Simulation of the plastic flow in Ni3Al: work hardening and strain-rate sensitivity

The origin of the anomalous temperature dependence of the giant work-harden ing rate and of the modest strain-rate sensitivity observed in many L1(2) a lloys is investigated by means of an 'end-on' simulation of dislocation dyn amics in Ni3Al. The present model reproduces most of the atypical mechanica l properties observed experimentally. The study of the evolution of the dis tribution of the Kear-Wilsdorf locks during plastic deformation indicates t hat the order of magnitude of the work-hardening rate stems from a preferre d exhaustion of the weakest locks. In addition, the low strain-rate sensiti vity measured is found to rely on the absence of a correlation between the dislocation properties which provide the plastic strain and those which det ermine the flow stress level.