Effect of hydrogen on the structural and phase state and the deformation behavior of the ultrafine-grained Zr–1Nb alloy

•SPD leads to formation of the UFG structure with an average grain size of 0.4 μm.•Formation of the UFG structure in the Zr–1Nb alloy increases its strength properties.•Hydrogen prevents the development of plastic strain localization in UFG structure.•Hydrogen increases the strain hardening effect and deformation of uniform elongation.•Presence of hydrogen in the UFG Zr–1Nb alloy increases its strength characteristics.

The formation of an ultrafine-grained structure with predominantly high-angle grain boundaries and an average grain size of grain–subgrain structure elements of 0.4 μm in zirconium alloys was shown by electron microscopy and X-ray diffraction analysis. The formation of such structure was found to result in the significant increase of the ultimate and yield strengths in comparison with the initial fine-grained state. The strength characteristics of ultrafine-grained Zr–1Nb–0.22H alloy are higher than the corresponding characteristics of the Zr–1Nb alloy. The presence of hydrogen in the solid solution of the ultrafine-grained Zr–1Nb–0.22H alloy during tension at room temperature is found to prevent the development of plastic deformation localization on the meso- and macrolevels and to increase the effect of strain hardening and deformation of uniform extension. At elevated temperatures, the presence of hydrogen reduces the resistance to deformation localization on the macrolevel and the deformation to failure in tensile tests.