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采用双脉冲MIG焊对6.35 mm厚7075-T651高强铝合金进行焊接。通过宏观形貌与金相观察、扫描电镜观察、X射线衍射分析、拉伸试验以及硬度测试,研究了焊接热输入对焊接接头组织及力学性能的影响。结果表明,随着焊接热输入的增加,焊缝区组织出现晶粒粗化,主要强化元素Zn蒸发烧损,强化相析出量减少,力学性能明显下降;焊接接头断裂形式呈现沿晶断裂与穿晶断裂的混合断裂,小的热输入下焊接接头断口韧窝中出现更多的第二相粒子;焊接接头软化程度与焊接热输入有着显著联系。
Using double pulse MIG welding of 6.35 mm thick 7075-T651 high-strength aluminum alloy welding. The effects of welding heat input on the microstructure and mechanical properties of the welded joint were studied by macroscopic morphology and metallographic observation, scanning electron microscopy, X-ray diffraction analysis, tensile test and hardness test. The results show that with the increase of welding heat input, grain coarsening occurs in the weld zone, and the main strengthening element Zn is burned by evaporation, the precipitation of strengthening phase is reduced, and the mechanical properties are obviously decreased. The rupture of welded joints presents intergranular fracture and wear The mixed fracture of crystal fracture shows more second-phase particles in the fracture dimples of the welded joint under the small heat input. The degree of softening of the welded joint is significantly related to the welding heat input.