-2.1Li-0.1Zr-0.01Sc, less than 0.06Fe, in wt pct) and 1421-T6 (Al-4.7Mg-1.9Li-0.09Zr-0.2Sc, less than 0.06Fe) Al-Mg-Li alloys was investigated, based on the R curves generated in accordance with ASTM E561-86 and fractography analyses. The crack resistance of 1420 and 1421 alloys was found to be comparable to that of the conventional Space Shuttle External Tank Al alloy, 2219-T87. The main differences in the fracture behaviors arose from differences in the alloys' microstructures. In the case of 1420 alloy, a slightly enhanced toughness behavior was observed, due to the T-phase precipitates, which may have promoted more homogeneous deformation and enhanced microvoid coalescence. In the case of 1421 alloy, the addition of Sc led to a refined grain size and resulted in slightly reduced toughness.

  7. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    DOE PAGESBeta

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

  8. Intrinsic fatigue crack growth rates for Al-Li-Cu-Mg alloys in vacuum

    SciTech Connect

    Slavik, D.C.; Gangloff, R.P.; Starke, E.A. Jr ); Blankenship, C.P. Jr )

    1993-08-01

    The influences of microstructure and deformation mode on inert environment intrinsic fatigue crack propagation were investigated for Al-Li-Cu-Mg alloys AA2090, AA8090, and X2095 compared to AA2024. The amount of coherent shearable [delta][prime] (Al[sub 3]Li) precipitates and extent of localized planar slip deformation were reduced by composition (increased Cu/Li in X2095) and heat treatment (double aging of AA8090). Intrinsic growth rates, obtained at high constant K[sub max] to minimize crack closure and in vacuum to eliminate any environmental effect, were alloy dependent; da/dN varied up to tenfold based on applied [Delta]K or [Delta]K/E. When compared based on a crack tip cyclic strain or opening displacement parameter ([Delta]K/([sigma][sub ys]E)[sup 1/2]), growth rates were equivalent for alloys except X2095-T8 which exhibited unique fatigue crack growth resistance. Tortuous fatigue crack profiles and large fracture surface facets were observed for each Al-Li alloy independent of the precipitates present, particularly [sigma][prime], and the localized slip deformation structure. Reduced fatigue crack propagation rates for X2095 in vacuum are not explained by either residual crack closure or slip reversibility arguments; the origin of apparent slip band facets in a homogeneous slip alloy is unclear. Better understanding of crack tip damage accumulation and fracture surface facet crystallography is required for Al-Li alloys with varying slip localization.

  9. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  10. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    SciTech Connect

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.

  11. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  12. Surface Integrity of Titanium Alloy Ti-6Al-4 V in Ball end Milling

    NASA Astrophysics Data System (ADS)

    Mhamdi, M.-B.; Boujelbene, M.; Bayraktar, E.; Zghal, A.

    With the evolution of machine tools and the emergence of new cutting tools such as cermet, CBN; and in framework of the production of parts with complex geometry, the manufacturers were able to realize more and more parts of complex shape. The multi-axis machining is the main technique for achieving the free form; in fact the multi-axis milling with ball end tools attracts the interest of the aerospace industry and the mussel industry which continues to seek ways to improve the surface quality of finished parts. The titanium alloy is widely used in aerospace industry is the subject of this study in fact, the integrity of the surfaces of parts produced by multi-axis milling is an issue more relevant than ever for the aerospace industry. This paper aims to study the influence of the tool position and the parameters cutting precisely the speed feed Vf, the engagement of the tool on the roughness 3 D, micro-hardness and microstructure alteration created in sub-surface during the milling of concave surface of titanium alloy type Ti-6Al-4 V.

  13. Structural properties of the quaternary Heusler alloy Co2Cr1-xFexAl

    NASA Astrophysics Data System (ADS)

    Wurmehl, Sabine; Martins Alves, Maria C.; Morais, Jonder; Ksenofontov, Vadim; Teixeira, Sergio R.; Machado, Giovanna; Fecher, Gerhard H.; Felser, Claudia

    2007-03-01

    The quarternary substitutional series Co2Cr1-xFexAl was investigated by means of surface and bulk sensitive techniques in order to exploit its structural and compositional properties. Both bulk and powder samples of the alloy series were investigated to obtain specific information about this material. The long range order was determined by means of x-ray diffraction and neutron diffraction, while the site specific (short range) order was proved by extended x-ray absorption fine structure spectroscopy. The magnetic structure was investigated by Mössbauer spectroscopy in transmission and scattering modes in order to compare and separate powder and bulk properties. The chemical composition was analysed by means of x-ray photo emission spectroscopy combined with Auger electron spectroscopy depth profiling. The results from these methods are compared to get an insight into the differences between surface and bulk properties and the appearance of disorder in such alloys. The material shows an extremely high sensitivity to oxygen. In particular, powder materials show a high amount of oxygen contamination. Therefore, an additional oxide-mediated tunnel magneto-resistance may always contribute to measurements of magneto-resistive effects because the oxide layers will provide natural tunnelling barriers. In addition, the results suggest that thin films have to be produced under ultra-high vacuum conditions.

  14. Microstructure characterization in upward directional solidification of Al-Cu and Mg-Al alloys under transient conditions

    NASA Astrophysics Data System (ADS)

    Amoorezaei, Morteza; Gurevich, Sebastian; Provatas, Nikolas

    Predicting and controlling the microstructure of cast alloys has been a driving force behind various studies on solidification of materials. Dendritic spacing and morphology established during casting often sets the final microstructure during manufacturing of alloys. This is par-ticularly true in emerging technologies such as twin belt casting, where a reduced amount of thermomechanical processing reduced the possibility of modifying microstructure from that de-termined at the time of solidification. Mg-based alloys are gaining importance due to the high demand for weight reduction in the transportation industry which accordingly reduces the gas consumption. While the solidified microstructure and its effect on the material properties have been the subject of intensive studies, little is known about the fundamental mechanisms that determine the microstructure and its evolution under directional growth conditions. We study the relationship between the microstructure and cooling conditions in unsteady state upward directional solidification of Al-Cu and Mg-Al alloys. The four-fold symmetry of Al-Cu alloys allows studying the dynamical spacing selection between dendrites, as the growth conditions vary dynamically, whereas, Mg-Al system with a six-fold symmetry introduces a competition between neighbouring, misoriented grains and remarkably influences the resulting microstruc-ture. We also present new phase field simulations wherein we dynamically vary the cooling conditions. Analysis of the phase field simulations is used to shed some light on the morpho-logical development of dendrite arms during solidification under transient conditions. We find that the final microstructure under transient conditions is strongly dependent on the history of the growth conditions changes as well as the initial morphology of the system, consistent with the results previously obtained by Warren and Langer and Losert et. al. Our phase field results are validated qualitatively by the

  15. Low-energy deposition of high-strength Al(0) alloys from an ECR plasma

    SciTech Connect

    Barbour, J.C.; Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Marshall, D.A.; Lad, R.J.

