Composition dependence of positive temperature dependence of yield stress for Co3(Al, W)–Co3Ti pseudo-binary alloy with the L12 structure

Abstract

Variations in the positive temperature dependence of yield stress for L12 intermetallic compounds in pseudo-binary alloys with the composition of Co3(Al, W)–Co3Ti have been investigated. Polycrystalline L12 compounds in the pseudo-binary system with a Co3(Al, W) to Co3Ti composition ratio of approximately 1:3 and 1:9 were prepared. The temperature dependence of the yield stress ranging from 293 to 1273 K was determined. The onset temperature for the positive temperature dependence of yield stress for each compound is located between that of Co3(Al, W) and Co3Ti. The activation energies for the positive temperature dependence of these compounds are evaluated to be 47.0 and 43.6 kJmol-1, respectively. The activation energies are also intermediate values between those of Co3(Al, W) and Co3Ti.The composition dependence of the positive temperature dependence of yield stress is estimated from the physical properties of Co3(Al, W) and Co3Ti. Although the activation energies estimated for the present compounds are slightly different from the experimentally determined values, the temperature dependences of the experimentally determined yield stress are almost represented from the estimated parameters. The composition dependence of the positive temperature dependence of the yield stress can be predicted from the physical properties of the base compounds.