"Shape Memory Effect in Ti-48%Ni-2%Fe Rolled Single Crystals"

The shape memory effect (SME) was measured for Ti-48%Ni-2%Fe single crystals, rolled in different initial orientations up to deformation degrees ~80% at 350^oC and annealed at 600^oC during 1 h. Measurements were carried out in the special thermo-cryogenic set, adjusted to the standard tearing machine. Rolled single crystals were deformed by tension at temperatures, chosen by curves of the electrical resistivity temperature dependence ρ(T) and corresponding to different stages of the martensitic transformation (MT). A significant plasticization of samples was revealed by their low-temperature deformation. Maximal values of the elongation were attained at temperatures of MT B2+R→B19’and indicate that in these cases MT is the main deformation mechanism. The shape recovery of stretched samples under their heating was observed by use of a dilatometer. Single crystals, rolled in stable initial orientations ({011}<011>, {111}<011> and {111}<112>), show the greatest SME; at that, for single crystals with rolling plane {111} a shape recovery of 100% was obtained by the setting deformation up to 15%. This value exceeds significantly those for rolled and annealed polycrystals. It was shown, that the width of temperature interval of SME manifestations varies depending on the orientation of single crystals from 30^o to 85^o. The X-ray study shows, that single crystals, rolled in stable orientations, have rolling textures with minimal scattering, minimal misorientations of the crystalline lattice in neighboring fragments and the minimal tendency to recrystallization under annealing.