Abstract
The present research was performed in an attempt to study the kinetics of hydrogen diffusion based on the results on hydrogen content measurements in B2 FeAl after heat treatment. A temperature-programmed hydrogen release test was also undertaken to investigate the existing states of hydrogen in FeAl. The single crystals and polycrystals of Fe-40Al were used for this experiment. Through a heat treatment in vacuum the hydrogen concentration in a Fe-40Al single crystal can be decreased significantly, while the hydrogen content increases significantly when the crystal is exposed in air at room temperature. The change of hydrogen content can be described as C{sub H} = C{sub s} {minus} C{sub 0}/2{pi}L {radical}Dt + C{sub 0}. The estimated hydrogen diffusivity for the Fe-40Al single crystal at room temperature is about 10{sup {minus}9} cm{sup 2}/s. It is revealed that hydrogen can be trapped in a vacancy or bonded inside the lattice of the single crystal. Because of the difference in stability, two different release temperatures are observed for hydrogen in a vacancy and hydrogen bonded in the lattice. The lattice hydrogen shows the highest stability. Grain boundaries also act as hydrogen condensation sites and hydrogen in grain boundaries possesses higher stability than in themore » vacancy.« less
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