    1995-12-31

    Low-energy deposition of Al(O) alloys from an electron cyclotron resonance (ECR) plasma offers a scaleable method for the synthesis of thick, high-strength Al layers. This work compares alloy layers formed by an ECR-0{sub 2} plasma in conjunction with Al evaporation to 0-implanted Al (ion energies 25-200 keV); and it examines the effects of volume fraction of A1{sub 2}0{sub 3} phase and deposition temperature on the yield stress of the material. TEM showed the Al(O) alloys contain a dense dispersion of small {gamma}-Al{sub 2}0{sub 3} precipitates ({approximately}l nm) in a fine-grain (10-100 nm) fcc Al matrix when deposited at a temperature of {approximately}100C, similar to the microstructure for gigapascal-strength 0-implanted Al. Nanoindentation gave hardnesses for ECR films from 1.1 to 3.2 GPa, and finite-element modeling gave yield stresses up to 1.3 {plus_minus} 0.2 GPa with an elastic modulus of 66 GPa {plus_minus} 6 GPa (similar to pure bulk Al). The yield stress of a polycrystalline pure Al layer was only 0.19 {plus_minus} 0.02 GPa, which was increased to 0.87 {plus_minus} 0.15 GPa by implantation with 5 at. % 0.

  16. Fabrication of Nb3Al superconducting bulks by mechanical alloying method

    NASA Astrophysics Data System (ADS)

    Qi, Ming; Pan, Xi Feng; Zhang, Ping Xiang; Cui, Li Jun; Li, Cheng Shan; Yan, Guo; Chen, Yong Liang; Zhao, Yong

    2014-06-01

    Since it can directly prepare the Nb-Al supersaturated solid solution, mechanical alloying is thought as a promising method to make high-performance Nb3Al superconductors at a low temperature annealing condition, without the complicated rapid heating, quenching and transformation (RHQT) process. In this paper, we investigate the effects of milling time, the content of Al and annealing temperature on phase formation and superconducting properties of mechanical alloying Nb3Al bulks in detail. The study results show that Nb-Al supersaturated solid solution could be obtained by high energy ball milling, as long as the Nb-Al blended powder is ball milled for 1 h, even the amorphous phase appears with the ball milling time prolonging to 10 h, the Nb-Al intermetalics do not come out either. Amorphous phase is hardly beneficial to synthesizing the Nb3Al phase, instead, it will make the products impurity. By optimizing the milling time, elements composition and annealing temperature , pure Nb3Al phase is obtained and the highest onset superconducting transition temperature (Tc-onset) reaches 15.8 K and the critical current density (Jc) 106 A/cm2 at 8 K without outer field. This paper also discusses the main reasons that affect the superconducting properties of mechanical alloying Nb3Al superconductor.

  17. Vickers hardness, indentation creep and corrosion behaviour of Al-5Ti-1B alloy with copper content

    NASA Astrophysics Data System (ADS)

    Said Gouda, El; Nassar, Amira

    2014-11-01

    The effects of 1, 3 and 5 wt.% Cu additions on structure, Vickers hardness, indentation creep and corrosion behaviour of Al-5Ti-1B ternary alloy were studied and analyzed. The Al-5Ti-1B alloy exhibited a mixture of Al3Ti and TiB2 intermetallic compounds (IMCs), and Al solid solution. Additions of 1 and 3 wt.% Cu showed the same phases, indicating a complete solubility of Cu atoms in Al matrix. In addition, the Al-5Ti-1B-5Cu alloy exhibited a precipitation of CuAl2 IMC. Furthermore, additions of Cu decreased the particle size of Al matrix. This structural behaviour increased rapidly the Vickers hardness number (HV) from 643 to 1395 MPa, increased the indentation creep resistance and improved corrosion behaviour of the Al-5Ti-1B alloy. Cu is anti-corrosion phase when completely dissolved or precipitated as IMC in Al matrix.

  18. Effects of Thermal Exposure on Properties of Al-Li Alloys

    NASA Technical Reports Server (NTRS)

    Shah, Sandeep; Wells, Douglas; Stanton, William; Lawless, Kirby; Russell, Carolyn; Wagner, John; Domack, Marcia; Babel, Henry; Farahmand, Bahram; Schwab, David; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Aluminum-Lithium (Al-Li) alloys offer significant performance benefits for aerospace structural applications due to their higher specific properties compared with conventional Al alloys. For example, the application of Al-Li alloy 2195 to the space shuffle external cryogenic fuel tank resulted in weight savings of over 7,000 lb, enabling successful deployment of International Space Station components. The composition and heat treatment of 2195 were optimized specifically for strength-toughness considerations for an expendable cryogenic tank. Time-dependent properties related to reliability, such as thermal stability, fatigue, and corrosion, will be of significant interest when materials are evaluated for a reusable cryotank structure. Literature surveys have indicated that there is limited thermal exposure data on Al-Li alloys. The effort reported here was designed to establish the effects of thermal exposure on the mechanical properties and microstructure of Al-Li alloys C458, L277, and 2195 in plate gages. Tensile, fracture toughness, and corrosion resistance were evaluated for both parent metal and friction stir welds (FSW) after exposure to temperatures as high as 300 F for up to 1000 hrs. Microstructural changes were evaluated with thermal exposure in order to correlate with the observed data trends. The ambient temperature parent metal data showed an increase in strength and reduction in elongation after exposure at lower temperatures. Strength reached a peak with intermediate temperature exposure followed by a decrease at highest exposure temperature. Friction stir welds of all alloys showed a drop in elongation with increased length of exposure. Understanding the effect of thermal exposure on the properties and microstructure of Al-Li alloys must be considered in defining service limiting temperatures and exposure times for a reusable cryotank structure.

  19. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Geanta, V.; Voiculescu, I.; Stanciu, E.-M.

    2016-06-01

    Due to their special properties at high temperatures, FeCrAl alloys micro-alloyed with Zr can be regarded as potential materials for use at nuclear power plants, generation 4R. These materials are resistant to oxidation at high temperatures, to corrosion, erosion and to the penetrating radiations in liquid metal environments. Also, these are able to form continuously, by the self-generation process of an oxide coating with high adhesive strength. The protective oxide layers must be textured and regenerable, with a good mechanical strength, so that crack and peeling can not appear. To improve the mechanical and chemical characteristics of the oxide layer, we introduced limited quantities of Zr, Ti, Y, Hf, Ce in the range of 1-3%wt in the FeCrAl alloy. These elements, with very high affinity to the oxygen, are capable to stabilize the alumina structure and to improve the oxide adherence to the metallic substrate. FeCrAl alloys microalloyed with Hf were prepared using VAR (Vacuum Arc Remelting) unit, under high argon purity atmosphere. Three different experimental alloys have been prepared using the same metallic matrix of Fe-14Cr-5Al, by adding of 0.5%wt Hf, 1.0%wt Hf and respectively 1.5%wt Hf. The microhardness values for the experimental alloys have been in the range 154 ... 157 HV0.2. EDAX analyses have been performed to determine chemical composition on the oxide layer and in the bulk of sample and SEM analyze has been done to determine the microstructural features. The results have shown the capacity of FeCrAl alloy to form oxide layers, with different texture and rich in elements such as Al and Hf.

