Microstructure and mechanical behavior of Al-Zn-Mg-Cu alloy fabricated by wire-arc directed energy deposition with rotating friction processing

This study introduces a novel hybrid manufacturing strategy by integrating interlayer rotary friction processing (RFP) with wire-arc directed energy deposition (WA-DED). This approach aims to resolve the microstructural heterogeneity and insufficient mechanical performance commonly observed in WA-DED Al–Zn–Mg–Cu alloys. A comprehensive investigation was conducted to evaluate the influence of RFP on columnar grain fragmentation and orientation redistribution. These effects collectively elucidate the multiscale mechanisms underlying the simultaneous microstructural transformation and mechanical performance enhancement. The results demonstrate that the synergistic effects of shear deformation and frictional heating during RFP effectively interrupt the directional growth of coarse columnar grains, leading to a heterogeneous structure composed of alternating fine- and coarse-grained regions. Simultaneously, the brittle S phase (Al₂CuMg), which was originally segregated along grain boundaries, undergoes dissolution, while the formation of a higher density of fine η′ precipitates is promoted. Benefiting from the combined strengthening mechanisms of dislocation accumulation, grain refinement, and Orowan looping, the ultimate tensile strength and yield strength increased by 33.3 % and 15.1 %, respectively, while a notable elongation of 9.1 % was achieved, indicating an excellent balance between strength and ductility. The proposed “additive deposition + interlayer plastic disturbance” strategy provides valuable theoretical insight and engineering potential for the high-integrity fabrication of high-performance aluminum alloy components.