Role of initial stored energy on hydrogen microalloying of ZrCoAl(Nb) bulk metallic glasses

In this paper, the role of primary stored energy and structural heterogeneity on the subsequent effects of hydrogen microalloying in glassy alloys was studied. For this purpose, two bulk metallic glasses with different chemical compositions and initial stored energy, i.e. Zr60Co30Al10 and Zr55Co30Al10Nb5, were fabricated in a hydrogen-induced environment. Dynamic mechanical analysis and nanoindentation tests were carried out to evaluate relaxation behavior and mechanical properties of bulk metallic glasses, respectively. The nanoindentation results indicated declining serrations in load–displacement curves of hydrogen-affected samples. This event was related to the annihilation of localized deformation in hydrogen-affected samples under the external load. Moreover, the dynamic mechanical analysis showed that the hydrogen microalloying process improved the plasticity behavior of metallic glasses by activating fast β′ relaxation. Finally, the results unveiled that the higher initial structural heterogeneity and stored energy in the bulk metallic glass with the alloying composition of Zr55Co30Al10Nb5 led to the improvement of microalloying effects on the corresponding properties.