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The Effect of Hydrogen on Martensite Transformations and the State of Hydrogen Atoms in Binary TiNi-Based Alloy with Different Grain Sizes

1
Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk 634055, Russia
2
Division for Experimental Physics, School of Nuclear Science and Engineering, National Research Tomsk Polytechnic University, Tomsk 634050, Russia
*
Author to whom correspondence should be addressed.
Materials 2019, 12(23), 3956; https://doi.org/10.3390/ma12233956
Received: 24 October 2019 / Revised: 21 November 2019 / Accepted: 26 November 2019 / Published: 28 November 2019
The analysis presented here shows that in B2-phase of Ti49.1Ni50.9 (at%) alloy, hydrogenation with further aging at room temperature decreases the temperatures of martensite transformations and then causes their suppression, due to hydrogen diffusion from the surface layer of specimens deep into its bulk. When hydrogen is charged, it first suppresses the transformations B2↔B19′ and R↔B19′ in the surface layer, and when its distribution over the volume becomes uniform, such transformations are suppressed throughout the material. The kinetics of hydrogen redistribution is determined by the hydrogen diffusion coefficient DH, which depends on the grain size. In nanocrystalline Ti49.1Ni50.9 (at%) specimens, DH is three times greater than its value in coarse-grained ones, which is likely due to the larger free volume and larger contribution of hydrogen diffusion along grain boundaries in the nanocrystalline material. According to thermal desorption spectroscopy, two states of hydrogen atoms with low and high activation energies of desorption exist in freshly hydrogenated Ti49.1Ni50.9 (at%) alloy irrespective of the grain size. On aging at room temperature, the low-energy states disappear entirely. Estimates by the Kissinger method are presented for the binding energy of hydrogen in the two states, and the nature of these states in binary hydrogenated TiNi-based alloys is discussed. View Full-Text
Keywords: binary TiNi-based alloy; hydrogen; martensitic transformations; electrical resistivity; thermal desorption spectroscopy binary TiNi-based alloy; hydrogen; martensitic transformations; electrical resistivity; thermal desorption spectroscopy
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Baturin, A.; Lotkov, A.; Grishkov, V.; Rodionov, I.; Kabdylkakov, Y.; Kudiiarov, V. The Effect of Hydrogen on Martensite Transformations and the State of Hydrogen Atoms in Binary TiNi-Based Alloy with Different Grain Sizes. Materials 2019, 12, 3956.

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