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用交流点焊机焊接了AZ31镁合金板材,测试了不同表面清理状态下点焊接头的力学性能,用光学显微镜和扫描电镜分析了接头的显微组织和拉伸断口形貌。结果表明:在其它参数不变的情况下,接头的拉剪强度随电极压力的增加先增大,后减小,中间有个峰值;焊接电流和焊接时间对接头断裂强度的影响规律与电极压力相似。表面清理状态对接头的质量有很大影响,焊前未经过清理的接头强度较低;焊前经机械打磨的接头总体焊接质量较好;焊前采用化学清理的接头,质量稳定,接头强度随焊接电流的增大而提高。焊缝组织由等轴晶和柱状晶构成,拉伸断口呈韧脆混合的断裂特征。
AZ31 magnesium alloy sheet was welded by AC spot welder. The mechanical properties of the spot welded joint under different surface cleaning conditions were tested. The microstructure and tensile fracture appearance of the joint were analyzed by optical microscope and scanning electron microscope. The results show that with other parameters constant, the tensile strength of the joint first increases with the increase of the electrode pressure, and then decreases with a peak in the middle. The influence of welding current and welding time on the fracture strength of the joint and the electrode pressure similar. The surface clean-up condition has a great influence on the quality of the joint, the strength of the joint without cleaning before welding is low, the quality of the joint welded by mechanical grinding before welding is better, the joint cleaned before welding is of a stable quality and the strength of the joint varies with Welding current increases and increases. Weld microstructure is composed of equiaxed grains and columnar grains, and the tensile fracture is characterized by ductile-brittle mixing.