  20. Lattice variations of Ti-6Al-4V alloy with hydrogen content

    SciTech Connect

    Zhu Tangkui Li, Miaoquan

    2011-07-15

    Effect of hydrogen content on the lattice parameter of Ti-6Al-4V alloy has been investigated by X-ray diffraction. The experimental results show that the solution of hydrogen in the Ti-6Al-4V alloy affects significantly on the lattice parameters of {alpha}, {beta} and {delta} phases, especially the {beta} phase. Furthermore, the critical hydrogen content of {delta} hydride formation for Ti-6Al-4V alloy is 0.385 wt.%. When the hydrogen content is lower than the critical hydrogen content, the {delta} hydride cannot precipitate and the lattice parameter ({alpha}) of {beta} phase linearly increases with the increasing of hydrogen content. When the hydrogen content is higher than the critical hydrogen content, the {delta} hydride precipitates and the lattice parameter ({alpha}) of {beta} phase varies inconspicuously with hydrogen content. In addition, the effects of lattice variations and {delta} hydride formation on microstructure are discussed. The {alpha}/{beta} interfaces of lamellar transformed {beta} phase become fuzzy with the increasing of hydrogen content because of the lattice expansion of {beta} phase. Compared with that of the Ti-6Al-4V alloy at low hydrogen content ({<=} 0.385 wt.%), the contrasts of primary {alpha} phase and transformed {beta} phase of Ti-6Al-4V alloy at high hydrogen content ({>=} 0.385 wt.%) were completely reversed due to the formation of {delta} hydride. - Research Highlights: {yields} A novel method for determining {delta} hydride in Ti-6Al-4V alloy is presented. {yields} The critical hydrogen content of {delta} hydride formation is 0.385 wt.%. {yields} The lattice parameter of {beta} phase can be expressed as follows: a=0.323(1+9.9x10{sup -2}C{sub H}) . {yields} Precipitation of {delta} hydride has a significant influence on the microstructure. {yields} The {alpha}/{beta} interfaces of transformed {beta} phase became fuzzy in the hydrogenated alloy.

  1. High-Temperature Tensile Strength of Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy (High-Entropy Alloy)

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A. M.; Wanderka, N.; Glatzel, U.

    2015-06-01

    Homogenizing at 1220°C for 20 h and subsequent aging at 900°C for 5 h and 50 h of a novel Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy (high-entropy alloy) produces a microstructure consisting of an L12 ordered γ' phase embedded in a face-centered cubic solid-solution γ matrix together with needle-like B2 precipitates (NiAl). The volume fraction of γ' phase is ~46% and of needle-like B2 precipitates <5%, which is in accordance with the prediction of calculation of phase diagram method (CALPHAD using Thermo-Calc software with TTNi7 database; Thermo-Calc Software, Stockholm, Sweden). The high-temperature tensile tests were carried out at room temperature, 600°C, 700°C, 800°C, and 1000°C. The tensile strength as well as the elongation to failure of both heat-treated specimens is very high at all tested temperatures. The values of tensile strength has been compared with literature data of well-known Alloy 800H and Inconel 617, and is discussed in terms of the observed microstructure.

  2. (Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units

    SciTech Connect

    Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J.; Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J.

    2012-01-09

    An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

  3. Fabrication and Characterization of novel W80Ni10Nb10 alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Saxena, R.; Patra, A.; Karak, S. K.; Pattanaik, A.; Mishra, S. C.

    2016-02-01

    Nanostructured tungsten (W) based alloy with nominal composition of W80Ni10Nb10 (in wt. %) was synthesized by mechanical alloying of elemental powders of tungsten (W), nickel (Ni), niobium (Nb) in a high energy planetary ball-mill for 20 h using chrome steel as grinding media and toluene as process control agent followed by compaction at 500 MPa pressure for 5 mins and sintering at 1500°C for 2 h in Ar atmosphere. The phase evolution and the microstructure of the milled powder and consolidated product were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The crystallite size of W in W80Ni10Nb10 powder was reduced from 100 μm at 0 h to 45.6 nm at 10 h and 34.1 nm at 20 h of milling whereas lattice strain increases to 35% at 20 h of milling. The dislocation density shows sharp increase up to 5 h of milling and the rate of increase drops beyond 5 to 20 h of milling. The lattice parameter of tungsten in W80Ni10Nb10 expanded upto 0.04% at 10 h of milling and contracted upto 0.02% at 20 h of milling. The SEM micrograph revealed the presence of spherical and elongated particles in W80Ni10Nb10 powders at 20 h of milling. The particle size decreases from 100 μm to 2 μm with an increase in the milling time from 0 to 20 hours. The crystallite size of W in milled W80Ni10Nb10 alloy as evident from bright field TEM image was in well agreement with the measured crystallite size from XRD. Structure of W in 20 h milled W80Ni10Nb10 alloy was identified by indexing of selected area diffraction (SAD) pattern. Formation of NbNi intermetallic was evident from XRD pattern and SEM micrograph of sintered alloy. Maximum sinterability of 90.8% was achieved in 20 h milled sintered alloy. Hardness and wear study was also conducted to investigate the mechanical behaviour of the sintered product. Hardness of W80Ni10Nb10 alloy reduces with increasing load whereas wear rate increases with increasing load. The evaluated

  4. Effects of Interstitial Boron and Alloy Stoichiometry on Environmental Effects in FeAl

    SciTech Connect

    Cohron, J.W.; George, E.P.; Zee, R.H.

    1998-04-22

    Room-temperature tensile tests were conducted on B-doped (300 wppm) and B-free polycrystalline FeAl alloys containing 37, 40, 45, and 48 at. % aluminum in pure hydrogen gas at pressures in the range of 10 sup minus 8 to 10 sup 3 Pa. The ductilities of both B-free and B-doped FeAl decreased with increasing Al content. However, at a given Al level, the ductility of B-doped FeAl was higher than that of its B-free counterpart. Fracture mode was independent of environment and dependent mainly on stoichiometry. Ductility was found to be very sensitive to environment, particularly in the lower Al alloys. Alloys that exhibited >10% ductility in UHV showed a decrease in elongation to fracture with increasing hydrogen pressure. Tests conducted in dry hydrogen gas result in greater ductilities than those conducted in air, indicating that water vapor is more detrimental than H sub 2 to the ductility of FeAl alloys.

  5. Reduction of nitric oxide with carbon monoxide on the Al-Mo(110) surface alloy

    NASA Astrophysics Data System (ADS)

    Grigorkina, G. S.; Tvauri, I. V.; Kaloeva, A. G.; Burdzieva, O. G.; Sekiba, D.; Ogura, S.; Fukutani, K.; Magkoev, T. T.

