Martensitic transformation in nanostructured TiNi shape memory alloy formed via severe plastic deformation

Martensitic transformation and mechanical behavior was investigated on TiNi shape memory alloy subjected to severe plastic deformation by cold rolling. Transmission electron microscopy revealed the sample to be a mixture of nanocrystalline and amorphous material after 40% cold rolling. Diffrential scaning calorimetry measurements and X-ray diffractometry suggested that the martensitic transformation was suppressed when the thickness reduction was over 25%. The pseudoelastic stress–strain curves of nanocrystalline/amorphous TiNi are characterized by the absence of a stress-plateau and by small hysteresis.