含镁高硅变形铝合金搅拌摩擦焊接研究

It has been proved that Si particles have an effect on the Al matrix microstructure and precipitates evolution in the friction stir welding (FSW) process of Mg bearing wrought Al-Si alloys. And the applicant found that Si coarsened in the FSW joints. In this project, the microstructures evolution in the FSW joints of Mg bearing wrought Al-Si alloys is studied using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), X-ray diffraction (XRD). And the research contents are as follows: the size and distribution of Si particles, the grain size, grain boundaries’ characteristic in the Al matrix and the morphology, structure, size and distribution of the precipitates in the FSW joints. Then the microstructure evolution mechanism of the FSW joint is analyzed. To explore the effect of Si particles on the microstructure and mechanical behavior of FSW joints, the wrought Al-Mg-Si alloy is prepared for FSW in the same conditions. Combined with the appropriate welding parameters scope, the relationship between the welded joint microstructure and mechanical properties is explored and established. And the strengthening and toughening behavior in the FSW joint of Mg bearing wrought Al-Si alloys is revealed. It is expected to provide necessary theoretical basis for the FSW of Mg bearing wrought Al-Si alloys.

含镁高硅变形铝合金在搅拌摩擦焊接（FSW）过程中，大量硅颗粒的存在不仅可影响铝基体组织及析出相的演化，而且其本身也会发生粗化现象。本项目以含镁高硅变形铝合金作为基础研究的出发点，利用扫描电镜（SEM）、电子背散射技术（EBSD）、透射电镜（TEM）、X-射线衍射仪（XRD）等手段，考察FSW过程中接头各区的硅颗粒的分布、尺寸、铝基体的晶粒尺寸、晶界特征及析出相的结构、形貌、尺寸及分布的演化规律，分析焊接接头微观组织的演化机理。并探讨大量硅颗粒的存在对FSW接头微观组织及力学行为的影响及其机理。结合合适的焊接工艺参数范围探讨并建立焊接接头的微观组织与力学性能的关联性，进而揭示含镁高硅变形铝合金FSW接头的强韧化行为，为新型含镁高硅变形铝合金的FSW提供必要的理论依据。

本项目以含镁高硅变形铝合金为研究对象，开展了含镁高硅变形铝合金的搅拌摩擦焊接研究，证实了高硅铝合金可在比较宽的工艺窗口范围内进行搅拌摩擦焊接；阐明了含镁高硅变形铝合金搅拌摩擦焊接接头的微观组织的演变及强韧化途径；分析了工艺参数对搅拌摩擦焊接过程中接头的温度分布、焊接接头的微观组织及力学性能的影响规律，建立了工艺参数-微观组织-力学性能之间的关联性；研究了硅颗粒的存在对搅拌摩擦焊接接头的微观组织及力学性能的影响；建立了含镁高硅变形铝合金搅拌摩擦焊接过程中的热力耦合模型，并对搅拌摩擦焊接接头的温度场、应力、应变及残余应力分布特征进行了分析。本项目丰富了新型含镁高硅变形铝合金的搅拌摩擦焊接的理论基础。