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References

2012

Articles:

Van Landeghem, H., Goune, M. and Redjaïmia, A.
Journal of Crystal Growth, 341 (1):53-60
2012

Equipe: Département SI2M : Microstructures et Contraintes

Dehmas, Moukrane, Salib, Matthieu, Geandier, Guillaume, Gautier, Elisabeth, Karnatak, Nikhil and Martin, Olivier
Matériaux et techniques, 100:103-105
2012

Equipe: Département SI2M : Microstructures et Contraintes

Geandier, G., Aeby-Gautier, E., Settefrati, A., Dehmas, M. and Appolaire, B.
Comptes Rendus Physique, 13(3):257-267
2012
ISSN: 1631-0705

Resume: High energy X-ray diffraction is a powerful tool, able to follow phase transformations during complex thermal or thermo-mechanical treatments. High energy allows one to study volumic specimens of a few mm(3) and get successive data within a few seconds or less. The technique is described with different experimental setups (heating devices, detectors for diverse acquisition times) allowing diverse ranges for heating and cooling rates. Three examples are considered to illustrate the results obtained by using high energy X-ray diffraction. The first one corresponds to a simple diffusive phase transformation during an isothermal thermal path for the alpha-beta transformation in a titanium alloy, highlighting the diffusive character considering the cell parameter evolutions of the parent phase. The second one illustrates the precipitation sequences observed during ageing of a beta-metastable phase in a titanium alloy that was not obtained by TEM. The last example illustrates the phase evolutions during ageing of a martensitic steel showing the complexity of cell parameters evolution and some evolutions of the stress state. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Borgese, L., Gelfi, M., Bontempi, E., Goudeau, P., Geandier, G., Thiaudière, D. and Depero, L. E.
Surface and Coatings Technology, 206(8-9):2459-2463
2012
ISSN: 0257-8972

Resume: Atomic Layer Deposition (ALD) allows the deposition of thin films onto flat as well as complex geometry surfaces with excellent conformality. Thicknesses of few atomic layers can be achieved. Moreover, low-temperature deposition is possible and this enables the change of surface properties of many kinds of materials. Good adhesion characteristics and also good mechanical performance of ALD deposited thin films make the technique extremely interesting for several applications, as for example micro-electronics. TiO2 is a well studied semiconductor material because of its multifunctional properties that open a wide range of applications for example in photocatalysis, optics and solar cells. ALD is extremely completive to other technique, to deposit titania thin films, employed even to improve the biocompatibility of many kind of materials. TiO2 thin films are deposited with ALD technique at low temperature (90 degrees C) onto Kapton substrate and then crystallized ex-situ after annealing at 300 degrees C. X-ray diffraction (XRD) techniques are very suitable for the analysis of structure and microstructure of films and surface layers. In this work, XRD in combination with in situ tensile testing has been applied for the first time to measure elastic properties (elastic modulus and Poisson ratio) of TiO2 anatase thin films obtained by ALD. For the experimental conditions, the tensile stage was installed in a Synchrotron laboratory of Soleil. The information extracted from diffraction patterns is presented. (C) 2011 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

2011

Articles:

Berveiller, S., Malard, B., Wright, J., Patoor, E. and Geandier, G.
Acta Materialia, 59(9):3636-3645
2011
ISSN: 1359-6454

Resume: Two synchrotron diffraction techniques, three-dimensional X-ray diffraction and Laue microdiffraction, are applied to studying the deformation behaviour of individual grains embedded in a Cu(74)Al(23)Be(3) superelastic shape memory alloy. The average lattice rotation and the intragranular heterogeneity of orientations are measured during in situ tensile tests at room temperature for four grains of mean size similar to 1 mm. During mechanical loading, all four grains rotate and the mean rotation angle increases with austenite deformation. As the martensitic transformation occurs, the rotation becomes more pronounced, and the grain orientation splits into several sub-domains: the austenite orientation varies on both sides of the martensite variant. The mean disorientation is similar to 1 degrees. Upon unloading, the sub-domains collapse and reverse rotation is observed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Borgese, L., Bontempi, E., Gelfi, M., Depero, L. E., Goudeau, P., Geandier, G. and Thiaudière, D.
Acta Materialia, 59(7):2891-2900
2011
ISSN: 1359-6454

