A Study on the Porosity of CO_2 Laser Welding of Titanium Alloy

摘要

In this paper the CO_2 laser welding of BT20 titanium alloy and Ti-23Al-17Nb titanium alluminide was conducted to investigate into the porosity in titanium alloy weld. The results show that there were two sorts of porosities observed in welds of titanium alloy laser welding according to the microscopic characteristics of the porosities. One was the small round metallurgical porosity with smooth inner wall, which results from the surface contamination. The other Was the larger irregular processing porosity with rough inner wall that appeared the trace of the pool flowing, which results from the ruffle on the keyhole wall gathering together locally and closing down the gas in the keyhole into bubbles because of the keyhole fluctuating. The CO_2 laser welding can break down easily the surface oxide film and produce little metallurgical porosity, but produced easily processing porosity when partial penetration or unstable-full penetration laser welding was conducted, which always occurred in the center of weld.