Low temperature superplasticity of a dual-phase Mg-Li-Zn alloy processed by a multi-mode deformation process

A dual-phase Mg-Li-Zn alloy was processed by a severe plastic deformation method which is a method of combination of extrusion and rolling processes and enables production of a very fine grain structure. After this processing, the Mg-Li-Zn alloy exhibited a significantly large fracture elongation of 1400% at 473 K at 0.001 s(-1) . Moreover, an elongation of more than 600% was observed at 473 K even at high strain rate of 0.01 s(-1). Also, at a lower temperature of 423 K, the alloy exhibited a large fracture elongation of 720% at 0.001 s(-1). The values of the strain rate sensitivity were approximated to 0.5, which suggested that the superplastic deformation is based on grain boundary sliding. Dislocation glide is identified to be an accommodation mechanism according to the texture evolution during the superplastic deformation. The different trends of the changes of the textures in the alpha and beta phases indicated an inhomogeneity of grain boundary sliding between phases.