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Macrosegregation caused by thermosolutal convection during directional solidification of Pb-Sb alloys

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Abstract

Pb-2.2 and 5.8 wt pct Sb alloys were directionally solidified with a positive thermal gradient of 140 K cm−1 at growth speeds ranging from 0.8 to 30 µm s−1, and then quenched to retain the mushyzone morphology. Chemical analysis along the length of the directionally solidified portion and in the quenched melt ahead of the dendritic array showed extensive longitudinal macrosegregation. Cellular morphologies growing at smaller growth speeds are associated with larger amounts of macrosegregation as compared with the dendrities growing at higher growth speeds. Convection is caused, mainly, by the density inversion in the overlying melt ahead of the cellular/dendritic array because of the antimony enrichment at the array tip. Mixing of the interdendritic and bulk melt during directional solidification is responsible for the observed longitudinal macrosegregation.

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Author notes

  1. S. N. Ojha (Visiting Professor)

    Present address: the Chemical Engineering Department, Cleveland State University, 44115, Cleveland, OH

Authors and Affiliations

  1. Department of Metallurgical Engineering, Banaras Hindu University, 221-005, Varanasi, India

    S. N. Ojha (Visiting Professor)

  2. the Chemical Engineering Department, Cleveland State University, 44115, Cleveland, OH

    G. Ding (Research Associate), Y. Lu (Graduate Student), J. Reye (Undergraduate Student) & S. N. Tewari (Professor)

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  1. S. N. Ojha
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  2. G. Ding
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  3. Y. Lu
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  4. J. Reye
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  5. S. N. Tewari
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Ojha, S.N., Ding, G., Lu, Y. et al. Macrosegregation caused by thermosolutal convection during directional solidification of Pb-Sb alloys. Metall Mater Trans A 30, 2167–2171 (1999). https://doi.org/10.1007/s11661-999-0028-6

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  • DOI: https://doi.org/10.1007/s11661-999-0028-6

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