Effect of Microstructure on Solute Element Segregation during Solidification of Liquid Aluminum
Received:June 10, 2023   Revised:June 19, 2023   Accepted:June 21, 2023      Published Online:October 09, 2023
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DOI:doi:10.3969/j.issn.1007-7545.2023.11.011
KeyWord:segregation; high purity aluminum; microstructure; impurity element; solidification
                 
AuthorInstitution
QIN Yiming 广西产研院新型功能材料研究所有限公司
WU Zhenyu 广西产研院新型功能材料研究所有限公司
HUANG Kelin 广西产研院新型功能材料研究所有限公司、广西壮族自治区产业技术研究院
FENG Enlang 吉利百矿集团有限公司
LU Tairong 广西产研院新型功能材料研究所有限公司
LI Yongdi 广西新雅复合材料有限公司
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Abstract:
      Taking Fe, Si, Ga and Zn, whose solute element partition coefficient is less than 1, as the research object, the change of impurity element content during solidification of liquid aluminum under industrial test conditions and the corresponding microstructure (including grain morphology, size and intermetallic compounds) were analyzed. The contents of impurity elements and precipitated phase under Scheil-Gulliver cooling condition calculated by thermodynamic software Factsage were compared. It is found that the content of impurity elements in the solid phase of liquid aluminum is the lowest at the initial solidification stage, and all of them are greater than the theoretical calculated value. With the progress of solidification, the content of impurity elements gradually increases and the deviation from the theoretical value becomes larger and larger. The reasons for the above phenomena include: 1) The boundary layer effect exists in the actual solidification process of liquid aluminum, that is, the impurity elements discharged from the solid phase are not fully diffused into the liquid phase; 2) There is microscopic segregation in the actual solidification process of liquid aluminum, that is, Al-Fe-Si intermediate phase precipitates along the grain boundary. In addition, under the experimental conditions of this study, it is found that the solidification structure includes coarse columnar crystals, fine columnar crystals and equiaxed crystals. The coarse columnar crystals are more beneficial to promote the segregation and purification efficiency of some impurity elements, and the formation of coarse columnar crystals can be promoted by controlling and increasing the cooling intensity.
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