Deformation and microstructure evolution of a high strain rate superplastic Mg-Li-Zn alloy

An Mg-8Li-2Zn alloy plate was prepared through a two-pass extrusion process, and the high-temperature behavior of the alloy was investigated at 473-593 K under the initial strain rate of 1.0 x 10(-2)-1.0 x 10(-1) s(-1). The results indicated that the alloy exhibits a significant high strain rate super-plasticity with a maximum elongation of 279% under an initial strain rate of 1.0 x 10(-2) s(-1). The activation energy is 89.4 kJ/mol, indicating that the dominant deformation mechanism in the alloy is grain-boundary sliding controlled by grain-boundary diffusion. Cavities nucleate and coalesce during deformation, which is one of the results leading to the fracture of the material. (C) 2011 Elsevier B. V. All rights reserved.