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CHAPITRE II : MAGNETO-HYDRO-ENERGETIQUE

II.5. FACTEURS D’INFLUENCES

II.5.4. La décélération de la vitesse de refroidissement

La décélération de la vitesse de croissance induit une augmentation ponctuelle de la température et de la concentration dans la zone interdendritique. Ce phénomène induit alors la refusion thermique et solutale des bras de dendrite.

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II.6. CONCLUSION PARTIELLE

Ce chapitre a permis de présenter les équations de base de la Magnéto-Hydro-Energétique (MHE) qui seront employées par la suite. Les différents nombres adimensionnels utiles à la description et l’analyse des cas traités dans le cadre de ce travail ont été explicités. Seulement l’aspect énergétique de ces équations sous forme d’une énergie de brassage électromagnétique a été abordé, afin de l’adapter aux applications de la solidification des alliages métalliques. Une étude sur les différentes configurations utilisées pour le brassage électromagnétique et leurs influences sur les structures de solidification à été effectuée. Plusieurs techniques de brassage ont montré leur efficacité pour améliorer la structure finale voir le perfectionnement des propriétés physiques des matériaux, notamment la technique du RMF-PSAD (rotating

magnetic field with pulse sequence of alternating direction) sur la diminution des canaux

ségrégés, et la technique de couplage RMF-TMF ((rotating magnetic field-travelling

magnetic field) sur l’affinage de la structure, sans oublier l’effet des forces thermoélectriques

induites par des forts champs magnétiques à courant continu sur la favorisation du processus de transition colonnaires-equiaxes (CET).

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