焊接工艺参数对10 mm厚2219铝合金双轴肩搅拌摩擦焊焊缝质量和性能的影响

以国内新一代运载火箭某模块共底贮箱中最厚的10 mm 2219C10S铝合金对接焊缝为对象，研究了焊接工艺参数对10 mm厚2219铝合金双轴肩搅拌摩擦焊焊缝质量和性能的影响。结果表明，从焊缝表面成形可以看出，搅拌头转速的选择对焊缝质量具有重要影响，当搅拌头转速n≥250 r/min时，焊缝表面均出现不同程度金属擦伤缺陷，而当搅拌头转速n=200 r/min时，较大焊接速度范围内均可得到表面成形良好的焊缝。通过焊缝组织形貌分析，当n≥250 r/min时，接头焊核区存在“焊核凸出”现象；当n=200 r/min时，焊核呈现典型的“哑铃形”，与焊缝表面成形规律一致。不同条件下接头显微硬度呈典型的W形分布，但随着焊接速度的增大，接头显微硬度平均水平逐渐升高。接头力学性能试验表明，接头抗拉强度均在310 MPa以上，断后伸长率稳定在7.0%～7.5%范围内，接头断口呈典型的韧性断裂。创新点： 研究了10 mm厚2219铝合金双轴肩搅拌摩擦焊工艺；确定了对接头质量和性能具有较大影响的工艺参数；得到了可获得良好接头性能的工艺参数范围，为后续该技术的工程化应用奠定基础。

Effect of welding parameters on the quality and properties of self-reacting friction stir welding of 10 mm thick 2219 aluminum alloy

Taking the thickest 10 mm 2219C10S aluminum alloy butt weld in the common bottom tank of a module of a new generation launch vehicle in China as the object, effects of welding parameters on the quality and properties of self-reacting friction stir welding of 10 mm thick 2219 aluminum alloy were studied. From the surface forming results, it could be seen that selection of rotation speed of tool had an important influence on the weld quality, when the rotation speed of tool was greater than or equal to 250 r/min, different degree of metal scratch defects appear on the weld surface, when rotation speed of tool was 200 r/min, the weld with good surface formation could be obtained in a large range of welding speed. According to analysis of weld microstructure, there was a phenomenon of “nugget bulge” in the nugget zone with the condition of n≥250 r/min. However, nugget zone presented a typical “dumbbell shape” with the condition of n=200 r/min, which was consistent with the forming law of weld surface. Under different conditions, micro-hardness of welded joints presented a distribution with typical “W” type, but with the increase of welding speed, average micro-hardness of welded joints increased gradually. The mechanical properties of the weld showed that tensile strength of welded joints was above 310 MPa, and elongation was stable in the range of 7.0%～7.5%, and fracture of welded joints was typical ductile fracture.Highlights: The friction stir welding process of 2219 aluminum alloy double shoulders with a thickness of 10 mm was studied. The process parameters which had great influence on quality of welded joints and performance were determined. The range of welding parameters for obtaining good performance of welded joints was obtained, which lay a foundation for the subsequent engineering application of this technology.