Constitutive base analysis of a 7075 aluminum alloy during hot compression testing

In the field of deformation process modeling, the constitutive equations may properly represent the flow behavior of the materials. In fact, these valuable relationships are used as a calculation basis to simulate the materials flow responses. Accordingly, in the present study a hot working constitutive base analysis has been conducted on a 7075 aluminum alloy. This has been performed using the stress-strain data obtained from isothermal hot compression tests at constant strain rates of 0.004, 0.04 and 0.4 s(-1) deformation temperatures of 450, 500, 520, 550 and 580 degrees C up to a 40% height reduction of the specimen. A set of constitutive equations for 7075 Al alloy have been proposed employing an exponent-type equation. The related material constants (i.e., A, n and alpha) as well as the activation energy Q for each temperature regime have been determined. The correlation of flow stress to strain rate and temperature can be deduced from the proposed equations. Furthermore, a change in deformation mechanism has been realized in the semi-solid temperature range. This has been related to the onset of lubricated flow mechanism during processing. (C) 2011 Elsevier Ltd. All rights reserved.