High Temperature Ordered Intermetallic Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
D. P. Pope
Keyword(s):  
High Temperature ◽  
Intermetallic Compounds ◽  
Low Temperatures ◽  
Current Knowledge ◽  
Research Work ◽  
Complex Structures ◽  
Intermetallic Alloys ◽  
Laves Phases ◽  
Melting Temperatures ◽  
Ordered Intermetallic

AbstractThis paper is intended to be a general introduction to this conference and is therefore not a review of the state of our current knowledge. Instead, it will address questions like the following: Why are intermetallic compounds interesting? What alloys are being studied, and which are being ignored? Since most research work is now being performed on L12 alloys, with by far the greatest emphasis on Ni3Al, the balanceof the paper will concentrate on strengthening mechanisms and mechanisms of ductility control in Ni3Al, pointing out the interesting questions and controversies which arose during this conference.The conclusions to be drawn from this paper are that ordered intermetallic alloys are very valuable materials for high temperature use, but engineers probably must become more sophisticated in the use of materials with limited ductilities at low temperatures before intermetallics will gain widespread usage. Furthermore, additional research needs to be performed on more complex intermetallic compounds than L12 since L12 compounds, as a group, do not have particularly high melting temperatures. However,since alloys with complex structures, e.g. Laves phases, are well known for their brittleness at low temperatures, it is all the more important that the properties of such alloys be studied and methods found to improve their ductilities.

scholarly journals Deformation Twinning in Ordered Intermetallic Compounds

1988 ◽  
Vol 133 ◽  
Author(s):  
M. H. Yoo ◽  
C. L. Fu ◽  
J. K. Lee
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Temperature ◽  
Intermetallic Compounds ◽  
Deformation Twinning ◽  
Intermetallic Alloys ◽  
High Temperature Mechanical Properties ◽  
Ordered Intermetallic ◽  
Specific Calculations ◽  
Superlattice Structures

ABSTRACTMechanistic understanding of deformation twinning in ordered superlattice structures is reviewed, and the inter-relationships between twinning and generalized plastic flow or fracture toughness are discussed. While general discussions refer to all the fcc-based and bcc-based cubic and noncubic ordered intermetallic alloys, specific calculations of the energetic and kinetic aspects of deformation twinning are made for TiAl. The importance of the twin-slip conjugate relationship on high temperature mechanical properties is emphasized. Discussion is given of possible effects of macro- and micro-alloying on twinning propensity.

The disordering process in an Ll2 ordered alloy

1984 ◽  
Vol 42 ◽  
pp. 486-487
Author(s):  
J. A. Horton ◽  
A. DasGupta ◽  
C. T. Liu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
High Temperature ◽  
Intermetallic Alloys ◽  
Antiphase Boundaries ◽  
High Temperature Mechanical Properties ◽  
Heat Treated ◽  
Ordered Intermetallic

Ordered intermetallic alloys potentially have good high temperature mechanical properties which often are obtained by macroalloying. Since service temperatures may be near the critical ordering temperature, Tc, it is important to understand the disordering processes. The disordering mechanism in an alloy of 52.5 at. % Ni—22.5 Fe—14.5 V—10 Al—0.5 Ti [which can be expressed as (Ni70Fe30)3(V58Al40Ti2)], will be presented here. The aluminum was added to increase Tc from 750 to 975°C and stabilize the Ll2 structure.All specimens were first fully ordered by a heat treatment consisting of 30 min at 1000°C, 1 d at 700°C and 2 d at 600°C which results in a “swirl” pattern of antiphase boundaries (APB) similar to Fig. 1. Specimens were then heat-treated for 24 h at temperatures from 600 to 950°C in 50°C increments and water quenched.

Research of Solid Compound Formation during Thermal Deformation Effect on Intermetallic Ni3Al-Alloy with a Heat-Resistant Alloy EP975 and Influence on the Physical, Mechanical and Performance Properties

2016 ◽  
Vol 838-839 ◽  
pp. 523-527 ◽  
Author(s):  
Vener Valitov ◽  
Kira Povarova ◽  
Olga Bazyleva ◽  
Andrey Drozdov ◽  
Sergey Ovsepyan ◽  
...  
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Al Alloy ◽  
Intermetallic Alloys ◽  
Compound Formation ◽  
Heat Resistant Alloy ◽  
Melting Temperatures ◽  
Initial Melting ◽  
And Performance ◽  
State Pressure

