Ferrofluid flow due to a rotating disk in the presence of a non-uniform magnetic field

The flow of a ferrofluid due to a rotating disk in the presence of a non-uniform magnetic field in the axial direction is studied through mathematical modeling of the problem. Contour and surface plots in the presence of10kilo-ampere/meter,100kilo-ampere/meter magnetization force are presented here for radial, tangential and axial velocity profiles, and results are also drawn for the magnetic field intensity. These results are compared with the ordinary case where magnetization force is absent.

Research of the Morphology and Distribution of the Primary Silicon in Al-18Si Alloy under a Gradient High Magnetic Field

A gradient high magnetic field effected significantly the morphology and distribution of the primary silicon grains in Al-18Si alloy. Experimental studies shew that in the gradient high magnetic field the primary silicon phase grains, which are large plate-like or five-star-like in the case of solidification without magnetic field, are accumulated on the top of the specimen and refined remarkably with the morphology of polygonal or nodular shapes when the alloy solidifies from the semisolid state. In the segregated layer of the silicon, the distribution of the silicon grains is homogeneous. The size of the primary silicon grains decreases and the grain number density rises with the increase of the magnetic strength maintaining the magnetization force unchangeable. It seems that the high magnetic field influences the diffusion of silicon. Theoretical models have been proposed to explain the refining and the distribution of the silicon grains.

Effects of High Gradient Magnetic Fields on Solidified Structures of Non-Magnetic Metals with Different Susceptibilities

In the present study, the influencing factors such as the intensity and the direction of gradient magnetic fields, the magnetic susceptibilities of non-magnetic metals on the structures are studied theoretically and experimentally. In the theoretical analyses, the influences of high gradient magnetic fields on nucleation and structures are investigated. In the experimental research, high gradient magnetic fields are imposed on paramagnetic material Al and diamagnetic one Sn during their solidification processes. Then the macro- and microstructures of these samples are examined and the influences of magnetic susceptibilities of metals, the intensity and the direction of high magnetic fields are analyzed in details. It is found that solidified structures could be refined when the magnetization force and gravity were in the same directions, while the solidified structures could be coarsened and the coarse dendrites grew along the direction of the imposed magnetic fields when the directions of these two forces were opposite. Those phenomena could be explained from the views of reduced gravity and elevated gravity effects caused by magnetization force and the convection suppression effect caused by high magnetic fields. The results indicate that high magnetic fields can be applied to control the solidified structures of metals and then improve the quality and the properties of materials for different purposes.

Crystal Orientation in High Magnetic Field

A new technology relating to crystal orientation and structure alignment has emerged by the development of superconducting technologies. Now, a high magnetic field covering a rather large space is available even in small-scale laboratories. Under this circumstance it has been found that the crystal orientation in materials can be controlled by imposition of the high magnetic field. This principle due to a magnetization force can be applied not only to magnetic materials but also to non-magnetic materials with asymmetric unit cells. In this paper, three novel processes for the crystal orientation of ceramics and metals are described.