Control of Precipitating Phase Alignment and Crystal Orientation by Imposition of a High Magnetic Field

In general, materials have different magnetic susceptibilities depending on the crystal orientation and the magnetic field inside a material is different from the imposed magnetic field due to demagnetization depending on the susceptibility and the shape of materials. The utilization of this property will enable us not only to control the crystal orientation but also to align reinforced fibers in a composite material. In this paper, the theoretical expressions which determine the alignment of a precipitating phase and the crystal orientation under a magnetic field have been derived. It was found that the application of a magnetic field makes the primary dendrite arms of MnBi in a Bi-4 mass%Mn alloy align along the magnetic field, and the Al-7 mass%Si-5 mass%Fe intermetallic compound precipitated in a planar shape from an Al-11 mass%Si-2 mass%Fe molten alloy aligns in perpendicular to the magnetic field. It should be noticed that the magnetic field rotates graphite particles so that the magnetic field is perpendicular to the a- and b-planes and parallel to the c-plane. The derived theoretical expressions agree well with the experimental results.