Metastable nanostructured SPD Ti-Ni alloys with unique properties

Ti50Ni25Cu25 alloy in amorphous state, fabricated by rapid quenching and coarse-grained Ti49.4Ni50.6 alloy were subjected to severe plastic deformation.(SPD) in order to produce nanocrystalline states. In the first case, we used SPD-controlled nanocrystallization of the initial amorphous alloy Ti50Ni25Cu25. In the second case, the nanostructures were obtained through microstructural refinement by SPD in the initial coarse-grained alloy Ti49.4Ni50.6. The fabrication of nanostructures has a strong impact on martensite transformations. Martensite transformations are suppressed at the grain size below the critical point (similar to 100 nm). The nanostructured states with the size of 100-200 nm demonstrate unique mechanical and functional properties, namely very high strength and ductility, as well as increased reactive stress and reversible strain.