Potential of multi-pass ECAP on improving the mechanical properties of a high-calcium-content Mg-Al-Ca-Mn alloy

In this study, the multi-pass equal channel angular pressing (ECAP) was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties. The obtained results showed that the network-shaped Mg2Ca and (Mg, Al)(2)Ca eutectic compounds in as-cast alloy were gradually crushed into ultra-fine particles after ECAP, which exhibited a bimodal particle size distribution and most aggregated at original grain boundaries. Dynamic recrystallization (DRX) of alpha-Mg occurred during hot deformation via a particle stimulated mechanism, and the almost complete DRX with an average grain size around 1.5 mu m was obtained after 12p-ECAP. Moreover, abundant nano-sized acicular and spherical precipitates were dynamically precipitated within alpha-Mg grains during ECAP. Tensile test results indicated that the maximum strength and ductility were acquired for 12p-ECAP alloy with ultimate tensile strength of 372MPa and fracture elongation of 8%. The enhanced strength of the alloy could be ascribed to fine DRX grains, ultra-fine Ca-containing particles and dynamically precipitated nano-precipitates, while the improved ductility was mainly due to the refined and homogeneous microstructure, and weak texture with high average Schmid factors. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.