An investigation on reorientation and textural evolution in a martensitic NiTi rolled sheet using EBSD

Variant reorientation is a ubiquitous phenomenon in shape memory alloys and has a great influence on their texture and mechanical response. In the present study, a martensitic NiTi rolled sheet is investigated by the electron backscattering diffraction (EBSD) technique; the variant reorientation and texture evolution are followed during bending. The initial weak texture components of martensite evolve by reorientation toward a strong texture around [104]M and a weak one around [112]M. The initial laths are transformed into blocks made of one or two variants. The EBSD maps were analyzed with the Interaction Work (IW) criterion associated with (a) the individual variant and (b) habit plane variants (a combination of two distortion variants). Compared with the experimental results, the prediction given with individual variant fits better than with the habit plane variants. An empirical quantification of the threshold on interaction work (IW) permits to rationalize and predict the variant pairs formed by the reorientation and their numbers in the blocks. A critical influence of the pre-texture of the parent B2 grains on the final texture and on the number of variants per block was revealed. This study could give insights into the mechanical response of the NiTi alloys with various textures during tensile and fatigue tests.