本项目基于回填式搅拌摩擦点焊生产效率低、接头中易出现焊接缺陷等难题，针对高强铝合金的局部液化特性，提出一种基于热量产生机制提高焊接热输入效率与材料流动性的新思路，即首先利用搅拌头下压速率对焊接热输入及焊接热输入效率的影响规律，通过增大搅拌头在其运动方向的表面积，实现在局部液化条件下继续增加焊接热输入和提高材料流动性，在较短时间内无缺陷焊接的目的。系统深入研究搅拌头下压速率和搅拌头结构对热量产生机制及材料流动行为的影响规律，阐明在局部液化条件下提高焊接热输入和材料流动性的热力耦合机制，获得搅拌头下压速率最佳参数及搅拌头结构优化设计，阐明被焊材料在不同焊接阶段的材料流动行为，揭示动态再结晶及大塑性变形的形成机制，阐明接头组织演化及疲劳失效机制，揭示高强铝合金高速大塑性变形回填式搅拌摩擦点焊的连接机理，为将其应用于航空航天领域高强铝合金点结构件的连接奠定理论基础。

Based on the problems of low production efficiency and defects formation in the welds, consider the local melting characteristic of high strength aluminum alloys, a new idea was proposed based the heat generation mechanism to improve heat generation rate and material flow, which is to use the influence law between the tool plunging rate and heat input rate, and improve the superficial area of the welding tool on the plunging direction to attain the goal to further improve heat generation and material flow in a local melting condition, and thus obtain a defect-free weld in a very short joining time. The influence law of the tool plunging rate and tool design on the heat generation and material will be systematically studied, the thermal coupling mechanism of improving the heat generation and material flow will be explained in a local melting condition, obtain the optimized tool plunging rate and tool design, explain the material flow pattern in different joining periods, reveal the mechanism of dynamic recrystallization and large plastic deformation, clarify the microstructure evolution and fatigue failure mechanism, reveal the joining mechanism of high speed large plastic deformation refill friction stir spot welded high strength aluminum alloys. The related research achievement will provide theoretical guidance and practical basis for spot welded high strength aluminum alloy structure in the aviation and aerospace fields.