Thermomechanical analysis of the deformation in tension of a nanocrystalline superelastic NiTi thin wire

Abstract : Manufacturing processes of NiTi Shape Memory Alloys (SMA) wires induce a complex microstructure with a mix between amorphous phase and highly strained nanocrystals [1]. Such a material, a cold worked Ti 50.8 at.% Ni wire with a diameter 0.5mm, was studied during a tensile loading. Before loading, a heat treatment at 325°C for 30min, which is bellow the recrystallization temperature (~350°C), was applied. Thanks to these relative low heat treatment temperature, comparatively to the usual ones around 500°C, no strain localization was observed. Latent heat measurement during a thermal induced transformation was impossible through a DSC because any peak can be observed. However, the knowledge of latent heat is important in some applications, i.e. elastocaloric effect [2], where temperature variations are expected. Our presentation will show a method to estimate this latent heat during a stress induced phase transformation. From experimental full field measurements, thermal and kinematics, and using a processing presented in previous papers ([3-4]) we performed a heat balance in order to calculate thermal power and thermal energy induced by a tensile loading. From these results and a thermodynamic approach, it was possible to estimate: (i) the forward and reverse phase transformation enthalpies, (ii) the ratio between inelastic thermal power and mechanical power, (iii) the martensite fraction in function of strain or stress.
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https://hal.umontpellier.fr/hal-01816031
Contributeur : François Gibier <>
Soumis le : jeudi 14 juin 2018 - 16:34:19
Dernière modification le : vendredi 15 juin 2018 - 13:32:30

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  • HAL Id : hal-01816031, version 1

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Henrique Martinni Ramos de Oliveira, Hervé Louche, Denis Favier. Thermomechanical analysis of the deformation in tension of a nanocrystalline superelastic NiTi thin wire. 10th European Solid Mechanics Conference, Jul 2018, Bologne, Italy. 〈http://www.esmc2018.org/drupal8/ 〉. 〈hal-01816031〉

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