Dependence of the functional characteristics of thermomechanically processed titanium nickelide on the size of the structural elements of austenite

Abstract

Effect of the size of the elements of the mixed structure of B2 austenite, which consists of nanosized grains and subgrains of a polygonized substructure, on the functional properties of the Ti–50.7 at % Ni alloy preliminarily subjected to a low-temperature thermomechanical treatment (LTMT) and post-deformation annealing (PDA), has been investigated. The generation of the shape-memory effect (SME) and reversible two-way SME (TWSME) was performed using bending deformation. A maximum (for the Ti–Ni alloys) value of the recovery strain ε_r = 15.5 ± 0.5% has been obtained after annealing at 600°C for 1 h (recrystallized structure) and after LTMT + PDA at 430°C for 10 h (mixed nanocrystalline and nanosubgrain structure). The behavior of the parameters of the SME and TWSME in different structural states has been considered. A comparative study of the effect of the temperature and time of holding at a temperature upon the PDA on the formation of the microstructure and submicrostructure of the B2 austenite has been performed.