(上海大学 材料科学与工程学院,上海 200072)
摘 要: 研究了Al-18%Si合金在10 T梯度强磁场下加热至半固态和全熔态后的凝固过程,观察了初生硅的分布和形态, 测定了其冷却曲线。 结果表明: 在磁场的磁感应强度和磁场梯度的乘积Bz·dBz/dz为正时,初生硅向上部聚集; 而在Bz·dBz/dz为负时,初生硅向下部聚集; 在强磁场下, 加热至全熔态冷却下来的凝固组织中初晶硅的形态发生了明显的改变, 由板片状转变为块状, 初晶硅显著细化。 对强磁场细化初晶硅的机制进行了探讨。
关键字: 梯度磁场; Al-18%Si合金; 磁场力; 凝固
( School of Materials Science and Engineering,
Shanghai University, Shanghai 200072, China)
Abstract: The solidification of Al-18%Si alloys heated to the mushy zone or completely melt in a gradient high magnetic field was investigated experimentally. The cooling curves during the solidification were measured, and the morphology of the primary Si was examined. It is shown that the primary silicon grains tend to segregate on the upper portion of the samples with the positive Bz·dBz/dz; while the primary silicon grains tend to gather on the bottom of the samples with the negative Bz·dBz/dz. With the gradient high magnetic field, the silicon grains gathered on the upper portion of the sample are small equiaxed grains, and those on the bottom of the sample are coarse flake, the same for the grains in the case of no magnetic field. These phenomena were discussed according to the magnetization of silicon in a high gradient magnetic field.
Key words: gradient magnetic field; Al-18%Si alloy; magnetic force; solidification