Effect of SiC particles on the microstructures and mechanical properties of Mg-9Al-1Zn based composites

The interfacial bonding between SiC and matrix in magnesium matrix composites (MMCs) has a crucial influence on their properties. In this work, SiC/AZ91 composites were prepared by stir casting and hot extruded. It was found that SiC refines grain size and decrease texture strength. The nano-state interfacial products Mg2Si and MgO adhered to the SiC surface, facilitating load transfer. The Al4C3 and Mg32(Al,Zn)49 are present near SiC, the brittleness of Al4C3 reduces the composite plasticity. After adding 1 wt% SiC, the yield strength (YS), ultimate tensile strength (UTS) and elongation (El) of AZ91 alloy increased to 250 MPa, 350 MPa and 15.1 %, respectively. El increased by more than 20 %. Higher SiC content increased YS, but UTS and El decreased significantly. The addition of few SiC can improve the properties, while high SiC content can bring excessive interfacial reaction and lead to degradation of composite properties.