Kinetics of phase separation in iron-based ternary alloys. II. Numerical simulation of phase separation in Fe-Cr-X(X = Mo, Cu) ternary alloys

Numerical simulations were performed using a model based on the Cahn-Hilliard equation in order to investigate asymptotic behavior of a minor element associated with phase decomposition of the major element in Fe-Cr-Mo and Fe-Cr-Cu ternary alloys. Bifurcation of peaks of Mo along peak tops of Cr concentration occurs in an Fe-40at.%Cr-5at.%Mo alloy at temperatures between 750 and 850 K. Bifurcation of peaks of Cr is also shown in an Fe-40at.%Mo-5at.%Cr alloy. The asymptotic behavior of Mo or Cr along a trajectory of a peak top of Cr or Mo concentration depends on the sign of the second derivative of the chemical free energy with respect to the concentrations of Cr and Mo. In an Fe-40at.%Cr-5at.%Cu alloy,the amplitude of Cu along peak tops of Cr concentration decreases with time, Simulated asymptotic behavior of Mo and Cr in Fe-Cr-Mo ternary alloys and Cu in an Fe-Cr-Cu alloy is in good agreement with that predicted by the theory proposed by the present authors.