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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.
•Fracture behaviors of TIG welded titanium alloy TA15 subjected to tensile and fatigue loadings were investigated.•The crystal orientation influence on fracture mechanism was discussed.•The reticular structure formed in the recrystallization had positive effect of the compatible deformation of TA15.•The grain boundary mismatch in the connection region of the base metal weakened the weldment fatigue strength.