Forging of the AA2618/20vol.%Al2O3p and AA6061/22vol.%Al2O3p composites: effects on microstructure and tensile properties.

The use of aluminium-based particulate reinforced MMCs for automotive components and aircraft structures have been shown to be highly advantageous over their unreinforced alloys, due to their high specific strength and stiffness and high wear resistance in a wide temperature range. The aim of this paper was to evaluate the effect of the hot forging process on the microstructure and tensile properties (at room and high temperature) of two particle reinforced composites, based on the aluminium alloys AA2618 and AA6061, reinforced respectively with 20vol.% and 23vol.% of alumina particles (Al2O3p). Microstructural analyses of the as-cast and heat-treated composites showed large grain size of the aluminum alloys matrix and a quite non-homogeneous distribution of the reinforcing particles. The forging process led to an evident grain refinement of the aluminum alloy matrix, while it did not lead to significant variations in the size and distribution of the reinforcement particles. Regarding the effect of the forging process on the mechanical properties, it induced a slight increase in hardness, tensile strength, elastic modulus and an evident increase in tensile elongation. SEM analyses of the fracture surfaces of the tensile specimens showed substantially similar morphologies for the as-cast and forged composites, both at room and high temperature. The mechanism of damage was mainly decohesion at the matrix-particle interface.