ANALYSIS OF THE ALMGSI-ALLOY STRUCTURE FORMED UNDER THE INFLUENCE OF LOW-FREQUENCY PULSED LORENTZ FORCE

The paper studies the influence of Al-alloy melt motion forced by a pulsed electromagnetic force on the solidification process. In order to estimate the influence, the final structure of solidified samples was considered. The investigation was performed experimentally in a cylindrical vessel. To generate electromagnetic force pulses with frequencies ranging 0.1 to 10 Hz, the generation of alternating magnetic field was interrupted. For comparison, the influence of two other regimes was considered: the crystallization process under natural convection and under a steadily applied alternating magnetic field. Variation of the average grain size along the ingots radius and axis was compared for all regimes. Under buoyancy, the effect of more homogeneous distribution of grains as well as their refinement was observed for the regimes of permanent stirring and EM force pulses with frequencies below 1 Hz. The effect decreases with increase pulsed frequency and for 5 and 10 Hz it only slightly differs from the influence of the uninterrupted field. With 0.2 Hz, the average grain diameter reduces by 36% with regard to the structure occurred under buoyancy. The factors causing this effect are discussed in the article.