Development of the functional structures by the solidification under a magnetic field

本项目旨在通过磁场下的凝固和晶体生长来开发功能结构。(1)通过熔化和/或粗化快速凝固产生的非平衡结构，获得了晶体取向相互排列的织构结构。在解释粗化过程中织构形成的模型中，考虑了包括曲率效应和磁效应在内的热力学和扩散动力学。也就是说，粗化是曲率效应和磁效应竞争的结果。该模型预测的织构结构的形成与BiMn系的实验结果相吻合。该模型还解释了顺磁和反磁材料在烧结过程中取向增加的原因。(3)结合棒结构是在磁场作用下定向凝固形成的。例如，在高于4T的磁场下，获得了Al-In合金中的棒状定向结构。(4)发展了交变磁场和静磁场相结合的悬浮技术。利用该技术，研究了凝固过程中对流作用对等轴组织的形成以及织构组织形成的影响。

This project aims to develop the functional structures though the solidification and the crystal growth under a magnetic field.(1) The texture structure, in which the crystallographic orientation of the grains are aligned each other, was achieved by melting and / or coarsening the nonequilibrium structure produced by the rapid solidification. The initial structure before processing under a magnetic field is a dominant factor for the texture structure.(2) In the model that explains the formation of the textured structure during the coarsening, the thermodynamics, including the curvature effect and the magnetic effect, and the kinetics by the diffusion are included. Namely, the coarsening occurs as a result of competition between the curvature effect and the magnetic effect. The formation of the textured structure predicted by the model agreed with the experimental results for the Bi-Mn system. The increase in the alignment during the sintering for the paramagnetic and the diamagnetic materials was also explained by the model.(3) The ligned rod structure was evolved by the unidirectional solidification under a magnetic field. For example, the rod aligned structure was obtained in the Al-In alloys under a magnetic field exceeding 4T.(4) The levitation technique using the alternating and the static magnetic fields was also developed. By using the technique, the formation of the equiaxed structure, which is favorable for the textured structure formation, was examined as a function of the convection during the solidification.