Dependence of microstructure characteristics and mechanical properties on nanosize SiC_p contents in Mg–9Al matrix composites fabricated by ultrasonic-assisted semisolid powder hot pressing

Nanosize SiCp(n-SiCp) reinforced Mg–9Al matrix composites (Mg–9Al–xSiC,x= 2.5, 5, 7.5, 10 wt%) with nearly full densification are fabricated by the semisolid powder hot pressing technique assisted with ultrasonic. The effect of SiC nanoparticle contents on microstructures and mechanical properties of the composites is systematically investigated. Grain size and density of Mg–9Al–xSiC composites and morphology of bonding interfacial between the n-SiCp and matrix are found to be greatly dependent on the n-SiCpcontents, resulting in the strength and ductility of the composites increase first and then decrease as the increase of n-SiCpcontents. As the SiCpcontent increasing to 7.5 wt%, superior mechanical properties with the yield strength of 191 MPa, ultimate tensile strength of 248 MPa, and elongation to failure of 5.3% are achieved. The improved mechanical properties could be attributed to grain boundary strengthening, Orowan strengthening, and load transfer strengthening.