2219铝合金搅拌摩擦焊接头拉伸断裂机理分析

doi:10.3901/JME.260113

摘要/Abstract

摘要： 搅拌摩擦焊接头组织结构不均匀，导致不同条件下拉伸断裂位置与断裂机制并不相同，而目前对焊接接头拉伸断裂机理的研究还较少。为了揭示2219中厚板搅拌摩擦焊接头拉伸断裂机理，进行了6 mm厚2219铝合金板搅拌摩擦对向焊接。对焊接接头进行了硬度测试，拉伸试验，并对断口进行金相，扫描电镜，电子背散射衍射观察分析，结果表明：焊接接头前进侧热机影响区内硬度最低；拉伸试验三维全场变形测量及分析系统测试结果显示，当焊接接头拉伸试样工程应变小于8.34%时，最大主应变发生在接头区域前进侧和后退侧热机影响区，当工程应变超过8.34%，最大应变区域转变为接头前进侧热机影响区，并在此区域附近沿近45°角延伸断裂；初始断裂区域形貌由撕裂棱间隔的较大韧窝构成，断裂终止位置形貌由大片解理平台和较小韧窝为主，接头断裂机制呈现韧脆混合型断裂特征。由于热机影响区第二相的明显取向性导致该区域变形协调能力下降；热机影响区晶粒受力偏转并被拉长且与热影响区晶粒大小差异过大产生应力集中；热机影响区到热影响区位错密度骤降，最终导致焊接接头最终于前进侧热影响区与热机影响区交界处断裂。上述研究结果可以为优化焊接条件、调控接头组织、提高力学性能提供技术参考。

关键词: 2219铝合金, 搅拌摩擦焊, 不均匀性, 微观组织, 断裂机理

Abstract: The microstructural inhomogeneity in friction stir welded joints has been shown to lead to diversified tensile fracture locations and fracture mechanisms under varying conditions, while investigations into the tensile fracture mechanisms of these joints have been limited. In order to reveal the tensile fracture mechanism of friction stir welded joints in 2219 medium-thick plates, friction stir butt welding was performed on 6 mm thick 2219 aluminum alloy plates. Hardness testing and tensile testing are conducted on the welded joints, and the fracture surfaces are analyzed using metallographic examination, scanning electron microscopy(SEM), and electron backscatter diffraction(EBSD). The results indicate that the lowest hardness is observed in the thermomechanically affected zone on the advancing side(AS-TMAZ) of the welded joint. The digital image correlation(DIC) test results of the tensile test have been shown that when the engineering strain of the welded joint tensile specimen is less than 8.34%, the maximum principal strain is observed to occur in the joint area AS-TMAZ and thermomechanically affected zone on the re-treating side(RS-TMAZ). When the engineering strain exceeds 8.34%, the region of maximum strain is transformed to the AS-TMAZ of the joint, and fracture is propagated at an angle of approximately 45° near this region. The morphology of the initial fracture region is characterized by large dimples separated by tear ridges, while the morphology of the final fracture region is dominated by large cleavage facets and smaller dimples. The fracture mechanism of the joint exhibits a mixed ductile-brittle fracture behavior. Due to the obvious orientation of the second phase in TMAZ, the deformation coordination ability in this region decreases. In the TMAZ, the grains are deflected and elongated under stress, and stress concentration is induced due to the significant difference in grain size compared to the heat-affected zone (HAZ). The dislocation density from TMAZ to HAZ drops sharply, and the welded joint ultimately fractures at the junction of AS-TMAZ and AS-HAZ. The above research results can provide technical references for optimizing welding conditions, controlling joint microstructure, and improving mechanical properties.

Key words: 2219 aluminum alloy, friction stir welding, uneven distribution, microscopic organization, fracture mechanism

中图分类号:

TG456

李群, 曹博, 姜延, 陈李杰, 胡建良, 陈雷. 2219铝合金搅拌摩擦焊接头拉伸断裂机理分析[J]. 机械工程学报, 2026, 62(4): 148-156.

LI Qun, CAO Bo, JIANG Yan, CHEN Lijie, HU Jianliang, CHEN Lei. Analysis of Tensile Fracture Mechanism of 2219 Aluminum Alloy Friction Stir Welded Joints[J]. Journal of Mechanical Engineering, 2026, 62(4): 148-156.

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