Processing maps, microstructure evolution and deformation mechanisms of extruded AZ31-DMD during hot uniaxial compression

Abstract

Processing maps for hot working of AZ31 magnesium alloy prepared by disintegrated metal deposition (DMD) technique followed by hot extrusion, have been developed in the temperature range 250–550°C and strain rate range 0.0003–10s−1. The starting extruded rod had a strong texture with the extrusion direction aligned with 〈101¯0〉. The map developed exhibits three domains in the temperature and strain rate ranges as follows: (1) 250–350°C and 0.01–0.0003s−1; (2) 350–500°C and 0.0003–0.01s−1; and (3) 350–450°C and 1–10s−1. Domains (1) and (3) represent dynamic recrystallization which is respectively controlled by lattice self-diffusion and grain boundary self-diffusion, as identified on the basis of apparent activation energy values. Within the two DRX domains, the grain size varies linearly with Zener–Hollomon parameter. In domain ♯2, grain boundary sliding occurs leading to wedge cracking in compression and intercrystalline cracking in tension. It is concluded that the relatively safe workability windows for this material are those for domains (1) and (3), the latter being preferable for industrial processing due to its higher strain rate range although the product properties will be anisotropic.