Study on the effects of matrix yield strength on hydride phase stability in Zircaloy-2 and Zr 2.5 wt% Nb

A study on the effect of matrix yield strength on precipitation of hydride phases in zirconium alloys is presented. X-ray diffraction measurements from the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory were used to characterise the quantity of δ (fcc) and γ (fct) hydride phases in zirconium alloys as a function of yield stress and cooling rate. While experimental results indicate that yield stress has a pronounced effect on hydride phase stability in the zirconium–hydrogen system, other factors including defect structure and β-phase distribution also influence the hydride phase stability, for material of a given yield stress. These results offer a possible explanation for the wide range of hydride phase stability reported in the literature for the zirconium–hydrogen system.