Measurement of the Diffusion Coefficient and Solubility of Hydrogen in Solid Aluminum

Abstract

The diffusion coefficient (D) and solubility (S) of hydrogen in solid aluminum (99.99%) were measured by the vacuum solid extraction method. The temperature dependence of D and S obtained for the specimens melted in vacuum and solidified unidirectionally are as follows:(This article is not displayable. Please see full text pdf.) \ oindentThese values represent the behavior of atomic hydrogen in aluminum lattice. For the specimen melted in air and solidified in a metal mold, it was found to decrease the diffusivity and to increase the solubility as compared with the above values, and these discrepancies were more remarkable at lower temperatures. These changes in D and S can be explained simply by a void model based on the equilibrium between gaseous hydrogen in voids and atomic hydrogen dissolved in the lattice. The apparent diffusivity and solubility are a function of total volume of voids which are formed by hydrogen gas during the solidification process of specimens. The differences in the melting or casting condition of specimens will be one of the most probable reason for the large scatter in the data reported previously for the diffusivity of hydrogen in pure solid aluminum.