THE EFFECT OF CERAMIC REINFORCEMENTS DURING SPRAY ATOMIZATION AND CODEPOSITION OF METAL MATRIX COMPOSITES .1. HEAT-TRANSFER

The effects of ceramic particulates on microstructure during spray atomization and codeposition of metal matrix composites (MMCs) were investigated, with particular emphasis on the transfer of thermal energy from the atomized matrix to the ceramic particulates. A thermal energy model, based on fundamental heat-transfer considerations, was formulated, and the numerical results were compared to the microstructural findings. In this model, the transfer of thermal energy from the atomized metal to the ceramic phase was computed for two separate stages: (a) atomization and (b) deposition. The numerical results obtained using SiC particulates in an aluminum matrix show that 10 pct of the enthalpy of the atomized spray is transferred to the ceramic particulates during atomization, whereas 10 pct of the thermal energy available after deposition will be consumed in the process of equilibrating the temperature of the particulates to that of the matrix. The enhanced heat transfer achieved as a result of the presence of ceramic reinforcement was correlated with the grain sizes of various unreinforced and reinforced spray-deposited MMCs.