Hydrogen permeability and diffusivity in amorphous Metglas 2826MB under AC excitation

Abstract

In this work the effect of magnetic field on hydrogen permeability and diffusivity in metglas 2826MB has been determined. The hydrogen permeability and hydrogen diffusivity were measured by the bi-electrode method. A magnetic field of fixed strength 20 Oe was applied parallel to the transverse direction of the ribbon, and both DC and AC excitation from 60 Hz to 400 Hz were employed. It was found that the magnetostriction constant increased linearly with the applied AC frequency, until a saturation level was reached at around 300 Hz. As the frequency increased, hydrogen permeability and diffusivity in the metglas increased accordingly. The effect can be attributed to the change in magnetoelastic strain induced by the applied excitation field. Microcracks were found on the specimens' surface after prolonged charging or charging with higher current density, showing that they were susceptible to hydrogen embrittlement. Hydrogen, however, did not affect the amorphous nature of the metglas.