Study on the forming characteristics and molten pool behaviour of low vacuum swing laser welding of zirconium alloy

A study was conducted on the vacuum oscillating laser welding process and its mechanisms for zirconium alloy, in response to the need for developing new welding techniques for zirconium alloy cladding structural materials. Through metallographic inspection, X-ray detection, and high-speed imaging analysis, an in-depth examination of the weld formation and defects was carried out. Experimental results indicate that as the environmental pressure decreases, the plume phenomenon is effectively controlled, leading to a significant increase in weld penetration depth during vacuum laser welding of zirconium alloy. A comparative study of different oscillation parameters revealed that a circular oscillation trajectory produces the best weld formation. Furthermore, welding simulation studies uncovered the flow characteristics of the molten pool and the periodic variations of the keyhole in vacuum oscillating laser welding. The results show that after 0.25 s, the weld pool reaches a stable state. Within a single oscillation cycle, the keyhole depth reaches its maximum when the laser reaches the endpoint of the circular trajectory. Additionally, under the stirring effect of the laser, the molten pool exhibits a flow pattern consistent with the laser's movement direction.