Weld formation and porosity in TC4 joint by oscillating laser beam welding with circle trajectory model

The pores problem is a challenging problem in laser beam welding titanium alloy TC4. Oscillating laser beam welding, as a new welding process, can effectively control the behavior of the molten pool, and is beneficial to the escape of pores, which holds promise for achieving high quality TC4 joint. Selecting appropriate oscillation parameters is the key to obtaining high quality TC4 joint by LBW. This project will focus on researching the effects of oscillating parameters on weld formation and porosity of TC4 joint by oscillating laser beam welding. Firstly, the oscillating laser beam welding experimental platform was set up, and experiments on oscillating LBW were designed and conducted. Subsequently, the microstructure of TC4 joint was analyzed, and the effects of oscillating frequency and oscillating amplitude on weld formation were studied, and the effects of oscillating frequency and oscillating amplitude on porosity were researched. The results indicate that oscillating laser beam welding with circle trajectory model can achieve high quality TC4 joint. The porosity of weld by oscillating LBW with oscillation amplitude as 1 mm and oscillating frequency as 80 Hz reaches 0.13% in value which is the lowest among the experiment cases under the condition as fixing the oscillation amplitude 1 mm in value and varying the oscillation frequency from 40 Hz to 240 Hz. When the oscillation amplitude exceeds the critical value 2.5 mm, the weld by oscillating LBW exhibits noticeable undercutting and asymmetry. The undercutting occurs on the advancing side in oscillating LBW with circle trajectory model. To a certain extent this study enriches the theory of oscillating LBW, and can provide fundamental data for oscillating laser beam welding on TC4.