Analysis of deformation mechanisms in nanocrystalline NiTi wire under various thermomechanical loads via in-situ synchrotron x-ray diffracti

In engineering materials, martensitic transformation/deformation twinning change the structure/reorient crystal lattice, which is far less understood than dislocation slips. For nanocrystalline NiTi wires, we have recently developed a multiscale approach combining grain-level reconstruction of martensitic/austenitic microstructures deformed by TEM SAED-DF method with deformation analysis from in-situ texture evolution. The former studies deformation in individual grains, while the latter studies the same statistically in thousands of grains upon synchrotron diffraction. We have conducted isothermal tensile tests, in this work we will perform in-situ synchrotron X-ray diffraction texture evolution experiments on two NiTi wires upon heating/cooling/loading. We aim to reveal deformation modes acting upon thermomechanical loads frequently used in engineering applications of NiTi, as thermal actuator cycling, functional fatigue, low temperature shape setting and two way shape memory effect.