The flat surfaces of a 7075 aluminum (Al) alloy plate were processed by sliding friction treatment (SFT), which is a technique for surface nanocrystallization of metals and alloys. The aim of this study was to investigate the microstructural evolution, mechanical behavior and strengthening mechanisms in this SFTed precipitation-strengthened Al alloy. The SFT resulted in a gradient structure (GS) with an effective depth of ~ 800 µm, and a nanostructured layer was formed within a depth of ~ 30 µm from the surface. Increasing boundary spacing and decreasing misorientation angle between boundaries were found with increasing depth from the surface, which was accompanied by a decrease in hardness from ~ 2436 MPa in the topmost surface layer to ~ 1568 MPa in the undeformed coarse grain (CG) matrix. Moreover, the GS revealed a prominent precipitate redistribution induced by the SFT. The GS revealed higher strength and especially exhibited a higher work-hardening rate at low strain (ε < 0.026) than the CG, attributed to a novel coupling of dislocations, boundaries and precipitates. Grain boundary strengthening, dislocation strengthening, precipitation strengthening and synergetic strengthening in the GS were quantitatively evaluated based on sufficient discussion.

7075铝（Al）合金板的平坦表面通过滑动摩擦处理（SFT）进行了处理，这是一种用于金属和合金表面纳米晶化的技术。这项研究的目的是研究这种SFT沉淀强化铝合金的组织演变，力学行为和强化机理。在SFT导致梯度结构（GS）具有〜800的有效深度μ m和〜30的深度范围内形成了纳米结构层μ距离表面m。随着距表面深度的增加，边界间距增加，边界之间的取向差角减小，伴随而来的是硬度从最表层的〜2436 MPa降低到未变形的粗晶粒（CG）基质的〜1568 MPa。此外，GS揭示了由SFT引起的明显的沉淀物重新分布。GS显示出更高的强度，特别是在低应变（ε <0.026）下比CG表现出更高的加工硬化率，这归因于位错，边界和析出物的新型耦合。在充分讨论的基础上，对GS中的晶界强化，位错强化，降水强化和协同强化进行了定量评估。