In-situ synthesis of novel Al-P-O master alloy and its refinement and modification effects on Si phases in hypereutectic Al-30Si alloys

Abstract In this work, a novel Al-P-O (Al-6Si-2.5P-Al2O3) master alloy has been developed via the in-situ salt-melt reaction route. The primary Si refinement and eutectic Si modification have been simultaneously achieved in hypereutectic Al 30Si alloy upon addition of Al-P-O master alloys. The refined and homogeneous microstructure leads to an improvement in the mechanical properties, especially ductility. Compared with the conventional Al P master alloys, the ultimate tensile strength and elongation of hypereutectic Al 30Si alloy are increased by 13.7% and 136.6%, respectively, after the addition of 0.5 wt% Al-P-O master alloys. The experimental results reveal that the enhanced nucleation potency and efficiency of AlP coupled with γ-Al2O3 particles induce the primary Si refinement while the γ-Al2O3 nanoparticle-induced TPRE poisoning causes the modification of eutectic Si.