Dynamic Interaction of Impurity Atmospheres with Moving Dislocations During Stress Relaxation

Abstract

The experimental results on stress relaxation show that in a certain range of temperatures and strain rates many dilute solid solutions, both interstitial and substitutional, exhibit a distinct transition from concave upward to concave downward logσ-log\dotε curves. This behavior is related with the Portevin-Le Chatelier effect as was described by Van den Beukel. The stress relaxation curves are described by a physical model, presented in an earlier paper, which includes specific mechanism for dislocation motion, for the internal structure and for the interaction between impurities and dislocations. The model is tested on a Cu-0.2 at% Zn alloy in the present work. Several microscopic parameters, such as the activation energy for the migration of the impurity, the binding energy between impurities and dislocations, the jog concentration and the index m+β in Van den Beukel's approach, are obtained from a fitting of the entire stress-relaxation curves to the model. The experimental evidence is in agreement with that from the onset of serrated yielding. © 1995, The Japan Institute of Metals. All rights reserved.