Abstract
An important issue connected to the stability of solid–liquid interfaces is that unstable interfaces, which give rise to cast microstructures that are cellular or, ultimately, even dendritic, also remain the basic cause of chemical microsegregation. Microsegregation, a chemical separation and concentration of alloy elements or impurities on small scales, has the identical thermodynamic origin as does macrosegregation, discussed in Chapter 5. The essential differences between micro- and macrosegregation are the length scales over which these phenomena operate. As a general rule, microsegregation may be removed, or at least reduced significantly, by annealing a cast sample in the solid state. By contrast, macrosegregation cannot be influenced much by annealing in the solid state.
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Notes
- 1.
Note that the cellular microsegregation parameter, a, is inversely proportional to the product of the interface speed, v, times the alloy concentration, C 0. So for highly dilute alloys undergoing slow solidification rates this parameter could become large in magnitude; moreover, at sufficiently slow freezing speeds and low solute concentrations, however, the interface will re-establish marginal stability, so the interfacial cells would disappear and chemical microsegregation would cease.
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Glicksman, M.E. (2011). Microsegregation. In: Principles of Solidification. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-7344-3_14
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DOI: https://doi.org/10.1007/978-1-4419-7344-3_14
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