Giant hardening and formation of nanograined supersaturated solid solution in Al-Zn system

Grain refinement via severe plastic deformation (SPD) can induce the decomposition of Al-Zn supersaturated solid solution, resulting in strain softening rather than hardening. So far, it is very challenging to improve the strength of binary Al-Zn alloy by refining grains through SPD. Herein, a single-phase supersaturated solid solution nanostructure with relaxed grain boundaries has been successfully generated in Al-21.7 at% Zn alloy by cryogenic high-pressure torsion. Instead of softening, giant hardening is achieved. The nanocrystalline Al-Zn alloy with grain size of 15 nm has an ultrahigh yield strength of about 642 MPa.

Automated summary

Grain refinement through severe plastic deformation (SPD) usually leads to strain softening in Al-Zn supersaturated solid solution. However, in this study, by cryogenic high-pressure torsion, a single-phase supersaturated solid solution nanostructure with relaxed grain boundaries was successfully achieved in Al-21.7 at% Zn alloy, resulting in giant hardening instead of softening. The nanocrystalline Al-Zn alloy with a grain size of 15 nm exhibits an ultrahigh yield strength of approximately 642 MPa.