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| Job Record #19354 | |
| Title | DNS of chemical segregation during solidification |
| Category | PhD Studentship |
| Employer | Institut Jean Lamour & Framatome |
| Location | France, Nancy |
| International | Yes, international applications are welcome |
| Closure Date | * None * |
| Description: | |
Direct numerical modeling of mesosegregations during the solidification of low alloy steelsBackgroundThe heavy components present in the primary circuit of a nuclear reactor (pressure vessel, steam generator, pressurizer) are made of forged and welded low-alloy steel parts. The chemical composition of the cast ingots used for forging is not uniform, they contain chemical heterogeneities, called segregations. These segregations cannot be entirely removed during the manufacturing process. Forged parts therefore contain local variations of chemical composition, which may significantly affect the mechanical properties. To limit these segregations is an important objective for FRAMATOME, one of the world's major nuclear reactor constructors. Segregations at the scale of the ingot (macrosegregations) have been studied for a long time. Segregations at a local, mesoscopic scale of 1–10 mm (mesosegregations), as well as the resulting segregation bands in the forged part, were recently characterized experimentally for the first time, using X-ray microfluorescence (PhD thesis of Lucie Gutman, 2024). Insight into the mechanism of formation of mesosegregations is the next step towards an improvement of the chemical homogeneity of the cast and forged parts.Objectives of the PhDThe objective of this project is to analyze the mechanisms of formation of mesosegregations and to propose realistic means for reducing them. Mesosegregation patterns are about the same size as the crystal grains that make up the material. They form during the solidification of the material and their formation is governed by convection of the chemical species with the flow of liquid and by diffusion. These species transport phenomena are strongly coupled with the growth of the solid grain structure. The size and shape of the individual grains must be therefore accounted for in a comprehensive theory of mesosegregation. In this project we aim at proposing a theory of mesosegregation using numerical simulations of the underlying transport and solidification phenomena. This will be achieved using state-of-the-art mesoscopic solidification models, such as the Grain Envelope Model (GEM) or the Voronoi Granular Model (VGM). These models can describe the grain growth, coupled with flow of the liquid between the grains, with heat transfer, and with diffusion and convection of the chemical species. They can simulate around a hundred (GEM) or tens of thousands (VGM) of grains. They are based on CFD solution methods (finite volume, finite element) for the transport equations, coupled with models of liquid-solid phase change. The models will be able to investigate the impact of the solidification conditions on the evolution of mesosegregations and help to formulate mesosegregation-risk criteria that can be incorporated into macroscopic process-scale models of casting. Finally, the numerical models will be used to explore the possibilities of reducing the intensity of mesosegregation by modifying the chemical composition of the steel. The modeling study will be compared to experimental characterizations that will be performed in parallel.Application of resultsThis PhD aims at proposing realistic measures and modifications of the casting practice in the casting plant. The ingot producer ArcelorMittal Industeel will therefore be informed of the project advancement. The project will also benefit from the environment of the Industrial Chair on Solidification at the Institut Jean Lamour in Nancy. Part of the results will be published.Work environmentThe PhD student will be employed by Framatome on a CIFRE PhD contract. The PhD student will work at Institut Jean Lamour in Nancy under the supervision of Drs. Miha Založnik, Jacob Kennedy, and Julien Zollinger, experts on solidification of metal alloys. She/he will be part of the Solidification group and will benefit from an interdisciplinary scientific environment: materials science, metallurgy, heat & mass transfer, computational modeling, experimentation and characterization at laboratory and industry scale. He/she will regularly meet with collaborators at Framatome in Paris and will occasionally interact with the ArcelorMittal Industeel steel plant and with the Framatome Technical Center in Le Creusot.Requirements
Additional informationInstitut Jean Lamour With around 500 researchers, PhD students and technical staff, IJL is one of the largest materials science research centers in Europe. We work in metallurgy, nanomaterials, plasma physics, surface physicochemistry. The Department of Science and Engineering of Materials and Metallurgy (SI2M) focuses on metallurgical processes ranging from liquid metal treatment over solidification to solid transformation processes; all with the objective to control the formation of the structure of the final product. We work in tight collaboration with the industry and with international academic partners on a wide spectrum of projects, integrating industrial and fundamental problems. Nancy has a population of 400 000 (metropolitan area) and is a major city in the region of Lorraine in the east of France. It is a strong center of higher education and research, with a total of 50 000 students. It has a flourishing student life and offers many social, cultural and sports activities. How to applyTo apply, send us a short statement of your interests, your CV, and full academic transcripts of the last two years of your master's studies. |
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| Contact Information: | |
| Please mention the CFD Jobs Database, record #19354 when responding to this ad. | |
| Name | Miha Založnik |
| miha.zaloznik@univ-lorraine.fr | |
| Email Application | Yes |
| Record Data: | |
| Last Modified | 21:43:45, Thursday, September 05, 2024 |
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