Enhancement of Strength and Hot Workability of AZX312 Magnesium Alloy by Disintegrated Melt Deposition (DMD) Processing in Contrast to Permanent Mold Casting

Abstract

AZX312 (AZ31-2Ca) magnesium alloy, with starting conditions of as-cast (AC), cast-homogenized (CH), and disintegrated melt deposition (DMD), is examined in terms of its compressive strength and hot working behavior to establish the relative merits and limitations of these processing routes. Processing maps are developed in the temperature range of 300–500 °C and strain rate range of 0.0003–10 s−1, and mechanisms of hot deformation are established based on microstructures, tensile ductility, and activation parameters. The alloy in AC and CH conditions has a large grain size with intermetallic phases at the grain boundaries and in the matrix. In DMD processed alloy, the grain size is very small and the phases are refined and distributed uniformly. The compressive strength is significantly improved by DMD processing, which is attributed to the grain refinement. The processing maps for AC and CH conditions are similar, exhibiting only a single workability domain, while the DMD processed alloy exhibited three domains that enhanced workability. The additional workability domain at higher strain rates is an advantage in designing forming processes that facilitates faster production, while the fine grain size produced by a finishing operation in the lower temperature domain will improve the mechanical properties of the product.