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The paper presents the experimental data observed in the microstructure and phase composition of ultrafine-grained Ti–40 mass % Nb (Ti40Nb) alloy after high-temperature annealings. The ultrafine-grained Ti40Nb alloy is produced by severe plastic deformation (SPD). This method includes multiple abc-pressing and multi-pass rolling followed by further pre-recrystallizing annealing which, in its turn, enhances the formation of ultrafine-grained structures with mean size of 0.28 µm involving stable β- and α-phase and metastable nanosized ω-phase in the alloy. It is shown that annealing at 500°C preserves the ultrafine-grained structure and phase composition. In cases of annealing at 800°C the ultrafine-grained state transforms into the coarse-grained state. The stable β-phase and the nanosized metastable ω-phase have been identified in the coarse-grained structure.

The paper describes the experimental results in microstructure thermal stability and mechanical properties of ultrafine-grained zirconium alloy with 1 mass % Nb (Zr–1 mass %Nb) under prolonged thermal exposure. Ultrafine-grained zirconium alloy is produced by severe plastic deformation (SPD) method. It was proved that SPD method including multiple аbс-pressing and multi-pass rolling, as well as further pre-recrystallizing annealing enhances the formation of ultrafine-grained structures with mean element size of 0.2 µm. Thermostability time interval of ultrafine-grained structure and the mechanical properties (in case of microhardness) under prolonged thermal exposure (up to 360 hours) for zirconium alloy was experimentally determined. It was proved that ultrafine-grained structure is stable at 400°С within 10 hours whilst keeping the microhardness level attained after SPD. In cases of continuous annealing time from 24 to 360 hours recrystallization processes develop intensively, followed by the decrease i...