(上海大學(xué) 材料科學(xué)與工程學(xué)院，上海 200072)
摘 要: 研究了Al-18%Si合金在10 T梯度強(qiáng)磁場(chǎng)下加熱至半固態(tài)和全熔態(tài)后的凝固過程，觀察了初生硅的分布和形態(tài)， 測(cè)定了其冷卻曲線。 結(jié)果表明： 在磁場(chǎng)的磁感應(yīng)強(qiáng)度和磁場(chǎng)梯度的乘積Bz·dBz/dz為正時(shí)，初生硅向上部聚集； 而在Bz·dBz/dz為負(fù)時(shí)，初生硅向下部聚集； 在強(qiáng)磁場(chǎng)下， 加熱至全熔態(tài)冷卻下來的凝固組織中初晶硅的形態(tài)發(fā)生了明顯的改變， 由板片狀轉(zhuǎn)變?yōu)閴K狀， 初晶硅顯著細(xì)化。 對(duì)強(qiáng)磁場(chǎng)細(xì)化初晶硅的機(jī)制進(jìn)行了探討。
關(guān)鍵字: 梯度磁場(chǎng); Al-18%Si合金; 磁場(chǎng)力; 凝固
LI Xi， LI Wei-xuan
（ 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
