SOLUBILITY OF HYDROGEN IN METALS UNDER HIGH HYDROGEN PRESSURES - THERMODYNAMICAL CALCULATIONS

The solubility of hydrogen was calculated up to high hydrogen pressures for ten metals having small solubilities under normal pressures. For this purpose, the equation of state of hydrogen was calculated by the procedure of Hemmes et al., and the values obtained for the molar volume, the enthalpy, the Gibbs free energy and the entropy are tabulated in the range 0.1 MPa less-than-or-equal-to p less-than-or-equal-to 100 GPa and 400 less-than-or-equal-to T less-than-or-equal-to 2000 K. For solubility calculations, the chemical potential of hydrogen in solid solution was estimated from heats of solution observed at low hydrogen pressures and concentrations, by including a p-upsilon(H) term (upsilon(H) congruent-to 2.5 x 10(-3) nm3/H atom), and concentration-dependent terms arising from interactions between hydrogen atoms. The solubilities obtained for fc.c. metals Al, gamma-Fe, Ni, Cu, Ag, Pt, Au and b.c.c. metals Cr, alpha-Fe, Mo, W are shown in the form of Arrhenius plots with pressures as a parameter. Strong enhancements of the solubility over Sieverts' law are found at high hydrogen pressures (p greater than or similar to 1 GPa).