Solidification and casting/mould interfacial heat transfer characteristics of aluminum matrix composites

The roles of the melt and the mould material on the cooling curve parameters and the heat transfer at the casting/mould interface during solidification of Al(356) alloy and its composites reinforced with silicon carbide and graphite particles are investigated. A dimensionless thermal parameter is used to model the effect of thermophysical properties of the alloy and the composite systems, the mould materials and the heat content on the cooling rate. The reduction in the effective thermal diffusivity of the composite system at high volume fractions of insulating dispersoids plays a dominant role in reducing the cooling rates, although the heat content of the matrix alloy is lower. Addition of Mg improves the casting/mould interfacial heat transfer of the alloys and the composites studied, thus proving its multifunctional role, apart from its well-known function as a wetting promoter of ceramic reinforcements with the aluminium alloy matrix. The graphite mould yields higher heat flux transients compared to steel and the sand moulds.