搅拌针对FSSW-B接头界面组织与力学性能的影响

铝/镁异种金属复合结构在结构轻量化领域具有极大的应用价值。采用新型搅拌摩擦点焊-钎焊技术(friction stir spot welding-brazing,FSSW-B)对铝/镁异种金属进行搭接点焊，同时与搅拌摩擦钎焊(friction stir spot brazing,FSSB)工艺进行对比，研究焊接工具中搅拌针的存在对接头界面组织与力学性能的影响。FSSW-B接头界面中间层分为明显上下2个部分，上层界面主要为MgZn₂相，下层界面主要为Mg₇Zn₃相；FSSB接头主要为MgZn₂相。接头的断裂模式主要为界面剥离断裂，由于搅拌针的存在，出现了眉状断裂模式。搅拌针的存在提高了接头的抗拉剪性能与疲劳性能，FSSW-B接头的最大抗拉剪力为7600 N，疲劳极限为3366.6 N；搅拌针使抗拉剪性能提升了53.5%，使疲劳性能提升了11.4%;FSSW-B中搅拌针的存在增加了接头疲劳性能的分散性。

Effect of stirring pin on interface microstructure and mechanical properties of FSSW-B joint

The aluminum / magnesium dissimilar metal composite structure has great application value in the field of structural lightweighting. In this paper, a novel friction stir spot welding - brazing (FSSW-B) technology was used for lap spot welding of aluminum / magnesium dissimilar metals. At the same time, it was compared with friction stir spot brazing (FSSB) technology to study the effect of the existence of the stirring pin in the welding tool on the microstructure and Mechanical properties of the joint. The middle layer of the interface of FSSW-B joint is divided into two parts: the upper interface is mainly composed of MgZn2, and the lower interface is mainly composed of Mg7Zn3; the FSSB joint is mainly composed of MgZn2 phase. The fracture mode of the joint is mainly interface peeling fracture, and the eyebrow-shaped fracture mode appears due to the existence of the stirring pin. The existence of the stirring stir improves the tensile shear resistance and fatigue performance of the joint. The maximum tensile shear force of the FSSW-B joint is 7600 N, and the fatigue limit is 3366.6 N; The contribution rate of stirring to tensile shear performance is 53.5%, and the contribution rate to fatigue performance is 11.4%; The existence of stirring pin in FSSW-B increases the dispersion of joint fatigue properties.