Nanoscale interwoven structure of B2 and R-phase in NiTi alloy film

•Nanoscale interwoven structure of B2 and R-phase was observed in an annealed NiTi alloy film.•The R-phase can nucleate in the precipitate-free area.•The full-field strain of B2 and R-phase was mapped.•The measured strains are consistent with the eigenstrains of the R-phase.

Ti–50.3Ni (at%) alloy film was prepared by vacuum magnetron sputtering, followed by heat treatment at 460 °C for 40 min. The microstructure of the NiTi alloy film was studied using transmission electron microscopy. A nanoscale interwoven structure of B2 and R-phase was observed. The lattice correspondences between B2 and R-phase were analyzed using an electron diffraction pattern. The R-phase can nucleate in the precipitate-free area of the NiTi alloy film at a rapid cooling condition. The full-field strain of B2 and R-phase was mapped through geometric phase analysis technique. The measured strains are consistent with the eigenstrains of the R-phase.