Specific features of the formation of the microstructure of titanium nickelide upon thermomechanical treatment including cold plastic deformation to degrees from moderate to severe

Gradation of Nanostructures in Cold-Rolled and Annealed Ti–Ni Shape Memory Alloys

“…The same trend was also observed in Ti-Ni shape memory alloys where different nanostructures can be created in high-temperature B2-austenite phase as a result of postdeformation annealing (PDA) after severe deformation by high-pressure torsion [3][4][5][6][7], cold rolling (CR) [8][9][10][11][12][13], and cold drawing [14][15][16] techniques.…”

“…Since a clear source of the discrepancies in the nanostructure elements interpretation is the plural meaning of the commonly used term ''nanocrystalline structure'' or NCS, we propose to reserve this term to designate nano-sized grain structure only, while applying different term, ''nanosubgrained structure'' or NSS, to designate nano-sized subgrain substructure. (Moreover, if the size of the regions consisting of nano-subgrains exceeds 100 nm [13,28], these regions should be regarded as submicrocrystalline. )…”

“…The structure formation features observed by transmission electron microscopy in cold-rolled and then annealed Ti-Ni alloys can be classified as a function of deformation intensity [11][12][13]17]. In the range of moderate true strains (up to e = 0.3), a well-developed dislocation substructure forms.…”

“…During PDA, the above-mentioned structures undergo specific structural changes: in the highly dislocated substructure, recovery, polygonization (which includes subgrain formation and growth), and finally recrystallization occur; the grains of the deformation-induced nanocrystalline structure grow, the amorphous phase crystallizes, and the crystallized nano-sized grains grow alongside their deformation-induced counterparts [11][12][13][15][16][17]. Note that individual groups of nano-sized subgrains can still be found in the latter case [5].…”

Nanostructured Titanium Nickelide: Realization of abnormally high recovery strain

“…The average size of structure elements evaluated from bright field images is about 90 nm. Spotted diffraction rings and azimuthally broadened diffraction spots, reflect high-angle as well as low-angle misorientations of structure elements across the selected area, respectively [19]. RHT at 700°C results in formation of the recrystallized austenite structure with average grain size about 11 µm (not shown).…”