Abstract Al5.5Zn2.5Mg2.2Cu aluminium alloys were butt welded using the robot cold metal transfer method. Optimal welding parameters were defined based on experiments to ensure penetration welding of low heat input. The morphology and evolution of the microstructure, mechanical properties and fracture behaviour of the welded joint after 360 h of natural ageing were investigated. The experimental results indicate that a Mg2Si phase existed in the weld zone, a large amount of MgZn2 in the solid solution zone near the weld dissolved into the Al matrix and MgZn2 precipitated in the overageing softening zone. Compared with the base metal, the matrix of the solid solution zone mainly consisted of coarse precipitates, η precipitates were continuously distributed in the grain boundaries, and a precipitate-free zone was not obvious. Coarse and discontinuous precipitates were distributed in the grain boundary of the overageing softening zone, and the width of the precipitate-free zone became larger with coarsening of the grain boundary precipitates in the overageing softening zone. The mechanical properties were measured by using local samples extracted from the base metal, heat affected zone and welded zone. The base metal had the highest tensile strength and yield strength, in contrast with the welded zone. The tensile strength of the heat affected zone was 92% that of the base metal, and its elongation was increased by 16.7% due to the coarsening of the grain boundary precipitates in the heat affected zone.

中文翻译：

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机器人冷金属转移Al5.5Zn2.5Mg2.2Cu铝合金接头组织与力学性能

摘要 采用机器人冷金属转移法对Al5.5Zn2.5Mg2.2Cu铝合金进行对接焊。根据实验确定最佳焊接参数，以确保低热输入的熔透焊接。研究了自然时效360 h后焊接接头的显微组织、力学性能和断裂行为的形貌和演变。实验结果表明，焊缝区存在Mg2Si相，焊缝附近固溶区大量MgZn2溶解在Al基体中，过时效软化区有MgZn2析出。与母材相比，固溶区的基体主要由粗大的析出物组成，η析出物连续分布在晶界，无析出物区不明显。过时效软化区的晶界处分布着粗大不连续的析出物，随着过时效软化区晶界析出物的粗化，无析出物区的宽度变大。通过使用从母材、热影响区和焊接区提取的局部样品测量机械性能。与焊接区相比，母材具有最高的抗拉强度和屈服强度。热影响区的抗拉强度是母材的92%，由于热影响区晶界析出物的粗化，其延伸率提高了16.7%。随着过时效软化区晶界析出物的粗化，无析出物区的宽度变大。通过使用从母材、热影响区和焊接区提取的局部样品测量机械性能。与焊接区相比，母材具有最高的抗拉强度和屈服强度。热影响区的抗拉强度是母材的92%，由于热影响区晶界析出物的粗化，其延伸率提高了16.7%。随着过时效软化区晶界析出物的粗化，无析出物区的宽度变大。通过使用从母材、热影响区和焊接区提取的局部样品测量机械性能。与焊接区相比，母材具有最高的抗拉强度和屈服强度。热影响区的抗拉强度是母材的92%，由于热影响区晶界析出物的粗化，其延伸率提高了16.7%。与焊接区相反。热影响区的抗拉强度是母材的92%，由于热影响区晶界析出物的粗化，其延伸率提高了16.7%。与焊接区相反。热影响区的抗拉强度是母材的92%，由于热影响区晶界析出物的粗化，其延伸率提高了16.7%。