High Magnetic Field Processing of Metal Alloys

Abstract

Recently, Direct Current (DC) magnetic field processing of materials has found widespread applications in metallurgy, especially in metals and semiconductor industries. The main goal is to control the behavior of melts during solidification so as to improve process performance and achieve better quality products. DC magnetic fields are effective in introducing some special magnetohydrodynamic effects, e.g., flow damping, which are commonly used in continuous casting of steels or crystal growth control. In parallel, the development of super conducting technology, which is able to produce high magnetic fields in a large space, has open many new possibilities in control of the processing of materials in solid and liquid state. The novelty comes from the creation of magnetization forces on non-magnetic or feeble magnetic materials due to high magnetic fields. Morerover, it has been realized quite recently that the thermo-electric phenomena under high DC magnetic field can produce strong electromagnetic forces in solid and liquid metals, leading to a phenomenon called Thermo-Electric-Magnetic Convection (TEMC). The forces are able to generate significant liquid motion especially when temperature gradients are present, and therefore strongly influence the solidification of metallic alloys. This chapter reviews the major progresses and applications related to the uses of strong/intense DC magnetic fields in processing of materials (mainly metallic alloys) in solidification processes. In the first section, we review the underlying principles in magnetohydrodynamics and magnetic effects. In the second section, we discuss the phenomena induced by DC magnetic fields in materials processing. We deal in particular with flow damping effects on liquid metals, and control of structure of materials during solidification, including texturing, phase separation and thermoelectric effect. Finally we give two examples of successful industrial applications.