Effects of beryllium and iron additions on iron-bearing phase in A357 aluminum alloys

Iron is the most deleterious impurity in the Al-Si-Mg casting alloys and can easily form inter-metallic compounds that can significantly affect the subsequent behavior of material properties. Using differential scanning calorimetry (DSC) and microstructural analysis, how the Be and Fe additions affect the iron-bearing phase in A357 alloys was investigated. The results show that the iron-bearing phase in A357 alloy comprises mainly the plate like β-AI₅FeSi and a small quantity of the script-type p{cyrillic}-AI₈FeMg₃Si₆; and that the plate-like β-AI₅FeSi proportion increases with increasing iron content in the alloy. The iron-bearing phase is mostly transformed from the plate-like β-AI₅FeSi to the script-type p{cyrillic}-AI₈FeMg₃Si₆ with the addition of Be in the alloy. The hardness of alloy samples was also tested. The results show that both the increasing iron content and Be content can increase the hardness of the alloy. This may be contributed to the change of morphology and distribution of the iron-bearing phase in A357 alloy with the addition of iron or Be to the alloy.