High angle annular dark field scanning transmission electron microscope imaging and electron energy loss spectroscopy were used to elucidate the heterogeneous nucleation interface of AlB2 in an Al-7Si alloy. Si particles were observed in the vicinity of a AlB2 particle, but no significant Si-B-rich layer (such as SiB6) was observed at the interface between AlB2 and Al, strongly indicating that the proposed creation of a layer of SiB6 at the interface between AlB2 and Al may only be metastable and further transform to other stable phase (e.g. Si) during solidification. The solidification path of Al-Si-B alloy was also discussed based on the binary phase diagrams and a ternary Thermo-Calc simulation using the Scheil module in conjunction with the TCAL3 database. These results provide new insight into the heterogeneous nucleation behavior of Al on AlB2 influenced by solute Si. Display omitted •Si particles were observed in the vicinity of a AlB2 particle in an Al-7Si alloy.•No significant Si-B-rich layer (such as SiB6) was observed at the interface between AlB2 and Al.•The solidification path of Al-Si-B alloy was discussed based on binary phase diagrams and a ternary Thermo-Calc simulation.