Achieving ultrahigh tensile strength of 1 GPa in a hierarchical nanostructured 2024 Al alloy

Abstract

A novel hierarchical nanostructure consisting of nanoscale grains (~115 nm), subgrains (~36 nm), needle-shaped S’/S precipitates (Al2CuMg, 6–16 nm in length) in grains and extremely fine oxide dispersions has been realized in a commercial Al–Cu–Mg alloy fabricated by high pressure torsion followed by natural aging using pre-sintered powders. The multiple strengthening effects of the hierarchical nanostructure including the grain boundary hardening by nano-sized grains/subgrains and the secondary phase strengthening by the nanoscale oxide particles and S’/S precipitates result in an ultra-high tensile strength approaching 1 GPa, which largely expands the known limit of strength for Al–Cu–Mg alloys. This work provides an effective pathway of designing super-strong Al alloys.