    2016-05-01

    Coadsorption and reaction of carbon monoxide (CO) and nitric oxide (NO) on Al-Mo(110) surface alloy have been studied by means of Auger electron, reflection-absorption infrared and temperature programmed desorption spectroscopies (AES, RAIRS, TPD), low energy electron diffraction (LEED) and work function measurements. The Al-Mo(110) surface alloy was obtained by thermal annealing at 800 K of aluminum film deposited on Mo(110) held at room temperature. Upon annealing Al penetrates the surface, most likely forming stoichiometric hexagonal surface monolayer of the compound Al2Mo. The NO and CO adsorb molecularly on this alloy surface at 200 K, unlike totally dissociative adsorption on bare Mo(110) and Al(111) film. Adsorption of CO on NO precovered Al-Mo(110) substrate dramatically affects the state of NO molecules, most probably displacing them to higher-coordinated sites with their simultaneous tilting to the surface plane. Heating to about room temperature (320 K) causes reduction of nitric oxide with carbon monoxide, yielding CO2, and substrate nitridation. This behavior can be associated with the surface reconstruction providing additional Al/Mo interface reaction sites and change of the d-band upon alloying.

  6. Fatigue characteristics and microcosmic mechanism of Al-Si-Mg alloys under multiaxial proportional loadings

    NASA Astrophysics Data System (ADS)

    Jiang, Xiao-Song; He, Guo-Qiu; Liu, Bing; Zhu, Zheng-Yu; Zhang, Wei-Hua

    2011-08-01

    With the increasing use of Al-Si-Mg alloys in the automotive industry, the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability. The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research. As low cycle fatigue life and material strengthening behavior are closely related, the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed. Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties. The fatigue life exhibits a stable behavior under multiaxial proportional loadings. The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy (TEM). The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles. Simultaneously, the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings. The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material, which is caused by multiaxial proportional loadings.

  7. Investigation of boron distribution in a TiAl-based alloy using particle-tracking

    SciTech Connect

    Pu, Z.; Wu, K.H.

    1996-01-01

    One of the key shortcomings of current TiAl intermetallic alloy is the inverse relationship between tensile properties and fracture/creep resistance. TiAl-based alloys with a fully lamellar structure generally display`s high fracture toughness and creep resistance, but poor ductility. Inversely, material with a duplex microstructure has very good ductility, but poor fracture toughness and creep resistance. Research efforts have focused on overcoming this deficiency. Now that it is widely accepted that the poor ductility of lamellar structures originates from the large grain size, refining the lamellar structure of TiAl-based alloys presents itself as a feasible solution. The question remains as to how to accomplish this goal. Microalloying is considered one approach for refining the fully lamellar structure. The present authors have reported that the addition of boron can effectively refine the grain size of fully lamellar structure. However, the distribution of boron in TiAl alloys and the mechanism in boron that suppresses grain growth are not yet clear. In the present paper, the distribution of boron in a Ti-rich TiAl-based alloy, as a function of the bulk boron content, annealing temperature, and thermomechanical process, is analyzed using a Particle-Tracking Autoradiography (PTA) technique.

  8. CONSTITUTIVE BEHAVIOR OF AS-QUENCHED Al-Cu-Mn ALLOY

    NASA Astrophysics Data System (ADS)

    Yang, Xia-Wei; Zhu, Jing-Chuan; Nong, Zhi-Sheng; Ye, Mao; Lai, Zhong-Hong; Liu, Yong

    2013-07-01

    The hot flow stress of as-quenched Al-Cu-Mn alloy was modeled using the constitutive equations. The as-quenched Al-Cu-Mn alloy were treated with isothermal hot compression tests in the temperature range of 350-500°C, the strain rate range of 0.001-1 s-1. The hyperbolic sine equation was found to be appropriate for flow stress modeling and prediction. Based on the hyperbolic sine equation, a constitutive equation is a relation between 0.2 pct yield stress and deformation conditions (strain rate and deformation temperature) was established. The corresponding hot deformation activation energy (Q) for as-quenched Al-Cu-Mn alloy was determined to be 251.314 kJ/mol. Parameters of constitutive equation of as-quenched Al-Cu-Mn alloy were calculated at different small strains (≤ 0.01). The calculated flow stresses from the constitutive equation are in good agreement with the experimental results. Therefore, this constitutive equation can be used as an accurate temperature-stress model to solve the problems of quench distortion of Al-Cu-Mn alloy parts.

  9. Ultra-fine grained Al-Mg alloys with superior strength via physical simulation

    NASA Astrophysics Data System (ADS)

    Sabirov, I.; Enikeev, N.; Kazykhanov, V.; Valiev, R.; Murashkin, M.

    2014-08-01

    The Al 5xxx alloys are widely used in form of sheets in marine, transport, and chemical engineering and, thus, they are often have to undergo hot/cold rolling as the final metal forming operations. Recent investigations have demonstrated that ultra-fine grained (UFG) Al 5xxx alloys have a significant potential for industrial applications due to their improved mechanical properties and enhanced corrosion resistance. However, the development of hot/cold rolling routes for the UFG Al alloys is very time consuming due to numerous experimental trials and very expensive due to higher cost of the UFG processed materials. In this work, physical simulation of cold rolling is applied to the UFG Al 5083 alloy obtained via equal channel angular pressing with parallel channels to analyze the effect of cold rolling on the microstructure and microhardness of the material. The cold rolling parameters are chosen based on the outcomes of physical simulation and the UFG Al 5083 alloy is successfully subjected to cold rolling resulting in superior mechanical strength of the material. It is concluded that physical simulation can significantly increase the efficiency of experimental work on development of thermo-mechanical processing routes.

  10. Mechanical behavior and phase stability of NiAl-based shape memory alloys

    SciTech Connect

    George, E.P.; Liu, C.T.; Horton, J.A.; Kunsmann, H.; King, T.; Kao, M.

    1993-12-31

    NiAl-based shape memory alloys (SMAs) can be made ductile by alloying with 100--300 wppm B and 14--20 at.% Fe. The addition of Fe has the undesirable effect that it lowers the temperature (A{sub p}) of the martensite {yields} austenite phase transformation. Fortunately, however, A can be raised by lowering the ``equivalent`` amount of Al in the alloy. In this way a high A{sub p} temperature of {approximately}190 C has been obtained without sacrificing ductility. Furthermore, a recoverable strain of 0.7% has been obtained in a Ni-Al-Fe alloy with A{sub p} temperature of {approximately}140 C. Iron additions do not suppress the aging-induced embrittlement that occurs in NiAl alloys at 300--500 C as a result of Ni{sub 5}Al{sub 3} precipitation. Manganese additions (up to 10 at.%) have the effect of lowering A{sub p}, degrading hot workability, and decreasing room-temperature ductility.

  11. Reactive wetting of amorphous silica by molten Al-Mg alloys and their interfacial structures

    NASA Astrophysics Data System (ADS)

    Shi, Laixin; Shen, Ping; Zhang, Dan; Jiang, Qichuan

    2016-07-01

    The reactive wetting of amorphous silica substrates by molten Al-Mg alloys over a wide composition range was studied using a dispensed sessile drop method in a flowing Ar atmosphere. The effects of the nominal Mg concentration and temperature on the wetting and interfacial microstructures were discussed. The initial contact angle for pure Al on the SiO2 surface was 115° while that for pure Mg was 35° at 1073 K. For the Al-Mg alloy drop, it decreased with increasing nominal Mg concentration. The reaction zone was characterized by layered structures, whose formation was primarily controlled by the variation in the alloy concentration due to the evaporation of Mg and the interfacial reaction from the viewpoint of thermodynamics as well as by the penetration or diffusion of Mg, Al and Si from the viewpoint of kinetics. In addition, the effects of the reaction and the evaporation of Mg on the movement of the triple line were examined. The spreading of the Al-Mg alloy on the SiO2 surface was mainly attributed to the formation of Mg2Si at the interface and the recession of the triple line to the diminishing Mg concentration in the alloy.

