THE EFFECT OF APPLIED PRESSURE ON PARTICLE-DISPERSION CHARACTERISTICSAND MECHANICAL-PROPERTIES IN MELT-STIRRING SQUEEZE-CAST SICP AL COMPOSITES/

The fabrication of metal-matrix composites (MMCs) by casting process i s a very promising way of manufacturing near net shape components at r elatively low cost. One of these casting processes, the squeeze-castin g technique, has characteristics such as fine microstructures as a res ult of rapid cooling, low porosity and good bonding between the partic le and the base alloy. This paper therefore examines, the microstructu re and mechanical properties of Al-15%SiCp composite fabricated by the melt-stirring and squeeze-casting method. The correlation between the fabrication conditions and the homogeneous dispersion of particles is investigated for SiCp-reinforced Al composites. The manufacturing par ameters in homogeneous mixing are the crucible size, the impeller size , the temperature of the molten metal, the stirring time and the stirr ing speed in the melt-stirring process. The composite slurry containin g SiCp is poured into a pre-heated die, and pressure applied in squeez e casting. The state of dispersion of the reinforcement and the fractu re surface are observed by the optical microscope and SEM. The primary product of MMCs billet is prepared under squeeze-casting conditions f or applied pressures of 70, 100, and 130 MPa. By assessing observed re sults systematically, correlation is proposed between the microstructu re, the particles behavior, the mechanical properties and the processi ng parameters for an optimum melt-stirring and squeeze-casting process of MMCs.