An Investigation Of The Microstructures And Mechanical Properties Of SiC Particles Reinforced Aluminum Matrix Composites

SiC reinforced aluminum alloy composites are widely used in aerospace, military and civil manufacturing industries due to their enhanced mechanical properties over the corresponding aluminum alloys. In this study, powder metallurgy method was used to fabricate SiC particle reinforced Al matrix composites. XRD, SEM, density analysis, hardness and tensile tests were used to investigate the effect of sintering temperature, extrusion, volume fraction, particle size and particle distribution on the microstructures, mechanical properties and fracture mechanisms of SiC reinforced aluminum composites. It has been shown that:(1) For SiC particles reinforced Al-Cu alloy composite, increasing the sintering temperature can significantly improve the density and mechanical properties of the composites by decreasing the number of pores, and improving the interfacial bonding strength.(2) Extrusion can break up the oxide coating on the matrix powder surfaces, increase the interfacial bonding strength, refine the particle size, decrease the number of pores, and thus, improve the density and mechanical properties of the composite. Extrusion can also significantly improve the distributed uniformity of SiC particles when the strength of the aluminum matrix is low.(3) The yield and tensile strengths of the composites decrease with increasing the volume fraction of the SiC particles, while the hardness of the composites increases with increasing the volume fraction of the SiC particles. Large-sized particles crack more easily during extrusion and tensile testing, and the fractured particles cannot withstand tensile load, but can endure indentation load.(4) The SiC particles distribute more uniformly in the matrix with increasing the mixing time. Small ratio between matrix/reinforcement particle sizes results in enhanced uniformity in SiC particle distribution in the matrix. Homogenous distribution of the SiC particles results in higher yield strength, ultimate tensile strength and elongation.(5) The decrease of the SiC particle size improves the tensile and yield strengths because of the larger interfacial surface area and higher work hardening rate, but decreases the ductility of the composites due to the smaller inter-particle spacing.(6) The fracture mechanism of SiC reinforced aluminum composites belongs to a mixed mode. During deformation, the fracture of the composites is dominated by the ductile fracture of the matrix and the brittle fracture of the SiC particles, if the interfacial bonding between the SiC particles and the matrix is strong. On the other hand, the main fracture mechanism changes to the ductile fracture of matrix and the interfacial decohesion between SiC particles and the matrix, if the interfacial bonding between the SiC particles and matrix is weak.This research systematically studied the effect of preparation parameters on the microstructures and mechanical properties of SiC particles reinforced aluminum matrix composites, and provide a reference for the fabrication of high performance metal matrix composites.