CRITICALITY IN THE PLASTIC-DEFORMATION OF L 1(2) INTERMETALLIC COMPOUNDS

It is argued that dislocations in the L1(2) intermetallic compounds di splaying the yield strength anomaly undergo a stress-driven pinning-de pinning transition. The transition is from a dynamic phase in which a moving dislocation becomes immobile to a dynamic phase in which a movi ng dislocation, in an infinite medium, remains mobile for all time. Th e distribution of event times and areas, where an ''event'' is the mob ilization and subsequent immobilization of a dislocation, is related t o measurements of the primary creep transient. At the critical point o f the proposed transition, the distribution of events becomes scale in variant. 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 proper ties 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 exper iments is proposed.