This study investigates the impact of refill friction stir spot welding (RFSSW) on Alclad-coated AA7075 aluminum alloy, specifically exploring the effects of two plunge depths (g = 1.55 mm and g = 1.9 mm) on the mechanical and fatigue properties. The influence of the Alclad layer on the final joint properties is assessed. Internal flow analysis reveals a concentration of the Alclad layer at the corners of the stir zone for an increased plunge depth. Notably, the sample using a plunge depth of 1.55 mm exhibits a 32 % increase in pure shear strength compared to the sample executed with a plunge depth of 1.9 mm, emphasizing the significance of the plunge depth for achieving superior mechanical performance. SEM analysis of the fracture surface highlights deformation and dimples in the g = 1.55 mm sample, while EDS confirms the Alclad layer's presence, indicating its positive influence on mechanical resilience. Additionally, peel tests demonstrate a 41 % strength increase for the g = 1.9 mm sample. Low and high cycle fatigue tests reveal superior fatigue performance in the g = 1.55 mm sample, supported by SEM analysis illustrating crack initiation and fracture mechanisms. These findings contribute to a nuanced understanding of the interaction between plunge depth, Alclad ldistribution and resulting mechanical and fatigue properties.

中文翻译：

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补充搅拌摩擦点焊工具切入深度对 Alclad 涂层 AA7075 铝接头剪切、剥离和疲劳性能的影响

本研究研究了补充填充搅拌摩擦点焊 (RFSSW) 对 Alclad 涂层 AA7075 铝合金的影响，特别探讨了两种切入深度（g = 1.55 mm 和 g = 1.9 mm）对机械和疲劳性能的影响。评估 Alclad 层对最终接头性能的影响。内部流动分析揭示了 Alclad 层在搅拌区拐角处的浓度，从而增加了插入深度。值得注意的是，与使用 1.9 mm 切入深度的样品相比，使用 1.55 mm 切入深度的样品的纯剪切强度增加了 32%，这强调了切入深度对于实现卓越机械性能的重要性。断裂表面的 SEM 分析突出显示了 g = 1.55 mm 样品中的变形和凹坑，而 EDS 证实了 Alclad 层的存在，表明其对机械弹性的积极影响。此外，剥离测试表明，g = 1.9 mm 样品的强度增加了 41%。低周和高周疲劳测试表明，g = 1.55 mm 样品具有优异的疲劳性能，并得到说明裂纹萌生和断裂机制的 SEM 分析的支持。这些发现有助于深入了解切入深度、Alclad分布与由此产生的机械和疲劳性能之间的相互作用。