Effect of Inhomogeneous Nucleation of Hydride at α/β Phase Boundary on Microstructure Evolution of Zr–2.5 wt%Nb Pressure Tube

Abstract

We analyzed the microstructural characteristics such as number density and length and width of hydrides in Zr–2.5 wt%Nb pressure tube. The hydrogen was charged cathodically and the hydride-contained sample was evaluated using the advanced analysis methodologies. We performed a differential scanning calorimetry analysis to more quantitatively understand the thermodynamics of the hydride formation/growth process. We characterized the micrograph of hydride-contained Zr samples to estimate the microstructural characteristics of the matrix and hydrides. We investigated effects of hydrogen concentration and microstructure of matrix on determining microstructural measures of the hydrides. Particularly, we found that β phase in the matrix becomes isolated during the heat treatment same or above 475 °C and this change increases the inhomogeneous nucleation sites significantly. We claim that the microstructure change of this matrix phase greatly increases the number density of hydride.