Hydrogen gettering by yttrium in zirconium alloys: Microstructural evidence from APT and SIMS

Yttrium (Y) exhibits strong hydrogen affinity and solubility, but its application as a getter in zirconium (Zr)-based systems has not yet been demonstrated through microstructural evidence. This study presents the first spatially resolved, multi-scale microstructural evidence of hydrogen/hydride redistribution and retention by yttrium, obtained using atom probe tomography (APT), nanoscale secondary ion mass spectrometry (SIMS), and optical-microscopy. Two complementary experimental configurations were examined: (1) a laser-welded Zr-2.5 Nb/Y couple, used to track progressive hydride redistribution in Zr-2.5 Nb during post-charging annealing; and (2) a Y-rich (∼60 wt%) Zr-Nb-Y alloy, used to examine hydrogen/deuterium uptake and hydride suppression. In a welded Zr-2.5 Nb/Y couple, after 32 h at 400°C, hydrides in Zr-2.5 Nb were nearly eliminated up to ~6 mm from the Y interface, while the Y-rich alloy showed no hydride formation despite high hydrogen loading (400 wppm). Both APT and SIMS confirmed preferential D enrichment in Y-rich regions. These findings offer direct evidence of Y-driven hydrogen gettering under realistic thermal conditions.