Fabrication and mechanical properties of SiCw/ZK51A magnesium matrix composite by two-step squeeze casting

A modified squeeze casting process, two-step squeeze casting, was proposed for fabrication of metal matrix composites (MMCs), and SiCw/ZK51A magnesium matrix composite was fabricated by this new technique. The mechanical properties of the composite were investigated by means of tension test, and the microstructure and fracture surface were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. It was revealed that the two-step squeeze casting is an effective route for fabrication of magnesium matrix composites. The SiCw/ZK51A composite fabricated by this new technique possesses very high modulus and mechanical strength as compared with the unreinforced matrix alloy, with the increment in modulus and 0.2% offset yield strength of the composite being linearly proportional to the whisker volume fraction. The optimal casting temperature for the fabrication of the SiCw/ZK51A composite was found to be about 760°C. Furthermore, no evidence of any interfacial reaction was found in the SiCw/ZK51A composite, attesting that SiC whiskers are very stable reinforcements for magnesium matrix composites.