Effect of oxidization of 3D-SiC preforms on the interfacial structure and mechanical properties of co-continuous SiC/Al composites

In this study, co-continuous SiC/Al composites with oxidized 3D-SiC preforms and pure aluminum (oxidized-SiC_3D/Al) were fabricated by the vacuum-pressure infiltration technique. The interfacial structure and mechanical properties of the oxidized-SiC_3D/Al composites were investigated. The results suggested an improvement in interfacial structure between Al and the oxidized SiC preforms due to the formation of a continuous interfacial reaction layer with a non-uniform thickness. This layer mainly consisted of an Al₂O₃ phase with non-oriented lamellae and approximately equiaxed particles. However, the Al₂O₃ phase could not form a sufficiently dense layer to provide complete protection from the effects of direct contact with Al and SiC. Segregation of Si atoms was observed next to and in the interfacial reaction layers, which existed as free state Si and a supersaturated solid solution in Al. The dissolution of a few Si atoms into the Al phase near the interface was observed, which probably resulted in the formation of stacking faults. There was an optimal thickness of the interfacial reaction layer (~580 nm) for the mechanical properties of oxidized-SiC_3D/Al composites, where the compressive strength (~887 MPa) and three-point bending strength (~251 MPa) were enhanced by 18% and 15%, respectively, compared with those of the as-received SiC_3D/Al composite.