Synergistic strengthening and ductility enhancement in 5A90 Al-Li alloy through multi-scale microstructural engineering

To overcome the engineering application bottleneck arising from the intrinsic strength plasticity tradeoff in 5A90 Al-Li alloy, this study proposes an innovative processing strategy integrating cold rolling (RC), liquid nitrogen treatment (LNT) and controlled recrystallization annealing (RA) to achieve synergistic microstructural optimization. Through systematic microstructural characterization (SEM, EBSD, TEM), the unique strengthening toughening mechanism induced by LNT is thoroughly elucidated. The results demonstrate that complete recrystallization characterized by rapid grain boundary migration and dislocation density inheritance is achieved via the RC-LNT-RA treatment. Macroscopically, this process yields a fine equiaxed grain structure. Microscopically, it effectively immobilizes high density dislocations within grain interiors while promoting pronounced grain rotation, thereby resulting in a crystallographic texture characterized by a dominant rotated cubic component alongside multiple minor texture components. This unique composite microstructure, consisting of fine grains, high density intragranular dislocations, and multiple textures, constructs a multi scale synergistic strengthening toughening mechanism. In addition, this study identified an Al₃Zr/amorphous Mg core shell structure, which further contributes to strengthening toughening via stress buffering effects. This work synergistically enhances the material’s deformation resistance and strain accommodation capacity, thereby providing a novel theoretical basis and technical pathway for the development of next generation high performance Al alloys.