Microstructure and Mechanical Properties of Squeeze-Cast Hypereutectic Al-Si Alloy

초록

The effects of squeeze casting process on the microstructure and mechanical properties of hypereutectic Al-Si alloy(A390) hve been studied. Specimens with diameter of 15mm and 25mm were fabricated by indirect squeeze casting and specimen with diameter of 50mm was fabricated by direct squeeze casting The cooling rates during solidification of the squeeze cast specimens with diameter of 50mm, 25mm and 15mm were estimated from the measured cooling curves to be about 36℃/sec, 83℃sec/sec, and 106℃/sec, respectively. The size of primary Si of the squeeze cast A390 alloy which was modified at 800℃ is sensitively affected by a cooling rates during solidification. Hovever, if the alloy was modified with P at 850℃, due to easy formation of AlP compound, the effects of cooling rates during solidification on the size of primary Si is negligible. It was found that the primary Si and eutectic Si phases of the A390 alloy could be refined simultaneously by squeeze casting process. The tensile strength of squeeze cast specimen were found much superior to that of gravity mold one, and the tensile strength were remarkably improved by subsequent T6 treatment. Due to refinement of primary Si and eutectic Si, the squeeze cast specimens exbibit superior wear resistance.