Effect of Calcium on the Hot Working Behavior of AZ31-1.5 vol.% Nano-Alumina Composite Prepared by Disintegrated Melt Deposition (DMD) Processing

AZ31-based nanocomposites are produced by disintegrated melt deposition (DMD) processing. In this investigation, the influence of the addition of Ca to AZ31-1.5 vol.% nano-alumina composite (base) on its hot working behavior is studied to develop a processing route for manufacturing components with these composites. A processing map for the base composite in the temperature range 250–500 °C and strain rate 0.0003–10 s−1 is compared with those for composites with 1% Ca and 2% Ca. The grain size of the base composite is refined by Ca addition and the texture is strengthened. Besides nano-alumina particles, the Ca-containing composites have intermetallic particles (Mg,Al)2Ca present at grain boundaries as well as in the matrix. All the three nanocomposites exhibit three DRX domains, with one of them at high strain rate that facilitates high productivity. Addition of Ca mitigates the occurrence of wedge cracking that occurs in AZ31-1.5NAl composite. Increasing of Ca addition to 2% prevents dynamic recrystallization (DRX) at lower temperatures and strain rates and causes only dynamic recovery. At lower temperatures and higher strain rates, DRX occurs by basal + prismatic slip along with recovery via climb controlled by grain boundary self-diffusion promoted by very fine grain size in the composites.