Hydrogen Solubility and Diffusivity in Aluminum

Hydrogen solubility in solid aluminum has also been studied from the perspective of hydride formation. The solubility of hydrogen in a metal is essential for nucleation and growth to occur, followed by hydride formation. The solubility of hydrogen in metals cited by Smith [1] can be expressed as 

Smith s expression is a combination of solubility s laws at isothermic conditions based on Sievert s law, Sr= and under the solubility isobaric condition by 

The results obtained by Ransley and Neufeld were expressed in terms of Eq. (9.1) as  

The reported results on the solubility ofhydrogen, in terms of cm ofhydrogen per 100 g, reported by the above groups were similar. They found that the solubility can change by an order of magnitude as the temperature increases. For example going from 10 at 300 °C to 10 at 600 °C and becoming 10 when the aluminum melted. 

These results were obtained, using hydrogen absorption into pure aluminum between 300 and 1050 °C and were calculated by temporal process degassing. Eichenauer et al. also reported that the square root Sievert s law is satisfied within the limit of error in the solid and in the liquid state. Utilizing the fact that diffusion in the metal is responsible for the hydrogen degassing rate of the solid aluminum they deduced the diffusion coefficient to be D = 0.11 exp (—9780/ RT) cm s . The heat of solution was calculated from these measurements by Birnbaum et al. [7] and Ichimura et al. [8] and found to be in the range of + 0.6 to + 0.7 eV. 

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