Friction self-piercing riveting (F-SPR) is an emerging technique for low ductility materials joining, which creates a mechanical and solid-state hybrid joint with a semi-hollow rivet. The severe plastic deformation of work materials and localized elevated temperatures during the F-SPR process yield complex and heterogeneous microstructures. The cut-off action of the work materials by the rivet further complicates the material flow during joint formation. This study employed the F-SPR process to join AA7075-T6 aluminum alloy sheets and systematically investigated the microstructural evolutions using electron backscatter diffraction (EBSD) techniques. The results suggested that as the base material approached the rivet, grains were deformed and recrystallized, forming two distinct fine grain zones (FGZs) surrounding the rivet and in the rivet cavity, respectively. Solid-state bonding of aluminum sheets occurred in the FGZs. The formation of FGZ outside the rivet is due to dynamic recrystallization (DRX) triggered by the sliding-to-sticking transition at the rivet/sheet interface. The FGZ in the rivet cavity was caused by the rotation of the trapped aluminum, which created a sticking affected zone at the trapped aluminum/lower sheet interface and led to DRX. Strain rate gradient in the trapped aluminum drove the further expansion of the sticking affected zone and resulted in grain refinement in a larger span.

摩擦自冲铆接（F-SPR）是一种用于延展性低的材料连接的新兴技术，该技术创建了具有半空心铆钉的机械和固态混合接头。在F-SPR过程中，工作材料的严重塑性变形和局部高温会产生复杂且异质的微观结构。铆钉对工作材料的切断作用使接头形成过程中的材料流动更加复杂。这项研究采用F-SPR工艺连接AA7075-T6铝合金薄板，并使用电子背散射衍射（EBSD）技术系统地研究了微结构的演变。结果表明，当基材接近铆钉时，晶粒变形并重结晶，从而在铆钉周围和铆钉腔中形成两个不同的细晶粒区域（FGZ），分别。FGZ中发生铝板的固态粘结。FGZ在铆钉外部的形成是由于在铆钉/片材界面处的滑动至粘着转变触发了动态再结晶（DRX）。铆钉腔中的FGZ是由截留的铝的旋转引起的，它在截留的铝/下层板的界面处形成了一个粘附影响区域，并导致了DRX。截留的铝中的应变率梯度驱使粘附影响区进一步扩展，并导致较大跨度的晶粒细化。铆钉腔中的FGZ是由截留的铝的旋转引起的，它在截留的铝/下层板的界面处形成了一个粘附影响区域，并导致了DRX。截留的铝中的应变率梯度驱使粘附影响区进一步扩展，并导致较大跨度的晶粒细化。铆钉腔中的FGZ是由截留的铝的旋转引起的，它在截留的铝/下层板的界面处形成了一个粘附影响区域，并导致了DRX。截留的铝中的应变率梯度驱使粘附影响区进一步扩展，并导致较大跨度的晶粒细化。