1060-H24纯铝无肩微搅拌摩擦焊接头的显微组织演化与强化机制

Microstructural Evolution and Strengthening Mechanisms of Shoulderless Micro-friction Stir Welded Joints of 1060-H24 Pure Aluminum

摘要:

评估了0.8 mm薄板微搅拌摩擦焊中带肩和无肩工具的差异。采用白光干涉法、电子背散射衍射和扫描电子显微镜等一系列表征方法，研究了焊缝表面形成、接头微观组织分布和断裂特征。通过Hall-Petch关系和Taylor硬化定律解释了力学性能的增强机制。结果表明，无肩工具接头屈服强度提高的主要原因是位错强化和细晶强化的综合机制。具体而言，使用轴肩工具可获得光滑的焊缝表面，平均晶粒尺寸为11.24 μm，焊核区大角度晶界含量为16.80%，观察到的主要织构组分为{011}<100> Goss织构和{112}<111> Copper织构，最大织构强度为3.70，同时断口韧窝尺寸减小、深度增加。而无肩工具焊缝表面出现轻微毛刺，试验结果表明，该类接头焊核区平均晶粒尺寸显著减小至0.59 μm，大角度晶界含量达到34.34%，并伴随以{111}<110>剪切织构和{001}<110>旋转立方织构为主要组分的形成，导致最大织构强度显著提高至6.65。

Abstract:

The differences between shouldered and shoulderless tools in the micro-friction stir welding of 0.8 mm thin plates were evaluated. Employing a suite of advanced characterization methods, including white light interferometry, electron backscatter diffraction (EBSD), and scanning electron microscopy, the formation of weld surface, joint microstructure distribution, and fracture characteristics were studied. The enhancement mechanism of mechanical properties was explained through the Hall-Petch relationship and Taylor's hardening law. Results indicate that the main reason for the increased yield strength observed in shoulderless tool joints is the combined mechanism of dislocation strengthening and fine-grain strengthening. Specifically, the utilization of shouldered tools results in a smooth weld surface, with an average grain size of 11.24 μm and a high-angle grain boundary content of 16.80% in the nugget zone. The primary texture components are the {011}<100> Goss and {112}<111> copper textures, yielding a maximum texture strength of 3.70. Simultaneously, the fracture dimples exhibit a reduction in size and an increase in depth. Whereas the welds produced with shoulderless tools display slight burrs on the surface. The experimental results demonstrate that the average grain size in the nugget zone of these joints is significantly reduced to 0.59 μm, while the high-angle grain boundary content reaches 34.34%. This process is accompanied by the formation of {111}<110> Shear textures and {001}<110> rotated cubic textures as the main components, resulting in a significant increase in maximum texture strength to 6.65.