Nonequilibrium Solidification and Chemical Heterogeneities

The partition coefficient is used as a mathematical tool to analyze chemical heterogeneities to produce concentration curves of cooling phenomena, which can be used to understand solidification of liquid metals (Scheil equation) contained in molds with different heat transport capacity, resulting in segregation of the normal, inverse, and gravity types. The relationship between undercooling and columnar structure is presented with steel ingots as examples. Furthermore, segregation produced by gas, crystal forming, or cracks is described. The effect of microsegregation (microshrinkages) and its possible elimination by homogenization heat treatments is examined. The effect of nonequilibrium conditions on phase reactions such as eutectic and peritectic ones, is indicated using an Al-Cu alloy to distinguish zones with considerable chemical segregation during dendrite growth, which can also be observed in Al-Mg or Cu-Sn systems where this type of equilibrium can result in partition coefficient modification.