Dynamic aging of dislocations in materials with a high crystalline relief: Competition between diffusion and impurity entrainment

A model of the dynamic interaction of dislocations with the impurity subsystem of crystals that have a high lattice potential relief (Peierls barriers) has been developed. It is shown that the microscopic structure of migration barriers for impurities near a dislocation core may cause qualitatively different behavior of the impurity atmosphere on a moving dislocation. It is justified that the impurity kinetics during atmosphere formation includes two stages. The first (initial) stage is fast and significantly nonequilibrium; it is followed by the second stage, characterized by a slower approach to equilibrium. The initial stage manifests itself at a sufficiently fast dislocation motion and may lead to an anomalous increase in the driving force (or the yield strength of the material) with an increase in the temperature in some range. Blocking of the dislocation motion by impurities may cause inverse brittle-ductile transition, which is observed in some materials with an increase (rather than the usual decrease) in temperature.