The influence of seven different tool pin profiles was investigated to appraise the tensile, flexural strength, fracture behavior, and microstructure evolution in friction stir welded similar AA6061-T6 joints. Results indicate that each tool pin profile affects the material flow/intermixing in different ways; consequently, the weld nugget feature and grain size in the stir zone (SZ) were also observed to be different. Relatively finer grains with homogenous microstructure in SZ were observed for joints prepared using cylindrical grooved with straight flutes (CGF) and cylindrical grooved (CG) tool pins. The highest tensile strength and flexural load were observed for joints obtained with CGF tool pin followed by CG tool pin. A relationship between average yield strength of the joint and inverse square root of average SZ grain size was established for these joints. EBSD analysis revealed that the SZ is the mixture of low angle grain boundaries and high angle grain boundaries (HAGBs) and the fraction is controlled by different pin profiles. The HAGBs and high shear texture components $B/\overline{B}$ and $C$ were found predominant in welds prepared with CGF and CG tool pins. Fractographic analyses showed the presence of numerous dimples in sound bonded regions indicating the ductile fracture; however, tearing/rupture and shear failure were witnessed near the vicinity of the tunnel region.

研究了七个不同工具销轮廓的影响，以评估搅拌摩擦焊接类似AA6061-T6接头的拉伸，弯曲强度，断裂行为和微观结构演变。结果表明，每个工具销轮廓均以不同方式影响物料的流动/混合。因此，搅拌区（SZ）的焊点熔核特征和晶粒尺寸也有所不同。使用直槽圆柱槽（CGF）和圆柱槽（CG）工具销制备的接头观察到在SZ中具有相对均匀的微细晶粒。对于使用CGF工具销然后使用CG工具销获得的接头，观察到了最高的拉伸强度和弯曲载荷。建立了这些接头的接头平均屈服强度与平均SZ晶粒尺寸的平方反比之间的关系。EBSD分析显示，SZ是低角度晶粒边界和高角度晶粒边界（HAGB）的混合物，并且分数由不同的销轮廓控制。HAGB和高剪切纹理组件$乙/\overline{乙}$ 和 $C$在使用CGF和CG工具销准备的焊缝中发现主要成分。分形分析表明，在健全的结合区域存在许多酒窝，表明韧性断裂。然而，在隧道区域附近观察到撕裂/断裂和剪切破坏。