한국주조공학회

In this study the fabrication technology and mechanical properties of AC8A/Al_2O_3 Composites by squeeze casting process were investigated to develope for application as the piston materials that require good friction, wear resistance, and thermal stability. AC8A/Al_2O_3 composistes without a porosity and the break of preform were fabricated at the melt temperature of 740℃, the preform temperature of 500℃, and mold temperature of 400℃ under the applied pressure of 1200kg/cm^2 as the results of the observation of microstructures. As the results of this study, the tensile strength of AC8A/Al_2O_3 composites was not increased linearly with Al_2O_3 volume fraction and so it seemed not to agree with the rule of mixture, which had been used often in metal matrix composite. Also the tensile strength after thermal fatigue test was little different from that before the test. Consequently it was thought that AC8A/Al_2O_3 composites fabricated under our experimental conditions had a good thermal stability and subsequently a good interface bonding. Wear rate(i.e., volume loss per unit sliding distance) of AC8A/Al_2O_3 composites was decreased with Al_2O_3 volume fraction and the sliding speed at both room temperature and 250℃ and so there was a good correlation between wear rate and hardness. Also the wear rate of AC/8A20% Al_2O_3 composities was obtained the value of 1.65cm^3/cm at sliding speed of 1.14m/sec as compared with about 3.0x10^{-8}cm^3/cm hyereutectie Al-Si alloy(Al-16%Si-2%Cu-1%Fe-1%Ni), which applied presently for piston materials. The wear behavior of Al_2O_3 composites was observed to a type of abrasive wear by the SEM view of wear surface.