Thermo-Mechanical and Transformation Behaviors of Ti-41.7Ni-8.5Cu (at) Shape-Memory Alloy Wire

摘要

We proposed the new model, "series combined model", for the deformation of Ti-Ni-Cu SMA subjected to thermo-mechanical cycle. The model was selected considering the mechanism in the generation of recovery stress and can be used in order to investigate the peculiar fatigue mechanism due to the cyclic phase transformation in thermo-mechanical cycle finally. In this paper, the model was used to predict the change of the martensite volume fraction during this cycle and the calculation of the volume fraction was carried out successfully using inverse analysis for stress-strain data obtained experimentally. The prediction for the change of the martensite volume fraction could clarify that the reverse transformation of sound martensite progressed further even in unloading process with keeping stress at a constant level and the increase of the martensite subjected to plastic deformation got the reverse transformation stress level in the unloading process to fall.