The Effect of Grain Size on the B2→B19′ Phase Transformation and Mechanical Properties of a NiTi Alloy Subjected to Uniaxial Monotonic and Cyclic Loading- Unloading In Tension

This study compares the effect of uniaxial monotonic loading and cyclic loading-unloading in tension on the localised B2 (austenite)>B19'(martensite) phase transformation and mechanical behaviour of a cold-drawn and solution-treated 56Ni-44Ti wt.% shape memory alloy. It also elucidates the grain size effect under these loading conditions. In-situ techniques including digital image correlation (DIC) and synchrotron X-ray diffraction were applied. In addition, the microstructure before and after mechanical testing was studied via optical microscopy, electron back-scattering diffraction and transmission electron microscopy.