| Tremendous magnetization energy can be inputted into a material without any contact when the material is placed in a high magnetic field. As a result, the thermodynamic state of the material is changed. At the same time, there are magnetic forces generated in the material. Therefore, the solidification and other phase transformations, the microstructure, shape and distribution of the crystals in the material may be influenced dramatically by the high magnetic field. It shows prosperous future in application and a new area about application of high magnetic fields in processing materials is opened for research.The solidification behaviors of the ferromagnetic MnBi precipitated phase in Bi-Mn alloys and the nonferromagnetic AlsNi precipitated phase in Al-Ni alloys under high magnetic fields up to 12T have been experimentally studied. The phenomena, behavior, and mechanism during the solidification, and the evolution of the precipitated phases structure have been examined intentionally and systematically, along with the theoretical analyses in terms of the magnetic anisotropy of the phases and their magnetic interactions to explain the experimental results. Moreover, the thermodynamics of solidification of pure metals in a high magnetic field has been studied primarily. Following are the main results:(1) The precipitated phases MnBi in Bi-Mn alloys and Al3Ni in Al-Ni alloys are all oriented with their c-axes parallel to the applied high magnetic field. The oriented MnBi crystals congregate and grow up along the field so that the alignment structure of the rod-like MnBi phase parallel to the applied field is generated. It is firstly found that the longitudinal axes of the AlsNi crystals are perpendicular to their c-axes and the laminated alignment structure perpendicular to the applied field is formed.(2) There are critical values of heating temperature in the semi-solid zone and magnetic intensity that the alignment structures of the precipitated phases in the alloys produced. Above the critical values the orientation factor increases gradually with the increase of the heating temperature and the magnetic intensity. The critical magneticintensity and heating temperature are increased with the increase of content of the solutes in the alloys.(3) It is a novel result that the transformation temperature of MnBi phase from the hexagonal crystals to flake crystals grown up along their ab-plane is raised from 340 C to 360 C by a 10.0T magnetic field during the solidification of Bi-Mn alloys from the semi-solid zone between 355 C and 446 C. Furthermore, the growth of the oriented MnBi crystals can be influenced greatly by the 10.0T field because the flake crystals of the MnBi phase are transformed to the hexag6nal crystals again during the following solidification.(4) When the alignment structure of the MnBi phase in Bi-Mn alloys has been formed in a magnetic field, the remanence increases about 1 time along the alignment direction compared with the samples solidified without a magnetic field. However, if the Bi-Mn alloys are solidified from the temperature above their liquidius temperatures or the semi-solid zone between 355 C and 446 C, the remanence decreases to one of tenth of the samples solidified from the semi-solid zone between 262 C and 355 C, no matter a magnetic field is applied or not.(5) After the MnBi crystals in the Bi-Mn alloys are magnetized and oriented in the applied field, the magnetization forces between the crystals play main role in the formation and the stability of the alignment structure in the alloys.(6) According to theoretical analyses, the ferromagnetic and paramagnetic crystals with magnetic anisotropy tend to turn their crystal axes with maximum susceptibility parallel to the direction of the magnetic field, and the diamagnetic crystals with magnetic anisotropy tend to turn the crystal axes with absolute maximum susceptibility perpendicular to the direction of the applied field. The magnetic interactions between the oriented crystals make the crystals aggreg...
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