A Study of the Sorption Properties and Changes in the Structure and State of the Ti-25Al-25Nb (at.%) Alloy System Under Thermocyclic Loading

Kozhakhmetov Y. Tabiyeva Y. Mukhamedova N. Urkunbay A. Aidarova M. Kizatov A. Sagymbekova E.
February 2025 Multidisciplinary Digital Publishing Institute (MDPI)

Crystals
2025 #15 Issue 2

This study is focused on the sorption properties and the changes in the structure and state of Ti-25Al-25Nb (at.%) system alloys under thermal cyclic loading. These samples were produced by combining high-energy processing methods through mechanization and spark plasma sintering in the temperature range of 1100–1300 °C, followed by two-stage heat treatment at temperatures of 800 °C and 1250 °C. Thermal cyclic experiments on hydrogen sorption/desorption with samples of the Ti-25Al-25Nb (at.%) system were conducted at the VIKA experimental installation at a saturation temperature of about 500 °C and a degassing temperature of 610 °C. It took about 41 min to reach pressure equilibrium at 500 °C. The hydrogen diffusion coefficient was calculated based on the Barrer formula and was 9.1 × 10⁻⁵ cm²/s at 500 °C. The maximum hydrogen content was recorded after the first sorption/desorption cycle and was 1.91 wt%. Due to the multiple thermal cyclic effects in the hydrogen medium, the predominantly two-phase (O + B2) alloy structure underwent transformation to form a new structure (O-AlNbTi₂). In the phase composition of the Ti-25Al-25Nb (at.%) alloy, the formation of hydrides in the form of independent phases as a result of thermal cycling was not detected. Hydrogen absorption is most likely to be associated with the formation of an interstitial solution based on existing crystalline phases.

phase analysis , sorption/desorption , thermal cycling , Ti-25Al-25Nb (at.%) system

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Center of Excellence “VERITAS”, NJSC D. Serikbayev East Kazakhstan Technical University, Ust-Kamenogorsk, 070004, Kazakhstan
Institute of Atomic Energy Branch of the National Nuclear Center of the Republic of Kazakhstan, Kurchatov, 180010, Kazakhstan

Center of Excellence “VERITAS”
Institute of Atomic Energy Branch of the National Nuclear Center of the Republic of Kazakhstan

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