Nanoparticle-induced nucleation of eutectic silicon in hypoeutectic Al-Si alloy

In this work, significant refinement of eutectic grains in Sr-modified Al-10Si alloys was achieved upon addition of TiC0.5N0.5 nanoparticles (NPs). Results showed that the addition of NPs can lead to a marked reduction in the eutectic grain sizes from 1416 μm for the matrix alloy to 328 μm for the sample with 1.5 vol.% additions. NPs within the eutectic were observed to exhibit two distribution types, i.e. intragranular distribution (within eutectic Si) and extragranular distribution (in the vicinity of eutectic Si). Based on TEM analysis, it is found that TiC0.5N0.5 possesses a specific crystallographic matching with Si, indicating that such NPs can act as heterogeneous nucleation sites for Si. By investigating NP effects on the eutectic nucleation, the NPs-induced nucleation mechanism is proposed to elucidate the refinement phenomenon.