Phase with spinel structure type in plastically deformed NiTi

The alloy samples Ni51Ti49, subjected to plastic deformation were investigated. The microstructure and the microdiffraction were investigated by transmission electron microscopy Hitachi 7700. Discs with a diameter of 3 mm for investigation by transmission electron microscopy (TEM) was cut from the fracture zone of the stretched sample. They were mechanically thinned, then electrochemically etched until the hole in the center. The final step was to prepare ion etching in install PIPS (Gatan). TEM specimens were subjected cryomechanical processing. This was done by in liquid nitrogen cooling cyclically. The phase composition of the samples was determined by X-ray diffraction diffractometer "Bruker" using copper radiation. The lens-form crystals Ni2Ti3, containing bending contours, indicating significant internal stresses in the zones of stress localization were detected. The lens-form crystals can be represented as a non-equilibrium phase Ni2Ti3 with spinel structure type with lattice parameter 11,53 ± 0,03 Å. For the formation of lenticular crystals of nonequilibrium phase Ni2Ti3 it is necessary redistribution of the original solid solution components. In local curvature of the crystalline lattice areas, the increased interatomic distances created the special structural states. These states increase the number of degrees of freedom in a deformable solid and thus contribute to the emergence of new phases.