Conspicuous rejuvenation of plasma-assisted hydrogenated Zr-based bulk metallic glasses via deep cryogenic cycling treatment

Abstract

To obtain a greater degree of a deep cryogenic cycle treatment (DCT)-induced rejuvenation, Zr-based bulk metallic glass samples were prepared under a mixed argon/hydrogen atmosphere prior to the deep cryogenic cycling treatment. The degree of rejuvenation is quantified by the increase of relaxation enthalpy ΔH_rel measured by differential scanning calorimetry (DSC). The purpose of this pretreatment was to change the chemical heterogeneity through the in situ absorption of hydrogen during melting and solidification. It was found that the hydrogenated specimens were more sensitive to DCT and exceeded the rejuvenation upper limit of uncharged specimens. The results were compared with previous reports, which further highlighted the distinctive advantage of the H-charged specimens for DCT. Furthermore, the plasticity of the hydrogenated metallic glass was enhanced significantly after DCT, as supported by hardness, compression ductility, and nanoindentation creep data. It is crucial to understand that DCT-induced rejuvenation is related to the content of hydrogen and may provide a new avenue to improve the mechanical properties or functional characteristics of BMG.