  12. Ductility enhancement in NiAl (B2)-base alloys by microstructural control

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Kainuma, R.; Ueno, N.; Nishizawa, T.

    1991-02-01

    An attempt to improve ductility of NiAl (B2)-base alloys has been made by the addition of alloying elements and the control of microstructure. It has been found that a small amount of fcc γ phase formed by the addition of Fe, Co, and Cr has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to the modification of Β-phase grains by the coexistence of γ phase. The effect of alloying elements on the hot forming ability is strongly related to the phase equilibria and partition behavior among γ, γ' (L12 structure), and Β phases in the Ni-Al-X alloy systems. The ductility-enhancement method shows promise for expanding the practical application of nickel aluminide.

  13. Effect of Micro Arc Oxidation Coatings on Corrosion Resistance of 6061-Al Alloy

    NASA Astrophysics Data System (ADS)

    Wasekar, Nitin P.; Jyothirmayi, A.; Rama Krishna, L.; Sundararajan, G.

    2008-10-01

    In the present study, the corrosion behavior of micro arc oxidation (MAO) coatings deposited at two current densities on 6061-Al alloy has been investigated. Corrosion in particular, simple immersion, and potentiodynamic polarization tests have been carried out in 3.5% NaCl in order to evaluate the corrosion resistance of MAO coatings. The long duration (up to 600 h) immersion tests of coated samples illustrated negligible change in weight as compared to uncoated alloy. The anodic polarization curves were found to exhibit substantially lower corrosion current and more positive corrosion potential for MAO-coated specimens as compared to the uncoated alloy. The electrochemical response was also compared with SS-316 and the hard anodized coatings. The results indicate that the overall corrosion resistance of the MAO coatings is significantly superior as compared to SS316 and comparable to hard anodized coating deposited on 6061 Al alloy.

  14. Interstitial solubility in {gamma} and {alpha}{sub 2} phases of TiAl-based alloys

    SciTech Connect

    Menand, A.; Huguet, A.; Nerac-Partaix, A.

    1996-12-01

    Measurements of interstitial concentrations were performed on ({alpha}{sub 2} + {gamma}) two-phase TiAl alloys and on {gamma} single-phase TiAl alloys. This study allowed the determination of the maximum solubility of oxygen and carbon in the {gamma} phase. The influence on this solubility of various parameters such as temperature, {alpha}{sub 2} and {gamma} phase stoichiometry and the alloying addition of a third element will be discussed. This paper also presents an explanation for the higher solubility of oxygen in {alpha}{sub 2} phase compared to {gamma} phase. From the results it is shown unambiguously that the better ductility of ({alpha}{sub 2} + {gamma}) two-phase alloys can no longer fit with the widespread idea of a scavenging effect of the {alpha}{sub 2} phase which would lower in that way the interstitial level in {gamma} phase.

  15. Effect of homogenization process on the hardness of Zn-Al-Cu alloys

    NASA Astrophysics Data System (ADS)

    Villegas-Cardenas, Jose D.; Saucedo-Muñoz, Maribel L.; Lopez-Hirata, Victor M.; De Ita-De la Torre, Antonio; Avila-Davila, Erika O.; Gonzalez-Velazquez, Jorge Luis

    2015-10-01

    The effect of a homogenizing treatment on the hardness of as-cast Zn-Al-Cu alloys was investigated. Eight alloy compositions were prepared and homogenized at 350 °C for 180 h, and their Rockwell "B" hardness was subsequently measured. All the specimens were analyzed by X-ray diffraction and metallographically prepared for observation by optical microscopy and scanning electron microscopy. The results of the present work indicated that the hardness of both alloys (as-cast and homogenized) increased with increasing Al and Cu contents; this increased hardness is likely related to the presence of the θ and τ' phases. A regression equation was obtained to determine the hardness of the homogenized alloys as a function of their chemical composition and processing parameters, such as homogenization time and temperature, used in their preparation.

  16. Aqueous sodium chloride induced intergranular corrosion of Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Daeschner, D. L.

    1986-01-01

    Two methods have been explored to assess the susceptibility of Al-Li-Cu alloys to intergranular corrosion in aqueous sodium chloride solution. They are: (1) constant extension rate testing with and without alternate-immersion preexposure and (2) metallographic examination after exposure to a NaCl-H2O2 corrosive solution per Mil-H-6088F. Intergranular corrosion was found to occur in both powder and ingot metallurgy alloys of similar composition, using both methods. Underaging rendered the alloys most susceptible. The results correlate to stress-corrosion data generated in conventional time-to-failure and crack growth-rate tests. Alternate-immersion preexposure may be a reliable means to assess stress corrosion susceptibility of Al-Li-Cu alloys.

  17. Effect of sonotrode material on grain refining of Mg–3Al and Mg–9Al alloys by ultrasonic melt treatment

    NASA Astrophysics Data System (ADS)

    Youn, Jeong IL; Lee, Young Ki; Jig Kim, Young; Park, Jeong Wook

    2016-07-01

    The new process, nucleation enhanced ultrasonic melt treatment (NEUMT), was proposed to increase the refining efficiency through heterogeneous nucleation by using the sonotrode which has been only concerned with the medium to transfer the ultrasonic energy. In the processing, the metal atoms and/or clusters eroded from the sonotrode were supplied and were simultaneously mixed uniformly into the melt by the ultrasound. These particles act as potential nuclei and refine the structure. The process was applied to assess grain refinement of Mg alloys, especially Mg–3Al and Mg–9Al. The refining efficiency was affected by the sonotrode material, and Ti was very effective in this process by the formation of proper intermetallic compound in the Mg alloy melt. The intermetallic compound was searched by the calculation of plane disregistry of the crystallographic orientation, and Al3Ti was suggested to be the heterogeneous nuclei.

  18. Atomistic Modeling of Quaternary Alloys: Ti and Cu in NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Mosca, Hugo O.; Wilson, Allen W.; Noebe, Ronald D.; Garces, Jorge E.

    2002-01-01

    The change in site preference in NiAl(Ti,Cu) alloys with concentration is examined experimentally via ALCHEMI and theoretically using the Bozzolo-Ferrante-Smith (BFS) method for alloys. Results for the site occupancy of Ti and Cu additions as a function of concentration are determined experimentally for five alloys. These results are reproduced with large-scale BFS-based Monte Carlo atomistic simulations. The original set of five alloys is extended to 25 concentrations, which are modeled by means of the BFS method for alloys, showing in more detail the compositional range over which major changes in behavior occur. A simple but powerful approach based on the definition of atomic local environments also is introduced to describe energetically the interactions between the various elements and therefore to explain the observed behavior.

  19. Deformation mechanisms responsible for the creep resistance of Ti-Al alloys

    SciTech Connect

    Morris, M.A.; Lipe, T.

