Regulation of Microstructure, Mechanical Properties, and Corrosion Properties of Laser-Melting-Deposited B4C/TC4 Composite by Heat Treatment

Abstract:

The TiB+TiC dual-reinforced B₄C/TC4 composite was in-situ fabricated via incorporating 0.5wt% B₄C reinforcement during the laser melting deposition process. Different heat treatments of annealing and solid solution were used to regulate the microstructure, mechanical properties, and corrosion properties of B₄C/TC4 composite. Results show that with the increase in temperature from 500 °C to 800 °C, partial lamellar α-Ti in the as-deposited sample is gradually transformed into equiaxed α-Ti, accompanied by the disappearance of basketweave microstructure. At 1100 °C, a small portion of TiC phase suffers fusion. This composite exhibits the optimal combination of strength and plasticity after annealing at 500 °C for 4 h followed by furnace cooling, which is attributed to the stress release effect and the refined basketweave microstructure. However, this composite shows a decline in corrosion resistance after various heat treatments due to grain coarsening and micro-galvanic corrosion.