7075铝合金激光-MIG复合焊接接头组织及性能的分析  

Microstructure and Mechanical Properties of Laser-MIG Hybrid Welded Joint of 7075-T6 Aluminum Alloy

作　　者：常丽艳[1] 宋西平[1] 李宏良[1] 吴圣川[2] 

机构地区：[1]北京科技大学新金属国家重点实验室,北京10083 [2]西南交通大学牵引动力国家重点实验室,四川成都610031

出　　处：《热加工工艺》2014年第9期25-28,共4页Hot Working Technology

基　　金：索引动力国家重点实验室开放基金项目(TPL1302);国家自然科学基金项目(51005068)

摘　　要：对激光-MIG复合焊7075铝合金焊接接头的显微组织和显微硬度进行了研究。结果表明,焊缝为树枝晶组织,熔合区为柱状组织,热影响区及母材仍保持了轧制组织形态,并且发现焊缝内存在枝晶偏析,在熔合区和热影响区出现过烧现象,存在大量白色析出相。焊缝区内主要强化元素Zn的含量低于母材。透射电镜进一步观察发现,焊接接头各部分均有大量的沉淀强化相,焊缝和热影响区中的位错密度低于母材。显微硬度测试结果显示,焊缝区和热影响区的硬度低于母材。硬度降低的原因同显微组织、第二相颗粒、合金元素含量、位错密度及晶粒粗化有直接的关系。The microstructure and microhardness of laser-MIG hybrid welding of 7075 aluminum alloy were investigated. The results show that the fusion zone has dendrites structure. Part fusion zone has directional columnar dendritic structure. Heat affected zone has similar structure to the base material, but the size of grain is larger than that in the base metal. Alloying elements are concentrated at the dendrite boundaries and second phases appear in the fusion zone and burning phenomenon appears and there is a large number of complex molten globules in the part fusion z6ne and the heat affected zone. The major strengthening element of Zn in the fusion zone is less than the base material. TEM further observes that the welded joint has a lot of precipitation hardening phase, weld and heat affected zone dislocation density is lower than the base metal. The microhardness results show that the fusion zone and heat affected zone is less than the hardness of the base material. The reasons for the hardness reducing has a direct relationship with the microstructure, the second phase particles, the content of alloying elements, the dislocation density and grain coarsening effect.

关 键 词：7075铝合金 焊接接头 显微组织 显微硬度 

分 类 号：TG456.7[金属学及工艺—焊接] TG407