The work is aimed at processing highly efficient one-piece units of gas turbine aircraft engines discs with blades (blisks) to exclude heavy locking joints and to reduce the weight of the units while improving their reliability. Intermetallic γ ́+γ alloys based on γ ́-Ni3Al phase of the VKNA type selected as blade material and Ni-based high alloy EP975 selected for discs have similar initial melting temperatures (~1340оС and~1300оC, respectively). Solid state joints (SSJ) EP975 //VKNA-mono are obtained at the homologous temperatures of 0.86-0.91 Tm (K).It is shown that the most efficient method for producing solid joints between the Ni3Al based intermetallic alloys and the EP975-type high-temperature nickel alloys is a solid state pressure welding in the conditions of high-temperature superplasticity; this technique has been developed in the IMSP RAS (grant RFBR No 130812200).

What Controls Temperature Dependence of Yield Stress in L12-Ordered Intermetallic Compounds?

2015 ◽  
Vol 1760 ◽  
Author(s):  
Haruyuki Inui ◽  
Norihiko L. Okamoto
Keyword(s):  
Temperature Dependence ◽  
Yield Stress ◽  
Intermetallic Compounds ◽  
Low Temperatures ◽  
Rapid Decrease ◽  
Partial Dislocations ◽  
Ordered Intermetallic ◽  
Image Position ◽  
Made In

ABSTRACTThe temperature dependence of yield stress and the associated dislocation dissociation in L12 intermetallic compounds are investigated in order to check the feasibility of the classification of L12 intermetallic compounds so far made in terms of the planarity of core structures of partial dislocations with b = 1/2<110> and 1/3<112> on {111} and {001} glide planes. In contrast to what is believed from the classification, the motion of APB-coupled dislocations is evidenced to give rise to the rapid decrease in yield stress at low temperatures for Pt3Al. In view of the fact that rapid decrease in yield stress at low temperatures is also observed in Co3(Al,W) and Co3Ti in which APB-coupled dislocations are responsible for deformation, the SISF-type dissociation is not a prerequisite for the rapidly decreasing CRSS for slip on (111) and the relative magnitudes of the APB energy on (111) and the SISF energy on (111) cannot be a primary factor that determines the type of the temperature dependence of CRSS for L12 compounds. The importance of the CSF energy as a factor determining the type of the temperature dependence of yield stress for L12 compounds through the changes in the planarity of the core structure of the APB-coupled partial dislocation with bp = ½[1$\overline 1$0] is discussed in the light of experimental evidence obtained from Pt3Al.

Temperature Dependence of Yield Stress and Dislocation Dissociation in L12-Ordered Intermetallic Compounds

2011 ◽  
Vol 1295 ◽  
Author(s):  
Haruyuki Inui ◽  
Norihiko L. Okamoto
Keyword(s):  
Solid Solution ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Intermetallic Compounds ◽  
Low Temperatures ◽  
Solid Solution Hardening ◽  
Solution Hardening ◽  
Partial Dislocations ◽  
Ordered Intermetallic ◽  
Dislocation Dissociation

ABSTRACTThe temperature dependence of yield stress and the associated dislocation dissociation in L12 intermetallic compounds are investigated in order to check the feasibility of the classification of L12 intermetallic compounds so far reported in terms of the planarity of core structures of partial dislocations with b = 1/2<110> and 1/3<112> on {111} and {001} glide planes. In contrast to what is believed from the reported classification, the motion of APB-coupled dislocations is proved to give rise to the rapid decrease in yield stress at low temperatures for Co3Ti and Co3 (Al,W). The temperature dependence of yield stress at low temperatures is newly interpreted in terms of a thermal component of solid-solution hardening, at least, for these two L12 compounds. We have proposed a new way to describe the yield stress–temperature curves of L12 compounds with three parameters (the athermal and thermal components of solid-solution hardening and the anomalous strengthening component) when the dislocation dissociation scheme is of the APB-type.

