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Caractérisation multiéchelle par diffraction de neutrons et rayonnement synchrotron de la transformation martensitique sous contrainte dans un alliage à mémoire de forme CuAlBe

Benoit Malard
Abstract : SUMMARY : The Shape Memory Alloys (SMA) have different mechanical properties than usual materials. Their exceptional properties such as superelasticity and shape memory are closely associated with the characteristic of the martensitic transformation in these alloys. The microstructural evolutions associated with this transformation play a considerable role in the nature of the observed macroscopic behaviour. The precise description of these evolutions is an important part of the understanding of the interactions between the microstructure and the macroscopic properties. In this context, diffractometric analyses allow us to obtain useful information on the volume fraction evolution the lattice strains and grain rotations. The use of neutron, synchrotron X-ray and hard X-Ray radiation appears to be the only alternative for quantifying the martensitic transformation at multiple length scales via reliable complementary measurements performed in a laboratory. This work, on superelastic CuAlBe SMA, contributes to the development experimental methodologies on biphasic alloys and sets up new in-situ multiscale analyses on the field of the martensitic transformation. At the macroscopic scale, the transfer stress loading from one to the other phase has been followed when the transformation begins. The plastic and residual transformation strains have been determined from the residual macroscopic strain. At the grain level, the formation and the rotation of small austenitic domains have been measured when the martensitic transformation starts. During unloading, the inverse rotation and the reconstitution of one austenitic domain have been observed. At the microscopic level, the rotations of the small austenitic domains have been confirmed and localized. The increase of the austenite crystal plane mosaicity has been tracked.
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https://pastel.archives-ouvertes.fr/pastel-00004479
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Submitted on : Tuesday, February 10, 2009 - 8:00:00 AM
Last modification on : Tuesday, February 10, 2009 - 8:00:00 AM
Long-term archiving on: : Friday, September 10, 2010 - 12:56:05 PM

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Benoit Malard. Caractérisation multiéchelle par diffraction de neutrons et rayonnement synchrotron de la transformation martensitique sous contrainte dans un alliage à mémoire de forme CuAlBe. Engineering Sciences [physics]. Arts et Métiers ParisTech, 2008. English. ⟨NNT : 2008ENAM0044⟩. ⟨pastel-00004479⟩

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