| 30vol.%SiC_p/AZ91 composite with the reinforcement diameter of 15μm averagely was successfully synthesized , and subsequently following vacuum semi-solid stir-casting and hot pressing. Microstructures,fracture morphalogies and SiC_p-Mg interface of SiC_p/AZ91 composite before and after heat-treatment were observed by optical microscopoe(OM),scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. Additionally,consisting elements of the composite fracture surfaces and phases by the SiC_p-Mg interface were analysed with energy dispersive spectrometer (EDS) and electron diffraction pattern.The results showed that semi-solid stir-casting method was suitable to fabricate particle-reinforced magnesium matrix composites and the particle sedimentation and clustering were under effective control,and uniform particle distribution was obtained; Vacuum semi-solid hot-pressing effectively reduced the porosity volume fraction and modified the particle distribution as well. After aging treatment ,the composites' ultimate strength were enhanced to a large extent when compared to that of AZ91 alloy ,while heat treatment only led to a slightly improvement in macrohardness.Nano-sized MgO particles were found at the SiC_p-Mg interface ,as well as typical fine interfacial precipitate,Mg17Al12. The 30vol.%SiC_p/AZ91 exhibited brittle fracture mode,similar to that of AZ91 alloy;During tensile test,SiC particles were identified as transcrystalline cleavage with secondary micro-cracks and the matrix showed brittle fracture surface after a slightly plastic deformation,and SiC_p-Mg interface debonding was also observed, and the main fracture behavior of 30vol.%SiC_p/AZ91 composite was interface failure.
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