Interface stair-like design and repair performance of Al-Zn-Mg-Cu aluminum alloy based on additive friction stir deposition

Abstract

Additive Friction Stir Deposition (AFSD) is an emerging solid-state additive technology for the fabrication and repair of high-strength alloy structural components, but the affected factors of the AFSD repaired quality remain unclear. In this paper, four types of grooves on the Al-Zn-Mg-Cu alloy plate were repaired using AFSD, the design of repair grooves introduced an interface stair-like structure, and the effect of structural features on the microstructure and properties were investigated. The grain refinement of the repaired grooves with a stair-like structure is significantly higher than the common structure. The V_stair structure has the best effect on grain refinement after repair, with 93.9 % refinement compared to the substrate. The ultimate tensile strength (UTS) on the advancing side was higher than that on the returning side. The UTS of the V_stair structure is the highest after repair, reaching 294 MPa, which reaches 53.8 % of the matrix. The introduction of the stair-like structure provides additional shear action and increases the material contact area during the repair process, and the continuous dynamic recrystallization coexists with geometric dynamic recrystallization at the repair interface, which contributes to microstructure mixing and grain refinement, and further enhances the properties. This research provides insights for guiding the design and optimization of aluminum alloy repair processes.