Thanks to their special functional properties, such as pseudo–elasticity or shape memory effect, NiTi alloys are more and more used in various fields. NiTi alloys are also characterized by high mechanical performances and high resistance to corrosion in many aggressive environments in presence of Cl- such as sea environments or biological environments. Shape memory effect or pseudoelastic effect are due to structural changes in presence of imposed deformation and/or temperature effects. In this work two NiTi alloy, once with a pseudo-elastic behavior and once with shape memory effect are investigated. Single cycle of load-unload for each alloy was effectuated on mini-specimens that allows X-ray analyses under imposed deformation. The results have been compared with those obtained after complete unload conditions.