MECHANICAL-PROPERTIES OF ALUMINUM-BASED PARTICULATE METAL-MATRIX COMPOSITES

A study has been made on a range of particulate-reinforced metal-matrix composites, all based on the aluminium alloy 7075, in underaged, peak aged and overaged conditions. Heat treatments were designed such that equivalent underaged and overaged matrix strengths were achieved. The reinforcement used was silicon carbide, in a range of particle sizes. All composites were produced by the co-spray deposition process. The tensile properties and fracture toughness of these materials were investigated at room temperature. Material reinforced with coarse particulate was observed to have poor yield strength, poor fracture stress and poor ductility compared with materials reinforced with finer particulate. Materials reinforced with the finest particulate had the greatest ductility. However, the coarse particulate-reinforced material exhibited reasonable toughness, similar to that of material containing the finest particles. A model to predict fracture toughness from tensile ductility and nominal interparticle spacing is proposed which offers an explanation for the observed experimental results.