A study on the porosity of CO2 laser welding of titanium alloy

0IntroductionTitanium alloys are increasingly applied in aeronauticindustry because of its higher strength to weight ratio thansteel and superior fatigue performance to aluminum alloy.At the same time there are many newtitanium-based alloysoccurring,such as Ti3Al-Nb titanium aluminide1].Weldsof titanium alloy are prone to porosity,presenting a poten-tial problem for many application requiring sealing,corro-sion and fatigue resistance and good fracture toughness.Many studies have demonstrate…

A study on the porosity of CO2 laser welding of titanium alloy

The CO2 laser welding of BT20 titanium alloy and Ti-23Al-17Nb titanium aluminide was conducted to investigate into the porosity in titanium alloy weld. The results show that there are two sorts of porosities observed in welds of titanium alloy laser welding based on the microscopic characteristics of the porosities. One is the metallurgical porosity with round and smooth inner wall, which results from the surface contamination. The other is the processing porosity with irregular and rough inner wall that displays 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 CO2 laser welding could break down easily the surface oxide film and produce little metallurgical porosity, but produces easily processing porosity when partial penetration or unstable-full penetration laser welding is conducted, which always occurs in the center of weld.