An internal variable approach for anomalous yield phenomena of beta-CuZn alloy

Abstract

A new interpretation for the anomalous yield phenomena of beta-CuZn alloy (132 ordered structure) has been made using an internal variable approach. The high temperature deformation behavior of beta-CuZn alloy has been examined through a series of load relaxation tests (28-430 degreesC) and analyzed. The deformation behavior has been well described by the internal variable theory of inelastic deformation, consisting of three deformation modes; plastic, inelastic, and dislocation creep deformation modes. Among these, the inelastic deformation mode has proved to be most important in affecting the anomalous phenomena. Microstructural factors related to the inelastic deformation mode characteristics in B2 ordered alloys are discussed. It has also been proposed that the anomalous phenomena can occur only when the reference strain rate (epsilon(o)) falls into the region of lower strain rate and lower stress with increasing temperature. The decrease of yield stress above anomalous peak temperature (T-p) in tensile results can be attributed to the dislocation creep process. The activation energy of the process is obtained as 159 kJ/mol, similar to that for the self-diffusion of Cu or Zn. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.