The effect of Nb-B inoculation on binary hypereutectic and near-eutectic LM13 Al-Si cast alloys

Hyper-eutectic Al-Si alloys are used for wear-resistant components, such as pistons, because their microstructure is composed by ductile aluminium dendrites and hard primary silicon particles. In this study the effect of Nb-B inoculation on the microstructural features of binary hyper-eutectic and near-eutectic LM13 Al-Si alloys is assessed. It is found that the inoculation with Nb-based compounds (i.e. NbB2 and Al3Nb) leads to the refinement of the microstructural features (i.e. finer and more homogeneous distribution of the eutectic phase as well as smaller primary Si particles as secondary effects). The study also demonstrates that the addition of Nb-B inoculants do not interfere with additions of strontium (used to modify the morphology of the eutectic phase) or phosphorous (added to nucleate primary Si particles).