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

Abstract

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 B2↔B19', B2↔R, B2↔B19, B2↔R↔B19', B2↔B19↔B19' were investigated in detail by TEM, X-ray diffraction, measurements of ρ(T), X(T).