铝合金搅拌摩擦焊关键物理冶金参数及微观组织演变的量化研究

Friction stir welding (FSW) has gained wide popularity in welding aluminum alloys due to its outstanding advantages. However, owing to the characteristics of FSW, there is no effective method to obtain the physical metallurgical parameters such as strain, strain rate and thermal history during the material flow, which makes it impossible to accurately predict the joint microstructure and mechanical properties through the selected welding conditions. This limits the further promotion and application of the FSW process. Therefore, this project intends to study the quantification of the main physical metallurgy parameters in the FSW of aluminum alloys, and based on this, the microstructure evolution is quantitatively study. The high-precision characterization of the three-dimensional material flow is realized by optimizing the design of the marker material. According to the migration and distortion of the marker material in the three-dimensional space, a method for characterizing the strain/strain rate during the material flow is developed. Based on the obtained material flow data, a more accurate heat source model is established, and the calculated welding temperature field is coupled with the experimentally measured material flow field to achieve an accurate description of the thermal history during the material flow. Based on the quantification of physical metallurgical parameters, the microstructure evolution during the material flow and its influence on the mechanical properties of the joint were studied to reveal the physical mechanism of the welding conditions affecting the microstructure and properties of the joint. This will lay a solid theoretical foundation for optimizing FSW welding parameters and achieving accurate prediction and effective regulation of FSW joint microstructure and mechanical properties.

搅拌摩擦焊（FSW）因其突出的优势而在铝合金焊接中广受青睐。但由于FSW的工艺特性，目前尚无有效的方法来获取材料流动过程中应变、应变速率和热历史等物理冶金参数，导致无法通过选定的焊接工艺条件去精确预测接头组织和性能，限制了其进一步推广应用。因此，本项目拟研究铝合金FSW物理冶金过程主要参量的定量化，并在此基础上定量研究接头微观组织的演变规律。通过优化设计标记材料来实现三维塑性金属流动和变形的高精度表征，根据材料在三维空间的迁移和畸变开发出定量描述材料流动过程中应变/应变速率的方法。基于材料流动数据，建立精确的组合式热源模型，实现材料流动过程中温度变化的精确描述。在物理冶金参数定量化的基础上，研究材料流动过程中的微观组织演变及其对接头力学性能的影响规律，从而揭示焊接工艺条件影响接头组织和性能的物理机制，为优化FSW焊接工艺参数，实现FSW接头组织与性能的精确预测与有效调控奠定坚实基础。

搅拌摩擦焊作为一种先进固相焊接技术，可以避免传统铝合金熔焊中容易出现的气孔、裂纹等一系列问题，在工业领域广受青睐。但由于人们对FSW物理冶金过程仍缺乏深入理解，使得目前对FSW焊接工艺参数的优化仍主要依靠经验，尚不能实现接头组织和性能的精确预测和有效调控，阻碍了该工艺的大规模工业化应用。由于FSW焊接工艺过程及其复杂，现有的研究尚未建立焊接工艺条件（如搅拌头转速、焊接速度、轴向压力、搅拌头几何形状等）与材料物理冶金参数（应变、应变速率、变形温度、高温停留时间、冷却速率等）之间的定量关系，导致无法根据焊接工艺条件去精确预测接头组织和性能。.本项目采用优化的标记材料表征FSW过程中材料的三维塑性流动，研究了材料在搅拌头周围三维空间内的迁移和畸变行为，建立FSW三维塑性流动和变形的数理模型，定量表征三维塑性流动中的材料流速、应变和应变速率；在此基础上，基于上述获取的物理冶金参数，表征了材料塑性流动中的微观组织演变过程，阐明微观组织随物理冶金参数动态变化的演变机理，揭示其对接头力学性能的影响规律。最后，基于对材料流动的深刻理解，提出了涡流搅拌摩擦焊新工艺，开展了工艺参数优化和工艺机理探索研究，揭示了涡流搅拌摩擦焊的热-流耦合机理。为搅拌摩擦焊在铝、镁及其合金等低熔点金属的工业化应用和钛合金、钢等高熔点金属材料应用探索奠定了坚实的理论基础。.总结本项目研究结果，已发表期刊论文12篇（其中SCI收录9篇，EI收录3篇），申请发明专利3项（已授权1项），作会议报告2次。以项目部分研究成果为支撑，获得2项科研奖励：2020年度山东省高等学校科学技术奖一等奖（排3）；2022年度大阪大学接合科学研究所Young Researcher Award in Joining and Welding.

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