Strengthening and Ductilization of D03-Type Fe3Al Intermetallic Alloys by Dispersion of Laves Phases Fe2Zr and Fe2Nb

2007 ◽  
Vol 561-565 ◽  
pp. 395-398 ◽  
Author(s):  
N. Matsumoto ◽  
Yasuyuki Kaneno ◽  
Takayuki Takasugi
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Room Temperature ◽  
Tensile Elongation ◽  
Minor Amount ◽  
Second Phase ◽  
Intermetallic Alloys ◽  
High Tensile Strength ◽  
Laves Phases ◽  
A Minor

Zr and/or Nb added Fe3Al based intermetallic alloys (i.e., Fe3Al-Zr, Fe3Al-Nb and Fe3Al-Zr-Nb) were arc-melted, homogenized, hot-rolled and then annealed to evaluate microstructure and tensile property at room temperature as well as at a high temperature (873K). After annealing, the rolled alloys exhibited a recrystallized microstructure containing coarse second phase particles, except for the Nb-added alloy with a minor content of Nb. Relatively high tensile elongation as well as high tensile strength was observed at room temperature in the Zr-added alloys with a minor amount of Zr. Also, these alloys showed relatively high tensile strength and elongation at high temperature (873K). The results suggest that tensile ductility as well as strength of Fe3Al-based alloys can be improved by introduction of the second phase dispersions.

Phase Stability in Processing of High Temperature Intermetallic Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
J. H. Perepezko ◽  
C. A. Nuñes ◽  
S.-H. Yi ◽  
D. J. Thoma
Keyword(s):  
High Temperature ◽  
Phase Equilibria ◽  
Phase Stability ◽  
Environmental Stability ◽  
Materials Processing ◽  
Intermetallic Alloys ◽  
Ductile Phase ◽  
Laves Phases ◽  
Recent Developments ◽  
Almost All

ABSTRACTIn the development of high temperature intermetallics involving various aluminides, suicides and Laves phases, it has become evident that it is essential to consider the strong influence of materials processing throughout all stages. The underlying basis for alloy synthesis, processing and the assessment of thermal stability is established by the relevant phase equilibria, the characteristic diffusivities and the possible solidification reaction pathways. In almost all cases the microstructures of the most useful metallic alloys are multiphase assemblies in which the relative phase fractions, compositions and morphologies play key roles in optimizing the performance under high temperature conditions. The microstructure designs are usually tailored for strength, toughness, creep resistance and environmental stability and involve a balance of features derived from mixtures of a ductile phase and intermetallic phases. There is a clear experience that the level of materials processing can only be as sophisticated as the level of knowledge of the phase equilibria and the underlying kinetics. In many of the contemporary intermetallic alloys the phase stability must be considered in terms of multicomponent equilibria and non-stoichiometric intermetallic compositions. Recent developments in several important intermetallic alloy classes illustrate the guidance into alloy design and processing options provided by systematic studies of phase stability.

Precipitate coarsening during hot-compression testing of NiAl + 2 at.% Nb

1986 ◽  
Vol 44 ◽  
pp. 598-599
Author(s):  
W. M. Sherman ◽  
K. M. Vedula
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Weight Ratio ◽  
Constant Strain Rate ◽  
Hot Compression ◽  
Compression Testing ◽  
Second Phase ◽  
Precipitate Coarsening ◽  
High Temperature Mechanical Properties ◽  
Ordered Intermetallic

The strength to weight ratio and oxidation resistance of NiAl make this ordered intermetallic, with some modifications, an attractive candidate to compete with many superalloys for high temperature applications. Recent studies have shown that the inherent brittleness of many polycrystalline intermetallics can be overcome by micro and macroalloying. It has also been found that the high temperature mechanical properties of NiAl can be enhanced through the addition of Nb by powder metallurgical techniques forming a dispersed second phase through interdiffusion in a polycrystalline matrix. A drop in the flow stress is observed however in a NiAl-2 at.% Nb alloy after 0.2 % strain during constant strain rate hot compression testing at 1025°C. The object of this investigation was to identify the second phase and to determine the cause of the flow stress drop.

Bonding and stability in the ordered alloys FeV and CoTi. Comparison with FeTi

1985 ◽  
Vol 50 (10) ◽  
pp. 2093-2100
Author(s):  
Štěpán Pick ◽  
Mojmír Tomášek ◽  
Mojmír Šob
Keyword(s):  
Phase Diagrams ◽  
Partial Wave ◽  
Partial Wave Analysis ◽  
Intermetallic Alloys ◽  
Wave Analysis ◽  
Ordered Alloys ◽  
Ordered Intermetallic ◽  
Cscl Structure ◽  
Ionic Effects

Partial wave analysis together with the qualitative examination of hybridization has been performed for two ordered intermetallic alloys with CsCl structure, FeV, and CoTi. The results resemble those obtained previously for FeTi, although important deviations are present as well. The stabilization of the ordered phase is again due to ionic effects. Qualitative arguments are suggested to explain the small stability of the CsCl phase of FeV and some differences in the FeTi and CoTi phase diagrams.

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