Effect of P and Sr complex modification on Si phase in hypereutectic Al–30Si alloys

In this paper, the complex modification process of P and Sr for hypereutectic Al–30Si alloys was investigated. After the addition of 2.0% Al–3P and 0.7% Al–10Sr master alloys continuously added during the melt inoculation and solidification process, the primary Si can be significantly refined from more than 200.0 μm decreasing to 32.8 μm with homogeneous distribution and eutectic Si was obviously modified as fibrous simultaneously. The modification mechanism was also studied. It is found that the melt temperature has influence in the interaction between P and Sr. At about 1000 °C, AlP is surrounded by Al4Sr phase to form encapsulation structure, which would react with Sr to form Sr3P2 at approximate 1300 °C. However, P and Sr take the respective form of AlP and Al4Sr at 770 °C, which just be the reason for the excellent complex modification of Si phase using continuous refining method.