EFFECT OF INTERSTITIAL NITROGEN ON HYDROGEN SOLUBILITY IN TITANIUM, ZIRCONIUM AND HAFNIUM

Hydrogen solubility in Hf-N alloys with a nitrogen content of 0.021-0.080 N/Hf was measured at a temperature of 600-850-degrees-C at a hydrogen pressure below 100 Pa. All the data for the hydrogen solubility in the Hf-N alloys closely followed Sieverts' law. The hydrogen solubility increased with nitrogen content, while the enthalpy of solution decreased with nitrogen content. These trends in the solubility and in the enthalpy of solution for the Hf-N alloy were almost the same as those for Ti-N and Zr-N alloys. Partial thermodynamic quantities of hydrogen in the Hf-N-H ternary system were estimated using a solution model. The changes in hydrogen solubility in the group IV metals due to interstitial nitrogen were discussed in terms of vibrational, dilatometric and configurational contributions.