强磁场作用下材料扩散型固态相变的微观机理

为探讨强磁场对物质原子尺度行为(电子运动、离子扩散)的影响,采用光学显微镜研究强磁场作用下Fe-0.12%C合金的扩散型固态相变;采用数字多用表测量强磁场作用下的纯铝板电阻研究其电子分布.结果表明:随磁感应强度增强,Fe-0.12%C合金室温显微组织中,铁素体晶粒平行于磁场方向伸长并呈链状排列的趋势增强,珠光体团的长轴方向平行于磁场方向伸长的程度也增强;纯铝板的电阻在平行于磁场方向放置时减小,垂直于磁场方向放置时电阻有增加趋势.这是由于组成金属晶体的自由电子和排列成晶格状的金属离子在磁场作用下受到洛伦兹力的作用,随磁感应强度增强,沿磁场方向的电子浓度、金属离子扩散有增强趋势,导致磁场作用下材料扩散型相变的室温组织出现形状各向异性.

Micromechanism of diffusion-controlled solid state phase transformation of material under high magnetic field

In order to study the effects of strong magnetic field on the atomic scale behaviors ( electronic motion and ion diffusion) of the matter, the diffusion-controlled solid phase transition of Fe-0. 12％C alloy under high magnetic field was investigated by optical microscope, and the resistance of pure aluminum plate under high magnetic field was measured by digital multimeter to investigate the electron distribution. The results show that the ferrite grains are elongated and the trend of chain arrangement is enhanced along the direction of magnetic field. The extent of elongation is also enhanced along long axis of the pearlite parallel to the magnetic field as the increase of the magnetic flux density. The resistance of aluminum sample decreases for the length direction parallel to the magnetic field direction, and increases for the length direction perpendicular to the magnetic field direction as the increase of the magnetic flux density, which can be attirbuted to the effect of the Lorenz force in the free electron and metal ions in the metal under high magnetic field. The electron concentration and the diffusion of metal ions in the materials parallel to the magnetic field direction becomes stronger with increasing the magnetic flux density, leading to shape anisotropy of the microstructure of diffusion-controlled phase transformation of the materials.