|Specific forward/reverse latent heat and martensite fraction measurement during superelastic deformation of nanostructured NiTi wires |
Auteur(s): Ramos De Oliveira Henrique, Louche H., Grassi Estephanie Nobre Dantas, Favier Denis
(Article) Publié: Materials Science And Engineering A, vol. 774 p.138928 (2020)
Ref HAL: hal-02470296_v1
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This study analyses the thermomechanical tensile behaviour of a cold drawn Ti-50.9at.%Ni wire submitted to heat treatment at 598 K for 30 min, which is below the recrystallization temperature (623 K). Such low temperature heat treatment induces a superelastic loop without a stress "plateau". However, the absence or weakness of peaks on its differential scanning calorimetry prevents the determination of specific latent heat. This is a common effect of nanostructured materials such as superelastic wires. A method using strain and temperature field measurements was developed and used to determine thermal power and thermal energy during superelastic tensile tests through a heat balance. From these results and using a thermodynamic approach, forward and reverse specific latent heat and the martensite fraction are estimated as a function of strain and stress.