HYDROGEN SOLUBILITY LIMITS IN ALPHA-ZIRCONIUM AND BETA-ZIRCONIUM

Specimens of pure zirconium and Zr-20Nb alloy were charged to differen t hydrogen concentrations from the gas phase at 673 K. Before and afte r charging with hydrogen, the Zr-20Nb specimens were annealed in vacuu m at 1123 K for 1 h and cooled to room temperature within about 30 min to produce a beta-Zr structure. Some of these specimens were annealed further at 773 K for about 500 h to completely transform them to (alp ha-Zr+beta-Nb) phase. The specimens were analyzed for hydride transiti on temperatures using differential scanning calorimetry and for hydrog en concentration using hot vacuum extraction mass spectrometry. The hy drogen solubility limits found for pure Zr are in good agreement with the previously reported values. The solubility limits found in beta-Zr are about two orders of magnitude higher than the solubility limits i n alpha-Zr and the solubility limits found in the aged Zr-20Nb alloy a re very close to those in alpha-Zr.