Synergetic double-sided probeless friction stir spot welding is a novel process proposed in this study, which is used to solve the contradiction between the improvement of metallurgical bonding and deterioration of hook defect. The effect of the coordinated movement of the tools on the joint formation was evaluated based on the coupled Eulerian-Lagrangian technique. By flexibly adjusting the welding parameters on both sides, the mechanical interlock caused by hook defect could be effectively regulated while significantly improving the metallurgical bonding, due to the enhancement of thermo-mechanical cycle along the thickness direction. According to the microstructure analysis, the interfacial evolution was ascribed to the combined effects of plastic deformation, material flow, atom diffusion, and recrystallization, as well as local abrasion. In addition, the microhardness profile exhibited a uniform distribution. Based on the above characteristics, the technology is expected to obtain higher strength joints, which will promote its applications in the manufacture fields.

协同双面无探针摩擦搅拌点焊是本研究提出的一种新工艺，用于解决冶金结合的改善与弯钩缺陷的恶化之间的矛盾。基于耦合的欧拉-拉格朗日技术评估了工具的协调运动对关节形成的影响。通过灵活地调节两侧的焊接参数，由于沿厚度方向的热机械循环的增强，可以有效地调节钩缺陷引起的机械互锁，同时显着改善冶金结合。根据微观结构分析，界面演化归因于塑性变形，材料流动，原子扩散和再结晶以及局部磨损的综合作用。另外，显微硬度分布表现出均匀的分布。基于上述特征，该技术有望获得更高强度的接头，这将促进其在制造领域的应用。