Effect of the Sic Particle Orientation Anisotropy on the Tensile Properties of a Spray-Formed Sicp/Al-Si Composite

The effects of the SiC particle orientation anisotropy on the tensile properties of spray-formed SiCp/Al-Si composites was investigated and compared with that of the unreinforced matrix alloy. The addition of SiC particles increased the elastic modulus but decreased ultimate tensile strength and elongation of an Al-Si alloy under peak-aged conditions. Microstructure disolayed a preferred orientation of the reinforcement particles, which were inclined to align parallel to the extrusion axis. Meanwhile, the degree of orientation anisotropy turned to be higher with larger reinforcement sizes particle. The elastic modulus, tensile strength and elongation in the longitudinal orientation (parallel to the extrusion axis) were higher than those in the transverse orientation (perpendicular to the extrusion axis). The fracture mechanism in a composite with 4.5 mu m particles was attributed to interfacial debonding between SiC and matrix in the two orientations. However, in case of aluminum reinforced wild 20 mu m particles, both cracking of SiC particles in the longitudinal orientation and the interfacial debonding in the transverse orientation played an important role in fracture.