Effect of thermal history on the terminal solid solubility of hydrogen in Zircaloy-4

Abstract

The terminal solid solubility (TSS) of hydrogen in zirconium alloys has a hysteresis. The TSS of hydrogen in Zircaloy-4 during cooling and heating were studied using differential scanning calorimetry (DSC) with a hydrogen content of 40-731 wppm. A significant hysteresis gap was observed between the TSS for dissolution (TSSD) and precipitation (TSSP). It was confirmed that the hydrogen dissolution temperature was unaffected by the previous thermal history in comparison with the hydride precipitation temperature. The TSSP temperature increased with a decrease in the maximum temperature, but a significant temperature gap remained even when the maximum temperature was equal to the TSSD temperature. The terminal solid solubility of hydrogen in Zircaloy-4 can be represented by the following equations. TSSD: C = 2.255 x 10(5) exp (-39101/RT). TSSP: C = 4.722 x 10(4) exp (-26843/RT). TSSP2: C = 8.612 x 10(5) exp (-30583/RT). Based on the experimental results hydrogen solubility path depending on the previous thermal history was proposed.