Strain states and unique properties in cold-rolled TiNi shape memory alloys

Martensitic transformation (MT), strain glass transition (SGT) and the corresponding stress-strain responses in cold-rolled Ti49.2Ni50.8 shape memory alloys (SMAs) at various amounts of cold-rolling deformation are investigated. A phase diagram describing all states transitions among them is established temperature – space. It shows a normal sharp, strong first-order B2 to B19? MT low levels (cold-rolling thickness reduction ?p < 27%), but continuous SGT high (?p ? 27%) upon cooling. Superelasticity with small hysteresis, tunable modulus functional-fatigue resistance properties achieved by altering behavior from 27%. Nanodomains single variant martensite atomic scale observed using aberration-corrected scanning transmission electron microscopy samples = Further in-situ loading synchrotron-based energy X-ray diffraction technique that quasi-linear superelasticity associated can be attributed stress-induced growth nanodomains. Geometrical analysis high-resolution image reveals nanoscale network severe lattice distortion accumulated high-density defects 27%, which microstructural origin state. This work provides detailed explanation for longstanding puzzle unique superelastic response plastically deformed TiNi SMAs, may shed light on achieving novel mechanical through defect engineering.