Laser melting deposition of in-situ (TiB+TiC) hybrid reinforced TC4 composites: Preparation, microstructure and room/high-temperature corrosion behaviour

Abstract

To enhance the anti-corrosion performance of TC4 alloy across a wide temperature range for modern aircrafts operating in increasingly harsh environments, the (TiB+TiC) hybrid reinforced TC4 composites were prepared by laser melting deposition (LMD) via the in-situ reaction between B₄C reinforcement and molten TC4 alloy. The effect of B₄C content (0, 0.5, 1.5, wt%) on the microstructure and room/high-temperature corrosion behaviour of the composites was investigated. Microstructural analysis revealed that the microstructure of the composites was significantly influenced by the B₄C content. The composite containing 0.5 wt% B₄C exhibited an optimal microstructure characterized by refined grains, equiaxed α-Ti transformed from lath-shaped α-Ti, well-distributed (TiB+TiC) phases with a proper amount and reduced pore/dislocation defects. This composite also demonstrated the best corrosion resistance at both room temperature (25°C) and high temperature (800°C), which was primarily attributed to its comprehensive advantages including a favorable microstructure, a uniform dispersion of thermally stable (TiB+TiC) phases and a stable passivation film.