Effect of extrusion-cladding rolling on microstructure and mechanical property of SiC_P reinforced magnesium alloy(AZ91) clad plate

The AZ91 alloy was introduced into SiC_P reinforced magnesium alloy(AZ91) (SiC_P/AZ91) composites by hot extrusion, and then the AZ91-(SiC_P/AZ91) clad plate with the thickness of 2 mm was prepared in present work. After that, the microstructure and mechanical properties of SiC_P/AZ91 clad plate influenced by hot rolling were investigated. The results indicate that the rolling formability of SiC_P/AZ91 is significantly improved by introducing AZ91 alloy. As compared with AZ91 layer, the SiC_P/AZ91 layer possesses much finer grain size and higher hardness. With the increase of rolling deformation amount, the grains in the AZ91-(SiC_P/AZ91) clad plate grow up, the amount of precipitated phase decreases accompanied with the increase of its size. All above phenomena account for the decreasing micro-hardness. As compared with the extruded AZ91-(SiC_P/AZ91) clad plate, the yield strength of rolled clad plate increases from 272 MPa to 341 MPa and the tensile strength increases from 353 MPa to 404 MPa with the deformation amount of 50%. During the tensile process, the crack initiation and propagation occur preferentially in the SiC_P/AZ91 layer due to the interfacial debonding between SiC_P and Mg matrix alloy. However, the existence of the AZ91 layer will hinder the propagation of micro-cracks.