Defect Structure and the Temperature Dependence of Hardness of an Intermetallic Compound

Abstract

The temperature dependence of hardness of the intermetallic compound normalAgMg was studied from −190°C to the solidus temperature over the entire homogeneity range. The effect of structure on hardness at high homologous temperatures differs radically from that at low temperatures. These results, over virtually the full homologous temperature range, appear to rationalize previously contradictory studies of the effect of defect structure on the room temperature strength of intermetallic compounds.

Diffusion in the intermetallic compound NiAl

“…structure, of the CsCltype, Its relatively low melting temperature of 960°C and fair workability have both made more accurate experimental data possible. Initially the hardness (Westbrook 1957) and tensile behaviour (Wood & Westbrook 1962) suggested the possibility that the greater strengthening and lower activation energies for flow stress observed in magnesium-rich alloys, when compared to those in silver-rich alloys, resulted from concentrations of constitutional vacancies -32-similar to those found in aluminium-rich NiAl alloys. Although a part of this effect was later found to result from grain-boundary hardening (Westbrook & Wood 1963), Hagel & Westbrook (1961) concluded, from lattice parameter and density measurements, that only substitutional defects exist on both sides of stoichiometry.…”

A constitutive model for hardness considering the effects of strain, strain rate and temperature

“…Typical strain rate distribution (10003) in a sectioned specimen obtained from simulation of (a) tensile Hopkinson bar and (b) Taylor test and (c) strain distribution in Taylor test. Compression 655 100 1 200 2 300 2 400 1 875 100 1 200 2 300 1 400 1 Tensile 600 100 1 200 1 300 2 400 1 750 100 1 200 2 300 1 400 3 this case, the strain rate and temperature terms (denoted by N( _ e) and Q(T * ), respectively) in equation (22) tend to unity. The reason is that for T = T room , Q(T * ) tends to unity and for quasi-static conditions, N( _ e) approaches one as D in equations (26) and (27) is nearly one.…”

“…The temperature term in equation (22) then becomes Now, substituting the relations for the strain (equation (24)), strain rate (equations (26) and (27)) and temperature (equation (30)) into equation (22) …”

“…They showed that the stress exponent ( n ) obtained from the hardness–time plots was weakly temperature dependent. Westbrook 22 has obtained a relation between the hardness and temperature as follows 22…”

Effects of Alloying Atoms on Antiphase Boundary Energy and Yield Stress Anomaly of L12 Intermetallics: First-Principles Study

“…In materials science, the yield stress anomaly (YSA) means the yield stress of the unusual materials has a positive dependence with the increasing temperature, in contrast to the usual materials which the yield stress decreases with temperature [1][2][3][4]. L1 2 structure intermetallics are one kind of those materials.…”