The fracture behaviors of tungsten inert gas (TIG) welded titanium alloy TA15 subjected to tensile and fatigue loadings were investigated. Using the staircase test method, the fatigue probabilistic S-N (P-S-N) curves of the titanium alloy were obtained. Electron back scattered diffraction (EBSD) and Scanning electron microscope (SEM) were utilized to study fracture mechanism. The results showed that the weldment had different microstructure sensitivity when it was subjected to different loading conditions. The tensile failure of TIG welded TA15 was mainly dominated by the geometry and plasticity deformation ability of the weldment. The grain boundary mismatch in the connection region of the base metal and heat-affected zone increased the grain boundary energy and hindered the dislocation movement in the fatigue test. The texture transformation between the base metal and the connection of base metal and heat-affected zone caused a slip mismatch region in which the material has weak fatigue strength. In short, the reason for the tensile and fatigue failure of TIG welded TA15 was discussed systematically in this study.

研究了钨极惰性气体（TIG）焊接钛合金TA15在拉伸和疲劳载荷作用下的断裂行为。使用阶梯测试方法，获得了钛合金的疲劳概率SN（PSN）曲线。电子背散射衍射（EBSD）和扫描电子显微镜（SEM）被用来研究断裂机理。结果表明，在不同载荷条件下，焊件具有不同的组织敏感性。TIG焊接TA15的拉伸破坏主要由焊件的几何形状和塑性变形能力决定。在疲劳试验中，母材与热影响区的连接区域的晶界失配增加了晶界能量，阻碍了位错运动。贱金属与贱金属和热影响区之间的连接处的织构转变导致了滑移失配区域，其中材料的疲劳强度较弱。简而言之，本研究系统地讨论了TIG焊接TA15的拉伸和疲劳失效的原因。