APPLICATION OF THE METHODS OF DISLOCATION DYNAMICS TO DESCRIBE PLASTIC-FLOW IN BOTH BCC AND FCC METALS

A dislocation dynamical model for low temperature plastic flow is developed from the Taylor-Orowan equation, ε{lunate} ̇ = αρmvb. This type of approach has been used in the past to model and predict flow phenomena in alkali halides and b.c.c. metals. However, a direct extension of this modelling fails to predict certain flow behavior in f.c.c. metals, particularly the strain rate sensitivity. It is argued that the mobile dislocation density can be a strong function of the applied stress. Also, dislocations are considered to be driven by an effective stress rather than the applied stress. Dislocation link length arguments are used to develop the stress dependence of the mobile dislocation density, and a strain dependent long range back stress is used to define the effective stress. By including these considerations, it is found that the differences in dislocation mobility between classes of materials give rise to their different mechanical properties, and a single dislocation dynamical model is capable of predicting low temperature plastic flow in a variety of materials. © 1979.