( 中国科学院 电工研究所应用超导重点实验室，北京 100080)
摘 要: 在3种不同凝固条件下， 制备了Bi-Mn合金， 研究了合金中MnBi相织构组织随磁感应强度和凝固时间的演化。结果表明， 合金从265~355 ℃的固液两相区凝固时， 随1.0 T磁场中凝固时间的延长， 取向棒状MnBi晶粒沿磁场方向聚合长大，长径比增大约50％； 合金从355~446 ℃的固液两相区凝固时， 随外磁场强度的增大（最大达10.0 T）和凝固时间的增加，取向片状MnBi晶粒沿磁场方向聚合长大， 形成疏松不规则的粗大棒状晶粒； 合金从完全熔化状态凝固时， 以0.15 ℃/s的速度冷却可以获得MnBi相织构组织， 以0.015 ℃/s或更小的速度冷却则不能； 延长磁场中Bi-Mn合金的凝固时间不能有效提高材料的剩磁性能。
关键字: 金属凝固； 磁取向； 强磁场； Bi-Mn合金； MnBi相
（ CAS Laboratory of Applied Superconductivity, Institute of Electrical Engineering,
Chinese Academy of Sciences, Beijing 100080, China）
Abstract: Bi-Mn alloys were prepared under three different solidification conditions respectively. The microstructure evolutions of magnetic aligned MnBi grains were investigated experimentally in dependence on magnetic flux density and solidified time. The results show that, solidifying from mushy zone between 265 ℃ and 355 ℃ in an 1.0 T magnetic field, the aligned rod-like MnBi grains congregate and grow up along the direction of magnetic field with the increase of solidified time so that the mean ratio of long axis to diameter of the grains increases about 50%; solidifying from mushy zone between 355 ℃ and 446 ℃, the aligned oblate-shaped MnBi grains also congregate and grow up along the direction of magnetic field with the increase of magnetic flux density (up to 10.0 T) and solidified time, while several huge rod-like MnBi grains appear, which are irregular and loose; solidifying from molten state, the textured structure of MnBi phase can form at a cooling rate of 0.15 ℃/s, but can not at 0.015 ℃/s or slower. The remanence of Bi-Mn alloys can hardly be enhanced by prolongating solidified time in a magnetic field.
Key words: metal solidification; magnetic alignment; high static magnetic field; Bi-Mn alloy; MnBi phase
