It is a crucial measure to refine Mg2Si phases for improving the strength and ductility of Mg-Al-Si alloys.In present study,TiB2 nanoparticles were selected as heterogeneous nucleating agents for Mg2Si and introduced into Mg-4Al-xSi(x=0.5,1.0,1.5,2.0)alloy melts using mechanical stirring in the semi-solid state followed by ultrasonic treatment,and TiB2 and Mg2Si hybrid reinforced magnesium matrix composites(TiB2/Mg-4Al-xSi(x=0.5,1.0,1.5,2.0))were prepared consequently.The morphology and size of the Mg2Si phase in the composites were observed using optical microscopy and scanning electron microscopy,and the volume fraction of the Mg2Si phase was statistically analyzed using image analysis software Image-J,focusing on the wear-resistant properties of the composites with different Si contents.The results showed that the incorporation of TiB2 nanoparticles significantly refined the eutectic Mg2Si phase and primary Mg2Si phase in the composites,and significantly improved the hardness and wear resistance of the composites.The wear resistance of the composites increased and then decreased with the increase of Si content and reached when Si content is 1.5 wt.％.
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