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Effet du champ magnétique sur la cristallographie et la microstructure à l'état brut de coulée d'alliages binaires à base d'aluminium

Abstract : In this work, the effects of magnetic field on the crystallography and microstructure of al alloys during solidification are systematically studied. Study on the primary Al3Fe and Al3Zr phases indicates that the faceted interface and twinning influence their morphology. For the Al3Fe, the low rate of the planes parallel to the extension direction result in the bar shape. The type I twinning causes the crystal to bend. For the Al3Zr, the different migration rates of the planes lead to the tabular shape and the compound twinning creates the dentrites. Twinning is achieved by shearing, reshuffling and atomic stacking fault. High magnetic field tends to eliminate the gravity segregation of the primary Al3Fe by the magnetic viscosity force. The magnetic torque induced by the magnetic anisotropy rotates the primary Al3Fe and Al3Zr and creates strong preferential crystallographic orientation in the field direction. The field also induces bifurcation and cracking of the Al3Fe through the thermoelectric magnetic force and the shrinkage coefficient difference between the Al3Fe and the matrix. Crystal detachment plus magnetization energy and solute diffusive suppression enhances the nucleation of the primary Al3Fe. During semi-continuous casting, the low DC magnetic field transfers the equiaxed and columnar grains in Al-Zn to twinned feathery ones, and the columnar grains in Al-Fe to twinned lamellas by modifying the solidification condition at the liquid/solid front, resulting in the formation of strong crystallographic texture and CSL [sigma]3 boundaries. The present work contributes to the enrichment of the theory of electromagnetic processing of materials
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https://hal.univ-lorraine.fr/tel-01749048
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Lei Li. Effet du champ magnétique sur la cristallographie et la microstructure à l'état brut de coulée d'alliages binaires à base d'aluminium. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2010. Français. ⟨NNT : 2011METZ015S⟩. ⟨tel-01749048⟩

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