An ab initio study on the electronic structures of the solid/liquid interface between TiB₂ (0 0 0 1) surface and Al melts

Highlights: • Interfacial electronic structures between Al melts and TiB₂ surface are investigated. • The Al ordered layer on TiB₂ surfaces results from different covalent hybridizations. • The 3d(Ti)–3p(Al) hybridization supports the continuous growth of Al layers. • The weak bonding at the B-terminated interface restricts the structural order. - Abstract: Crystallographic match working as the conventional criterion for heterogeneous nucleation encounters problems when explaining the refinement mechanism of Al melts inoculated by Al–Ti–B master alloys. To reveal how the solid–liquid interaction determines the interfacial structure evolution, we use ab initio simulation to investigate the interfacial electronic structures between Al melts and TiB₂ (0 0 0 1) surfaces with Ti and B terminations, respectively. The formation of the first ordered Al layer on two TiB₂ surfaces results from different types of covalent hybridizations, which influences the bonding states of further stacking Al atoms and the extension of ordered Al layers into the liquid during the early stage of heterogeneous nucleation. In the Ti-terminated interface, the 3d(Ti)–3p(Al) hybridization leads to the first Al layer with strong covalent bonding, which induces the corresponding 3p(Al)–3p(Al) hybridization between further stacking Al layers to guarantee the extension of ordered structure. However, the 2s(B)–3s(Al) and 2p(B)–2p(Al) hybridizations between the B-terminated surface and the first Al layer are too weak to induce strong bonding between the further stacking Al atoms, leading to the restricted interfacial structural order on the B-terminated TiB₂ substrate