Duplex Nucleation and Its Effect on the Grain Size and Properties of Near Eutectic Al-Si Alloys.

Duplex nucleation and its effect on the grain size and properties of near eutectic Al-Si alloys were investigated in this work. It is found that the grain size of Al-13Si-1Cu alloy can be greatly refined by addition of Al-2Ti-0.5B-0.5C and Al-P master alloys, and TiB/AlP duplex nucleation was observed at the nuclei of primary silicon in the process of studying the refinement mechanism. TiB phase coated by Al co-existed with AlP in the nuclei of primary Si. The existence of Al phase should not only guarantee the promotion of TiB particles on the nucleation of AlP particles, but also made TiB particle stable in the core of primary silicon through the interaction with the Si phase. Duplex nucleation can not only affect the grain size of Al-Si alloy, but also effect of the distribution of strengthening phases in Al-Si alloy and improve the properties. Compared with single Al-P master alloy treatment, the tensile strength of Al-12Si-4Cu-2Ni-1Mg alloy after duplex nucleation treatment are improved obviously. The fatigue performance of Al-12Si-4Cu-2Ni-1Mg alloy is also improved significantly by the duplex nucleation.