TERMINAL SOLUBILITY AND PARTITIONING OF HYDROGEN IN THE ALPHA PHASE OF ZIRCONIUM, ZIRCALOY-2, AND ZIRCALOY-4.

The effects of alloy composition, grain size and cold work on the terminal solubility and thermodynamic activity of hydrogen in the alpha phase of zirconium, Zircaloy-2, and Zircaloy-4 were determined by a diffusion sample method. The terminal solubility for Zircaloy-2 and Zircaloy-4 below 550°C was found to be given by 9.9 x 104 exp(− 8250/RT) ppm. The solubilities given by this function approximate those given for unalloyed zirconium by 1.61 x 105 exp(− 8950/RT) ppm which is the combined result from nine investigations. The best-fit curve for the combined data for all three materials is given by 1.2 x 105 exp(− 8550/RT). The activity of hydrogen in the alpha phase, as measured by partitioning in diffusion couples, was found to vary only slightly among the three materials in the range 329°C to 796°C. An average P-C-T relationship derived from published data for these materials is represented by CP12 = 1.4 x 10−2 exp(11840/RT) at % mm−12.