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

本项目旨在通过磁场作用下的凝固和晶体生长来发展功能结构。(1)通过熔化和/或粗化快速凝固产生的非平衡组织，获得了晶粒的结晶取向相互排列的织构结构。磁场作用下加工前的初始结构是决定织构结构的主要因素。(2)在解释粗化过程中织构结构形成的模型中，包含了热力学，包括曲率效应和磁效应，以及扩散动力学。也就是说，粗化是曲率效应和磁效应相互竞争的结果。该模型预测的织构结构的形成与Bi-Mn体系的实验结果一致。该模型还解释了顺磁性和抗磁性材料在烧结过程中对中率的增加。(3)磁场作用下的定向凝固形成了棒状结构。例如，在超过4T的磁场下，Al-In合金中出现了棒状排列结构。(4)利用交变磁场和静磁场的悬浮技术也得到了发展。利用该技术，研究了有利于织构组织形成的等轴组织的形成与凝固过程中对流的关系。

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.