(a) Consider the figure given below, where the miscibility gap is shown. Here, it is possible that we can obtain Spinodal decomposition. Let us say, I cool down from temperature T1, an alloy with composition (a) Xo and (b) Xo' to temperature T2. After cooling down, I stay at temperature T2 and observe the phase transformation of the alloy. Are the transformation mechanisms in (a) and (b) different? How are they different? Explain with simple plots of concentration map of the alloy in real space along a certain direction x to explain the evolution of the phase transformation in both the cases. Also, show suitable Gibbs free energy plots to establish your inferences about the transformation mechanism.  

T H T 0 (a) + a X, X 1 Xo XB Chemical spinodal X 1