AZ31镁合金氩弧焊接接头组织与力学性能研究

Microstructure and mechanical properties of welded joint of AZ31 magnesium alloy by DC-TIG welding

钨极氩弧焊(TIG)为镁合金焊接中最常用的一种焊接方法。本文采用直流钨极氩弧焊对6.0 mm厚AZ31镁合金挤压板材进行了双面焊接实验。采用光学显微镜、扫描电镜、拉伸试验机考察分析了焊接接头显微组织与力学性能。显微组织分析表明,AZ31镁合金直流TIG焊接头由母材、热影响区、焊缝区组成,焊缝组织呈现焊丝熔化后凝固组织;在母材热影响区与焊缝区之间坡口处形成过渡区,晶粒细小,为母材与焊丝的熔合区。采用AZ31焊丝焊接接头平均抗拉强度为241.0 MPa,延伸率为13.8%,分别达到了母材的86.0%和63.6%。焊接接头的断裂均位于热影响区,断口呈现韧脆混合断裂特征。

Argon tungsten-arc welding （TIG） is the most popular welding method for magnesium alloys. AZ31 extruded plates with thickness of 6.0 mm were welded by DC-TIG welding. Microstructure and mechanical properties of welded joint of AZ31 magnesium alloy were studied by optical microscopy, scanning electron microscopy and tensile test machine. The microstructure analysis shows that the welded joint is composed of base material, heat affected zone and weld zone. A transition zone appears near the groove between the heat affected zone and the weld zone, whicb is the mix-fusion zone. The average tensile strength and the elongation of the welding joint is 24]. 0 MPa and 13.8% respectively, which arrives to 86.0% and 13.8% respectively of the base material. The fracture of welding joints is located in heat affected zone and the fracture surface presents mix fracture characteristics.