增材修复对激光沉积制造TC4组织与力学性能的影响

Effects of Additive Repair on Microstructure and Mechanical Properties of Laser Additive Manufactured TC4 Titanium

采用激光沉积修复技术和电弧增材修复技术分别对预制损伤激光沉积制造TC4进行修复,然后对其进行不同的热处理,研究两种修复制件在热处理前后的组织和力学性能。结果表明:两种修复件的修复区均与基材形成了致密的冶金结合,无明显的热影响区;两种修复件的显微组织存在差异,激光修复区中的β柱状晶由基材延伸到修复区顶部,整体组织较为一致,而电弧修复区中出现了粗大的β等轴晶,晶内α相较基材的更细长;激光修复件的综合性能较好,其强度与塑性均高于TC4锻件标准,电弧修复件的强度与激光修复件的相当,但断面收缩率较激光修复件的低;600℃退火处理对组织及性能的影响较小,而固溶时效处理能使α相明显粗化,大幅提升其塑性,且对强度的影响不大,可使制件获得较佳的强度/塑性匹配;两种热处理态修复件的拉伸断裂机制不同,激光修复件的断口表面布满大而深的韧窝,为韧性断裂,而电弧修复件断口上的颈缩不明显,韧窝较浅且起伏较小,表现为准解理断裂特征。

Laser deposition technology and weld additive manufacturing technology are used to repair the laser deposition manufactured TC4 titanium alloy with defects, and then different heat treatments are carried out. Microstructures and mechanical properties of two kinds of repaired specimens are analyzed before and after heat treatments. The results show that there is dense metallurgical bonding between repaired zone and the substrate, and there is no obvious heat affected zone. In the laser repaired zone, prior columnar beta grain extends from the substrate to the top of repaired zone and the whole structure is almost same. In the weld repaired zone, there are huge equiaxed beta grains, the transgranular alpha phases are longer than alpha phases in the substrate. The strength and plasticity of laser repaired specimen are higher than those of TC4 forging standard. The strength of the weld repaired specimen is similar to that of the laser repaired specimen, but the reduction of area of the former is lower than that of the latter. The annealing heat treatment has little effects on microstructure and mechanical. The solution and aging treatment can coarse the alpha phase obviously and promote the plastic sharply of the specimen, and it has slight effect on strength, so the specimen can obtain good strength and plasticity. The two kinds of repaired specimen in heat treatment state have different tensile fracture mechanisms. The fracture surface of laser repaired specimen is covered with big and deep dimples, and the fracture shows ductile characteristics. The weld repaired specimen exhibits quasi-cleavage fracture with slight necking fracture, and shallow and flat dimples.