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Étude théorique et expérimentale des microstructures martensitiques dans les alliages à mémoire de forme

Abstract : Shape Memory Alloy (SMA) are metallic materials which own outstanding mechanical properties : superelasticity, memory effect and a great damp capacity. These mechanical properties generally exist in a given SMA, but at different temperatures. The chemical composition of SMA is an important parameter of the macroscopic behaviour. The objective of this work is to study the microstructural mechanisms which cause these properties. They take their source in a solid-solid change of phase named "martensitic transformation". The parent phase (austenite) exhibits a bold centred cubic structure for all known SMA. The main consequence of the martensitic transformation is to break this BCC symmetry. It gives birth to new crystalline structures which mainly depend of the chemical composition of the SMA. The present work deals with the understanding of the spatial organization of austenite and (variants of) martensite phases which exist in a SMA : martensitic microstructures. In the first part of the report, an evolution of the concept of Coherent Stress Free (CSF) microstructure is proposed. A martensitic microstructure can be in fact " not CSF" without causing "too many " mechanical irreversibilities, thus without altering the reversibility of the phase transformation. Such microstructures are referred to as "almost compatible ". Martensitic microstructures obtained under uniaxial tests in a single crystal of Cu-Al-Be are discussed in the second part of this report. Two types of full-field measurement techniques are associated for this purpose : infrared thermography, which provides temperature fields, and the grid method, which provides strain fields. Some martensitic microstructures are revealed and analysed.
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https://tel.archives-ouvertes.fr/tel-00626616
Contributor : Didier Delpueyo <>
Submitted on : Tuesday, November 8, 2011 - 10:49:03 AM
Last modification on : Wednesday, May 11, 2016 - 1:19:55 PM
Long-term archiving on: : Thursday, February 9, 2012 - 2:31:23 AM

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  • HAL Id : tel-00626616, version 3

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Didier Delpueyo. Étude théorique et expérimentale des microstructures martensitiques dans les alliages à mémoire de forme. Mécanique [physics.med-ph]. Université Blaise Pascal - Clermont-Ferrand II, 2011. Français. ⟨tel-00626616v3⟩

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