Abstract
The paper reports the results of the study aimed to increase the Ti2Ni phase content in Ti–Ni powder by mechanochemical alloying with titanium and subsequent heat treatment. The interaction of the alloyed Ti–Ni powder with hydrogen was investigated. It is shown that before mechanochemical alloying the phase composition of Ti–Ni powder included three phases: TiNi (B2, B19’), Ti2Ni, and Ni3Ti. After mechanochemical alloying followed by heat treatment, Ti–Ni powder contained TiNi (B2, B19’) and Ti2Ni phases, where the latter phase was of different genesis. Ti2Ni (I) phase was present in Ti–Ni powder before mechanochemical alloying; its unit cell size after alloying with titanium remained unchanged and was equal to 1.1283 ± 5 × 10−4 nm Ti2Ni (II) phase was formed during mechanochemical alloying; its lattice parameter decreased as the Ti content in Ti–Ni powder during alloying increased. Electrochemical hydrogenation of the Ti–Ni (85 wt%) – Ti (15 wt%) powder mixture increased the cell size of both Ti2Ni (I) and Ti2Ni (II), which indicates the interaction of hydrogen with both Ti2Ni phases. The Ti2Ni (I) cell volume increased by 0.3% due to solid solution formation, and the Ti2Ni (II) cell volume increased by 17.6% due to hydride formation. The Ti2Ni (II) phase formed by mechanochemical alloying is more prone to interact with hydrogen with the formation of Ti2NiHx hydride than with the Ti2Ni (I) phase present in Ti–Ni powder before alloying. The number of hydrogen atoms in chemical formulas of Ti2Ni (II)-based hydride was determined. Hydrogenation of the Ti–Ni (85 wt%) – Ti (15 wt%) powder mixture for 90 min caused formation of Ti2NiH1.9 hydride; 360 min hydrogenation yielded Ti2NiH2.8 hydride.
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