**Anna Churakova 1,2,\* and Dmitry V. Gunderov 1,2**


Received: 30 December 2019; Accepted: 4 February 2020; Published: 6 February 2020

**Abstract:** The influence of thermal cycling (TC) with a large number of cycles on the microstructure, the parameters of martensitic transformations (MTs), and the mechanical properties of a Ti-50.8 at.% Ni shape-memory alloy in coarse-grained (CG) and ultrafine-grained (UFG) states was investigated. The effect of microstructural and mechanical stability was found in both coarse-grained and ultrafine-grained states starting from the 100th cycle of martensitic transformations. In addition, an unusual temperature change was observed in martensitic transformations occurring with the formation of an intermediate R phase.

**Keywords:** TiNi alloy; thermal cycling; ultrafine-grained structure; microstructural and mechanical stability
