Optimization of chemical composition-heat treatment conditions in niti shape memory alloys

In this study, the chemical composition-heat treatment conditions of NiTi Shape Memory Alloys, and it?s fatigue behaviour are investigated. Ti-% 51 at. Ni alloy helical spring was used in order to test speciment. Fatigue behaviour of helical spring has been showed with experimentally and numerically under tensile and compression stress. A testing unit has been developed for this aim. Chemical Composition of test speciment exhibits the persence of TiNi+TiNi3 phase region. Increasing of TiNi3 precipates as a result of fatigue cycling has been obtained in micrographs. In addition, existance martensitic variables has been detected by deformation. During the fatigue experiment, spear like martensitic crystals, which were generated by application were not disappeared under austenitic region. Therefore, end of the heating and cooling cycle has to be explained with percentage. Hysteresis loops of structural and functional fatigue behaviour of helical spring have been obtained. Loop interspaces have been verified for different forces numerically by using Lagrange polynomial interpolation method.