https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 07 Jun 2026 13:32:38 GMT 2026-06-07T13:32:38Z http://hdl.handle.net/10985/8435 Friction stir welding of AZ31 magnesium alloy rolled sheets: Influence of processing parameters COMMIN, Loreleï; DUMONT, Myriam; MASSE, Jean-Eric; BARRALLIER, Laurent The temperature evolution during friction stir welding (FSW) and the resulting residual stresses of AZ31 Mg alloy were studied to get a better understanding of the mechanisms involved in this process. The relationship between the processing parameters, the heat and plastic deformation produced and the resulting microstructure and mechanical properties was investigated. Increasing the shoulder diameter or the tool rotation speed or decreasing the welding speed produced an increase in the heat generated during the process and then promoted grain growth. The temperature distribution on the advancing side and on the retreating side differed, and stress levels were higher on the retreating side. The grain size heterogeneity produced by FSW was not the prevailing cause of failure. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/10985/8435 2009-01-01T00:00:00Z COMMIN, Loreleï DUMONT, Myriam MASSE, Jean-Eric BARRALLIER, Laurent The temperature evolution during friction stir welding (FSW) and the resulting residual stresses of AZ31 Mg alloy were studied to get a better understanding of the mechanisms involved in this process. The relationship between the processing parameters, the heat and plastic deformation produced and the resulting microstructure and mechanical properties was investigated. Increasing the shoulder diameter or the tool rotation speed or decreasing the welding speed produced an increase in the heat generated during the process and then promoted grain growth. The temperature distribution on the advancing side and on the retreating side differed, and stress levels were higher on the retreating side. The grain size heterogeneity produced by FSW was not the prevailing cause of failure. http://hdl.handle.net/10985/10896 Microstructure Characterization of a Nitrided Fe- 3wt.%Cr-0.3wt.%C Model Alloy by Anomalous Small Angle X-ray Scattering DUMONT, Myriam; BARRALLIER, Laurent; JÉGOU, Sébastien Nitriding is a thermo-chemical surface treatment of steels providing an improved fatigue and wear resistance. This treatment is based on nitrogen diffusion involving the precipitation of nano-scaled nitrides from the solid solution at the near surface of the nitrided piece. Nitriding involves a complex microstructural evolution both in time and depth including diffusion of nitrogen and precipitation of nitrides but also coarsening and dissolution of carbides resulting in diffusion of carbon. However the chemical composition of nano-scaled precipitates remains controversial, in particular regarding the iron content in nano-nitrides that may substitute alloying elements. In this framework, anomalous small-angle X-ray scattering was used to bring quantitative data on the distribution and composition of the nano-scaled phases in a Fe-3Cr-0.3C steel as a function of depth. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10896 2015-01-01T00:00:00Z DUMONT, Myriam BARRALLIER, Laurent JÉGOU, Sébastien Nitriding is a thermo-chemical surface treatment of steels providing an improved fatigue and wear resistance. This treatment is based on nitrogen diffusion involving the precipitation of nano-scaled nitrides from the solid solution at the near surface of the nitrided piece. Nitriding involves a complex microstructural evolution both in time and depth including diffusion of nitrogen and precipitation of nitrides but also coarsening and dissolution of carbides resulting in diffusion of carbon. However the chemical composition of nano-scaled precipitates remains controversial, in particular regarding the iron content in nano-nitrides that may substitute alloying elements. In this framework, anomalous small-angle X-ray scattering was used to bring quantitative data on the distribution and composition of the nano-scaled phases in a Fe-3Cr-0.3C steel as a function of depth. http://hdl.handle.net/10985/10004 Chemical composition of nano-phases studied by anomalous small-angle X-ray scattering (ASAXS) MORFIN, I.; DE GEUSER, F.; COMMIN, Loreleï; LEGENDRE, F.; MAUGIS, P.; DUMONT, Myriam; BARRALLIER, Laurent; JÉGOU, Sébastien Anomalous small-angle X-ray scattering (ASAXS) is a technique developed in the 1980s. It offers the opportunity to go further in the investigation of nano-objects by providing chemical information besides characteristic features like size and volume fraction given by classical SAXS. ASAXS is an element-selective technique based on the anomalous variation of the scattering factor near the absorption edge of one chosen element. This technique requires a tunable wavelength of the incident beam that is available on synchrotron radiation sources. In this study, a simple approach is proposed and detailed to extract chemical information from anomalous SAXS data. To illustrate the procedure, two examples are treated by applying this data processing. The first one aims to discriminate between different possible phases in the Y- Ti-O system that may form nano-oxides in oxide-dispersion-strenghtened (ODS) steels, materials for future nuclear plants. The second one deals with the composition of nano- precipitates formed in the diffusion layer of nitrided steels. Such information is of prime importance to evaluate the maximum nitrogen that can be introduced by such a surface treatment and thus the mechanical properties that can be achieved. