Microstructural Refinement and Enhancement in Mechanical Properties of Magnesium/SiC as-Cast Composites via Friction Stir Processing Route

Abstract

In the current investigation, friction stir processing (FSP) was applied to pure magnesium/SiC (silicon carbide) microcomposites. The cylindrical threaded tool pin profile, tool travel speed of 50 mm/min and tool rotational speeds of 1000 rpm, 1300 rpm and 1600 rpm were used to perform the experiments. The effect of FSP on SiC particle's distribution and matrix microstructure were evaluated by using an optical microscope and scanning electron microscope techniques. The mechanical characterization involving tensile yield strength, ultimate tensile strength and microhardness was carried out. The results of the study revealed that FSP was clearly successful in breaking the SiC particle's clusters, refinement of the particle size and uniform distribution of SiC in the magnesium matrix, which subsequently led to the betterment of tensile strength and ductility of the composite. It was also observed that the grain size of composite increased when the rotational speed was enhanced to 1600 rpm owing to high heat input. The study concluded that the friction stir-processed composites with refined grain size and reduced porosity resulted in much higher hardness (106 Hv), yield tensile strength (90 MPa) and elongation (10.6%) as compared to their counterparts.