Research On Twin Spot Laser Welding Of Two Kinds Of Aluminum Alloys

Aluminum alloy is one of the most important materials and find extensive application in aerospace industry, because of its light weight ,superior strength-to-weight ratio ,and excellent corrosion resistance. Laser welding with higher energy density can offer remarkable advantage over conventional fusion welding processes ,,such as minimal component distortion and high productivity ,and is specifically suitable for joining aerospace structures. However,a number of defects, such as suface holes ,undercut ,porosity, irregular beads,dumping and solidification cracking, are often found in laser welding of aluminum alloy.In order improving weld quality and mechanical properties of joint, the experiment of twin spot laser welding of A5052 aluminum alloy and 1420 Al-Li alloy is investigated in this study, and offer theory and practice base for joint technology of aluminum alloy in aerospace.Laser power ,welding speed ,spots distance, spots energy ratio, and spots arrangement are five important process parameters in twin spot laser welding and their variety will change welds width , affect stability in twin spot welding process.It is key to choose the right parameters for well quality welds.When Laser power and welding speed is definite, with increasing spot distance the weld width increase with increasing spot distance, and the defects(undercut and spatter) reduced evidently under 0.54-0.9mm spot distance with well shaped welds. Weld process is more stable in twin spot welding process by adjusting spots power ratio and the most stable when spots power ratio is 60/40 or 40/60.It is suitable to butt welding when the spots are transverse arrangement (uprightness on welding direction).The weld porosity is the main defect in laser welding of aluminum alloy .It is shown that there are two sorts of porosity observed in welds of laser welding of aluminum alloy .One was small round metallurgical porosity with smooth inner wall, which results from the hydrogen separating out from melt pool. The other was large irregular processing porosity with rough inner wall that was the trace of the pool flow, they always appear in welds root or middle when unfull penetration or welding process is unstable.In the study, it shown that twin spot laser welding can reduce the number of processing porosity with diameter larger than 0.6mm.It is also shown that the intensity of joints in twin spot laser welding is more strength than single laser welding and the average hardness in 5052 aluminum alloy joint of laser welding is higher than base metal, and the hardness in twin spot laser welding joint is lower than single laser welding. Meanwhile the average hardness of 1420 Al-Li alloy laser welding joint is lower than base metal and hardness in twin laser welding is higher than single laser welding.