铝锂合金YAG-MIG复合焊缝成形特征及性能研究

Weld Appearance and Mechanical Properties of Aluminum-lithium Alloy by YAG-MIG Hybrid Welding

对5A90铝锂合金薄板YAG-MIG复合焊缝成形特征及性能进行了研究。结果表明:YAG-MIG复合焊可以显著改善5A90铝锂合金激光焊缝下塌、咬边等现象,扩大激光焊的最大间隙容许裕度,使之可达1.0mm。复合焊接头的主要组织特征为细晶层和焊缝区大范围等轴晶,与激光焊接头类似。而不同之处表现为复合焊接头的显微组织相对粗化,柱状晶区范围相对减小。复合焊缝区硬度(83.57HV0.2)低于激光焊缝区硬度(95.65HV0.2),但前者硬度分布更加均匀。复合焊接头的抗拉强度和断后伸长率均低于激光焊接头,拉伸断裂往往发生在熔合区附近,呈现以脆性断裂为主的混合断裂。若使复合焊接头的综合力学性能达到使用要求,不仅需要焊后热处理强化,还需要与母材匹配性更好的焊丝。

The weld appearance and mechanical properties of 5A90 Al-Li alloy sheet by YAG-MIG hybrid welding are studied.The results show that the weld appearance（collapse,undercut,and so on） of 5A90 alloy by laser beam welding（LBW） is improved by YAG-MIG hybrid welding significantly.And the maximal tolerant gap of the hybrid welding could reach to about 1.0mm.The major microstructure characteristics of joint by hybrid welding are fine-grained layer and the equaixed grain in most of welded seam,which are similar to the joint by LBW.Compared with the latter,the microstructure of the former tends to coarse,and the range of the columnar crystals zone is prone to decrease.The microhardness of welded seam by hybrid welding（83.57HV0.2） is lower than that by LBW（95.65HV0.2）,but the uniformity of the former is better than that of the latter.The ultimate strength and the elongations after fracture of the joint by hybrid welding are lower than that by LBW.The fracture of the tensile samples always occur near the fusion zone,and the tensile fracture presents mixed rupture of brittle and ductile,which is mainly composed of the former.Therefore,if the combined mechanical properties of joint by hybrid welding meet the operation requirements,it should be improved by heat treatment after welding,and it also should develop a better filler wire matched with the base metal.