    1997-12-31

    Two {gamma}-based Ti-Al alloys with similar grain sizes and, respectively, lamellar and duplex microstructures have been creep tested at 700 C and constant stresses ranging between 280 and 430 MPa. TEM observations have confirmed that the duplex alloy deforms by extensive mechanical twinning whose density increases with applied stress and increasing strain. The new twin interfaces subdivide the {gamma} grains throughout the primary stage of creep. At the onset of the minimum creep rate, the twin interfaces in the duplex alloy behave in the same way as the {gamma}/{gamma} or the {alpha}{sub 2}/{gamma} interfaces in the lamellar alloy. However, single dislocations were also present and it appears that in both alloys the deformation process is controlled by the accumulation and emission of dislocations from the different interfaces.

  20. Kinetics and mechanism of the oxidation process of two-component Fe-Al alloys

    NASA Technical Reports Server (NTRS)

    Przewlocka, H.; Siedlecka, J.

    1982-01-01

    The oxidation process of two-component Fe-Al alloys containing up to 7.2% Al and from 18 to 30% Al was studied. Kinetic measurements were conducted using the isothermal gravimetric method in the range of 1073-1223 K and 1073-1373 K for 50 hours. The methods used in studies of the mechanism of oxidation included: X-ray microanalysis, X-ray structural analysis, metallographic analysis and marker tests.

  1. Grain growth in Al alloy conductors as a result of rapid annealing

    NASA Astrophysics Data System (ADS)

    Towner, Janet M.; van de Ven, Evert P.; Hopkins, Craig G.

    1984-01-01

    Aluminum and aluminum alloy thin films were rapidly annealed using high intensity visible light. Under suitable conditions, substantial grain growth was achieved in the Al-Cu and Al-Si-Cu conductors and this grain growth had a beneficial effect on electromigration. Unfortunately, this growth did not occur uniformily across the wafer. A second phenomenon, which resulted from thermal cycling, was the solid phase reduction of SiO2 by the overlying Al film.

  2. Improved Wear Resistance of Al-Mg Alloy with SiC and Al2O3 Particle Reinforcement

    NASA Astrophysics Data System (ADS)

    Mehedi, Md. A.; Bhadhon, K. M. H.; Haque, M. N.

    2016-01-01

    Al-3.73Mg alloy was reinforced with a different ratio of SiC and Al2O3 particulate mixtures, and their corresponding wear properties were investigated by pin-on-disk method. The investigation revealed that the mass loss of the hybrid composite at different loads and sliding velocities reduced with the increase of the SiC volume. Only 6% particulate reinforcement in the Al-Mg matrix was enough to reduce the wear of the surface by one-fourth. The wear mechanism was also investigated by examining the worn surface with a scanning electron microscope.

  3. Interdiffusion Behavior in y-Phase U-Mo Alloy Versus Al-6061 Alloy Couples Fabricated by Friction Stir Welding

    SciTech Connect

    Dennis D. Keiser, Jr.

    2007-09-01

    To better understand interactions between fuel and cladding in research reactor fuels, diffusion couples between y-phase U-7 wt% Mo and U-10 wt% Mo alloy fuels and a Si-bearing, Al alloy were fabricated using a friction stir welding technique. The advantage of such a fabrication technique is that it can potentially reduce the amount of aluminum-oxide that might be present at the diffusion couple interface. The presence of oxides at the interface can affect the interdiffusion process. These couples were annealed and characterized using a scanning electron microscope equipped with energy-dispersive and wavelength-dispersive spectrometers. Images were taken of the developed diffusion structures; x-ray maps were generated to identify partitioning behavior of the various components; and, point-to-point analysis was employed to generate composition profiles and to determine phase compositions. To try and determine how the presence of Si in an Al alloy affects the interdiffusion behavior of fuel and cladding components in research reactor nuclear fuels, the results from this study were compared to those from earlier diffusion studies using U-Mo alloys and Al. The formed diffusion zones in some samples annealed for 30 minutes are comprised of Si-rich aluminide phases that appear to be (U,Mo)0.9(Al,Si)4 and (U,Mo)(Si,Al)2, based on composition. The diffusion rates observed and the types of phases that form can be correlated to the stability of the y-U phase, which is a metastable phase. For a sample annealed for a much longer time, large diffusion structures formed and no Si-rich phases were observed.

  4. In Situ Assessment of Lattice in an Al-Li Alloy

    NASA Technical Reports Server (NTRS)

    Beaudoin, A. J.; Obstalecki, M.; Tayon, W.; Hernquist, M.; Mudrock, R.; Kenesei, P.; Lienert, U.

    2013-01-01

    The lattice strains of individual grains are measured in an Al-Li alloy, AA 2195, using high-energy X-ray diffraction at a synchrotron source. The diffraction of individual grains in this highly textured production alloy was isolated through use of a depth-defining aperture. It is shown that hydrostatic stress, and in turn the stress triaxiality, can vary significantly from grain to grain.

  5. The fabricability and corrosion resistance of several Al-Cu-Li aerospace alloys

    SciTech Connect

    Walsh, D.W.; Danford, M.; Sanders, J.

    1996-12-31

    Al-Li-Cu alloys are attractive to the aerospace industry. The high specific strength and stiffness of these alloys will improve lift efficiency, fuel economy, performance and increase payload capabilities. The objectives of this study were to measure the fabricability of Al 2195 (Al-4Cu-1Li) and to assess the effect of welding on corrosion behavior. Al 2219 samples were used in parallel tests to provide a baseline for the data generated. In this study samples were exposed to 3.5% NaCl and mild corrosive water solutions in both the as received and as welded conditions. Fabricability was assessed using Gleeble testing, Varestraint testing and differential scanning calorimetry (DSC). Results indicate that Alloy 2195 is much more susceptible to hot cracking than Al 2219, and that cracking sensitivity is a strong function of chemical composition within specification ranges for Al 2195. Furthermore, for base metal samples, corrosion in mild corrosive water was more severe than corrosion in salt water. In addition, welding increases the corrosion rate in Al 2195 and 2219, and causes severe localization in Al 2195. Furthermore, autogenously welded Al 2195 samples were more susceptible to attack than heterogeneously welded Al 2195 samples and autogenously welded Al2219 samples were less susceptible to corrosion than autogenously welded Al 2195 samples. Heterogeneously welded samples in both materials had high corrosion rates, but only the Al 2195 material was subject to localization of attack. The partially melted zones of Al 2195 samples were subject to severe, focused attack. In all cases, interdendritic constituents in welded areas and intergranular constituents in base material were cathodic to the Al rich matrix materials. Fabricability and corrosion resistance were correlated to material microstructure using optical microscopy, scanning electron microscopy, electron probe microanalysis, polarization resistance and environmental scanning electron microscopy.

  6. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-08-01

    Rapidly solidified hypoeutectic Al-10Si- xMg ( x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  7. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-05-01

    Rapidly solidified hypoeutectic Al-10Si-xMg (x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  8. Bulk-alloy microstructural analogues for transient liquid-phase bonds in the NiAl/Cu/Ni system

    SciTech Connect

    Gale, W.F.; Abdo, Z.A.M.

