Solidification of Metallic Alloys under the Influence of Various Types of AC Magnetic Fields

摘要

The objective of the present paper is to study how the segregation characteristics in the mushy zone are influenced by laminar flows driven both by buoyancy and by AC magnetic fields of moderate intensity. A numerical model aimed at simulating the segregations during the columnar solidification of a binary alloy is used to investigate the effects of a forced convection. Various types of magnetic fields have been tested, namely travelling, rotating magnetic field and slowly modulated electromagnetic forcfes. The calculations have been achieved on two types of alloys, namely tin-lead and aluminium-silicon. It is shown that the flow configuration changes the segregation pattern. The change comes from the coupling between the liquid flow and the top of the mushy zone via the pressure distribution along the solidification front. The pressure difference along the front drives a mush flow which transports the solute in the mushy region. An other interesting type of travelling magnetic field has been tested. It consists of a slowly modulated travelling magnetic field. It is shown that in a certain range of values of the modulation period, the channels are almost suppressed.