Microstructure and mechanical properties of SiC_p/AZ91 composites prepared by freeze casting and hot extrusion

In this work, the SiC_p/AZ91 composites prepared by freeze casting were subjected to hot extrusion, and then the microstructure, mechanical properties and fractural behavior were given and analyzed. The results showed that, the particle distribution of SiC_p/AZ91 composites changed from lamellar to uniform distribution after extrusion, which significantly improved the mechanical properties of the composites. With increasing volume fraction of SiC_p, the thermal expansion coefficient of the as-extruded SiC_p/AZ91 composites decreased significantly, accompanied by the improvement in elastic modulus. When the content of SiC_p was 25 vol.%, the ultimate tensile strength (UTS) and elastic modulus of the composite reached ∼513 MPa and ∼91 GPa, respectively, which exhibited the best combination of tensile strength and modulus. During the loading process, microcracks were more likely to initiate at the interface between the SiC_p and magnesium matrix, and excessive SiC_p could aggravate the stress concentration at the interface significantly, which led to the interconnection of microcracks and failure of the composite.