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/10004 2014-01-01T00:00:00Z MORFIN, I. DE GEUSER, F. COMMIN, Loreleï LEGENDRE, F. MAUGIS, P. DUMONT, Myriam BARRALLIER, Laurent JÉGOU, Sébastien Anomalous small-angle X-ray scattering (ASAXS) is a technique developed in the 1980s. It offers the opportunity to go further in the investigation of nano-objects by providing chemical information besides characteristic features like size and volume fraction given by classical SAXS. ASAXS is an element-selective technique based on the anomalous variation of the scattering factor near the absorption edge of one chosen element. This technique requires a tunable wavelength of the incident beam that is available on synchrotron radiation sources. In this study, a simple approach is proposed and detailed to extract chemical information from anomalous SAXS data. To illustrate the procedure, two examples are treated by applying this data processing. The first one aims to discriminate between different possible phases in the Y- Ti-O system that may form nano-oxides in oxide-dispersion-strenghtened (ODS) steels, materials for future nuclear plants. The second one deals with the composition of nano- precipitates formed in the diffusion layer of nitrided steels. Such information is of prime importance to evaluate the maximum nitrogen that can be introduced by such a surface treatment and thus the mechanical properties that can be achieved. http://hdl.handle.net/10985/23008 Restructuring in high burn-up UO2 fuels: Experimental characterization by electron backscattered diffraction ZACHARIE-AUBRUN, Isabelle; DOWEK, Rebecca; NOIROT, Jean; BLAY, Thierry; CABIÉ, Martiane; DUMONT, Myriam This paper discusses the use of electron backscattered diffraction to characterize restructuring in a set of UO2 samples, irradiated in a pressurized water reactor at a burn-up between 35 and 73 GWd/tU, including standard UO2 samples and Cr-doped UO2 samples, to provide a better understanding of restructuring occurring both on the periphery and in the center of high-burn-up pellets. The formation of a high burn-up structure on the periphery of high burn-up UO2 was confirmed in our experiment. We found restructuring associated with bubble formation of all the samples in the central area, with higher irradiation temperatures when the burn-up exceeded 61 GWd/tU, regardless of their initial microstructure. This restructuring tended to progress with the increasing burn-up and to sub-divide the initial grains into sub-grains, with orientations close to that of the parent grains. Radial changes and differences between these samples showed that the burn-up and the temperature were not the only relevant parameters involved in restructuring. Tue, 01 Nov 2022 00:00:00 GMT http://hdl.handle.net/10985/23008 2022-11-01T00:00:00Z ZACHARIE-AUBRUN, Isabelle DOWEK, Rebecca NOIROT, Jean BLAY, Thierry CABIÉ, Martiane DUMONT, Myriam This paper discusses the use of electron backscattered diffraction to characterize restructuring in a set of UO2 samples, irradiated in a pressurized water reactor at a burn-up between 35 and 73 GWd/tU, including standard UO2 samples and Cr-doped UO2 samples, to provide a better understanding of restructuring occurring both on the periphery and in the center of high-burn-up pellets. The formation of a high burn-up structure on the periphery of high burn-up UO2 was confirmed in our experiment. We found restructuring associated with bubble formation of all the samples in the central area, with higher irradiation temperatures when the burn-up exceeded 61 GWd/tU, regardless of their initial microstructure. This restructuring tended to progress with the increasing burn-up and to sub-divide the initial grains into sub-grains, with orientations close to that of the parent grains. Radial changes and differences between these samples showed that the burn-up and the temperature were not the only relevant parameters involved in restructuring. http://hdl.handle.net/10985/26542 In Situ Monitoring of Retained Austenite Decomposition During Tempering of High-Strength Tool Steels DUMONT, Myriam; MESSAADI, Maha; LACHAL, Marine; QUIDORT, David; PERRUCHOT, Maxime; MALARD, Benoît; SCHELL, Norbert; MAAWAD, Emad; DELAGNES, Denis; DEHMAS, Moukrane