Microstructure and mechanical properties of Al matrix composites reinforced by TiN-coated β-Si3N4 whiskers

The poor wettability between the ceramic reinforcements and the metal matrix makes it difficult to realize the densification process of composites, which is severely detrimental to their mechanical properties. To improve the mechanical properties of Al matrix composites (AMCs) reinforced by β-Si3N4 whiskers (β-Si3N4w), we prepare TiN coating on the surface of β-Si3N4w via molten salt process, remarkably strengthening the interface bonding between Al matrix and β-Si3N4w. By optimizing the coating layer thickness, the bending strength of AMCs reinforced by TiN-coated β-Si3N4w reaches 439 MPa at 850°C, exhibiting remarkable enhancement relative to the composites without TiN coating (335MPa). Meanwhile, the interfacial test shows that TiN-coated β-Si3N4w is well bonded with the Al matrix, and no interfacial defects were detected. Moreover, the TiN coating with appropriate thickness can efficiently alleviate the agglomeration of β-Si3N4w, promote the densification of AMCs, and modify the Al/β-Si3N4w interface.