The present study attempts to examine monotonic and fatigue response of friction-stir-welded (FSW) Al 6061-T6 joints. Surface-rolling techniques of in situ and sequential were adapted to evaluate the influence of generated surface deformation on static and fatigue properties of the welded joints. A custom-made tool with four balls with the capability of changing in ball sizes and ball indentations was employed to burnish, while stir-weld beads are formed in situ. The sequential technique, however, rolled the top surface of joints after completion of welding operation. Tensile strength values measured from in situ-rolled FSW joints undergoing static loading were found to be, respectively, 25 and 40% higher with ball sizes of 6 and 8 mm as compared with those un-burnished FSW joints. Fatigue lives of in situ-rolled samples were also enhanced, respectively, 4 and 6 times in magnitudes for these ball diameters. Sequential rolling technique, however, resulted in a negligible elevation in static and fatigue properties of FSW joints. The in situ rolling process on the FSW samples led to more uniform and refined grains especially in HAZ region as compared with those of AW specimens. This resulted in higher static strength and longer fatigue lives. SEM images of the fractured surface revealed brittle fracture over crack initiation site followed by a mixed cleavage and ductile dimples at the rupture stage.

本研究试图检查搅拌摩擦焊接（FSW）Al 6061-T6接头的单调和疲劳响应。采用原位和顺序的表面轧制技术来评估所产生的表面变形对焊接接头的静态和疲劳性能的影响。使用定制的具有四个滚珠的工具进行抛光，同时在原位形成搅拌焊珠，该工具带有四个滚珠，可以改变滚珠的尺寸和凹痕。但是，在焊接操作完成后，顺序技术会轧制接头的顶面。发现从原位轧制的FSW接头承受静态载荷时测得的抗拉强度值分别比未抛光的FSW接头高25％和40％，球尺寸为6和8 mm。原位轧制样品的疲劳寿命也得到了提高，这些球直径的大小分别是4倍和6倍。然而，连续轧制技术导致FSW接头的静态和疲劳特性的升高可忽略不计。与AW试样相比，FSW试样的原位轧制过程导致晶粒更加均匀和细化，尤其是在热影响区。这导致更高的静态强度和更长的疲劳寿命。断裂表面的SEM图像显示出裂纹产生部位的脆性断裂，然后在断裂阶段出现了混合的乳沟和韧性凹痕。与AW试样相比，FSW试样的原位轧制过程导致晶粒更加均匀和细化，尤其是在热影响区。这导致更高的静态强度和更长的疲劳寿命。断裂表面的SEM图像显示出裂纹产生部位上的脆性断裂，然后在断裂阶段出现了混合的乳沟和韧性凹痕。与AW试样相比，FSW试样的原位轧制过程导致晶粒更加均匀和细化，尤其是在热影响区。这导致更高的静态强度和更长的疲劳寿命。断裂表面的SEM图像显示出裂纹产生部位的脆性断裂，然后在断裂阶段出现了混合的乳沟和韧性凹痕。