Ultrasonic shot peening enhances microstructure and mechanical properties of AFSD-processed 6061-7075 dissimilar aluminum alloys

Résumé fourni par la source

To clarify how USP-induced surface deformation regulates the microstructure–property relationship, This study systematically investigates the regulatory effects of Ultrasonic Shot Peening (USP) on the microstructure and mechanical properties of 6061-7075 dissimilar aluminum alloys fabricated via Additive Friction Stir Deposition (AFSD). On the basis of solution treatment at 460 °C for 2 h followed by aging at 120 °C for 24 h and 160 °C for 8 h, USP was applied for different durations (2, 4, and 8 min). The material's microstructural evolution and performance responses were examined through EBSD analysis and mechanical testing. Results indicate that USP introduces significant plastic deformation on the side surfaces of the deposited layers, forming a through-thickness gradient structure. The degree of deformation increased with peening time; the 4 min condition produced a relatively uniform grain structure, whereas 8 min peening generated pronounced deformation bands, elevated KAM values, and localized deformation accumulation, thereby increasing microstructural heterogeneity., thereby increasing microstructural heterogeneity. Regarding precipitate behavior, moderate USP (4 min) introduces additional deformation-induced defects, which may provide favorable sites for the interaction between dislocations and existing precipitates. Excessive peening (8 min), however, leads to severe dislocation entanglement and localized strain accumulation, resulting in microstructural heterogeneity. Mechanical tests reveal that USP significantly enhances material strength, with the 4 min condition achieving optimal overall performance: ultimate tensile strength increased from 251 MPa to 290 MPa, and elongation reached 10.1%. Further extension of peening time to 8 min resulted in a reduction of ductility due to excessive plastic deformation. These results demonstrate that moderate USP improves the strength–ductility balance through grain refinement and near-surface deformation hardening, whereas excessive deformation causes strain localization and microstructural instability. These findings provide valuable guidance for the optimization of USP processing and microstructure-property design in dissimilar aluminum alloy AFSD components.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.