It was recalled that experimental results on stress relaxation showed that, in certain ranges of temperature and strain-rate, many dilute solid solutions (both interstitial and substitutional) exhibited a distinct transition from concave upwards to concave downwards log-log plots of stress versus strain-rate. This behavior was related to the Portevin-Le Chatelier effect. The stress relaxation curves were described in terms of a physical model which included specific mechanisms for dislocation motion, for the internal structure and for the interaction between impurities and dislocations. The model was here tested against data for a Cu-0.2at%Zn alloy. Several microscopic parameters, such as the activation energy for impurity migration, the binding energy between impurities and dislocations, and the jog concentration, were obtained by fitting entire stress-relaxation curves to the model. The experimental evidence was in agreement with that for the onset of serrated yielding.

G.H.Rubiolo, P.B.Bozzano: Materials Transactions, 1995, 36[9], 1124-33