The influence of quantum-mechanical athermal phenomena on the thermal instability of plastic deformation in crystals at low temperatures

Abstract

The way in which athermal (quantum) mechanisms that allow dislocations to overcome local barriers affect the thermal instability of plastic deformation of crystals is discussed theoretically for the case of low and ultralow (<1 K) temperatures. Calculations show that increasing the athermal component of the dislocation activation leads to a considerable narrowing of the temperature/strain-rate region where discontinuous strains appear, and that further increases in the quantum component of the process by which dislocations surmount local barriers leads to the complete disappearance of these discontinuous strains. Experimental situations in which the effects of thermal instability and athermal effects are observed at the same time in a number of crystals under conditions of low-temperature strain are discussed in light of these results.