Effect of Inhomogeneous Nucleation of Hydride at α/β Phase Boundary on Microstructure Evolution of Zr–2.5 wt%Nb Pressure Tube
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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.
KeywordsPressure tube Delayed hydride cracking Zirconium hydride
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the government of Korea (Ministry of Science and ICT) (NRF-2017M2A8A4015157). Kunok Chang was also supported by “Human Resources Program in Energy Technology” of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20184030202170).
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