DOI: https://doi.org/10.22184/1993-8578.2023.16.1.48.57

The paper considers the corrosion behavior of the Ti50.0Ni50.0 martensitic alloy in coarse-grained and ultrafine-grained states in various solutions. In the coarse-grained state, no significant corrosion damage is observed; corrosion products are clearly visible in a dark field taken with an inverted microscope. In the ultrafine-grained state, significant corrosion damage is observed in the form of pitting which size is several micrometers. X-ray phase analysis of the Ti50.0Ni50.0 alloy made it possible to determine the presence of a high proportion (more than 70%) of TiNiH1.4 hydride in the ultrafine-grained state after corrosion tests while the proportion of hydride in the coarse-grained state is less than 2%. The TiNi alloy contains the Ti2Ni phase enriched with Ti, both in the coarse-grained and ultrafine-grained states. Moreover, in the ultrafine-grained state its share is 6 times higher. In addition, 5.3% of the Ti3Ni3Ox phase is observed in the ultrafine-grained state, while this phase was not found in the coarse-grained state. There is also a phase redistribution of the TiNi matrix in the ultrafine-grained state.