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References

2010

Articles:

Xiong, X. C., Redjaïmia, A. and Goune, M.
Scripta Materialia, 63 (12)(12):1232-1235
2010
ISSN: 1359-6462

Resume: In situ transmission electron microscopy investigations were carried out on a supersaturated nitrogen ferrite to characterise the precipitation kinetics of alpha `'-Fe16N2 nitrides at 85 degrees C. The coarsening behaviour consists of two stages. The first stage obeys the LSW theory and the coarsening rate was determined as 11.2 nm(3) s(-1). The second stage corresponds to the stabilization of coarsening, and was assumed to be related to the coherency loss between the precipitates and the matrix. (c) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Xiong, X. C., Redjaïmia, A. and Goune, M.
Materials Characterization, 6 (11)(11):1245-1251
2010
ISSN: 1044-5803

Resume: Acicular shaped crystals precipitate from gamma Fe4N nitride in an iron-nitrogen alloy and were identified by electron microdiffraction as alpha ferrite Acicular ferrite develops both the Nishiyama-Wassermann and the Kurdjumov-Sachs orientation relationships with gamma' Fe4N nitride These orientation relationships were discussed in terms of the symmetry theory The driving force for acicular ferrite formation was related to the increasing nitrogen content of gamma' Fe4N, in equilibrium with alpha ferrite, with decreasing temperature The passage from lamellar to acicular structure in Fe-N system was proposed (C) 2010 Elsevier Inc All rights reserved

Equipe: Département SI2M : Microstructures et Contraintes

2009

Articles:

Xiong, X. C., Redjaïmia, A. and Goune, M.
Journal of Materials Science, 44(2):632-638
2009
ISSN: 0022-2461

Resume: In this study, hypoeutectoid Fe-N binary specimens have been prepared by gas nitriding pure iron in austenite domain at 840 A degrees C. The slow cooling of these specimens led to the alpha-ferrite + gamma'-Fe(4)N pearlitic microstructure which is similar to the pearlite in Fe-C binary system. This pearlitic microstructure has been characterized by electron microscopy. The crystal structure of the gamma'-Fe(4)N nitride has been identified by electron microdiffraction and the Nishiyama-Wassermann (N-W) and near Kurdjumov-Sachs (K-S) orientation relationships have been found between the alpha-ferrite and the gamma'-Fe(4)N.

Equipe: Département SI2M : Microstructures et Contraintes

2008

Articles:

Douce, J F., Bellot, J.P., Denis, S., Chaffotte, F., Pellegrino, G., Gouhinec, F., Lamesle, P. and Maury, J.
International Journal of Microstructure and Materials Properties, 3(1):150
2008
ISSN: 1741-8429

Equipe: Département SI2M : Microstructures et Contraintes

Bruneseaux, Fabien, Aeby-Gautier, Elisabeth, Geandier, Guillaume, Teixeira, Julien Da Costa, Appolaire, Benoit, Weisbecker, Patrick and Mauro, Anthony
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 476(1-2):60-68
2008
ISSN: 0921-5093

Resume: The beta(BCC) -> alpha(HCP) + beta(BCC) phase transformation kinetics of the beta-metastable titanium alloy Ti17 was studied by in situ high energy X-ray diffraction (XRD) and electrical resistivity. The use of synchrotron radiation (E = 89.12 keV, lambda = 0.01402 nm) allowed to characterize specimens 6 mm in diameter, limiting thus oxidation effects. The alpha + beta -> beta phase transformation kinetics was characterized during continuous heating up to the P temperature range. The beta -> alpha + beta transformation was studied in isothermal conditions (dwell at 708 degrees C or 750 degrees C) and during continuous cooling (cooling rates of 0.05 degrees C/s, 0.1 degrees C/s and 0.61 degrees C/s). The evolutions of the phase fractions are analyzed and compared to kinetics measured by electrical resistivity, showing a good correlation between both methods. In addition, the evolutions of the cell parameters of each phase obtained from XRD patterns are analyzed in regard of the transformation kinetics. (C) 2007 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Morniroli, J. P., Houdellier, F., Roucau, C., Puiggali, J., Gesti, S. and Redjaïmia, A.
Ultramicroscopy, 108 (2)(2):100-115
2008
ISSN: 0304-3991

Resume: By combining the large-angle convergent-beam electron diffraction (LACBED) configuration together with a microscope equipped with a C., corrector it is possible to obtain good quality spot patterns in image mode and not in diffraction mode as it is usually the case. These patterns have two main advantages with respect to the conventional selected-area electron diffraction (SAED) or microdiffraction patterns. They display a much larger number of reflections and the diffracted intensity is the integrated intensity. These patterns have strong similarities with the electron precession patterns and they can be used for various applications like the identification of the possible space groups of a crystal from observations of the Lane zones or the ab-initio structure identifications. Since this is a defocused method, another important application concerns the analysis of electron beam-sensitive materials. Successful applications to polymers are given in the present paper to prove the validity of this method with regards to these materials. (c) 2007 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

2007

Articles:

Aeby-Gautier, E., Bruneseaux, F., Teixeira, J. Da Costa, Appolaire, B., Geandier, G. and Denis, S.
Journal of Materials, 59(1):54-58
2007
ISSN: 1047-4838

Resume: The prediction of microstructure during processing needs to characterize the phase transformation occurring during the thermal treatments and their kinetics. In-situ high-energy synchrotron x-ray diffraction experiments performed during temperature variations allow the characterization of the phase evolution. For some transformation conditions, the continuous recording of diffraction diagrams evidences clearly intermediate phases. The quantitative analysis of the diffraction diagrams gives the transformation kinetics of each phase as well as their cell parameters. Transformation kinetics obtained by this method are compared to results obtained by electrical resistivity.

Equipe: Département SI2M : Département SI2M : Microstructures et Contraintes

Hutchinson, C.R., Goune, M. and Redjaïmia, A.
Acta Materialia, 55(1):213-223
2007
ISSN: 1359-6454

Resume: A physically based process model for the room temperature yield strength of an age-hardenable alloy subject to selected monotonic non-isothermal heat treatment schedules is developed and used to examine the possible efficiencies in processing and enhancements in strength that may be realistically achieved. `Processing Maps' are generated which illustrate both the yield strengths achievable and the processing routes necessary to achieve them, as well as estimates of the energy consumed in the thermal treatment. A Fe-2Cu (wt.%) alloy is used as an example and the results of physical experiments are compared with the model predictions. For the conditions examined, enhancements in yield strength of similar to 8% above those achievable in comparable isothermal treatments are illustrated with 65% of the energy input. Alternatively, similar yield strengths to those from comparable isothermal treatment are shown to be achievable with similar to 35% of the energy input. The physical origins of the observed effects and the potential implications of coupled process-property optimization are considered. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

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