Hydrogen and its effect on the grinding of Ti-Ni powder

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 3 2021 Ta b l e 2 Microstructural parameters of phases Treatment type FWHM (degree) TiNi (austenite) (110) Ni 3 Ti (202) Ti 2 Ni (511) Initial state 0.300 ± 0.025 (3.4 ∙ 10 11 ) cm –2 0.084 ± 0.025 (0.3 ∙ 10 11 ) cm –2 0.726 ± 0.025 (20.2 ∙ 10 11 ) cm –2 Mechanical treatment 0.296 ± 0.025 (3.3 ∙ 10 11 ) cm –2 0,185 ± 0,025 (1.3 ∙ 10 11 ) cm –2 0,917 ± 0,025 (32.6 ∙ 10 11 ) cm –2 Mechanical treatment with pre-hydro- genation for 90 minutes 0.314 ± 0.025 (3.7 ∙ 10 11 ) cm –2 0.260 ± 0.025 (2.5 ∙ 10 11 ) cm –2 0,904 ± 0,025 (31.2 ∙ 10 11 ) cm –2 Mechanical treatment with pre-hydro- genation for 180 minutes 0.330 ± 0.025 (4.1 ∙ 10 11 ) cm –2 0.143 ± 0.025 (0.8 ∙ 10 11 ) cm –2 0.690 ± 0.025 (18.0 ∙ 10 11 ) cm –2 An insignificant decrease in the defect density of powders hydrogenated for up to 180 minutes is apparently due to hydrogen enrichment of defects, which decreases the dislocation density according to [32–34]. Conclusions The study showed the following: 1. During mechanical treatment of the powder hydrogenated for 180 minutes, the average particle size of titanium nickelide powder decreases almost twice, while the average particle size of the initial powder hardly changes during mechanical treatment. 2. The lattice parameters of the TiNi (austenite), Ti 2 Ni, and Ni 3 Ti phases in the powder do not change after mechanical treatment and are in good agreement with the literature data. After mechanical treatment of the hydrogenated powders, only the lattice parameter of the Ti 2 Ni phase increases and its value is close to the lattice parameter of hydride with Ti 2 NiH 0.5 stoichiometry. 3. The estimated dislocation density in the Ti 2 Ni phase is almost an order of magnitude higher than that in TiNi and Ni 3 T phases. Thus, pre-hydrogenation can be effective for powder grinding due to formation of brittle hydride and prevention of fine particle aggregation during high-intensity mechanical treatment. References 1. Wade N., Adachi Y., Hosoi Z. A role of hydrogen in shape memory effect of Ti-Ni alloys. Scripta Metallurgica et Materialia , 1990, vol. 24 (6), pp. 1051–1055. DOI: 10.1016/0956-716x(90)90298-u. 2. Yokoyama K., Kaneko K., Ogawa T., Moriyama K., Asaoka K., Sakai J. Hydrogen embrittlement of work-hardened Ni-Ti alloy in fluoride solutions. Biomaterials , 2005, vol. 26, pp. 101–108. DOI: 10.1016/j. biomaterials.2004.02.009. 3. Astafurova E.G., Melnikov E.V., Astafurov S.V., Ratochka I.V., Mishin I.P., Maier G.G., Moskvina V.A., Zakharov G.N., Smirnov A.I., Bataev V.A. Hydrogen embrittlement of austentic stainless steels with ultrafine- grained structures of different morphhologies. Physical Mesomechanics , 2019, vol. 22, no. 4, pp. 113–126. DOI: 10.1134/S1029959919040076. Translated from Fizicheskaya mezomekhanika , 2018, vol. 21, no. 2, pp. 103– 117. DOI: 10.24411/1683-805X-2018-12011. 4. Kolachev B.A. Vodorodnaya khrupkost’ metallov [Hydrogen embrittlement of metals]. Moscow, Metallurgiya Publ., 1985. 216 p. 5. Gadel’shin M.Sh., Anisimova L.I., Boitsova E.S. Vodorodnoe plastifitsirovanie titanovykh splavov [Hydrogen plasticisation of titanium alloys]. Mezhdunarodnyi nauchnyi zhurnal al’ternativnaya energetika i ekologiya = International Scientific Journal Alternative Energy and Ecology , 2004, vol. 17, no. 9, pp. 26–29.