(1. 哈尔滨理工大学 材料科学与化学工程学院，哈尔滨 150022；
2. 哈尔滨焊接研究院有限公司，哈尔滨 150028；
3. 重庆科技学院 冶金与材料工程学院，重庆 401331)
摘 要: 采用高温激光共聚焦显微镜原位观察方法，研究TC4钛合金激光填药芯焊丝焊缝区在模拟焊接热循环作用下冷却过程中组织形成特征及相变规律。结果表明：当焊缝区分别以0.5 ℃/s、5 ℃/s、20 ℃/s和80 ℃/s的冷却速率降温到889.5 ℃、864.2 ℃、835.5 ℃和818.9 ℃时，在相界位置开始出现新相的微观组织形貌；当焊缝区分别降温到725.7 ℃、749.3 ℃、769.4 ℃和789.2 ℃时，新相完成转变，即相变的温度区间随着冷却速率的增大而逐渐变窄。随着冷却速率的增加，新相的片层间距逐渐减小；随着冷却速率的增大，冷却到室温的试样硬度逐渐增大，由339 HV10增大到368 HV10；试样全部由密排六方(HCP)晶体结构组成，没有斜方晶格和体心立方的晶体结构产生。
关键字: TC4钛合金；激光填丝焊；药芯焊丝；相变；原位观察
（1. School of Material Science and Chemical Engineering, Harbin University of Science and Technology, Harbin 150022, China;
2. Harbin Welding Institute Limited Company, Harbin 150028, China;
3. School of Metallurgy and Materials Engineering, Chongqing University Science & Technology, Chongqing 401331, China）
Abstract:The microstructure formation and phase transformation of TC4 titanium alloy laser flux-cored wire weld zone during cooling process under simulated welding thermal cycle were studied by in situ observation with high temperature laser confocal microscope. The results show that when the cooling rates of 0.5 ℃/s, 5 ℃/s, 20 ℃/s and 80 ℃/s are lowered to 889.5 ℃, 864.2 ℃, 835.5 ℃ and 818.9 ℃, respectively, the microstructure of the new phase in weld zone begins to appear at the phase boundary. When the temperature of welded zone is lowered to 725.7 ℃, 749.3 ℃, 769.4 ℃ and 789.2 ℃, respectively, the temperature range of the new phase transition gradually narrows with the increase of cooling rate. It is found that the lamellar spacing of the new phase decreases with the increase of cooling rate, and the hardness of samples cooled to room temperature increases with the increase of cooling rate, from 339 HV10 to 368 HV10. The samples are all composed of HCP crystal structure without rhombic lattice and BCC crystal structure.
Key words: TC4 titanium alloy; laser filler wire welding; flux-cored wire; phase transformation; in-situ observation
