Hot shear deformation constitutive analysis and processing map of extruded Mg–12Li–1Zn bcc alloy

Abstract

The hot shear deformation behavior of an extruded Mg–12Li–1Zn alloy was studied by shear punch test (SPT) in the temperature range 200–300°C, and in the shear strain rate range 1.2×10−3–6.0×10−2s−1. Based on the constitutive analysis of the SPT data, it was found that a sine hyperbolic function could properly describe the hot shear deformation behavior of the material. The activation energy of 108kJmol−1 calculated from sine hyperbolic function together with the power-law stress exponents of 3.6–4.7 is indicative of lattice-diffusion-controlled dislocation climb mechanism as an operative deformation mechanism. As a new approach, the shear processing map was developed in order to determine the optimum processing condition, which was found to be 300°C and 1.2×10−3s−1. Domains of the processing map are also interpreted on the basis of the associated microstructural observations. It was found that the post-deformation microstructure is sensitive to the Zener–Hollomon parameter, so that DRX was encouraged with decreasing Z-value.