CONTROL OF PRECIPITATING PHASE ALIGNMENT AND CRYSTAL ORIENTATION BY IMPOSITION OF A HIGH MAGNETIC-FIELD

In general, materials have different magnetic susceptibilities dependi ng on the crystal orientation and the magnetic field inside a material is different from the imposed magnetic held due to demagnetization de pending on the susceptibility and the shape of materials. The utilizat ion of this property will enable us not only to control the crystal or ientation but also to align reinforced fibers in a composite material. In this paper, the theoretical expressions which determine the alignm ent of a precipitating phase and the crystal orientation under a magne tic field have been derived. It was found that the application of a ma gnetic field makes the primary dendrite arms of MnBi in a Bi-4 mass%Mn alloy align along the magnetic field, and the AI-7 mass%Si-5 mass%Fe intermetallic compound precipitated in a planar shape from an Al-ll ma ss%Si-2 mass%Fe molten alloy aligns in perpendicular to the magnetic f ield. It should be noticed that the magnetic field rotates graphite pa rticles so that the magnetic field is perpendicular to the a- and b-pl anes and parallel to the c-plane. The derived theoretical expressions agree well with the experimental results.