Numerical Study Of Crystal Orientation And Alignment In Al-Ni Alloy By Imposition Of A High Uniform Magnetic Field

The application of a high magnetic field on new materials has extended to almost all the material science fields by developing superconducting technologies in these days. The solidification morphologies and precipitating phases of alloys will be significantly changed during their solidification processes in high magnetic field due to the potential effects of magnetic field on the concentration field of the alloy, the melt around the alloy elements, the growth of the crystals, the lattice constant and the preferred orientation of the crystals, etc. The systematical study for the physics in high magnetic field is still in its elementary stage. From the viewpoint of microcosmos, the research on the effects of a high magnetic field on the solidification microstructures of alloys has many significant practical meanings to discover the physics of the high magnetic field on the solidification structure in order to control the precipitating phases and improve the properties of materials with the application of a high magnetic field during the process of solidification.This paper focuses on the analysis of the forces acting on a crystal grain and its movement under the high magnetic field. The characteristics of the crystal orientation and alignment a Al3Ni crystal grain in Al-Ni alloy melt under a high magnetic field are proposed after the simplifications from the existing experimental phenomena and analyses. Based on the rotational motion of an ellipsoid magnetic grain in the magnetic field, the models for rotational motion of a magnetic anisotropic crystal around a centroid or an endpoint of a certain axis are established. The orientating effects of the uniform magnetic field on an anisotropic crystal characterized by an anomaly of magnetic susceptibility along two mutually-perpendicular axes can be received in accordance with the theory of minimum energy of the system within the two-dimensional plane in the direction of the magnetic field. The length of time and the characteristic features of orientation with the change of magnetic field, the size of the crystal and the effective viscosity of the melt are discussed deeply. Further, the paper developed the magnetic dipole model and analyzed the coupling effects of two kinds of forces on the final states of the grains. The forces are the attractive interaction force between two neighboring grains and the force acting on the crystal grain under the magnetic field.