Strengthening of Zr-based metallic glass at low dose helium ion irradiation

Metallic glasses commonly demonstrate softening due to excessive free volume or hardening through partial nanocrystallization when subjected to irradiation. However, this study demonstrates a unique strengthening effect on plasticity without sacrificing hardness in Zr-based metallic glass under low-dose helium ion irradiation in the absence of nanocrystals. Nanoindentation hardness measurements reveal an initial increase in hardness with low irradiation doses, followed by a rapid decrease at higher doses. In situ mechanical transmission electron microscopy experiments confirmed the switch from localized shear banding to homogeneous shear flow with low-dose helium ion irradiation. Notably, a remarkable increase in tensile plasticity -18 % was achieved without compromising the strength -1.74 GPa. The improvement can be attributed to the formation of local dense packing regions filled with helium atoms, which elevate the critical stress for plastic deformation. These regions interact with the loosely packed surroundings and facilitate shear band formation. Our findings offer invaluable atomic-scale insight into the structure-property relationships in irradiated metallic glasses, thereby supporting their potential applications in advanced fission and fusion reactors.