Microstructure, tensile properties and fracture behaviour of Al2O3 particulate-reinforced aluminium alloy metal matrix composites

Abstract

The tensile deformation and fracture behaviour of aluminium alloy 2014 discontinuously-reinforced with particulates of Al2O3 was studied with the primary objective of understanding the influence of reinforcement content on composite microstructure, tensile properties and quasi-static fracture behaviour. Results reveal that elastic modulus and strength of the metal-matrix composite increased with reinforcement content in the metal matrix. With increase in test temperature the elastic modulus showed a marginal decrease while the ductility exhibited significant improvement. The improved strength of the Al-Al2O3 composite is ascribed to the concurrent and mutually interactive influences of residual stresses generated due to intrinsic differences in thermal expansion coefficients between constituents of the composite, constrained plastic flow and triaxiality in the soft and ductile aluminium alloy matrix due to the presence of hard and brittle particulate reinforcements. Fracture on a microscopic scale initiated by cracking of the individual or agglomerates of Al2O3 particulates in the metal matrix and decohesion at the matrix-particle interfaces. Failure through cracking and decohesion at the interfaces increased with reinforcement content in the matrix. The kinetics of the fracture process is discussed in terms of applied far-field stress and intrinsic composite microstructural effects.