A normalization method for relationship between yield stress and delayed hydride cracking velocity in Zr-2.5Nb alloys

The delayed hydride cracking (DHC) in pressure tube of CANDU reactors was measured on specimens which had different yield stresses. It is difficult to compare DHC velocities at different temperatures among materials with different yield stresses after heat-treatment or irradiation. To evaluate the effect of the yield stress on DHC velocity, a normalization method, based on Puls' DHC model, was proposed. When DHC velocity was normalized by dividing with the terminal solid solubility and the diffusion coefficient of hydrogen, the relationship between yield stress and DHC velocity was representable on one master curve. The equation from the master curve could explain the difference between theoretical activation energy and experimental activation energy in DHC. The difference was found to be ascribed to the decrease of yield stress with increasing temperature.