On the effect of detwinning during compressive deformation of martensitic NiTi: in situ neutron diffraction and micromechanical

A combined experimental and computational effort was undertaken to provide insight into the microscopic deformation behavior of B19 ' martensitic NiTi during compressive loading-unloading. In situ neutron diffraction experiment was performed under quasi-static compression on a modified Eulerian cradle, where orientations rotated 50 degrees away from the loading axis were selected to capture the hkl reflections all the way during compres-sion. A domino detwinning scheme was deducted and implemented in an elastic-viscoplastic self-consistent (EVPSC) model in order to interpret the experimental data and elucidate the deformation mechanisms. Predictions of the model adequately fit the in situ load-unload stress-strain curve and lattice strains. Validity of the model was also confirmed by validation against deformed texture and evolution of individual microstrains from published work. Effects of domino detwinning on the intergranular stresses were analyzed. Possible deformation systems during compressive load and unload processes, including detwinning, slip and deformation twinning, were thoroughly discussed by comparisons between simulations and experiments.