Abstract In order to expand the direct current-cold metal transfer (DC-CMT) method to include large-thickness plate welding, a tungsten inert gas–CMT (TIG–CMT) hybrid welding process was employed in this work. Adding a stable TIG arc can increase the total heat input on the workpiece and the penetration capacity of the DC-CMT welding process. Al6061 plates 4 mm thick were welded successfully by this method. As the TIG current increased, the heat input of the welding process increased. The effect of TIG current on the microstructure and mechanical properties of the joints was investigated. The hardening phase in Al6061 was sensitive to the heat input provided by the welding process. Because of microstructural transformation, a decrease in the mechanical properties (softening phenomenon) invariably appeared in the heat-affected zone (HAZ). With increasing TIG current, the microstructures of the joints coarsened, and the width of the partially melted zone (PMZ) and HAZ of the joints broadened. A precipitation strengthening phase of Mg2Si appeared in HAZ. The hardness curve of the joint presented roughly W-type distribution. The hardness obtained in the softened zone was approximately 50% that of the base metal (BM). The joints demonstrated good deformation capability before fracture. As compared to the base material, the strength and the elongation of the joints decreased approximately 40% and 50%, respectively.

中文翻译：

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TIG电流对TIG-CMT复合焊6061-T6铝合金接头显微组织和力学性能的影响

摘要 为了将直流-冷金属转移（DC-CMT）方法扩展到大厚度板焊接，本文采用钨惰性气体-CMT（TIG-CMT）复合焊接工艺。添加稳定的 TIG 电弧可以增加工件的总热量输入和 DC-CMT 焊接工艺的熔深能力。4 mm 厚的 Al6061 板通过这种方法成功焊接。随着 TIG 电流的增加，焊接过程的热量输入增加。研究了 TIG 电流对接头微观结构和力学性能的影响。Al6061 的硬化阶段对焊接过程提供的热输入很敏感。由于微观结构转变，热影响区（HAZ）总是出现力学性能下降（软化现象）。随着TIG电流的增加，接头的显微组织变粗，部分熔化区（PMZ）和接头HAZ的宽度变宽。热影响区出现Mg2Si 的析出强化相。接头硬度曲线大致呈W型分布。在软化区获得的硬度约为母材 (BM) 的 50%。接头在断裂前表现出良好的变形能力。与基材相比，接头的强度和伸长率分别降低了约 40% 和 50%。接头硬度曲线大致呈W型分布。在软化区获得的硬度约为母材 (BM) 的 50%。接头在断裂前表现出良好的变形能力。与基材相比，接头的强度和伸长率分别降低了约 40% 和 50%。接头硬度曲线大致呈W型分布。在软化区获得的硬度约为母材 (BM) 的 50%。接头在断裂前表现出良好的变形能力。与基材相比，接头的强度和伸长率分别降低了约 40% 和 50%。