( 1. 中国科学院 电工研究所， 北京 100080；
2. 上海大学 材料科学与工程学院， 上海 200072)
摘 要: 在Bi-6%Mn合金从高于355℃(升温过程中MnBi化合物磁性转变温度)的固液两相区凝固过程中， 研究了MnBi析出相组织在无磁场和强磁场条件下的演化过程。 结果表明： 在无磁场条件下MnBi析出相形态在340℃（MnBi相顺磁-铁磁转变温度）附近发生突变， 由较规则的六方块状变为沿ab面长大的不规则片状； 10T磁场条件下析出相形态突变的温度提高到355℃左右。另外， 10T磁场能够控制析出相晶粒以c轴平行磁场取向、 定向聚合和熔合长大，使析出相的最终形态又趋向较规则的六方块状。
关键字: 强磁场； 金属凝固； 晶体生长； Bi-Mn合金； 磁性相变
precipitated phase in Bi-Mn alloy solidified from mushy zon
（ 1. Institute of E1ectrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Department of Materials Science and Engineering,
Shanghai University, Shanghai 200072, China）
Abstract: The structural evolution of the MnBi precipitated phase in Bi-6%Mn alloy was experimentally studied with or without a high magnetic field applied during the alloy solidified from the semi-solid zone above 355℃, the magnetic transition temperature of MnBi compound upon heating. In the absence of a magnetic field, it was found that the precipitated phase changed suddenly from a shape similar to its hexagonal single crystal to an irregular oblate shape formed by a rapid growth of the grains along their ab-planes at the temperature near 340℃, the magnetic transition temperature of MnBi compound upon cooling. In the present of a 10T magnetic field, the temperature at which the shape changed abruptly was increased to 355℃ or so. Furthermore, the MnBi grains were controlled by the 10T field to be oriented with their c-axes, directionally aggregated and grown up along the field so that the ultimate shape of the precipitated phase was tend to be regular again.
Key words: high magnetic field; metal solidification; crystal growth; Bi-Mn alloy; magnetic transformation
