Effects of microstructure and concavity on damage behavior of laser beam welded Ti-2Al-1.5Mn titanium alloy joints

Pulsed laser beam welding (PLBW) and continuous fiber laser beam welding (CFLBW) of Ti-2Al-1.5Mn titanium alloy thin sheets were proceeded in the given welding conditions, and the unfilled and undercut defects were found in the weld joints, separately. The finite element simulation result shows that there is great geometrical discontinuity in joints due to the concavity defects. The microstructure observation indicates that strong nonlinear distributions of microstructures exist both in the same joint from base metal (BM) to fusion zone (FZ) and in different joints under different welding conditions. Furthermore, effects of microstructure and concavity on plastic damage behavior were investigated using a multispecimen tensile method. The results show that the plastic damage behavior relates to both the microstructure and the tensile stress level. Existence of concavity accelerates the plastic damage nearby the concavity area while decelerates the plastic damage of fusion line area.