Achieving intrinsic wetting of SiC in A356 Al alloy via mechanically dislocating the absorbed alumina film

SiC is a common reinforcement in Al matrix composites, which can improve the mechanical and physical properties. However, the widespread application of Al-SiC composites is limited by the poor wettability of SiC in molten Al. Herein, we investigated the underlying mechanism in A356/SiC composites synthesised by semi-solid stir casting. The microstructure at the interface between the Al matrix and SiC was characterised by SEM and TEM. Microstructural characterisation uniquely identified alumina films at the interface as the critical factor responsible for interfacial cracking and wettability inhibition. The wettability of SiC can be improved when SiC achieves intrinsic contact with Al by removing alumina film during collisions with SiC particles and primary α-Al. Strikingly, the operative wetting mechanism of SiC in molten Al is not lattice mismatch, but rather depends on the chemical nature of the SiC particle surface.