Study on the influence and mechanism of oscillating laser wire feed welding process on the weld formation of TC4 titanium alloy

In order to investigate the influence and mechanism of oscillating laser on weld formation in titanium alloy laser wire feed welding, resurfacing welding experiments on TC4 plates are conducted, and the welding process is observed using high-speed camera. The results demonstrate, compared with conventional laser welding, oscillating laser welding demonstrates significant enhancement in weld bead morphology within an expanded process window. where wire feeding speed, oscillation amplitude, and oscillation frequency are identified as critical parameters exerting substantial influences on cross-sectional characteristic dimensions. Besides the wire feed speed, oscillation amplitude, and oscillation frequency significantly influence the weld forming characteristic parameters. High-speed imaging reveals that under conventional laser conditions, molten droplets predominantly exhibit large droplet transition. When the oscillation amplitude of laser is set to 1 mm, stable liquid bridge transition is achieved at both 80 Hz and 160 Hz oscillation frequencies. However, with an increased oscillation amplitude of 2 mm, the droplet transition shifts to a solid-liquid mixing particle transition. Analysis reveals that sustained laser irradiation in conventional welding processes increases the propensity for large droplet transition from the wire, resulting in violent molten pool fluctuations and irregular weld bead formation. In contrast, oscillating laser actively stirs the molten pool, enhancing wire-pool interfacial contact to facilitate stable liquid bridge transition and achieve uniform weld morphology. However, when the oscillation amplitude reaches 2 mm, insufficient laser energy density fails to completely melt the wire causing the wire fracturing in the middle that generates solid-liquid mixing particles. These particles exhibit incomplete melting and spreading in the molten pool, ultimately leading to serrated weld edges.