Processing of nanostructured TiNi-shape memory alloys: Methods, structures, properties, application

In recent years nanostructured materials have been the subjects of intensive research due to their superior physical and mechanical properties. The present study is a review of our own works on the processing and investigation of nanostructured TiNi-based shape memory alloys. Various methods of production have been developed, which can be classified into three groups, based on their approaches: i – superrapid solidification (melt quenching), ii – severe plastic deformation, and iii – combinations of the deformation and thermal treatments. Influence of alloying, different mechanical-thermal treatments on mechanical properties of alloys (shape memory effects, superelasticity, superplasticity, strengthening and so on), critical temperature and sequence of martensitic transformations was studied. Peculiarities of pretransition states and phase transitions in alloys, microstructure and morphology of martensitic phases at the transitions $\rm B2\leftrightarrow B19'$, $\rm B2\leftrightarrow R$, $\rm B2\leftrightarrow B19$, $\rm B2\leftrightarrow R\leftrightarrow B19'$, $\rm B2\leftrightarrow B19\leftrightarrow B19'$ were investigated in detail by TEM, X-ray diffraction, measurements of $\rho$(T), $\chi$(T)

Martensitic Transformation and Shape Memory Effect in Polycomponent TiNi-Based Alloys

The results of martesitic transformation (MT) and shape memory effect (SME) in quaternary Ti50(NiCoCu)50’ Ti50(NiFeCu)50 and (TiAl)50(NiCu)50 alloys studies arc generalized in this paper. On alloying TiNi simultaneously by two elements, their individual effect on MT and SME is conserved. Martensitic transformations B2→R and B2→B19' are almost simultaneously realizing in a binary TiNi. One can selectively control each of two MT channels by selecting property of alloying elements. As a result, the alloys having any sequences of MT and their realizations temperatures, including simultaneous realization of two MTs at low temperatures, which was not observed earlier, can be produced