This study investigates the decomposition of retained austenite (RA) in tool steels for plastic molding in correlation with the alloy chemical composition and the tempering parameters. Two grades differing in their silicon content with initial mixed bainitic/martensitic microstructures were investigated using in situ synchrotron high-energy X-ray diffraction (HEXRD) during tempering in the 550 °C to 600 °C temperature range for one-hour holding time. Results indicated carbide formation during heating or isothermal holding; however, retained austenite remained untransformed up to the end of the tempering holding time in all investigated conditions for both grades. In situ HEXRD provides direct evidence of the transformation of retained austenite into fresh martensite on cooling from the tempering stage. This behavior is correlated to the evolution of carbon enrichment of retained austenite and the effect of silicon is discussed. Thu, 19 Jun 2025 00:00:00 GMT http://hdl.handle.net/10985/26542 2025-06-19T00:00:00Z DUMONT, Myriam MESSAADI, Maha LACHAL, Marine QUIDORT, David PERRUCHOT, Maxime MALARD, Benoît SCHELL, Norbert MAAWAD, Emad DELAGNES, Denis DEHMAS, Moukrane This study investigates the decomposition of retained austenite (RA) in tool steels for plastic molding in correlation with the alloy chemical composition and the tempering parameters. Two grades differing in their silicon content with initial mixed bainitic/martensitic microstructures were investigated using in situ synchrotron high-energy X-ray diffraction (HEXRD) during tempering in the 550 °C to 600 °C temperature range for one-hour holding time. Results indicated carbide formation during heating or isothermal holding; however, retained austenite remained untransformed up to the end of the tempering holding time in all investigated conditions for both grades. In situ HEXRD provides direct evidence of the transformation of retained austenite into fresh martensite on cooling from the tempering stage. This behavior is correlated to the evolution of carbon enrichment of retained austenite and the effect of silicon is discussed. http://hdl.handle.net/10985/23006 Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy NOIROT, Jean; DOWEK, Rébecca; ZACHARIE-AUBRUN, Isabelle; BLAY, Thierry; CABIÉ, Martiane; DUMONT, Myriam Focussed ion beam - scanning electron microscope (FIB-SEM) 3D examination was conducted on three standard UO2 and one Cr doped UO2 high burn-up pressurized water reactor (PWR) fuel samples. This work complemented other microanalysis examination, including an electron backscattered diffraction (EBSD) work on the polished surface. A parallel article giving the EBSD results was submitted simultaneously. Together, they found, in all the central area of these high burn-up samples: (i) a restructuring of the initial grains into smaller sub-grains forming low angle boundaries and with crystal orientations around that of their parent grains; and (ii) intragranular bubbles mostly situated on these low angle boundaries. The FIB-SEM 3D examination showed how such inter-sub-grain bubbles start as small compact but also small lenticular bubbles, similar to typical small intergranular lenticular bubbles. With increasing burn-up, these lenticular bubbles get thicker and locally interlink to form more complex bubbles. However, no long distance networks, between the sub-grains or between the original grains, were found. Such networks could have been a path for part of the fission gases to reach the grain boundaries, the grain edges (the intersection line of three grain boundaries), and the rod free volumes. These FIB-SEM 3D examinations brought details on the intragranular and intergranular bubbles situation for each studied volume. The distribution of the intragranular bubbles according to their sizes and shapes was exposed. The central restructuring, studied in this work, is likely to play a role in the increase of the fission gas release fractions at high burn-up. This work is an incentive to study further this restructuring and the bubbles formed, combining different approaches. Tue, 01 Nov 2022 00:00:00 GMT http://hdl.handle.net/10985/23006 2022-11-01T00:00:00Z NOIROT, Jean DOWEK, Rébecca ZACHARIE-AUBRUN, Isabelle BLAY, Thierry CABIÉ, Martiane DUMONT, Myriam Focussed ion beam - scanning electron microscope (FIB-SEM) 3D examination was conducted on three standard UO2 and one Cr doped UO2 high burn-up pressurized water reactor (PWR) fuel samples. This work complemented other microanalysis examination, including an electron backscattered diffraction (EBSD) work on the polished surface. A parallel article giving the EBSD results was submitted simultaneously. Together, they found, in all the central area of these high burn-up samples: (i) a restructuring of the initial grains into smaller sub-grains forming low angle boundaries and