Morphology, mechanical property, and molten pool dynamics in spot modulated-PLBW of Ti6Al4V alloy sheets with air gap condition

The tailor joining of thin metal sheets frequently suffers from the assembly error of air gap. Herein, an improved laser welding scheme, integrating the pulsed laser power and the modulated beam spot size is developed and applied on 1.5 mm-thick Ti6Al4V sheets with a predetermined air gap range. Weld beads of high continuity and homogeneity are obtained while the tensile property has a nonlinear decrease when increasing the air gap. During the welding, the over-gap metal bridge is obtained due to melt accumulation and periodical keyhole penetration, and the gap bridging capacity, mainly featuring bilateral metal bridges can be weakened as the air gap increases. This evaluation would provide a basis for processing optimization regarding seam appearance and property.