EFFECT OF CASTING OVER-PRESSURE ON THE FATIGUE RESISTANCE OF ALUMINUM ALLOY A356-T6

摘要

The fatigue resistance of an Al-Si casting alloy (A356) solidified under pressures up to 20 atm and under a vacuum was investigated. Pressures of 10 and 20 atm mitigated microporosity in plate-castings, and this enhancement significantly improved fatigue resistance. Cooling rate during solidification, which affects the dendrite arm spacing (DAS), was also varied. Also studied were Sr-modification and the use of a flux to capture oxide-bifilms. Fatigue life increased as the maximum pore size decreased, which resulted from the over-pressures and/or a decrease in DAS. The use of flux in the mold and Sr-modification, especially when employed simultaneously, also increased fatigue life.