Criticality in the plastic deformation ofL12intermetallic compounds

It is argued that dislocations in the L$1_2$ intermetallic compounds displaying the yield strength anomaly undergo a stress-driven pinning-depinning transition. The transition is from a dynamic phase in which a moving dislocation becomes immobile to a dynamic phase in which a moving dislocation, in an infinite medium, remains mobile for all time. The distribution of event times and areas, where an ‘‘event’’ is the mobilization and subsequent immobilization of a dislocation, is related to measurements of the primary creep transient. At the critical point of the proposed transition, the distribution of events becomes scale invariant. A simple scaling hypothesis connects the scaling behavior of the transition to the time dependence of the creep tests. A simplified model of dislocation motion is presented and used to study the properties of the transition. The properties so calculated are not obviously consistent with the published interpretations of experiments, but are consistent with the published data. A reinterpretation of those experiments is proposed.