Fabrication of AZ91D/SiC Magnesium Matrix Composite with High Particle Reinforcement Loading, Produced by Mechanical Milling of Chips and Semi-Solid Powder Processing

Semi-solid powder processing (SPP) is a technology that combines traditional powder metallurgy and semi-solid forming methods and has potential to produce metal matrix composites with low cost and high efficiency. In this research, SPP was used to fabricate magnesium alloy AZ91D matrix composite with high SiC reinforcement loading. First, for preparing powder, AZ91D magnesium alloy chips with average size of 4 × 2 × 1 (mm) were mechanically milled with a planetary ball mill and then, for mechanical alloying, the obtained powder with 50 wt.% (36 vol.%) 2 µm silicon carbide were milled again. The milled powder and also AZ91D/SiC composite powder were investigated by a field emission scanning electron microscopy (FESEM), particle size analyzer (PSA) and X-ray diffractometery (XRD). Spark plasma sintering (SPS) apparatus was used to densify the prepared composite powder by heating the powder mixture to semi-solid temperatures 561 °C (equivalent to liquid fraction of 30% in the whole sample) and 576 °C (equivalent to liquid fraction of 40% in the whole sample) applying pressure simultaneously. Microstructure, density, hardness, compressive strength and also present phases in the sintered samples were studied. The results show composites with few porosities and good mechanical properties can be prepared by SPP.