La formation des structures équiaxes : mouvement des grains, croissance-refusion, conséquences sur les macroségrégations

Abstract : In order to improve the predictions ofheterogeneitiesof composition observed on steel ingots at the end of solidification, a numerical study which takes into account the movement and the growth of equiaxed grains has been realized. After a bibliographic part related to the formation of the equiaxed grains, a diphasic approach has been adopted to describe the growth and the remelting of globular grains moving in the liquid bulk. This numerical study was implemented in the computer code SOLill. The movement of the grains has been described in a first part with the assumption that the grains move at the same speed than that of the liquid phase. The results obtained ." showed the influence of the movement and growth-remelting of the grains on solidification, especially in the evolution of the superheated zones. Then, we have taken into account the own movement of the grains which differs from that of the liquid phase. ln this case, a solid fraction of coherence beyond which grains are imposed to be fixed has been introduced. This study showed that the final macrosegregation is strongly dependent on this fraction of coherency and on the flux density of fragments. Finally, we have demonstrated that it was possible to adjust the input data of the model in order to get a good agreement between the numerical and the experimental results.
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Rabia Boubeker. La formation des structures équiaxes : mouvement des grains, croissance-refusion, conséquences sur les macroségrégations. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL063N⟩. ⟨tel-01749954⟩

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