Resume: Amorphous TiO2 thin films were deposited by means of atomic layer deposition on Kapton substrates and then crystallized ex situ by annealing at 300 degrees C to obtain the anatase phase. The morphology, structure and microstructure of films treated for 12, 24, 72 and 90 h were investigated. The local Ti coordination changes were studied by X-ray near-edge structure (XANES). On the basis of X-ray diffraction residual stress calculations, the elastic anisotropy of the films is experimentally determined for the first time (A*(comp) = 0.07, A*(shear) = 0.03). The film macro-strains increased with the time of treatment, while the micro-strains decreased. This effect may be correlated with the incipient anatase-to-rutile transformation as suggested by the changes observed in the XANES pattern of the film treated for 90 h. However, the contribution of the substrate cannot be excluded. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Grigorieva, Raisa, Drillett, Pascal, Mataigne, J. -M. and Redjaïmia, A.
Solid State Phenomena, 172-174(Part 1):784-790
2011
ISSN: 1012-0394

Resume: Nowadays more and more hot stamped steel sheets dedicated for the automotive body-in-white structure are pre-coated to prevent the steel surface against iron oxidation and decarburization during the austenitization step. For these applications, the coating is deposited by continuous hot-dipping the steel in an Al-Si bath. The Al-Si coating, at the delivery state, contains Al-grains, Al-Fe-Si ternary phases, Al-Fe binary phases. During the austenitization, the Al-Si coating transforms completely by inter-diffusion and solidification reactions. The mechanisms of Al-Fe-Si phase transformations at high temperature are almost unknown. The phase transformations occurring during austenitization define the final coating microstructure responsible for the in use properties of the product like spot welding, painting adherence or corrosion behavior. It is the aim of this paper to propose a new way of understanding the mechanisms of phase transformation in the Al-Si coating during the austenitization step (between 900 and 930 degrees C) before the transfer into the hot-stamping press.

Equipe: Département SI2M : Microstructures et Contraintes

Settefrati, A., Aeby-Gautier, E., Dehmas, M., Geandier, G., Appolaire, B., Audion, S. and Delfosse, J.
Solid State Phenomena, 172-174(Part 1):760-765
2011
ISSN: 1012-0394

Resume: In the present study we focus on the precipitation processes during heating and ageing of beta-metastable phase in the near beta Ti-5553 alloy. Transformation processes have been studied using continuous high energy X-Ray Diffraction (XRD) and electrical resistivity for two different states of the beta-metastable phase. Microstructures have been observed by electron microscopy. Different transformation sequences are highlighted depending on both heating rate and chemical composition of the beta-metastable phase. At low temperatures and low heating rates, the hexagonal omega(iso) phase is first formed as generally mentioned in the literature. Increasing the temperature, XRD evidences the formation of an orthorhombic phase (alpha"), which evolves toward the hexagonal pseudo compact alpha phase. For higher heating rates or for richer composition in beta-stabilizing elements of the beta-metastable phase, omega phase may not form and alpha" forms directly and again transforms into alpha phase. A direct transformation from beta-metastable to alpha phase is observed for the highest heating rate. The formation of the metastable omega(iso) and alpha" phases clearly influences the final morphology of alpha.

Equipe: Département SI2M : Microstructures et Contraintes

Faurie, D., Renault, P. -O., Geandier, G. and Le Bourhis, E.
Thin Solid Films, 520(5):1603-1607
2011
ISSN: 0040-6090

Resume: Synchrotron x-ray radiation was used for in situ strain measurements in gold films on polyimide substrate during uniaxial deformation tests. We have used an area detector that allows inspecting multiple directions in the polycrystalline thin film without serial sectioning during straining. We show in this paper the configuration used and the attainable orientations on a pole figure for which the x-ray strains are measured. Moreover, we show the effect on the x-ray strains of the onset on plasticity, which was not detected by optical (macroscopic) strain measurement. (C) 2011 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Mourot, Mickael, Courleux, Alice, Dehmas, Moukrane, Gautier, Elisabeth, Geandier, Guillaume, Dezellus, Olivier, Claude Viala, Jean, Martin, Olivier, Karnatak, Nikhil and Danoix, Frederic
Solid State Phenomena, 172-174:747-752
2011

Equipe: Département SI2M : Microstructures et Contraintes

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