Phase Diagrams

· Between the melting points of the two constituents, the alloy exists as two distinct phases for certain composition ranges.

· The total Gibbs function can be minimized by this phase separation, and lies on the common tangent to the liquid and solid G(X) curves. Phases with the compositions G_S and G_L have the same chemical potential
μ_S = μ_L

· In the two phase zone, the Gibbs function, G₀,associated with a mean alloy composition, C₀,that lies between C_S and C_L is given by:
G₀ = G_S +{(C₀ - C_S )/(C_L - C_S )}[G_L - G_S ]