Effects of micro-twin lamellar structure on the mechanical properties and fracture morphology of AZ31 Mg alloy

Abstract

The effects of a micro-twin lamellar structure on the mechanical properties and fracture morphology of AZ31 Mg alloy have been investigated through impact test, tensile test, and SEM observation of the failure surface. A hot-rolled AZ31 Mg alloy sheet was subjected to dynamic plastic deformation with the aim of introducing a {101¯2} twin lamellar structure prior to tee tensile test, because dynamic plastic deformation with a high strain rate (4–6 × 102 s–1) can activate a greater number of deformation twins in AZ31. Compared with the mechanical properties of hot-rolled and annealed Mg alloy before dynamic plastic deformation, it was found that the tensile yield stress and maximum flow stress of the AZ31 Mg alloy increase after dynamic plastic deformation, and ductility improves under tension in the range 0–30°. Based on the analyses of microstructure and fracture morphology, the phenomenon can be ascribed to the fact that the micro-twin lamellar structure can refine the matrix grain and render the microstructure more homogeneous.