The Research On The Laser-arc Hybrid Welding And Dual-spot Laser Beam Welding Technology Of Aluminium-Lithium Alloy

Aluminum-Lithium alloy is an important discovery of aluminum alloy, prefering Al-Li alloy to normal aluminum alloy can decrease 10～15%structure's weight and increase 10～20%stiffness,so it is a ideal material for aerospace.Laser beam welding is considered as the most suitable welding method for aluminum alloy because of its high energy density,low heat input and little deformation and so on. However,there are also some disadvantages of laser beam welding during welding aluminum alloys,such as the worse weld shaped,underut and porocity.According to these problems,this paper carried on the laser-arc hybrid welding and dual-spot laser beam welding on 5A90 Aluminum-Lithium alloy.And these researches will enrich the research contents of laser-arc hybrid welding and dual-spot laser beam welding, and provide evidence for application.Reasonable adjusting the laser power,spot distence and power ratio could enhance the stability and improve the weld shape during dual-spot laser beam welding.The weld width increased by altering the arrangement of the spots.The weld penetration depented on laser power and the weld width was determined by arc.More faster the welding speed was,more less contribution to the weld penetration by arc. When welding speed increased to above 3m/min,the arc had no effection to the welding penetration.The "synergistic effect"between the laser and arc would disappear when the distence between laser and filler wire increase to 10mm.The gap adaptability was extremly improved during laser-arc hybrid welding,and the maximal gap could reach to 1mm.This was 6 times wider than single laser beam welding.The weld shape defect and porocity was the main weld defects of Aluminum-Lithium alloy.The results indicated that the weld shape quality was improved signifiantly using laser-arc hybrid welding and dual-spot laser beam welding.Their are two types porocity in the weld:metallurgical porocity and processing porocity.The research showed that using dual-spot laser beam welding could decreace the large processing porocities,and the metallurgical porocity was the main types in the weld welded by laser-arc hybrid welding.Using the suitable surface clearing process and keeping the stability of full penetration is the effective way to abtain high quality weld.A fine equiaxed grain zone(FEQZ)was found at the boundary of the fusion zone. The FEQZ grains are known to form through a heterogeneous nucleation mechanism aided by Al₃Zr phases.The inteneration of the weld was a serious problem of the Aluminum-Lithium alloy.The reason of the hardness declining was that the solute element enriching on the grain boundry which leaded to the aging insufficient.