超薄板的高转速微型搅拌摩擦焊接机理研究

Recently there are more and more requirements of ultra thin-walled components manufacture technology in the many fields such as aviation, aerospace, electrical and electronic industry. For meeting this requirement, the new kind of welding technology suitable for the ultra thin-walled components manufacture will be developed in this project. That is micro friction stir welding with high rotational speed(short for HRS-μFSW). The HRS-μFSW weldability and the related mechanisms for the similar and dissimilar materials in the form of ultra thin plates with the thinkness of 0.5mm be studied systematically. The results will solve the key fundamental theory and technology in the deformation and quality stability control in the manufacture of the ultra thin-walled components. The research will provides theoretical and practical foundation for the development of the HRS-μFSW technology and equipment, as well as propel the application of HRS-μFSW technology in many manufacture areas. . This research mainly concentrated on the following aspects: (1)Reveal the influence of HRS-μFSW welding technology on the microstructure, interface diffusion and mechanical property of the ultra-thin plates and the related mechanism.(2)Explore the influence factors on the heat generation mechanism as well as the plastic deformation, material flow and dynamic recrystallization behavior in weld zone during the HRS-μFSW process of the ultra-thin plates. (3)develop the numerical simulation methods used for the predict of temperature field and plastic flow filed during the HRS-μFSW process of the ultra-thin plates. Study the influence of welding technology on temperature field and plastic flow filed during the HRS-μFSW process of the ultra-thin plates as well as their control methods. (4) explore the influence of the texture evolution on the mechanical property and fracture behavior in the HRS-μFSW welded ultra-thin plates. Optimize HRS-μFSW technology for the ultra-thin plates with different joint geometry.

基于电子电器行业及航空航天等领域超薄壁零部件的制造需求，开发高转速微型搅拌摩擦焊接(μFSW)工艺，系统研究同质和异质超薄板(0.5mm)的高转速μFSW焊接机理，形成超薄壁件焊接变形及质量稳定性控制所急需的关键技术与基础理论。相关成果可为高转速μFSW工艺与设备开发，及其在超薄壁结构制备中的工程应用提供基础理论指导与实践依据。主要研究内容包括：（1）揭示超薄板高转速μFSW焊接工艺条件对焊接组织、界面扩散及力学性能的影响规律与作用机理；（2）探讨超薄板高转速μFSW产热机制、焊缝金属的塑性流动与动态再结晶行为，揭示其主要的影响因素与作用机理；（3）开发能够预测超薄板高转速μFSW焊接温度场和塑性流动场的数值模拟技术，探讨焊接工艺条件对焊接温度场和塑性流动场的影响规律及控制方法；（4）揭示其焊接织构对接头力学性能与断裂行为的影响规律，优化不同接头型式超薄板的高转速μFSW工艺。

基于电子电器行业及航空航天等领域超薄结构制造需求，开发了高转速(6000-10000rpm)超薄板(1.0mm及以下)微型搅拌摩擦焊接(μFSW)工艺，获得了工艺条件对组织与力学性能影响规律，阐明了其织构对力学性能与断裂行为影响规律，获得了不同接头型式超薄板高转速μFSW优化工艺。同时探讨了其产热机制、焊缝金属塑性流动与动态再结晶行为主要影响因素，揭示了工艺条件对温度场和塑性流动场影响规律，实现了其焊接过程温度场和塑性流动场的数值模拟。相关成果解决了超薄件高速μFSW焊接质量控制的基础理论与关键技术，可为其工艺与设备开发及工程应用提供指导依据。重要研究成果有：.(1)在本实验条件下，适合不同铝合金超薄板高速μFSW参数范围是：转速6000-10000rpm，焊速1200-1500mm/min。优化的超薄板高转速μFSW轴肩为三螺旋线型内凹面；采用10mm夹持距离、钢垫板和焊后时效处理时，6061铝合金高转速μFSW接头抗拉强度为317.8MPa，约为母材的90%。.(2)铝合金超薄板高转速μFSW接头NZ区晶粒细化，且有大量弥散分布析出相和高密度位错，抗拉强度较常规转速FSW提高30%左右。.(3)转速8000rpm和焊速1500mm/min时，6061铝合金高转速μFSW焊接峰值温度为350℃；转速6000rpm和焊速1200mm/min时，7075铝合金高转速无针μFSW焊接峰值温度为294.6℃，均比常规μFSW要低。.(4)高转速μFSW时，铝合金对接接头AS侧塑性金属纵向流动距离减小40.2%，流速提高6倍；RS侧塑性金属纵向和横向流动距离分别减小84.6%和21.3%，流速提高13倍。高转速μFSW搭接接头界面沿板厚方向在AS侧向上和RS侧向下迁移距离减小，其有效承载板厚和有效搭接宽度分别提高46.9%和50.4%。.(5)6061铝合金高转速μFSW接头NZ区和TMAZ区发生了完全动态再结晶，转速10000rpm时，其NZ区再结晶晶粒和亚晶粒占比分别为78.1%、20.7%，AS侧和RS侧的TMAZ区占比分别为54.9%、43.5%和61.4%、34.5%。.(6)7075铝合金超薄板高速无针μFSW接头呈反马鞍状变形。高速焊(转速8000/焊速1200)的焊接变形量最小，焊缝中心纵向最大翘曲变形量为5.7389mm，且随夹持距离增大而增大。