Theory of plastic flow in strain-hardened metals

Abstract

A major unsolved problem in the theory of plastic flow of strain-hardened metals is the falling reversible flow-stress ratio at high temperature. In this paper it is argued that both the irreversible and reversible changes in stress at high temperature are a consequence of dislocation climb. The reversible difference is a consequence of climb-controlled rearrangement while the irreversible difference is the result of the loss of dislocations through climb. As a result of rearrangement and of the non-regular obstacle structure, soft local regions exist in which plastic flow occurs preferentially. This preferential flow occurs to a large degree at high temperature so that thc flow stress is low. For the same structure at low temperature, local flow is not so pronounced and the stress is high. The theory is presented formally and the equations are derived with only moderate reference to dislocation models. In addition to the reversible change in stress, the equations suggest explanations for linear hardening and dynamic recovery, work softening, transient crecp and the nature of slip lines.