Microstructure and martensitic transformation behavior of crystallized Ti–36Ni–7Sn (at%) alloy ribbons

Amorphous Ti–36Ni–7Sn (at%) alloy ribbons prepared by melt spinning were annealed at various temperatures for crystallization and then microstructures and transformation behavior were investigated by means of electron microscopy, X-ray diffraction and differential scanning calorimetry. Crystallized Ti–36Ni–7Sn alloy ribbons consisted of Ti3Sn, Ti2Ni and TiNi phases. Size of Ti3Sn phase was in the range of 50–850 nm depending on annealing temperature. Average size of TiNi phase increased from 25 nm to 100 nm with raising annealing temperature from 873 K to 1073 K. Volume fraction of Ti2Ni phase decreased by raising annealing temperature through decomposition reaction of 3Ti2Ni + Sn (solved in TiNi phase) → 3TiNi + Ti3Sn and then Ti2Ni almost disappeared by annealing at 1173 K. The TiNi phase in crystallized Ti–36Ni–7Sn alloy ribbons showed the B2–R–B19′ transformation behavior. DSC peak temperature associated with the B2–R transformation (TR*) decreased from 303 K to 292 K with raising annealing temperature from 973 K to 1173 K, while DSC peak temperature associated with the R–B19′ transformation (Ms*) increased from 187 K to 237 K with raising annealing temperature from 1073 K to 1173 K and thus the temperature gap between TR* and Ms* decreases from 112 K to 55 K.

► We crystallized Ti–36Ni–7Sn (at%) alloy ribbons by annealing at various temperatures.
► We found that crystallized Ti–36Ni–7Sn alloy ribbons consisted of Ti3Sn, Ti2Ni and TiNi phases.
► We also found that the TiNi phase in crystallized Ti–36Ni–7Sn alloy ribbons showed the B2–R–B19′ transformation.
► Volume fraction of Ti2Ni phase decreased by raising annealing temperature through decomposition reaction of 3Ti2Ni + Sn (solved in TiNi phase) → 3TiNi + Ti3Sn.