Effect of hydrogen on the yielding behavior and shear transformation zone volume in metallic glass ribbons

The effect of hydrogen (H) charging on the shear yield strength (τmax) and shear transformation zone volume (Ω) of Ni–Nb–Zr metallic glass ribbons, with varying Zr content, were studied through the first pop-in loads during nanoindentation. Weight gain measurements after H charging and desorption studies were utilized to identify how the total H absorbed during charging is partitioned into mobile and immobile (or trapped) parts. These, in turn, indicate the significant role of H mobility in the amorphous structure on the yielding behavior. In high-Zr alloys, τmax increases significantly whereas Ω decreases. In low-Zr alloys, a slight decrease in τmax and increase in Ω were noted. These experimental observations are rationalized in terms of the mobility of the absorbed H in the amorphous structure and the possible role of it in the shear transformation zone dynamics during deformation of the metallic glass.