热处理对激光熔化沉积B4C/TC4复合材料微观组织、力学性能及腐蚀性能的调控作用

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

摘要:

在激光熔化沉积过程中加入0.5wt%的B₄C作为增强相，通过原位制备TiB+TiC双重增强TC4复合材料。通过固溶与退火2种不同热处理制度，对B₄C/TC4复合材料的微观结构、力学性能和腐蚀性能进行调控。结果表明：随着温度从500 ℃升高至800 ℃，沉积样品中的部分层状α-Ti逐渐转变为等轴状α-Ti，网篮组织也逐渐消失；在1100 ℃时，少量TiC相发生熔粒现象。复合材料在500 ℃退火 4 h后炉冷的热处理制度下，强度和塑性的组合达到最佳状态，其性能提升主要归因于退火过程中产生的应力释放以及网篮组织的细化。然而，经各种热处理后，由于晶粒粗化和微电偶腐蚀的影响，复合材料的耐腐蚀性能有所下降。

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.