We establish the macro- and microfractographic features of the tensile fracture of cylindrical specimens made of nitinol (Ni–Ti alloy) at room temperature and at 0°C caused by their preliminary electrolytic hydrogenation. The revealed hydrogen embrittlement of the metal was associated with the facilitation of martensite transformation, which is more clearly pronounced at the lower testing temperature. This explains the phenomenon of reorientation of the macroscopic fracture surfaces of specimens from the tensile mode into the shear mode under the influence of the conditions of embrittlement. On the microlevel, the appearance of brittle cleavages along the boundaries of martensite crystals is regarded as a specific feature of the fracture of nitinol caused by its hydrogenation. Under more severe hydrogenation conditions, the width of the cleavage zone in the subsurface layers of the specimens increases, which is explained by the deeper penetration of hydrogen into the metal favorable for the structural and phase transformations.
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Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 55, No. 3, pp. 80–85, May–June, 2019.
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Iasnii, V.P., Student, O.Z. & Nykyforchyn, H.М. Influence of Hydrogenation on the Character of Fracture of Nitinol Alloy in Tension. Mater Sci 55, 386–391 (2019). https://doi.org/10.1007/s11003-019-00314-y
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DOI: https://doi.org/10.1007/s11003-019-00314-y