Editing Eutectic system (section)

==Eutectic phase transition==
[[File:Various eutectic structures.png|thumb|Four eutectic structures: A) lamellar B) rod-like C) globular D) acicular.]]

The eutectic solidification is defined as follows:<ref name="smith327">{{harvnb|Smith|Hashemi|2006|p=327}}.</ref>

:<math>\text{Liquid} \quad \xrightarrow[\text{cooling}]{\text{eutectic} \atop \text{temperature}} \quad \alpha \text{ solid solution} \ + \ \beta \text{ solid solution}</math>

This type of reaction is an invariant reaction, because it is in [[thermal equilibrium]]; another way to define this is the change in [[Gibbs free energy]] equals zero. Tangibly, this means the liquid and two [[solid solution]]s all coexist at the same time and are in [[chemical equilibrium]]. There is also a [[thermal arrest]] for the duration of the [[phase transition|phase change]] during which the temperature of the system does not change.<ref name="smith327"/>

The resulting solid [[wikt:macrostructure|macrostructure]] from a eutectic reaction depends on a few factors, with the most important factor being how the two solid solutions nucleate and grow. The most common structure is a [[lamellar structure]], but other possible structures include rodlike, globular, and [[Acicular (crystal habit)|acicular]].<ref>{{harvnb|Smith|Hashemi|2006|pp=332–333}}.</ref>