Numerical simulation on porosity formation and suppression in oscillation laser welding of Ti-6Al-4V alloy

Porosity formation and suppression in oscillation laser beam welding of Ti-6Al-4V alloy is simulated in this study. The results show that, in nonoscillation welding, slender keyholes with a depth and width radio of about 3.66 are continually formed. In oscillation welding, shallow and wide keyholes with a depth and width ratio of about 0.97 are formed. In nonoscillation welding, a positive pressure appears at the front of the keyhole, which gives the keyhole a wasp-waist structure and makes it easily break into small parts. In oscillation welding, the positive pressure appears at the bottom of the keyhole, and the average value decreases from 5.23 to 1.04 MPa when the laser beam oscillating frequency increases from 50 to 200 Hz. This kind of pressure distribution results in a more stable keyhole and suppresses the formation of porosity. In the meantime, with the increase in oscillation frequency, the interval of porosity formation becomes longer. The results of this study are helpful in understanding the porosity formation mechanism in oscillating laser beam welding.