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A diffusion boundary layer model of microsegregation
Journal article   Peer reviewed

A diffusion boundary layer model of microsegregation

X TONG and C BECKERMANN
Journal of crystal growth, Vol.187(2), pp.289-302
1998
DOI: 10.1016/S0022-0248(97)00878-6

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Abstract

A microsegregation model, based on a boundary layer concept, is proposed for solidification of alloys. The model is derived by considering finite-rate solute diffusion both in the liquid and in the solid. A solutal Fourier number is used to characterize the extent of finite-rate solute diffusion in the liquid phase ahead of the moving solid/liquid interface. This new parameter is the liquid counterpart of the solutal Fourier number in the solid phase used before to characterize finite-rate back-diffusion in the solid. It can be obtained through the knowledge of either the local solidification time or the operating point of the cell/dendrite tip (among other parameters). The present microsegregation model covers the entire spectrum of solidification rates, up to the limit of a microsegregation free solid. The model predictions show good agreement with a previous rapid solidification experiment involving an Ag–Cu alloy. Also, a new relation is derived for the primary dendrite arm spacing.
Materials Science Applied Sciences Physics Metals. Metallurgy Exact sciences and technology Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation Methods of crystal growth; physics of crystal growth Growth from melts; zone melting and refining Cross-disciplinary physics: materials science; rheology

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