Hydrogen permeation behavior in a Fe3Al-based alloy at high temperature

The hydrogen permeation behavior in a Fe3Al-based alloy, with three types of heat treatments, was investigated by an ultrahigh vacuum gaseous permeation technique at the temperature range of 240-320 °C. A well-defined second stage is observed in hydrogen permeation curves of the Fe3Al alloy superimposed on the basic curves. On the basis of optical microstructures, determined permeabilities and diffusivities, corresponding activation energies, it is suggested that the two sigmoidal curves result from the ordered B2 phase and disordered α-Fe phase in the Fe3Al alloy; the first stage of permeation reflects the hydrogen transport in matrix disordered α-Fe phase, while the second stage reflects the hydrogen transport in ordered B2 phase.