A constitutive theory for metallic glasses at high homologous temperatures

The elastic-viscoplastic constitutive theory of Anand and Su [Anand L, Su C. J Mech Phys Solids 2005;53:1362] for metallic glasses has been extended to the high homologous temperature regime. The constitutive equations appearing in the theory have been specialized to model the response of metallic glasses in the temperature range 0.7v(g) <= v <= v(g) and strain rate range [10(-5),10(-5)] s(-1). The material parameters appearing in the theory have been estimated for the metallic glass Pd40Ni40P20 from the experimental data of De Hey et al. [De Hey P, Sietsma J, Van Den Beukel A. Acta Mater 1998;46:5873]. The model is shown to capture the major features of the stressstrain response, and the evolution of an order-parameter for this metallic glass. In particular, the phenomena of stress overshoot and strain softening in monotonic experiments at a given strain rate and temperature, as well as strain rate history effects in experiments involving strain rate increments and decrements, are shown to be nicely reproduced by the model. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.