Study of Microstructure, Hydrogen Solubility, and Corrosion of Ta-Modified Zr–1Nb Alloys for Nuclear Applications

Abstract

Modified Zr–1Nb alloys with Ta additions is a potential strategy to improve structural alloys for nuclear reactors. The effects of Ta on microstructural stability and resistance to corrosion of Zr–1Nb alloys were systematically investigated and elucidated. The \((\alpha +\beta )\) microstructure in Zr–1.05Nb, Zr–0.85Nb–0.20Ta, and Zr–0.85Nb–0.40Ta (wt.%) alloys were obtained with the following two thermomechanical processes after a water quenching from βZr: (a) annealed at 570 °C for 3840 h and (b) a combination of intermediate annealing temperatures and cold rolled steps. Quantitative EDS-TEM analysis together with DSC measurements were used to characterise the changes in phase compositions and the fraction of beta-phase precipitates. Hydrogen solubility was measured in alloys with the first annealed condition. The Ta additions increase the monotectic transformation temperature, improves the steam corrosion at 400 °C and 10 MPa up to 14 days, and decreases slightly the hydrogen solubility. The higher thermal microstructural stability compared to Ta-free Zr–1Nb alloys provides potential advantages for increases in operating temperature or acceleration of precipitation kinetics during thermomechanical processing.KeywordsZr–Nb alloysTa additionPhase transformationCorrosionHydrogen solubility