COOPERATIVE DISLOCATION GENERATION AT FINITE TEMPERATURES IN LOADED SOLIDS : Transition from Brittle to Ductile Regime(Special Issue on Hierarchical Estimations of Materials Strength)

Abstract

This paper describes a theoretical model and a Monte Carlo simulation of cooperative dislocation generation in loaded crystals at finite temperatures. The theoretical work, employing a mean-field approach, is presented for the three-dimensional case when dislocation loops are formed. It describes how extensive plasticity can be initiated in dislocation-free crystals above a critical temperature due to 'homogeneous' cooperative nucleation and expansion of many dislocation loops. The Monte Carlo simulation is carried out to demonstrate the feasibility of the theoretical model. It is performed for a two dimensional case when dislocation dipoles are formed on an underlying lattice under applied loads. The application of this model to the brittle-to-ductile transition and the yielding of whiskers is discussed.