The role of partial crystallinity on hydrogen permeation in Fe-Ni-B-Mo based metallic glass membranes

► Crystallization and composition identified under argon, air and hydrogen gas environments. ► Hydrogen permeation in crystalline samples reduced by an order of magnitude. ► In situ studies at 400 °C showed stabilization of the flux and crystalline content over a 3-h period. ► Combined TEM, permeation and XRD analysis used to interpret results as crystalline phase co-existing in an amorphous matrix.