Additive Friction Stir Deposition (AFSD) has emerged as a promising solid-state technique for manufacturing large-scale 7XXX series aluminum components, offering refined microstructures with minimal solidification defects. However, the interplay between precipitate evolution and dislocation/substructure dynamics during multilayer deposition, particularly in the post-dynamic stage, remains inadequately understood. This study systematically investigates the microstructural evolution of AFSD-processed 7075 aluminum alloy through multiscale characterization of dislocation density, precipitate distribution, and substructure morphology. Key findings reveal that η/η′ phases partially dissolve during the dynamic stage, forming Grain Boundary Precipitates (GBPs) and Intragranular Clusters (IPCs), which stabilize grain boundaries while retaining substructures. Subsequent cooling within the η/η′ precipitation window triggers GBPs/IPCs dissolution and static recovery, enhancing grain boundary mobility and reducing dislocation density. Post-dynamic cooling further homogenizes GBPs/IPCs, enabling nucleation of new precipitates (η′, η, Al₂Cu) that generate interfacial dislocations to accommodate lattice mismatch. These interactions, coupled with insufficient thermal activation energy, stabilize dislocation networks and substructures (e.g., dislocation loops, low-angle boundaries) within recrystallized grains, ultimately triggering their transformation into substructured grains. Crucially, the inherent thermal cycling in AFSD induces heterogeneous microstructures, highlighting the necessity of location-specific heat treatments tailored to GBPs/IPCs distributions to ensure uniform post-processing.

This study aims at investigating the impact of using the Magnetorheological Elastomers (MREs) medium to improve the formability of T-shaped Inconel 718 tubes during the bulging process. Besides, the influence of the punch size and the intensity of the magnetic field on the branch height and wall thickness distribution of the T-shaped Inconel 718 tubes are also explored. The results showed that the parts formed by the punch with a length of 5 mm in the pressurization zone have better forming quality. The external magnetic field can promote a high branch, and by increasing the intensity of the magnetic field, the branch height was increased and then decreased. At the same time, the magnetic field reduced the amount of material accumulation between the guiding zone and the bulging zone. Besides, it promotes the material in the guiding zone to enter the bulging zone and improve the bulging ability of the T-shaped tube.