Structural ordering governs stiffness and ductile-to-brittle transition in Al-Li alloys

The trade-off of stiffness and ductility of metals has long plagued materials scientists. To address this issue, atomic structure designs of short-range ordering (SRO) to sub-nanometer and nanometer scales have received much interest in tailoring the atomic environment and electronic interaction between solute and solvent atoms. Taking an example of Al-Li alloy with high specific stiffness and reverse correlation of Young's modulus and melting point, in this work, we investigate the SRO-dependent stiffness and intrinsic ductile-brittle properties by performing a full-configuration strategy containing various structural ordering features. It suggests that the short-range ordered arrangement of Li atoms can effectively enhance the stiffness while keeping ductility, playing a hydrostatic pressure-like role. Our findings present fundamental knowledge to enable high stiffness and ductility for solvent phases with low modulus through designing local short-range ordered cluster structures.