Effect of annealing on structural and phase transformations and mechanical properties of ultrafine-grained E125 zirconium alloy obtained by high-pressure torsion

The structure, phase composition, and mechanical properties of commercial zirconium E125 (Zr-2.5% Nb) alloy, which was subjected to high-pressure torsion (HPT) and subsequent annealings, were studied. The HPT of alloy samples 20 mm in diameter at 200 °C at a pressure of 4 GPa using 5 revolutions (N) leads to the formation of grain-subgrain nano- and submicrocrystalline structure characterized by a high fraction of equiaxed grains 80-100 nm in size. The phase α-Zr → (ω-Zr + β-Zr) transformation during HPT makes the main contribution to the strength of the alloy. Changes in the mechanical properties of the HPT-alloy during heating are related to both the decomposition of ω-Zr phase and grain growth.