Research on formation and properties of adjustable-ring mode (ARM) laser scanning welding of TA1 titanium alloy thin sheet

A new welding method using adjustable-ring mode (ARM) scanning laser was employed to weld 0.5 mm thick TA1 titanium alloy thin sheets. Effects of process parameters on weld formation, microstructure and mechanical properties were studied. A single factor method was adopted in the experiment. One parameter was changed at a time, while other parameters remained unchanged. The values of the process parameters were as follows: the central power P_z=800 W, the ring power P_w=1200 W, the welding speed v=100 mm/s, and the scanning frequency F=300 Hz. When the parameters were changed, the variation ranges are distributed as: the central power P_z=200~800 W, the ring power P_w=1200~1800 W, the welding speed v=40~100 mm/s, and the scanning frequency F=100~400 Hz. The results show that compared with non-scanning laser welding, the ARM scanning laser leads to broader bead width and larger penetration, which is highly suitable for thin sheet welding. Compared with conventional scanning laser welding, the ARM scanning laser not only leads to larger bead width and depth, but also produces smoother bead formation and prettier weld appearance, with smaller stress concentration due to lower weld reinforcement. The microstructure of the ARM scanning laser weld metal consists of α phase. The influence of the central power and outer ring power of the ARM laser have insignificant effects on the microstructure, tensile strength and elongation. The tensile strength of the welded joints reaches 95%~96% of the base metal, while the extensibility achieves 54%~60% of the base metal.