with crystal orientations around that of their parent grains; and (ii) intragranular bubbles mostly situated on these low angle boundaries. The FIB-SEM 3D examination showed how such inter-sub-grain bubbles start as small compact but also small lenticular bubbles, similar to typical small intergranular lenticular bubbles. With increasing burn-up, these lenticular bubbles get thicker and locally interlink to form more complex bubbles. However, no long distance networks, between the sub-grains or between the original grains, were found. Such networks could have been a path for part of the fission gases to reach the grain boundaries, the grain edges (the intersection line of three grain boundaries), and the rod free volumes. These FIB-SEM 3D examinations brought details on the intragranular and intergranular bubbles situation for each studied volume. The distribution of the intragranular bubbles according to their sizes and shapes was exposed. The central restructuring, studied in this work, is likely to play a role in the increase of the fission gas release fractions at high burn-up. This work is an incentive to study further this restructuring and the bubbles formed, combining different approaches. http://hdl.handle.net/10985/21058 Determination of the pressure in micrometric bubbles in irradiated nuclear fuels DOWEK, Rébecca; CAGNA, Céline; NOIROT, Jean; ZACHARIE-AUBRUN, Isabelle; BLAY, Thierry; HANIFI, Karine; BIENVENU, Philippe; ROURE, Ingrid; CABIÉ, Martiane; DUMONT, Myriam In oxide nuclear fuels, at high burn-up or during high temperature periods such as ramp tests, out-of- pile heating tests, or any irradiations at high linear heat rates, fission gases can form micrometric or quasi-micrometric bubbles. During nominal operations, these bubbles participate to the pellet swelling, to the decrease of the fuel thermal conductivity and are involved in the mechanisms leading to fission gas release. During events involving a temperature increase, the resulting increase in the internal pres- sure of the bubbles might play a role in fuel fragmentation and in the opening of grain boundaries. The gas densities inside these bubbles are therefore one of the useful experimental information for the un- derstanding of the fuel behaviour, and for the fuel behaviour code progress and validation. Two methods were developed to evaluate the gas density in the quasi-micrometric bubbles, using electron probe micro analyser, secondary ion mass spectrometry and focused ion beam scanning electron microscope together. The first method provides a mean gas density for all quasi-micrometric bubbles in a given area. The sec- ond method provides a gas density in a single selected bubble. In addition to the gas density, the 3D size and shape of the selected bubble is measured and can be related to the gas density result. In this work, these methods were applied to the bubbles formed in the centre of a PWR Cr doped UO 2 at 38.8 GWd/t U after a ramp test in the Osiris reactor, with a 12 h plateau at 470 W/cm, and to the bubbles formed in a PWR Cr doped UO 2 at 62.8 GWd/t U in the centre of the pellet and on the bubbles of the high burn-up structure on the rim. Both show the high pressures reached in these bubbles. Fri, 01 Jan 2021 00:00:00 GMT http://hdl.handle.net/10985/21058 2021-01-01T00:00:00Z DOWEK, Rébecca CAGNA, Céline NOIROT, Jean ZACHARIE-AUBRUN, Isabelle BLAY, Thierry HANIFI, Karine BIENVENU, Philippe ROURE, Ingrid CABIÉ, Martiane DUMONT, Myriam In oxide nuclear fuels, at high burn-up or during high temperature periods such as ramp tests, out-of- pile heating tests, or any irradiations at high linear heat rates, fission gases can form micrometric or quasi-micrometric bubbles. During nominal operations, these bubbles participate to the pellet swelling, to the decrease of the fuel thermal conductivity and are involved in the mechanisms leading to fission gas release. During events involving a temperature increase, the resulting increase in the internal pres- sure of the bubbles might play a role in fuel fragmentation and in the opening of grain boundaries. The gas densities inside these bubbles are therefore one of the useful experimental information for the un- derstanding of the fuel behaviour, and for the fuel behaviour code progress and validation. Two methods were developed to evaluate the gas density in the quasi-micrometric bubbles, using electron probe micro analyser, secondary ion mass spectrometry and focused ion beam scanning electron microscope together. The first method provides a mean gas density for all quasi-micrometric bubbles in a given area. The sec- ond method provides a gas density in a single selected bubble. In addition to the gas density, the 3D size and shape of the selected bubble is measured and can be related to the gas density result. In this work, these methods were applied to the bubbles formed in the centre of a PWR Cr doped