Measurement of hydrogen diffusivity in aluminum and a dilute alloy by thermal evolution spectroscopy

The introduction of hydrogen into aluminum by mechanical abrasion which has been investigated in our previous paper [S. Hayashi: Jpn. J. Appl. Phys. 35 (1996) 6191] is applied to the determination of hydrogen diffusivity in high purity aluminum and Al-1000at.ppmSi dilute alloy by coupling with thermal evolution spectroscopy (TES). The obtained diffusivity in high purity aluminum is expressed by D (m(2)/s) = 3.0(+/- 0.5) x 10(-6) exp(-30(+/- 1) (kJ/mol)/RT). The diffusivity is larger than the values reported previously by other authors. This suggests that the interstitial mechanism is dominant for hydrogen diffusion in high purity aluminum even in the low temperature region. A similar measurement was performed on Al-1000at.ppmSi dilute alloy. From the analysis using the trap-detrap model, the binding energy of a hydrogen atom with a silicon atom in aluminum is estimated as 16kJ/mol. This result shows that silicon atoms in aluminum serve as weak trapping centers.