Optimization of liquid metal flow pattern generated by rotating magnetic field and the effect on solidification structure of wrought aluminium alloys

AC magnetic fields provide a contactless method to control the flow inside a liquid metal. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, melt convection may also produce segregation freckles on the macroscale. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification. Previous investigations considered the use of time-modulated AC magnetic fields to control the heat and mass transfer at the solidification front. It has been shown that an accurate tuning of the magnetic field parameters can avoid segregation effects. The present study examines the directional solidification of wrought aluminium alloys from a water-cooled copper chill. Rotating magnetic fields were used to agitate the melt.