    1999-12-01

    Transient liquid-phase (TLP) bonds between dissimilar materials can have complex microstructures that evolve both during holding at the bonding temperature and on cooling. In this article, an examination is made of the feasibility of producing bulk-alloy microstructural analogues for individual microstructural features of dissimilar material TLP bonds. The ultimate intent of this work is to enable the contribution of individual microstructural features to the overall properties of TLP bonds to be determined. Specifically, the article focuses on the production, characterization, and applications of microstructural analogues for TLP bonds in an NiAl/Cu/Ni model system. The article examines the use of five different cast Ni-Al-Cu alloys, together with heat treatment of selected materials, as bulk analogues for six distinct microstructural regions of the NiAl/Cu/Ni bonds. Each of these analogues is characterized in detail by transmission electron microscopy (TEM) and compared to the relevant target region of the bond. An initial examination is also made of the use of bulk alloys in aiding an understanding of phase transformations and structure-property relationships in these bonds.

  9. Thermophysical properties of substantially undercooled liquid Ti-Al-Nb ternary alloy measured by electromagnetic levitation

    NASA Astrophysics Data System (ADS)

    Zhou, K.; Wang, H. P.; Wei, B.

    2013-03-01

    The thermophysical properties of undercooled liquid alloys at high temperature are usually difficult to measure by experiment. Here, we report the specific heat of liquid Ti45Al45Nb10 ternary alloy in the undercooled state. By using electromagnetic levitation technique, a maximum undercooling of 287 K (0.15 T L) is achieved for this alloy. Its specific heat is determined to be 32.72 ± 2.51 J mol-1 K-1 over a broad temperature range of 1578-2010 K.

  10. Thermophysical properties of Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy

    NASA Astrophysics Data System (ADS)

    Bykov, V. A.; Kulikova, T. V.; Vedmid', L. B.; Fishman, A. Ya.; Shunyaev, K. Yu.; Tarenkova, N. Yu.

    2014-07-01

    The thermophysical properties of the Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy in a wide range of temperatures from room temperature to 1000°C have been studied by the methods of differential scanning calorimetry, the laser flash method, and dilatometry. The obtained data on heat capacity, thermal diffusivity, and thermal expansion have been used for calculating coefficient of thermal conductivity. The sequence and temperatures of structural transformations during heating of the alloy have been established. It has been shown that the studied alloy possesses a coefficient of thermal conductivity that is 3.5-4 times smaller than that of pure titanium.

  11. Transmission electron microscopy characterization of microstructural features of Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Avalos-Borja, M.; Pizzo, P. P.; Larson, L. A.

    1983-01-01

    A transmission electron microscopy (TEM) examination of aluminum-lithium-copper alloys was conducted. The principal purpose is to characterize the nature, size, and distribution of stringer particles which result from the powder metallurgy (P/M) processing of these alloys. Microstructural features associated with the stringer particles are reported that help explain the stress corrosion susceptibility of the powder metallurgy-processed Al-Li-Cu alloys. In addition, matrix precipitation events are documented for a variety of heat treatments and process variations. Hot rolling is observed to significant alter the nature of matrix precipitation, and the observations are correlated with concomitant mechanical property variations.

  12. Recycling of aluminium scrap for secondary Al-Si alloys.

    PubMed

    Velasco, Eulogio; Nino, Jose

    2011-07-01

    An increasing amount of recycled aluminium is going into the production of aluminium alloy used for automotive applications. In these applications, it is necessary to control and remove alloy impurities and inclusions. Cleaning and fluxing processes are widely used during processing of the alloys for removal of inclusions, hydrogen and excess of magnesium. These processes use salt fluxes based in the system NaCl-KCl, injection of chlorine or mixture of chlorine with an inert gas. The new systems include a graphite wand and a circulation device to force convection in the melt and permit the bubbling and dispersion of reactive and cleaning agents. This paper discusses the recycling of aluminium alloys in rotary and reverberatory industrial furnaces. It focuses on the removal of magnesium during the melting process. In rotary furnaces, the magnesium lost is mainly due to the oxidation process at high temperatures. The magnesium removal is carried out by the reaction between chlorine and magnesium, with its efficiency associated to kinetic factors such as concentration of magnesium, mixing, and temperature. These factors are also related to emissions generated during the demagging process. Improvements in the metallic yield can be reached in rotary furnaces if the process starts with a proper salt, with limits of addition, and avoiding long holding times. To improve throughput in reverberatories, start the charging with high magnesium content material and inject chlorine gas if the molten metal is at the right temperature. Removal of magnesium through modern technologies can be efficiently performed to prevent environmental problems. PMID:20837560

  13. Tensile Properties of Al-Cu 206 Cast Alloys with Various Iron Contents

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The Al-Cu 206 cast alloys with varying alloy compositions ( i.e., different levels of Fe, Mn, and Si) were investigated to evaluate the effect of the iron-rich intermetallics on the tensile properties. It is found that the tensile strength decreases with increasing iron content, but its overall loss is less than 10 pct over the range of 0.15 to 0.5 pct Fe at 0.3 pct Mn and 0.3 pct Si. At similar iron contents, the tensile properties of the alloys with dominant Chinese script iron-rich intermetallics are generally higher than those with the dominant platelet phase. In the solution and artificial overaging condition (T7), the tensile strength of the 206 cast alloys with more than 0.15 pct Fe is satisfactory, but the elongation does not sufficiently meet the minimum requirement of ductility (>7 pct) for critical automotive applications. However, it was found that both the required ductility and tensile strength can be reached at high Fe levels of 0.3 to 0.5 pct for the alloys with well-controlled alloy chemistry and microstructure in the solution and natural aging condition (T4), reinforcing the motivation for developing recyclable high-iron Al-Cu 206 cast alloys.

  14. Effect of silicon alloying additions on growth temperature and primary spacing of Al{sub 3}Fe in Al-8wt%Fe alloy

    SciTech Connect

    Liang, D.; Jones, H.; Gilgien, P.

    1995-05-15

    Alloys of Al-8.4Fe-1.7Si, Al-8.5Fe-3.4Si and Al-8.5Fe-5.6Si (wt%) designated A, B and C, respectively, were prepared from high purity (99.99%) aluminum, Japanese electrolytic iron (99.9%) and superpure silicon (99.99%). Melting was carried out in a recrystallized alumina crucible by using a Radyne induction furnace and was followed by chill casting under flowing argon into steel molds of cavity dimension 15 mm thick, 50 mm wide and 150 mm high. Rods 3 mm in diameter were fabricated directly from the ingots. Lengths of the rods, which were contained in 3 mm bore tubular alumina crucibles, were melted in a Bridgman growth facility. After maintaining the melt at 100K above the liquidus temperatures liquidus: 1,118, 1,108 and 1,092 K for 1.7, 3.4 and 5.6 wt%Si, respectively, for about 10 minutes, crucibles containing the melt were withdrawn at a speed of 0.34 mm/s into a water bath. The following conclusions can be drawn from analysis of the specimens. Addition of silicon to Al-8wt%Fe alloy results in an increase in growth undercooling and primary spacing of Al{sub 3}Fe dendrites Bridgman grown at 0.34 mm/s and 10K/mm. This increase in growth undercooling, relative to predicted local liquidus temperatures which have been corrected for observed macrosegregation of Fe, is in good accord with the predictions of the Kurz-Giovanola-Trivedi model for needle-like dendrite growth. The silicon content of the Al{sub 3}Fe dendrites obtained is consistent with previously reported measurements for a range of cast Al-Fe-Si alloys.

