Influence of Internal Architectures of Cast AlSi10Cu5Ni1-2 on High Temperature Strength

The strength of AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys is studied at room temperature and at 300 C as cast and after different spheroidization heat treatments (ST). The strength of both alloys decreases with increasing solution treatment periods and stabilizes at 4 h. The interconnectivity and contiguity of aluminides and eutectic Si present in both alloys as cast and after 4h ST are analyzed by means of synchrotron computed microtomography. The contiguity between eutectic Si and the aluminides in both alloys is conserved after ST. The AlSi10Cu5Ni2 alloy shows about 40% higher contiguity between aluminides and eutectic Si as compared to the AlSi10Cu5Ni1 alloy. The contiguity in AlSi10Cu5Ni2 retards fragmentation and spheroidization of eutectic Si resulting in larger interconnected structures of Si as compared to AlSi10Cu5Ni1 alloy after 4h ST. The decrease in strength of AlSi10Cu5Ni2 from as cast to 24h ST is significantly less than that of the AlSi10Cu5Ni1 alloy, where the interconnectivity of eutectic Si is reduced severely.