Influence of the Magnetic Field on the Crystallization of Aluminum Melts

Resumo

In order to control the crystallization of metals consciously with the purpose of forming the specified ingot microstructure, various physical fields are used. They vary the internal state of the melt and, consequently, the crystallization kinetics when affecting the melt. In this article, the thermodynamic and kinetics of the crystallization of aluminum under melt processing with the magnetic field is described. A rather simple experimental setup which makes it possible to investigate the magnetic-field effect on the melts of aluminum or other metals and alloys is designed. It consists of several main units: (1) the electrical furnace, (2) the water-cooled copper crystallizer combined with an electromagnetic coil, (3) mechanical facility for the rapid motion of a crucible with the aluminum melt, (4) the monitoring and control system of the melt temperature, and (5) the electronic part for recording and processing information. It is established experimentally that the magnetic field varies the temperature of the melt–crystal phase equilibrium, latent heat of the phase transition, and supercooling temperature of the melt during crystallization. It is shown that the variation in these parameters leads to a decrease in the radius of critical nuclei and an increase in their nucleation rate. The temperature–temporal dependences of crystallization are found. It is established experimentally that the crystallization time shortens under the aluminum melt treatment with the magnetic field. The analysis of aluminum samples formed under the magnetic-field effect showed that their structure is finer grained when compared with the samples not subjected to such treatment.