Effect of β-Zr decomposition on the solubility limits for H in Zr–2.5Nb
- 作者：Khatamian ; D.
- 关键词：Hydrogen ; Solubility ; Zr&ndash ; Nb alloys ; TSS ; CANDU® ;
- 刊名：Journal of Alloys and Compounds
- 出版年：2003
- 期刊代码：45_09258388
- 类别：ms
- 出版时间：August 11, 2003
- 卷：356-357
- 期：Complete
- 页码：22-26
- 文件大小：304 K
摘要
The zirconium alloy Zr–2.5Nb (Zr–2.5 wt.%Nb) is used to fabricate pressure tubes for CANDU®1 nuclear reactors. The microstructure of the as-extruded tubes consists of elongated h.c.p. α-Zr grains surrounded by a network of b.c.c. β-Zr containing at least 20 wt.%Nb. The β-Zr phase is meta-stable at temperatures below 900 K and gradually dissociates into its constituent elements α-Zr and β-Nb. The aim of this study was to determine the effect of β-Zr decomposition on the terminal solid solubility for dissolution (TSSD) for H in Zr–2.5Nb. Specimens of Zr–2.5Nb were charged to different hydrogen concentrations and aged at temperatures ranging from 673 to 773 K for 30 to 6000 min, to decompose their β-Zr component by different amounts. Hydride dissolution temperature and hydrogen concentration were determined using differential scanning calorimetry and hot vacuum extraction mass spectrometry, respectively. The results show that the as-extruded pressure tube structure, with the β-Zr almost intact, has the highest TSSD and that the TSSD for structures with fully decomposed β-phase is the lowest and approaches that of unalloyed Zr.