Quantitative investigation of hot tearing sensitivity in Al-9Si-Fe(Mn) alloys

The effect of Fe addition (0.5, 1, 1.5 and 2 wt %) and Mn modification (Mn/Fe=0.5) on hot tearing behavior of F332 Al alloys was investigated. The results show that due to the formation of fine interdendritic -Al5FeSi platelets, Fe addition up to 0.5 wt% improves high temperature tensile properties and promotes the formation of equiaxed grains thereby increases the hot tearing resistance of the alloy by about 25%. Further addition of Fe up to 2 wt%, however, increases the size and volume fraction of -platelets, decreases the tensile properties, reduces the fluidity and interdendritic feeding and consequently substantially increases the hot tearing susceptibility (HTS). Mn addition, however, was shown that changes the morphology of -platelets to less harmful Chinese script, polyhedral or star-like α-Al15(Fe,Mn)3Si2 whereby improves the tensile properties and interdendritic feeding characteristic of the alloy. Therefore, the HTS value is decreased to zero for 0.5 and 1 wt% Fe alloys, but increased by 50 and 40 %, respectively in the case of 1.5 and 2 wt% Fe containing alloys.