Anomalous Plasticity of Alloys at Low Temperatures

Abstract

A statistical dislocation model is proposed of the anomalous temperature dependences of flow stress below about 50 K found in many alloys. A thermal unit process is assumed to consist of a triggering thermal unpinning of an obstacle and mechanical unzippings following it. The dimensions of the unit vary with temperature and stress. A selfconsistency condition on fluctuation and relaxation of the distribution of dislocation configurations is taken into account. The model can explain the experiments well without detailed assumptions. The anomalies are found to occur, due to the onset of cooperative two dimensional propagations of unzipping motion of dislocations assisted by inertial effects.