Thermo-mechanical behavior and bulk texture studies on AA5052-H32 under dynamic compression

Abstract

In this paper, the thermo-mechanical response of commercially important AA5052-H32 alloy was investigated under dynamic compression over a wide range of strain rates and temperatures. Very high strain rate experiments were conducted using a miniaturized Kolsky bar to reach a peak strain rate of 105s−1. Dynamic flow stress was found to increase by 180MPa at this peak strain rate, which was twice the value obtained under quasi-static loading. At room temperature the material showed negative strain rate sensitivity under quasi-static loading with serrated flow behavior and positive strain rate sensitivity under dynamic loading. The strain rate transition occurred around a strain rate of 6000s−1. Furthermore, thermal softening under dynamic compression was investigated up to a temperature of 0.75Tm at a constant strain rate. It was found that the flow stress decreased linearly with temperature indicating that thermal activation dominates the deformation over this temperature range. Detailed study of microstructure of the deformed specimens showed that the texture development was less under high strain rate as well as high temperature loading when compared to the quasi-static room temperature deformation. Based on the stress vs. strain curves, a comparison between two constitutive models, Johnson-Cook and Voyiadjis-Almasri, was made to capture the flow stress behavior as a function of strain rate.