Evolution of interfacial microstructures and mechanical properties of C_f/AZ91 composite during heat treatment

C_f/AZ91 composite was fabricated by liquid-solid extrusion following vacuum pressure infiltration technique (LSEVI). There were some inevitable shortcomings, such as interfacial mismatch stress, in spite of the advantages of LSEVI. Heat treatment was conducted to modify the composite. It was confirmed that the interface and mechanical properties of the C_f/AZ91 composite could be modified by heat treatment. The number of interfacial precipitates Mg₁₇Al₁₂ decreased and the size of the granular precipitates was reduced from about 500 nm to about 200 nm due to recovery. Nanocrystalline ceramic particles MgO with disordered intergranular films and dislocations, resulting from unusual deformation mechanisms and interfacial stress, were observed at the interface. The tensile strength of 2D-C_f/AZ91 composite increased from 400 MPa to 420 MPa after heat treatment. The strengthening of the composite after heat treatment was attributed to recovery, relief of interfacial stress and nano-sized MgO interfacial layer.