Inhibiting segregation enabled outstanding combination of mechanical and corrosion properties in precipitation-strengthened aluminum alloys

Abstract

Segregation of solutes to grain boundary (GB) is the dominant restriction on enhancement of mechanical properties and corrosion resistance during aging in precipitation-strengthened aluminum alloys. Here, we innovatively introduce the cyclic deformation by the vibration during aging to eliminate the GB segregation, resulting in the formation of the narrow precipitate-free zone (PFZ) widths near the GB, as well as the fine and discontinuous grain boundary precipitations (GBPs). Compared with the traditional peak-aging, the 2014 aluminum alloy treated by thermal cooperative vibration aging (TCVA) exhibits a superb combination of impact toughness and corrosion resistance, and retains the strength and ductility. In addition, the atomic simulations show that TCVA generates numerous vacancies near the GB, but does not change the dislocation density with the increase of cycle time. These results indicate that the vacancy significantly promotes the nucleation and growth of precipitates in the vicinity of GB, resulting in the narrow PFZs and fine discontinuous GBPs. The present work provides the fundamental knowledge and method to inhibit the equilibrium segregation of solutes to GB during aging, and further realizes the precipitation-strengthened aluminum alloys with excellent mechanical and corrosion properties.