(1. 哈爾濱理工大學(xué) 材料科學(xué)與化學(xué)工程學(xué)院，哈爾濱 150022；
2. 哈爾濱焊接研究院有限公司，哈爾濱 150028；
3. 重慶科技學(xué)院 冶金與材料工程學(xué)院，重慶 401331)
摘 要: 采用高溫激光共聚焦顯微鏡原位觀察方法，研究TC4鈦合金激光填藥芯焊絲焊縫區(qū)在模擬焊接熱循環(huán)作用下冷卻過程中組織形成特征及相變規(guī)律。結(jié)果表明：當(dāng)焊縫區(qū)分別以0.5 ℃/s、5 ℃/s、20 ℃/s和80 ℃/s的冷卻速率降溫到889.5 ℃、864.2 ℃、835.5 ℃和818.9 ℃時，在相界位置開始出現(xiàn)新相的微觀組織形貌；當(dāng)焊縫區(qū)分別降溫到725.7 ℃、749.3 ℃、769.4 ℃和789.2 ℃時，新相完成轉(zhuǎn)變，即相變的溫度區(qū)間隨著冷卻速率的增大而逐漸變窄。隨著冷卻速率的增加，新相的片層間距逐漸減小；隨著冷卻速率的增大，冷卻到室溫的試樣硬度逐漸增大，由339 HV10增大到368 HV10；試樣全部由密排六方(HCP)晶體結(jié)構(gòu)組成，沒有斜方晶格和體心立方的晶體結(jié)構(gòu)產(chǎn)生。
關(guān)鍵字: TC4鈦合金；激光填絲焊；藥芯焊絲；相變；原位觀察
（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
