静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接新方法及接头形成机理研究

The kissing bond is inevitably formed in the conventional friction stir welded joint due to the fact that the length of tool pin is shorter than the workpieces thickness, and thus resulting in the reduction of joint mechanical properties. Aiming at the elimination of kissing bond and the improvement of joint properties, an innovative welding process, i.e. stationary shoulder supporting and oblique pin penetrating friction stir welding (SOFSW), is proposed. In such a process, in order to bear the axial load exerted by the shoulder, the backing plate used in conventional friction stir welding is replaced by a stationary shoulder with a blind hole in the center. This key design ensures that the workpieces are penetrated by the pin and thus the kissing bond is completely eliminated. Moreover, the heat input during welding could be significantly reduced. As a result, the sound SOFSW joints with high quality are obtained. .By means of experimental research, theoretical analysis and numerical simulation, a set of SOFSW system is developed. The research is focused on the temperature field distribution, material flow mechanism, evolution of welding load with welding parameters, correlation between microstructures and properties, and the formation mechanism of SOFSW joints. Based on this, the optimization of welding process parameters is accomplished. The final objective is to provide an advanced welding process and lay a theoretical basis for the reliable joining of high-strength aluminium alloys used in aerospace structures, and thus promoting the innovative developing of friction stir welding technique.

针对常规搅拌摩擦焊由于搅拌针长度小于被焊工件厚度而难以避免焊缝根部形成未焊合缺陷及其引起接头性能降低的问题，提出一种静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接新方法。该方法摒弃了常规搅拌摩擦焊采用的背部垫板，设计带有中心盲孔的静轴肩承受轴向载荷，能够实现带有倾角的穿透型搅拌摩擦焊接，在完全避免未焊合缺陷产生的同时，有效降低焊接过程的热输入，获得优质高强的搅拌摩擦焊接头。.采用试验研究、理论分析和数值模拟相结合的研究方法，建立一套静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接系统，重点研究焊接温度场及材料流动行为，分析焊接载荷随焊接工艺参数的变化规律，阐明接头微观组织与接头性能的相关性，揭示静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接头形成机理，实现焊接工艺参数优化，为高强铝合金构件的焊接制造提供新的技术手段和理论依据，推动搅拌摩擦焊接技术的创新发展。

搅拌摩擦焊接是一种优质高效的新型连接技术，能够有效改善接头的组织和性能。然而，常规搅拌摩擦焊由于搅拌针长度小于被焊工件厚度而难以避免焊缝根部形成未焊合缺陷及其引起接头性能降低的问题。因此，本研究提出一种静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接新方法。该方法能够实现带有倾角的穿透型搅拌摩擦焊接，在完全避免未焊合缺陷产生的同时，有效降低焊接过程的热输入，获得优质高强的搅拌摩擦焊接头。.通过试验研究、理论分析和数值模拟相结合的研究方法，开发了一套静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接系统，研究了焊接温度场及材料流动行为，分析了焊接载荷随焊接工艺参数的变化规律，阐明了接头微观组织及其与接头性能的相关性，揭示了静轴肩支撑搅拌针倾斜穿透搅拌摩擦焊接头形成机理，实现了焊接工艺参数的优化，为高强铝合金构件的焊接制造提供了新的技术手段和理论依据，促进了搅拌摩擦焊接技术的创新发展。