Effect of reinforcement concentration on the properties of hot extruded Al-Al2O3 composites synthesized through microwave sintering process

In this study, Aluminum matrix composite reinforced with 5, 10 and 15 vol% Al2O3 particles were fabricated using microwave assisted rapid sintering technique followed by hot extrusion. The effect of concentration of Al2O3 reinforcement particles on physical, structural, mechanical and thermal behavior of the extruded Al-Al2O3 composites was investigated. Results showed that, as the content of hard ceramic particles increases, it improves overall mechanical properties including microhardness, 0.2% yield strength, ultimate compression/tensile strength, and Young's modulus while the ductility and co-efficient of thermal expansion decreases. XRD patterns and SEM/EDS mapping images show a uniform distribution of Al2O3 particles in the Al matrix. Owing to the existence of the reinforcement particles, the Al-15vol%Al2O3 composite attains an ultimate tensile strength and yield strength of 154±6 MPa and 139±8 MPa, respectively, representing an enhancement of 33% and 32.4% compared to the pure aluminum. In particular, the extruded Al-15vol%Al2O3 composite exhibited superior tensile strength at higher temperatures (~128±3 MPa at 100 °C and 110±4 MPa at 200 °C) when compared to Al matrix. The reduction of coefficient of thermal expansion (CTE) was ascribed to the strong interface bonding in the Al/Al2O3 composites. Findings presented are expected to pave the way to design, develop and synthesize aluminum based composites for weight critical applications at ambient and reasonable elevated temperatures.