Theory of the temperature-dependent plastic flow in L12, alloys with unstable APBs on {111} planes

Abstract

A model is developed for the thermally activated motion of 1/2〈110〉 superpartial dislocations on {010} planes and 1/3〈112〉 superpartials on {111} planes, when antiphase boundaries on {111} planes are unstable. These two superpartials are sessile because they have non-planar cores. The model is based on Duesbery′s model for the thermally activated formation of double kinks on sessile dislocations and on the results presented in the accompanying paper. The model successfully replicates the behaviour observed in single-crystal Pt₃Al: the temperature dependence of the yield stress, (111) slip occurring for compression axes located on the [001] side of the unit triangle, and (001) slip occurring on the other side. The model also predicts that the location of the boundary between these two areas in the unit triangle should be temperature-dependent, and furthermore that in this boundary region (11l)[[lbar]l0] slip may also occur.