Improving the Mechanical and Wear Properties of Mg-Mg2Si In-Situ Composite via Hybrid SiCp and Hot Working

Numerous investigations have been performed on Mg/SiCp or Mg-Si systems; however, there is a shortage of research papers about Mg-Mg2Si-SiCp in the literature. Therefore, the structural evolution, tensile performance, and wear behavior of the Mg-Mg2Si-xSiC (x = 0, 1, 3, and 5 wt.%) hybrid composites were investigated. SiC particles (15 mu m) were inserted into the Mg-Mg2Si in-situ composite using a stir casting system to form alpha-Mg, eutectic structure, primary Mg2Si, and SiC particles in the microstructure. Although SiCp addition reduced the grain size of the Mg-Mg2Si in-situ composite, no remarkable enhancement was found on ultimate tensile strength (UTS) in the as-cast state. On the other hand, by adding SiCp, yield stress (YS) was improved by decreasing the grain size due to grain refinement and particle strengthening mechanisms. The usage of hot extrusion led to structural refinement and uniform structures with less SiCp agglomeration. The optimum percentage of SiCp was 3 wt.% which diminished the grain size from similar to 153 mu m to similar to 5 mu m and developed the UTS values from 140.7 MPa to 246.2 MPa for the as-cast and hot extruded composites, respectively. Also, YS values met an increasing trend, from 146.5 to 190.3 MPa, than that of UTS in the extruded state. According to the Hall-Petch equation, the essential strengthening mechanism was grain refinement with about 73% effectiveness. Moreover, the fracture behavior of the composite shifted to a ductile form by applying the extrusion process, which revealed itself in the form of dimples. Wear analyses exhibited that the addition of SiCp and extrusion improved the wear properties, and the abrasion, adhesion, and the oxidation mechanisms played essential roles in the composites' wear behavior.