Fabrication and characterisation of graphite/alumina reinforced copper composites

The infiltration of graphite/alumina preforms with a bronze alloy has been investigated taking into account the influence of the binder type, the graphite/alumina content in the preform and the percentage of binder in water. The preforms showing an acceptable rigidity have been infiltrated with a CuSn12 bronze alloy by squeeze casting considering two different pouring temperatures. The composite produced has been characterised in terms of density, Brinell hardness, coefficient of thermal expansion, as well as friction and wear behaviour. The coefficient of friction for the bronze matrix composite is around 0.17, being three times lower than that shown by the unreinforced copper alloy. Given the contact geometry (ball of steel against a planar sample) and testing conditions (20°C, dry sliding, 40% humidity), the composite wear rate is around twenty times lower that of the bronze, being 10^–6mm²/kg for the composite and 2 × 10^–5 mm²/kg for the bronze.