Hardening by Point Defects and Solutes in B2 Intermetallics

2002 ◽  
Vol 753 ◽  
Author(s):  
L. M. Pike ◽  
Y. A. Chang ◽  
C. T. Liu ◽  
I. M. Anderson
Keyword(s):  
Solid Solution ◽  
Point Defect ◽  
Point Defects ◽  
Solid Solution Hardening ◽  
Quenching Temperature ◽  
Solid Solution Softening ◽  
Ordered Intermetallic ◽  
Multiple Defect ◽  
Binary Compounds ◽  
Hardness Values

ABSTRACTThis paper provides a review of recent progress on point defect and solute hardening in binary and ternary B2 intermetallics. As is the case for disordered metallic solutions, the presence of point defects and solute atoms in ordered intermetallic compounds results in solid solution hardening (SSH). However, factors unique to ordered systems are often responsible for unusual hardening effects. Binary compounds with identical crystal structures can exhibit significantly different hardness behavior. Ternary solute additions to ordered compounds can give rise to apparent solid solution softening as well as unexpectedly rapid hardening. These effects arise from the interaction of multiple defect types as well as the presence of multiple sublattice sites available for solute occupation. Therefore, before the SSH behavior of ordered intermetallics can be properly studied, it is necessary to develop an understanding of the types and quantities of the point defects which are present. Three recent studies by the authors are reviewed. Much of the work was done on NiAl and FeAl in binary form as well as with ternary additions. Defect concentrations over wide ranges in alloy composition and quenching temperature were determined using the ALCHEMI (atom location by channeling enhanced microanalysis) technique combined with vacancy measurements. Hardness values were also measured. It was found that most of the observed SSH effects could be rationalized on the basis of the measured point defect concentrations.

On the Correlation of the Hardness of B2 Compounds with Point Defect Concentrations

1994 ◽  
Vol 364 ◽  
Author(s):  
L. M. Pike ◽  
Y. A. Chang ◽  
C. T. Liu
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Point Defect ◽  
Point Defects ◽  
Defect Structure ◽  
Experimental Methods ◽  
Structure Defect ◽  
Quenching Temperature ◽  
Solid Solution Strengthening ◽  
Solution Strengthening

AbstractPoint defects such as vacancies and anti-site atoms are known to strongly affect the mechanical properties of B2 compounds. The variations in the hardness of these compounds with composition and quenching temperature can often be correlated with the concentrations of these point defects. Simple themodynamic models using a quasi-chemical approach can be used to estimate the concentrations of point defects with composition and temperature. These estimates can often be supported by experimental methods. Knowledge of the concentrations of defects can then be compared to the variations in hardness using solid solution strengthening models. A consistent relationship is found for several B2 compounds. The hardening rates of vacancies are found to be greater than those of anti-site atoms. B2 compounds having the anti-structure defect structure (AuZn, FeCo) are investigated as well as those with the triple-defect structure (FeAl, NiAl, CoAl).

Point Defect Thermodynamics of Compound Semiconductors and their Alloys

1982 ◽  
Vol 14 ◽  
Author(s):  
F. A. Kröger
Keyword(s):  
Physical Properties ◽  
Point Defect ◽  
Phase Diagrams ◽  
Point Defects ◽  
Compound Semiconductors ◽  
Defect Chemistry ◽  
Ternary Compounds ◽  
Partial Pressures ◽  
Binary Compounds

ABSTRACTThe physical properties of crystalline solids depend on the presence of point defects. The concentrations of these defects in turn depend on the conditions of preparation and the presence of dopants. Quantitative relations between these conditions (partial pressures of components, concentrations of dopants, temperature) and the defect concentrations is arrived at on the basis of defect chemistry. Examples of pure and doped binary compounds, alloys of binary compounds, and ternary compounds, are given. Whereas binary compounds have one composition variable, the alloy systems and the ternary compounds have two. The role of phase diagrams in preparing systems of required composition and properties is stressed.

Mechanical Hardness as a Probe of Nanocrystalline Materials

1994 ◽  
Vol 362 ◽  
Author(s):  
C. C. Koch ◽  
T. D. Shen ◽  
T. Malow ◽  
O. Spaldon
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Size Dependence ◽  
Solid Solution Hardening ◽  
Solution Hardening ◽  
Softening Effect ◽  
Mechanical Hardness ◽  
Solid Solution Softening

AbstractThe use of mechanical hardness as a probe of nanocrystalline materials is reviewed. The fact that the grain size dependence of hardness is very different for nanocrystalline materials compared to conventional (≥1 μm diameter) polycrystals suggests a different deformation mechanism may be operative in nanocrystalline materials. Hardness is useful for following the sintering, densification reactions of nanoparticles. Solid solution hardening in nanocrystalline alloys is found to be overwhelmed by the grain boundary hardening. If alloying decreases the grain boundary hardening, i.e. increases grain size, an apparent solid solution softening effect is observed.

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.

Site occupancies, point defect concentrations, and solid solution hardening in B2 (Ni,Fe)Al

2002 ◽  
Vol 50 (15) ◽  
pp. 3859-3879 ◽  
Author(s):  
L.M. Pike ◽  
I.M. Anderson ◽  
C.T. Liu ◽  
Y.A. Chang
Keyword(s):  
Solid Solution ◽  
Point Defect ◽  
Solid Solution Hardening ◽  
Solution Hardening

Point Defect Characterization of Zn- and Cd-Based Semiconductors Using Positron Annihilation Techniques

1998 ◽  
Vol 510 ◽  
Author(s):  
G. Tessaro ◽  
P. Mascher
Keyword(s):  
Point Defect ◽  
Positron Annihilation ◽  
Point Defects ◽  
Compound Semiconductors ◽  
Defect Characterization ◽  
Defect Complexes ◽  
Defect Profile ◽  
Profile Changes ◽  
Binary Compounds

AbstractA study of point defects in II-VI compound semiconductors was undertaken and has revealed that open volume defects are present in a wide variety of these samples. Zn-based binary compounds contain primarily neutral divacancy defects in concentrations in the mid 1016 cm−3. CdTe samples contain neutral monovacancy sized defect complexes in the high 1016 cm−3 range. When a small fraction of Zn or Se is alloyed into CdTe the defect profile changes dramatically to one dominated by divacancy sized defects at roughly half the original concentration.

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