Evolution of microstructure and property of NiTi alloy induced by cold rolling

We investigated the combination effect of plastic deformation and phase transformation on the evolution of microstructure and property of NiTi alloy. Samples of Ni50.9Ti49.1 alloy were deformed by cold rolling to different strains/thickness reductions (4%–56%). X-ray diffraction, transmission electronic microscopy (TEM) and microhardness measurements were applied for characterization of the microstructure and property of the cold-rolled samples. Experimental results indicated the non-monotonic variations of microstructure parameters and mechanical property with strain, indicating the different processes in microstructure and property evolution of NiTi subjected to cold rolling. TEM observations further showed the dominating mechanisms of microstructure evolution at different strain levels, leading to the gradual reduction of grain size of NiTi to the nanoscale by cold rolling. The results were discussed and related to deformation of martensite, forward and reverse martensitic transformations and dynamic recrystallization. The present study provided experimental evidences for the enhanced formation of nanograins in NiTi by plastic deformation coupled with phase transformation. [Display omitted] •Cold rolling of NiTi to thickness reductions from 4% to 56%.•Fluctuation behaviors in microstructure and property evolutions of NiTi.•Deformation coupled with phase transformation enhanced nanocrystallization of NiTi.