Chemical composition of the Ni-containing intermetallic phases in the multicomponent Al alloys

In this study an effect of the alloying elements content and cooling rate on the morphology and chemical composition of the Ni-containing intermetallic phases in the Al-Si piston alloys has been examined. Compiled procedure of the selection and classification of the point X-ray microanalysis results allowed to estimate homogeneity range of the particular classes of the Ni-containing intermetallic phases occurred in the AlSi12MCuNiMg and AlSi21CuNi alloys. Replacement range: Cu → Ni in the Al3(CuNi)2 phase, and Fe → Ni or Cu → Fe in the Al9(FeNi)2 phase has been estimated and compared to that reported previously. The obtained results showed that chemical composition of the Ni-containing microstructure constituents locally reflected the sequence of precipitation processes on the alloy solidification path. The process of the formation of the Ni-containing intermetallic phases in form of terminal solid solutions of alloying elements in the crystal structure of the base phase through series of both peritectic and eutectic reactions has been discussed.