(1. 沈阳航空航天大学 机电工程学院，沈阳 110136；
2. 沈阳航空航天大学 航空制造工艺数字化国防重点学科实验室，沈阳 110136)
摘 要: 基于飞机机身壁板中T形接头在飞行过程中常因承受空气循环阻力而导致疲劳断裂的问题，分别采用激光双光束焊接技术和激光点焊接技术对TC4钛合金进行T形接头焊接，研究两种接头的显微组织特征、拉伸性能、疲劳性能及断裂机理。结果表明：利用两种不同激光焊接方法焊接后，熔合区组织均为针状α′马氏体组成的网篮组织；与激光双光束焊相比，激光点焊焊接接头网篮状组织中的α′网篮状组织的体积分数增大，针状α′马氏体尺寸增大且相间距减小。与母材拉伸性能相比，激光点焊接接头抗拉强度提高了5.5%，激光双光束焊接接头抗拉强度提高了5.8%。激光双光束焊接试件中值疲劳寿命提高2.23倍，主要原因在于网篮组织对焊接接头产生界面强化效果进而增加接头强度，而激光点焊试件的裂纹穿过焊点进入母材扩展导致试件的裂纹扩展抗力降低。
关键字: TC4钛合金；激光双光束焊；激光点焊；疲劳寿命；断裂机理
（1. School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China;
2. Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136, China）
Abstract:Based to the problem that the T-joint in the aircraft fuselage wall was often subjected to fatigue resistance during flight due to air circulation resistance, the laser double beam welding technology and laser spot welding technology were used on T-joint welding of TC4 titanium alloy. And the microstructure, tensile properties, low cycle fatigue behavior and fracture mechanism of the two joints were investigated. The results show that after welding by two different laser welding methods, the fusion zone structure is a basket structure composed of needle-shaped α′ martensite. Compared with laser double-beam welding, the volume fraction of α'''' basket-like structure in the laser spot welded joint mesh basket increases, the needle-shaped α′ martensite size increases and the phase spacing decreases. Compared with the tensile properties of the base metal, the tensile strength of the laser spot welded joint increases by 5.5%, and the tensile strength of the laser double beam welded joint increases by 5.8%.The median fatigue life of the laser double-beam welding specimen increases by 2.23 times. The main reason is that the mesh basket structure produces an interface strengthening effect on the welded joint and increases the joint strength, while the crack propagation of laser spot welding specimen penetrates the solder joint into the base material, causing the decrease of crack propagation resistance of the specimen.
Key words: TC4 titanium alloy; laser dual-beam welding; laser spot welding; fatigue life; fatigue fracture mechanism
