The present study focused on two dissimilar metal alloys: AA7075-T651 and Ti-6Al-4V alloys with additional carbon fiber-reinforced polymer (CFRP) as an interlayer were welded together by friction stir spot welding (FSSW). The effect of welding parameters (rotational speed and dwell time) and carbon fiber-reinforced polymer on mechanical and microstructural properties of a weld joint was investigated. The obtained results explore the parametric effects on mechanical properties of the weld joint. The maximum tensile shear load 2597.8 N was achieved at the rotational speed of 2,000 rpm and dwell time of 10 s. While at the same rotational speed, 54.7% reduction in the tensile shear load was attained at shorter dwell time of 5 s. Therefore, dwell time plays an important role in the tensile shear load of a weld joint. The scanning electron microscope (SEM-EDS) results show the formation of intermetallic compound of Ti 3 Al and Ti-Al-C that significantly affect the mechanical and microstructural properties of the weld joint. Moreover, the effect of the rotational speed on micro-hardness was found at significant than dwell time. The micro-hardness of the weld joint increase by 18.90% in the keyhole rather than the stir zone and the thermomechanical affected zone, which might be due to the presence of ternary (Ti-Al-C) intermetallic compound. Graphical abstract

中文翻译：

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异种接头AA7075-T651/Ti-6Al-4V合金CFRP夹层搅拌摩擦点焊力学性能和显微组织性能试验研究

本研究侧重于两种不同的金属合金：AA7075-T651 和 Ti-6Al-4V 合金，并通过搅拌摩擦点焊 (FSSW) 将附加碳纤维增强聚合物 (CFRP) 作为夹层焊接在一起。研究了焊接参数（转速和停留时间）和碳纤维增强聚合物对焊接接头机械和微观结构性能的影响。所得结果探讨了参数对焊接接头力学性能的影响。在 2,000 rpm 的转速和 10 s 的停留时间下实现了最大拉伸剪切载荷 2597.8 N。在相同的转速下，在 5 秒的较短停留时间下，拉伸剪切载荷降低了 54.7%。因此，停留时间在焊接接头的拉伸剪切载荷中起着重要作用。扫描电子显微镜（SEM-EDS）结果表明，Ti 3 Al 和 Ti-Al-C 金属间化合物的形成显着影响了焊接接头的力学和显微组织性能。此外，发现转速对显微硬度的影响比停留时间更显着。与搅拌区和热机械影响区相比，键孔处焊缝显微硬度提高了18.90%，这可能是由于三元(Ti-Al-C)金属间化合物的存在。图形概要 与搅拌区和热机械影响区相比，键孔处焊缝显微硬度提高了18.90%，这可能是由于三元(Ti-Al-C)金属间化合物的存在。图形概要 与搅拌区和热机械影响区相比，键孔处焊缝显微硬度提高了18.90%，这可能是由于三元(Ti-Al-C)金属间化合物的存在。图形概要