  15. The decomposition of the beta phase in Ti-44Al-8Nb and Ti-44Al-4Nb-4Zr-0.2Si alloys

    SciTech Connect

    Cheng, T.T.; Loretto, M.H.

    1998-08-10

    The decomposition of the beta phase has been studied in Ti-44Al-8Nb and Ti-44Al-4Nb-4Zr-0.2Si alloys cooled from the ({alpha} + {beta}) phase field using TEM and SEM. The morphology of the transformation products is shown to be sensitive to cooling rate and the results of the microstructural observations are used to construct a schematic continuous cooling transformation (CCT) diagram for these alloys. It is shown that under slow cooling, the beta phase is mainly consumed by the neighboring alpha grains via {alpha}/{beta} interfacial migration. During the subsequent {alpha} {yields} {alpha} + {gamma} transformation which occurs at lower temperatures and produces a lamellar microstructure, the retained beta phase can transform partially to {gamma} by a process analogous to the discontinuous coarsening of {gamma} lamellae. It has also been shown that, at higher cooling rates, the beta phase can decompose to alpha via secondary lath formation and/or a Widmanstaetten transformation although transformation by {alpha}/{beta} interfacial migration still occurs. The decomposition of beta directly to faceted gamma has also been observed both in slowly cooled and rapidly cooled materials. In the slowly cooled materials this is attributed to direct nucleation of gamma grains, whereas in the rapidly cooled materials they are thought to be the result of discontinuous coarsening. Furthermore, a B2 to {omega} transformation occurs readily in these alloys at temperatures higher than 700 C in both cases. Possible mechanisms for each of these transformations are discussed.

  16. Work of Adhesion in Al/SiC Composites with Alloying Element Addition

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Fan, Tongxiang; Zhang, Di

    2013-11-01

    In the current work, a general methodology was proposed to demonstrate how to calculate the work of adhesion in a reactive multicomponent alloy/ceramic system. Applying this methodology, the work of adhesion of Al alloy/SiC systems and the influence of different alloying elements were predicted. Based on the thermodynamics of interfacial reaction and calculation models for component activities, the equilibrium compositions of the melts in Al alloy/SiC systems were calculated. Combining the work of adhesion models for reactive metal/ceramic systems, the work of adhesion in Al alloy/SiC systems both before and after the reaction was calculated. The results showed that the addition of most alloying elements, such as Mg, Si, and Mn, could increase the initial work of adhesion, while Fe had a slightly decreasing effect. As for the equilibrium state, the additions of Cu, Fe, Mn, Ni, Ti, and La could increase the equilibrium work of adhesion, but the additions of Mg and Zn had an opposite effect. Si was emphasized due to its suppressing effect on the interfacial reaction.

  17. Bulk metallic glass formation in Zr-Cu-Fe-Al alloys

    SciTech Connect

    Jin Kaifeng; Loeffler, Joerg F.

    2005-06-13

    We have discovered a series of bulk metallic glass-forming alloys of composition (Zr{sub x}Cu{sub 100-x}){sub 80}(Fe{sub 40}Al{sub 60}){sub 20} with x=68-77 and have investigated them by x-ray diffraction, small-angle neutron scattering, and differential scanning calorimetry. All of these alloys exhibit a calorimetric glass transition temperature of 670 Kalloy Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}. In rod shape this alloy has a critical casting thickness of 13 mm, as verified by detailed casting experiments, while alloys with x=68 and 77 can still be cast to a thickness of 5 mm. Furthermore, the region where glassy samples with a thickness of 0.5 mm can be prepared extends from x=62-81. The best glass-former, Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}, has a tensile yield strength of 1.71 GPa and shows an elastic limit of 2.25%. This new class of Ni-free Zr-based alloys is potentially very interesting for biomedical applications.

  18. The effects of zinc addition on the environmental stability of Al-Li alloys

    NASA Technical Reports Server (NTRS)

    Kilmer, Raymond J.; Stoner, Glenn E.

    1990-01-01

    It was found that relatively small addition of Zn can improve the stress corrosion cracking (SCC) resistance of Al-Li alloys. However, the mechanism by which this is accomplished is unclear. The role that Zn plays in altering the behavior of Alloy 8090 is investigated. Early results suggest that Zn additions increase the volume fraction of delta(Al3Li) precipitation and differential scanning calorimetry (DSC) on these alloys confirms this. The four alloys studied each had initial compositions lying in the 8090 window and had varying amounts of Zn added to them. Alloy 8090, like other Al-Li alloys, displays a delta' precipitate free zone (PFZ) upon artificial aging along the grain and subgrain boundaries. However Zn additions greatly decreased or eliminated a delta' PFZ after 100 hours at 160 C. This implies that the subgrain boundary precipitation kinetics are being altered and suppressed. Furthermore, there appears to be a window of Zn concentration above which a delta ' PFZ can reappear with the nucleation and growth of a currently unidentified precipitate on the boundaries. Polarization experiments were performed and the results presented. The experiments were performed in deaerated 3.5 w/o NaCl in both as received (T3) condition and at peak aging of 100 hours at 160 C. The aging profile was determined via Vickers Hardness tests.

  19. Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an AL-Zn-Mg-(Cu) Alloy

    SciTech Connect

    Young, G A; Scully, J R

    2002-04-09

    Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.

  20. Experimental and theoretical analyses on the ultrasonic cavitation processing of Al-based alloys and nanocomposites

    NASA Astrophysics Data System (ADS)

    Jia, Shian

    Strong evidence is showing that microstructure and mechanical properties of a casting component can be significantly improved if nanoparticles are used as reinforcement to form metal-matrix-nano-composite (MMNC). In this paper, 6061/A356 nanocomposite castings are fabricated using the ultrasonic stirring technology (UST). The 6061/A356 alloy and Al2O3/SiC nanoparticles are used as the matrix alloy and the reinforcement, respectively. Nanoparticles are injected into the molten metal and dispersed by ultrasonic cavitation and acoustic streaming. The applied UST parameters in the current experiments are used to validate a recently developed multiphase Computational Fluid Dynamics (CFD) model, which is used to model the nanoparticle dispersion during UST processing. The CFD model accounts for turbulent fluid flow, heat transfer and the complex interaction between the molten alloy and nanoparticles using the ANSYS Fluent Dense Discrete Phase Model (DDPM). The modeling study includes the effects of ultrasonic probe location and the initial location where the nanoparticles are injected into the molten alloy. The microstructure, mechanical behavior and mechanical properties of the nanocomposite castings have been also investigated in detail. The current experimental results show that the tensile strength and elongation of the as-cast nanocomposite samples (6061/A356 alloy reinforced by Al2O 3 or SiC nanoparticles) are improved. The addition of the Al2O 3 or SiC nanoparticles in 6061/A356 alloy matrix changes the fracture mechanism from brittle dominated to ductile dominated.