Solidification of A356 Alloy in a Linear Electromagnetic Stirrer

Abstract

In the present work, a 2-pole linear electromagnetic stirrer (LEMS) is developed to study the effect of stirring during solidification of aluminium alloys. The stirrer design entails the placement of a stack of coils around the mold to generate a primary motion that recirculates along the longitudinal direction. The stirrer is first tested and validated by measuring the electromagnetic forces on solid aluminum cylinders of different diameters as a function of excitation current. The alloy to be stirred and solidified is placed in a cylindrical graphite mould located in the annulus of the LEMS. A suitable cooling arrangement is provided at the bottom of the mould to extract heat from the melt, in order to produce a rheocast billet inside the mould. Rheocasting experiments with A356 aluminium-silicon alloy are performed using a stirring current of 250A, in order to assess the effect of electromagnetic stirring on microstructure formation. The resulting microstructures and cooling curves with stirring are compared with those obtained without stirring.