ESOMAT 2009, 07003 (2009)
DOI: 10.1051/esomat/200907003

Analysis of Niobium precipitates effect on the thermo-mechanical behavior of a NiTiNb Shape Memory Alloy and Modeling

Boris Piotrowski^{1, 2, 3}, Tarak Ben Zineb¹, Etienne Patoor² and André Eberhardt<sup>2

1</sup>  Laboratoire d’Energétique et de Mécanique Théorique et Appliquée, Nancy University, CNRS, 2 rue Jean Lamour; 54500 Vandoeuvre-les-Nancy, France
²  Laboratoire de Physique et Mécanique des Matériaux, Paul Verlaine University, ENSAM, ENIM, CNRS, Ile du Saulcy; 57045 Metz cedex 01, France
³  Etudes et Productions Schlumberger, 1 rue Henri Becquerel, 92140, Clamart France

boris.piotrowski@esstin.uhp-nancy.fr

Published online: 1 September 2009

Abstract
Commercial Ni₄₇Ti₄₄Nb₉ Shape Memory Alloy (SMA) has attracted important attention for connection applications thanks to its wide transformation hysteresis. Indeed, it has been shown that reverse transformation temperature (As) can increase by 80 °C, with martensitic reorientation under tensile loading. The aim is to model this behavior in order to design industrial applications, by taking into account the Niobium inclusions effects upon the amplification of this phenomenon for NiTiNb. Niobium precipitates have been identified by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), and characterized. It seems that the smallest β-Nb Niobium inclusions have the most important impact on the phenomenon, explained by Niobium low yield stress and important scattering and number of inclusions. A two phases thermo-mechanical model has been developed. It describes the global effective behavior of an elastic-plastic inclusion (Niobium precipitates) embedded with SMA Matrix. The constitutive law of the matrix is that developed by Peultier et al. and improved by Duval et al.. The elastic-plastic constitutive law for inclusion is a classical one proposed by Simo and Hughes, the Mori-Tanaka scale transition is adopted in order to lead to the effective constitutive law. Numerical results are discussed and compared to experimental ones.

© Owned by the authors, published by EDP Sciences 2009