Kinetics of initial phase separation and coarsening of nanoscale phase in Fe-Cr alloys

The initial phase separation and coarsening of the Cr-enriched α′ phase in Fe-Cr alloys were studied by utilizing phase field model. The phase separations of the α′ phase via non-classical nucleation and growth, the transition state from nucleation and growth to spinodal decomposition, and the spinodal decomposition were investigated at 700 K for the alloys containing 25, 28 and 35 at.% Cr. The time exponent of the average radius of α′ phase decreases from the growth and coarsening stage to the steady-state coarsening stage for the nucleation growth mechanism, the slope of number density of α′ phase increases at the steady-state coarsening stage with the increased Cr concentration. The velocity of phase separation in 25 at.% Cr alloy with a nucleation growth mechanism are slower than that in high Cr alloys with a spinodal decomposition mechanism. The results indicate that a low concentration alloy is more stable at high temperature, and the phase separation is fast at the early stage, which supply a reference for the alloy composition selection, and for the analysis of the relationship of property and morphology.