Unidirectional solidiˆcation experiments of TbFe2 and Tb0.3Dy0.7Fe2 (Terfenol-D) alloy using a static magnetic field in microgravity were performed in the JapanMicrogravity Center ( JAMIC). In case of TbFe2, a  crystallographic alignment dominated for magnetic and cooling direction and the maximum magnetostriction constant increased from 1000 ppm to 4000 ppm when the magnetic field strength was increased from 0 T to 4.5×10－2 T during unidirectional solidification in the microgravity. For unidirectional solidiˆcation of TbFe2 in the normal gravity, the maximum magnetostriction constant was at 2000 ppm with increasing of magnetic field. In case of Tb0.3Dy0.7Fe2, a  crystallographic alignment of the grains dominated for magnetic and cooling direction, and the maximum magnetostriction increased from 500 ppm to 2000 ppm when the magnetic field strength was increased from 0 T to 3.7×10－2 T during unidirectional solidiˆcation in the microgravity. The magnetostriction of Tb0.3Dy0.7Fe2 solidified in the magnetic field above 3.7×10－2 T decreased to 1000 ppm, because the cracks were formed perpendicularly along the cooling direction. For unidirectional solidification of Tb0.3Dy0.7Fe2 in normal gravity, the maximum magnetostriction was at 1000 ppm in the magnetic field of 3.7×10－2 T.
We conducted experiments for the solidiˆcation of a giant magnetostrictive TbFe2 alloys under a micro gravity condition using the JAMIC facility, Hokkaido, Japan. The kinetic process of the solidiˆcation of an intermetallic compound TbFe2 (C15 Laves phase) formed through a peritectic transformation was investigated. Attention was made with respect to dropping condition of a drop apparatus, and to melting and cooling manners of the alloy sample using a Cu-chill. The relation between the experimental conditions and microstructure of the samples was investigated. In the experiments from 1999 to 2001, we improved the dropping system to obtain a concrete picture of the kinetic process of solidification during under a microgravity. In addition, we measured temperature profiles of a sample during solidiˆcation process using thermocouples in order to search for an optimized experimental conditions such as drop timing and a manner of touching of the chill with a sample to cooling down in order to start of solidification accompanied by a peritectic transformation. In the microgravity condition, we were able to obtain microstructures containing high amounts of the TbFe2 phase compared with those obtained under the normal condition on the ground.
The Laves phase that consists of Fe and rear earth elements, is known as the alloy showing high magneto-striction. In particular, the alloys with Nd and Pr have been theoretically predicted to show the highest amount of magneto-striction. The Laves phase, however, has never been formed in equilibrium because of the incompatibility of atomic sizes in the rear earth element and Fe. In the present experiment, it was succeeded to form directly high amount of Laves phases from the undercooled melts of the materials where the some amounts of Nd and Pr were substituted respectively to Dy and Tb using the technique of containerless processing combined with splat quenching. It can be concluded that the technique, containerless processing combined with splat quenching, is a well-applicable method for forming a meta-stable phase as well as a peritectic phase.
Splat solidification experiments in microgravity were performed for Nd-Fe-B permanent magnet materials to produce high performance magnet. (BH)max of 58.3 kJ/m3 was obtained on the composition of Nd2Fe10.8B sample by splat solidification in 13.6 m drop tube facility.
Containerless solidification of the wide area Nd2Fe14B primary phase composition samples were carried out using a melt-droplet melting and solidification apparatus. The undercooling solidification, nucleation behavior of Nd2Fe14B phase crystallization and mono-variant eutectic reaction for boundary phase formation were measured by a high-speed type optical temperature system. Consequently, homogeneous and fine particle microstructure formation of main phase in Nd-Fe-B magnetic materials and c axis orientation of Nd2Fe14B phase were obtained in Nd20Fe72B8 undercooled dropt-like sample by the effect of the Cu chill cooling and high temperature compression. The above result thinks an extremely effective new process for the magnetic anisotropy improvement of NdFeB system permanent magnet material.
Experiments were carried out to create anisotropic Sm-Fe system nitriding compounds with TbCu7-type structure. Sm10Fe90 and Sm10(Fe0.95Co0.05)89.4W0.3Cu0.3 compounds were prepared by the splat-cooling and unidirectionally solidiˆcation in microgravity, and some of them were annealed in high purity Ar atmosphere at 675°C for 60min and nitrogenated in high purity N2 atmosphere at 420°C for 15 hours. Magnetic and the physical properties of these sampleswere investigated. From these results, samples prepared by the splat-cooling and the unidirectionally solidfication methods in microgravity were obtained the anisotropic ones, and nitriding samples were the anisotropic nitriding compounds. From torpue curve of Sm10(Fe0.95Co0.05)89.4W0.3Cu0.3 oriented particles measured at 27 kOe, torque (L) was (3.8 sin2 u＋0.4 sin4 u＋0.1 sin6 u)×10－6 [erg/cm3]. It was found that sample was almost uniaxial magnetic anisotropy and uniaxial magnetic anisotropy constant (KA) was KA＝6.0×106 [erg/cm3].
Marangoni convection, driven by an interfacial instability due to a surface tension gradient, presents a significant
problem in crystal growth. It is important to suppress and control the convection phenomenon for better material processing, especially in crystal growth by the Liquid Encapsulated Czochralski or Liquid Encapsulated Floating Zone techniques, in which the melt is encapsulated in an immiscible medium. Marangoni convection can occur both on the liquid-liquid interface and on the gas-liquid free surface. Buoyancy driven convection can also affect and complicate the ‰ow. In the present study, experiments were carried out with two liquid layers, silicone oil and fluorinert, in open and enclosed rectangular cavities. The flow in the cavity was subjected to a horizontal temperature gradient. The interactive flow near the liquid-liquid interface was measured by the Particle Image Velocimetry (PIV) technique. The measured flow field is in agreement with numerical predictions.
Effect of high frequency magnetic fields on natural convection in the FZ (Floating Zone) silicon melt has been investigated numerically. The purpose of the study is to clarify the applicability of the high frequency magnetic field on the control of the melt natural convection induced by both the Marangoni and the buoyancy forces. The numerically obtained results reveal that the high frequency magnetic field can be used to control the melt natural convection; the melt convection intensity is decreased under the higher applied frequency with an adequate applied current density; the melt convection intensity is increased under the lower frequency and higher current density.
Nucleation is a fundamental process in materials processing. The well-known theory is the classical nucleation theory. The theory contains two fundamental approximations, that is, (1) the equilibrium distribution of nucleating clusters and (2) the treatment of small clusters as though they had bulk properties. The former approximation transforms a kinetic nature of nucleation into a thermodynamic one. The latter, often called capillarity approximation, oversimplifies the microscopic treatment of interfacial energy of nucleates. Recently, experimental studies on the nucleation of macro-molecular crystals, such as proteins and colloids showed the new aspects of nucleation dynamics that is different from the pictures predicted by the classical nucleation theory. The study on nucleation of those materials is promising from the viewpoint of industrial and scientific interests. The future microgravity experiments are suggested to overcome the fundamental approximations of the classical nucleation theory using the materials.