Two-Level Constitutive Model of Metal with a Comprehensive Account of Temperature and Strain Rate Changes

An important goal of industrial development is to improve the forming and thermomechanical processing technologies, both in order to get the best characteristics of finished products and to reduce energy costs and material consumption. The key step in solving such problems is the correct formulation of a material constitutive model. The temperature and strain rate attained in particular metal forming processes can vary significantly and have a strong influence on the structural evolution of the material and, consequently, on the resulting physical and mechanical properties. However, there are almost no processes in which the temperature and strain rate are constant and equal at all points of the processed product. In this regard, it is relevant to build constitutive models that correctly account for the influence of changing temperature and strain rate on the material response. Based on our previous review, we propose here a modified two-level statistical model that correctly accounts for the temperature and strain rate effects on intragranular dislocation slip and the associated material response. The model parameters are determined for an fcc polycrystal of Al 2024-T351 alloy using literature data on the compression behavior of this alloy at different temperatures and strain rates. A detailed description is given for an algorithm developed to identify the model parameters using data from constant temperature and constant strain rate experiments. The proposed model showed adequate results for loading conditions with changing temperature and strain rate.