Refinement of primary Si in Al-20%Si alloy by MRB through phosphorus additions

A Si phase refining process involving phosphorus additions and a mechanical rotational barrel (MRB) is described. The microstructure of Al-20%Si alloys obtained under different pouring temperature and rotation speed was investigated. The average particle size of primary Si first decreased and then increased with the decrease of pouring temperature, meanwhile decreased continuously with the increase of rotation speed. Finest primary Si with size of about 15 μm was achieved when the rotation speed was 90 r/min and the pouring temperature was around 700-720 °C. The refinement and uniform distribution of primary Si were mainly attributed to the presence of AlP particles provided by the phosphorus addition, and chilling and stirring effects induced by the rotational barrel.