Optimisation des microstructures et propriétés des matériaux par traitement électromagnétique (EPM) – OPTIMAG

Control of the microstructure of metallic alloys is one of the ultimate goals of materials science. Conventionally, microstructure results from solidification and solid-state transformation during casting and thermo or/and thermo-mechanical treatment. Because, on the one hand the atoms of matters inherently possess magnetism and on the other hand, thermal and chemical gradients in mushy zone generate thermoelectric currents in the mushy zone, the use of external high intensity DC magnetic field during solidification and solid-state transformation may generate body forces able to control microstructures and enlarge the number of materials processing routes. The present proposal aims at exploring and revealing the mechanisms of microstructure evolution of metallic alloys during high static magnetic field processing (solidification and solid state heat treatment) with special attention to the effect on convection, diffusion, interface characteristics, microstructure and crystallographic orientation evolution during solidification and solid state phase transformation to achieve properties optimization. The project will be on 4 tasks. The goal of Task 1and 2 is to fundamentally study the effect of a DC magnetic field on microstructure due to Thermo-Electric convection in liquid state metals, the diffusion behaviors in liquid-solid state and the grain orientations and crystallographic orientation during solidification and solid-state phase transformation during the elaboration of materials by means of experimental observation and theoretical simulation. The goal of Task 3 and 4 is to investigate novel treatment technique with a DC magnetic field to produce highly textured ferromagnetic shape memory alloys, notably Ni-Mn-Ga alloys. The project will be undertaken under the frame of a general cooperation between the 2 groups of teams: LETAM (UMR CNRS 7078 UPVM, Metz) and its partner Northeastern Univeristy, Shenyang China and SIMAP (UMR CNRS 5266 INPG-UJF, Grenoble) and its partner, Shanghai Univerity. SIMAP and Shanghai (elaboration, analysis, characterization and modeling) has successfully conducted the research work on the control of solidification of non-ferrous alloys, e.g., Al-Cu and Mn-Bi under a high magnetic field, while LETAM and Shenyang (microstructural characterization, crystallographic calculation and Ab initio simulation) are well known for their innovative work on solid state phase transformation under a high magnetic field and martensitic transformation of ferromagnetic shape memory alloys. The complementary of the available experimental platforms and skills in each partner laboratory is a pillar of those pre-existing successes and a reasonable and solid foundation for the present proposal (For the detailed description of the pre-existing work, see Section 2). From the previous intensive research on EPM conducted separately by the two groups of teams, they recognized their common interest in further developing the new field of the processing of materials under DC magnetic fields, its multi-disciplinary nature and their scientific complementary capacities in this domain. Moreover, the multi-disciplinary characteristics of the present proposal requires the cooperation of the two teams. The valuable and successful cooperation experience of the two teams in research work on electromagnetic processing of materials (EPM) in different states of materials offers a sound basis for this enlarged research on EPM. The complementary scientific competences and the appropriate materials preparation and analysis equipment and devices guarantees the level and quality of the implementation of the project. The present project will allow the partners to consolidate and develop basis knowledge (control, enhancement and consequence of thermoelectric and/or diffusion effects) and forward new and promising applications (optimization of solidification and texturing of polycrystalline magnetic shape memory alloys).