Temperature dependence of yield stress and dislocation dissociation in L1₂-ordered intermetallic compounds

The 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.