Control of melt convection by a travelling magnetic field during the directional solidification of Al–Ni alloys

International audienceIn the field of the metallic alloy development, the main industrial goals are the control of the metallurgical structure and defects. Hydrodynamic movements in the liquid phase have a significant influence on properties of the solidified product. We focus our attention on two major effects influenced by forced convection induced by a travelling magnetic field: the macrosegregation and the grain structure for Al-3.5 wt% Ni alloys. We show that this configuration can control macrosegregations and that, moreover, the dendritic primary spacing maybe modified by varying the applied field. With regards to the grain structure, we exhibit the effect of the forced convection on the microstructure. For the equiaxed regimegrowth, the effect of the travelling magnetic field on the constitutional undercooling and on the refiner distribution induces an equiaxed to an elongated transition. This mechanism enhances the nucleation and the growth of equiaxed grains. In the case of non-refined alloys, a mode of elongated free grains is obtained most likely because of fragmentation