Microstructure and hydride embrittlement of zirconium model alloys containing niobium and tin

To investigate the effects of the addition of Nb and Sn to Zr alloys on hydride embrittlement, experimental alloys with different Nb and Sn contents were prepared and charged with hydrogen up to 850 ppm. When Nb and Sn were added, recrystallization was delayed in Zr alloys, mainly due to β-Nb precipitates in Nb containing alloys and Sn solute atoms in Sn containing alloys, respectively. Among the two alloying elements, Sn was more effective in delaying recrystallization. Tensile test results showed that both Nb and Sn strengthened the Zr alloys, and tensile strengths were nearly independent of the absorbed hydrogen content. While resistance to hydride embrittlement was significantly improved with Nb addition to Zr alloys due to increased hydrogen solubility and delayed recrystallization, no effect of Sn addition was observed.

Research highlights
► Addition of Nb and Sn delayed recrystallization during final annealing treatment.
► Sn was more effective in modifying hydride morphology and alignment.
► Both Nb and Sn strengthened Zr alloys, where Sn was more effective.
► Degree of ductility loss with hydrogen depended on Nb and Sn contents.