横向磁场下二元合金Cz法定向凝固过程中热电磁对流对凝固组织的影响
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- 英文论文题名：Effect of thermoelectric magnetic convection on solidification structure of binary alloy during directional solidification by the Czochralski method under a transverse magnetic field
- 论文作者：沈喆 ; 钟云波 ; 董立城 ; 王怀 ; 任维丽 ; 雷作胜 ; 王江 ; 任忠鸣
- 英文论文作者：SHEN Zhe ; DONG Lichen ; WANG Huai ; ZHONG Yunbo
- 年：2016
- 作者机构：上海大学省部共建品质特殊钢冶金与制备国家重点实验室;
- 论文关键词：横向磁场 ; 热电磁流 ; Cz法 ; 二元合金
- 英文论文关键词：Transverse magnetic field ; Thermoelectric magnetic flows ; Czochralski method ; Binary alloy
- 会议召开时间：2016-08-15
- 会议录名称：第三届全国电磁冶金与强磁场材料科学会议学术论文集
- 语种：中文
- 分类号：TG291
- 学会代码：ZGJS
- 会议名称：第三届全国电磁冶金与强磁场材料科学会议
- 会议地点：中国河南焦作
- 主办单位：中国金属学会电磁冶金与强磁场材料科学分会
- 学会名称：中国金属学会
- 页数：9
- 文件大小：5528k
- 原文格式：O
- 会议级别：全国
摘要
本文主要研究横向磁场对Cz法定向凝固纯Sn、Sn-15wt%Pb和Sn-13wt%Bi合金试样外形、凝固组织和成分偏析等的影响,实验结果显示:当磁场强度≤0.3 T时,试样外形、凝固组织与溶质成分都未发生明显变化;但当磁场强度≥0.5 T时,试样垂直于磁场方向一侧发生明显弯曲,且另一侧表面呈现"枝晶"状形貌。当改变外加磁场方向,试样弯曲方向与出现"枝晶"状表面位置也随之改变。从凝固组织分析可以看出,"枝晶"状表面内部凝固组织出现大量非柱状晶,且该区域内溶质发生富集。理论分析认为:这主要是由于磁场下定向凝固过程中固液界面处产生的热电磁流动定向运输溶质,并使溶质在试样一侧偏聚,从而抑制该侧枝晶的生长。数值模拟分析结果显示,当磁场强度≤0.43 T时,坩埚中对流由自然对流占主导,并不会发生溶质的单向传输;而当磁场强度>0.43 T时,坩埚中对流由单向的热电磁流主导,单向运输的溶质会富集于试样一侧,形成偏析,这与实验结果保持一致。
The pure Sn,Sn-15 wt.%Pb and Sn-15 wt.%Pb alloys were directional solidified by Czochralski method under various magnetic flux densities in this paper.The influence of thermoelectric magnetic flows and buoyancy flows on solidification morphology and microstructures had been investigated experimentally,and the velocity magnitude of thermoelectric magnetic flows and buoyancy flows had been studied by 3D numerical simulations.The experimental results indicate that the solidification morphology and microstructures do not change under a weak transverse magnetic field(B≤ 0.3 T),and with the increase of magnetic flux density,the sample bends to one side(perpendicular to the direction of magnetic field),and the surface of the sample at other side(perpendicular to the direction of magnetic field)shows dendrite-like.The solidification structure shows that the columnar dendrite transfers into equiaxed dendrite and the Pb solutes segregate at the right side of the sample.When the external magnetic field direction turns to the opposite,the sample bends to the opposite side and the segregation also occurs on the opposite side of the sample.Thus,it is reasonable that the modification of solidification morphology and microstructures is attributed to the unidirectional Pb solutes transport caused by thermoelectric magnetic flows.The 3D numerical simulations results show that the buoyancy flows dominate the flows in the melt under a weak transverse magnetic field(B ≤0.43 T),and then the unidirectional TEM flows at the vicinity of solid-liquid interface become the dominant flows in the melt with the increase of magnetic field.The interaction of TEM flows and buoyancy flows affecting solidification morphology and microstructures during directional solidification of alloys by Czochralski method under various magnetic flux densities has been discussed and a corresponding simple evolution mechanism of dendritic growth has been proposed.
The pure Sn,Sn-15 wt.%Pb and Sn-15 wt.%Pb alloys were directional solidified by Czochralski method under various magnetic flux densities in this paper.The influence of thermoelectric magnetic flows and buoyancy flows on solidification morphology and microstructures had been investigated experimentally,and the velocity magnitude of thermoelectric magnetic flows and buoyancy flows had been studied by 3D numerical simulations.The experimental results indicate that the solidification morphology and microstructures do not change under a weak transverse magnetic field(B≤ 0.3 T),and with the increase of magnetic flux density,the sample bends to one side(perpendicular to the direction of magnetic field),and the surface of the sample at other side(perpendicular to the direction of magnetic field)shows dendrite-like.The solidification structure shows that the columnar dendrite transfers into equiaxed dendrite and the Pb solutes segregate at the right side of the sample.When the external magnetic field direction turns to the opposite,the sample bends to the opposite side and the segregation also occurs on the opposite side of the sample.Thus,it is reasonable that the modification of solidification morphology and microstructures is attributed to the unidirectional Pb solutes transport caused by thermoelectric magnetic flows.The 3D numerical simulations results show that the buoyancy flows dominate the flows in the melt under a weak transverse magnetic field(B ≤0.43 T),and then the unidirectional TEM flows at the vicinity of solid-liquid interface become the dominant flows in the melt with the increase of magnetic field.The interaction of TEM flows and buoyancy flows affecting solidification morphology and microstructures during directional solidification of alloys by Czochralski method under various magnetic flux densities has been discussed and a corresponding simple evolution mechanism of dendritic growth has been proposed.
引文
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