Mechanical behavior and microstructural evolution of a Mg AZ31 sheet at dynamic strain rates

摘要

The mechanical behavior of an AZ31 Mg sheet has been investigated at high strain rate (10~3 s~(-1) ) and compared with that observed at low rates (10~(-3) s~(-1)). Dynamic tests were carried out using a Hopkinson bar at temperatures between 25 and 400 °C. Tensile tests were carried out along the rolling and transverse directions and compression tests along the rolling and the normal directions in both, strain rate ranges. The tension-compression yield asymmetry as well as the yield and flow stress in-plane and out-of-plane anisotropies were investigated. The micro structure of the initial and tested samples was examined by electron backscatter diffraction. The dynamic mechanical behavior is characterized by the following observations. At high temperatures the yield asymmetry and the yield anisotropies remain present and twinning is highly active. The rate of decrease in the critical resolved shear stress of non-basal systems with temperature is smaller than at quasi-static rates. Rotational recrystallization mechanisms are activated.