Hydrogen diffusion in aluminium at high temperatures

Abstract

The diffusion of hydrogen in aluminium has been measured by the permeation method using a quadrupole mass spectrometer. Hydrogen was introduced by gas phase charging in the temperature range of 300-400 degrees C, and by electrochemical charging at room temperature. It was found that the diffusivity of hydrogen depends on the relative concentration of vacancies to the dissolved hydrogen concentration. The activation energy for the diffusion of hydrogen was found to be 0.61-0.62 eV at high temperatures where the concentration of vacancies was much higher than that of dissolved hydrogen. The value is near the migration energy of a vacancy in aluminium. On the other hand, at room temperature where the hydrogen showed a diffusivity considerably larger than that extrapolated from high temperatures. These facts suggest that hydrogen in aluminium migrates together with a vacancy at high temperatures due to a large binding energy between them.