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Alliages base Cobalt en surfusion sous champ magnétique intense : propriétés magnétiques et comportement à la solidification

Abstract : This work is devoted to the investigation of the magnetic field effect on the magnetic properties and solidification behavior of undercooled Co based alloys in high magnetic field. Co based alloys are promising candidates to be undercooled below or approaching their Curie point in strong magnetic field due to their small temperature difference between liquid line and Curie point. In this dissertation, a high temperature undercooling facility with magnetization measurement system is built in a superconducting magnet, and is used for in situ measurement of the magnetization of the undercooled melts and study the undercoolability and solidification microstructure evolution in magnetic field. The deep undercooled Co melt is strongly magnetized in magnetic fields, and its magnetization is even larger than the magnetization of heated solid at the same temperature. The magnetization of undercooled Co-B near eutectic alloy is related with overheating temperature while the undercooled Co-Sn melt is always in paramagnetic state. Mean undercooling and recalescence extent of different metals and alloys are affected by external field. In uniform magnetic field, the undercooling of Cu is enhanced while the undercoolings of Co and Co-Sn keep constant. However, the recalescence extents of Co and Co-Sn alloys are reduced, and with the increasing Co content, the effect becomes larger. Magnetic field promotes the precipitation of αCo dendrite phase and the formation of anomalous eutectics in solidified microstructure of undercooled Co-Sn alloys. The microstructure evolution processes are affected by magnetic field depending on the field intensity and undercooling. This work opens a new way to investigate the magnetic properties of deeply undercooled metallic melts and non-equilibrium solidification in strong magnetic fields.
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Jun Wang. Alliages base Cobalt en surfusion sous champ magnétique intense : propriétés magnétiques et comportement à la solidification. Autre [cond-mat.other]. Université de Grenoble; 216 Northwestern Polytechnic Univ, 2012. Français. ⟨NNT : 2012GRENY070⟩. ⟨tel-00870412⟩

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