Recalescence and Segregation Phenomena During Equiaxed Dendritic Solidification of Fe-C Alloy
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Recalescence and Segregation Phenomena During Equiaxed Dendritic Solidification of Fe-C Alloy WEILING WANG, SHIWEI YIN, SEN LUO, and MIAOYONG ZHU Recalescence and segregation are two characteristic phenomena for the equiaxed dendritic solidification of alloys. The present work developed a two-dimensional dendritic model with cellular automaton (CA) method to investigate influence mechanisms of thermal conditions on recalescence and segregation behaviors of Fe-0.82wt pct C alloy. The released latent heat reduces the undercooling around the equiaxed dendrite, and thus eases its growth velocity. The predicted steady growth velocity agrees well with the analytical results as the melt undercooling is 9 K. Additionally, the present CA model can ensure the growth consistence of equiaxed dendrites in the undercooled melt. With improving the convective heat transfer coefficients applied around the domain boundaries, the temperature recalescence in the domain center becomes more significant, and the corresponding solid fractions enhance. It is because that the stronger cooling promotes the solidification, resulting in more latent heat released. Accordingly, the heat dissipation can be neutralized. Moreover, a deeper undercooling for the temperature recalescence is needed under a stronger cooling condition. With the increase of both the cooling rate and the convection coefficient, secondary arms of the equiaxed dendrite become more developed. At the lower cooling rate range, the segregation ratio in the domain enlarges with the improvement of the cooling rate. However, it gets weaker under the condition with super cooling intensity due to the expansion of the low concentration region. As the convection coefficient is enhanced, the solute segregation in the domain gets less pronounced. https://doi.org/10.1007/s11663-019-01582-4 Ó The Minerals, Metals & Materials Society and ASM International 2019
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INTRODUCTION
AS the main solidification structure of continuously cast strand, the dendrite contributes much to the formation of solidification defects such as inclusions, cracks, and segregation, which are unfavorable to the yield and the performance of steel products.[1–3] Compared with the columnar structure, the equiaxed dendrite is more favored for a majority of steel grades, because it avoids the preferential push of the enriched solute to the strand center leading to a more homogenous distribution of the solute. The equiaxed dendrite prefers to grow in the undercooled melt and can move with the melt, which changes the solute distribution at the macroscopic scale. At the microscopic scale, the release of the latent heat and the solute at the solidification interface alters the undercooling and solute distributions around the equiaxed
WEILING WANG, SHIWEI YIN, SEN LUO, and MIAOYONG ZHU are with the School of Metallurgy, Northeastern University, Shenyang 110819, China and also with the Key Laboratory for Ecological Metallurgy of Multimetallic Ores (Ministry of Education), Northeastern University, Shenyang 110819, China. Contact e-mails:
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