Efficient use of iron impurity in Al-Si alloys

An efficient way of using iron to optimize the as-cast microstructure of Al-Si alloys was investigated in this study. Before pouring, Al-12.1%Si-0.1%Fe melts were cooled from 830 °C and held for 10 min at 587 °C, 600 °C and 620 °C, respectively, and then these melts were homogenized at 830 °C for another 20 min. Both the cooling curves of melts and the as-cast microstructure indicate that a lower-temperature holding can result in a considerable amount of (AlFeSi) clusters which subsequently enhance the silicon phase nucleation. Due to the late occurrence of these (AlFeSi) clusters in naturally cooled melts and without a low-temperature holding, the enhancement effect of iron on silicon nucleation is too weak and often neglected.