UO 2 at 38.8 GWd/t U after a ramp test in the Osiris reactor, with a 12 h plateau at 470 W/cm, and to the bubbles formed in a PWR Cr doped UO 2 at 62.8 GWd/t U in the centre of the pellet and on the bubbles of the high burn-up structure on the rim. Both show the high pressures reached in these bubbles. http://hdl.handle.net/10985/23007 Temperature-dependent modelling of magnetic ageing of FeSi electrical steels HELBLING, H.; TOTO JAMIL, Meryeme; DUMONT, Myriam; BENABOU, Abdelkader; CLENET, Stephane This paper deals with the temperature-dependent modelling of iron losses in the context of magnetic ageing of electricals steel used in high power electrical machines. First, two electrical steel sheet grades were heat treated at three temperatures in order to study the ageing effect evolution as a function of temperature. Results show a significant increase in iron losses for both steel grades. Then, considering the link between the macroscopic magnetic properties evolution (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. By coupling this model with the Arrhenius’ law, a model is developed to be able to predict the ageing for several temperature levels. Thu, 01 Dec 2022 00:00:00 GMT http://hdl.handle.net/10985/23007 2022-12-01T00:00:00Z HELBLING, H. TOTO JAMIL, Meryeme DUMONT, Myriam BENABOU, Abdelkader CLENET, Stephane This paper deals with the temperature-dependent modelling of iron losses in the context of magnetic ageing of electricals steel used in high power electrical machines. First, two electrical steel sheet grades were heat treated at three temperatures in order to study the ageing effect evolution as a function of temperature. Results show a significant increase in iron losses for both steel grades. Then, considering the link between the macroscopic magnetic properties evolution (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. By coupling this model with the Arrhenius’ law, a model is developed to be able to predict the ageing for several temperature levels. http://hdl.handle.net/10985/8438 Texture evolution in Nd:YAG-laser welds of AZ31 magnesium alloy hot rolled sheets and its influence on mechanical properties COMMIN, Loreleï; ROTINAT, René; PIERRON, Fabrice; DUMONT, Myriam; MASSE, Jean-Eric; BARRALLIER, Laurent AZ31 hot rolled magnesium alloy presents a strong basal texture. Using laser beam welding (LBW) as a joining process induces high temperature gradients leading to major texture changes. EBSD was used to study the texture evolution, and tensile tests coupled with speckle interferometry were performed to understand its influence on mechanical properties. The random texture obtained in the LBW fusion zone is mainly responsible for the yield strength reduction. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/8438 2011-01-01T00:00:00Z COMMIN, Loreleï ROTINAT, René PIERRON, Fabrice DUMONT, Myriam MASSE, Jean-Eric BARRALLIER, Laurent AZ31 hot rolled magnesium alloy presents a strong basal texture. Using laser beam welding (LBW) as a joining process induces high temperature gradients leading to major texture changes. EBSD was used to study the texture evolution, and tensile tests coupled with speckle interferometry were performed to understand its influence on mechanical properties. The random texture obtained in the LBW fusion zone is mainly responsible for the yield strength reduction. http://hdl.handle.net/10985/8412 Influence of the microstructural changes and induced residual stresses on tensile properties of wrought magnesium alloy friction stir welds COMMIN, Loreleï; ROTINAT, René; PIERRON, Fabrice; DUMONT, Myriam; MASSE, Jean-Eric; BARRALLIER, Laurent Friction stir welding induces a microstructural evolution and residual stresses that will influence the resulting mechanical properties. Friction stir welds produced from magnesium alloy hot rolled plates were studied. Electron back scattered diffraction was used to determine the texture evolution, residual stresses were analyzed using X ray diffraction and tensile tests coupled with speckle interferometry were performed. The residual stresses induced during friction stir welding present a major influence on the final mechanical properties. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8412 2012-01-01T00:00:00Z COMMIN, Loreleï ROTINAT, René PIERRON, Fabrice DUMONT, Myriam MASSE, Jean-Eric BARRALLIER, Laurent Friction stir welding induces a microstructural evolution and residual stresses that will influence the resulting mechanical properties. Friction stir welds produced from magnesium alloy hot rolled plates were studied. Electron back scattered diffraction was used to determine the texture evolution, residual stresses were analyzed using X ray diffraction and tensile tests coupled with speckle interferometry were performed. The residual stresses induced during friction stir welding present a major influence on the final mechanical properties.