材料期刊网

The kinetic details of the microstructure evolution during a liquid-liquid phase transformation under the common action of the nucleation, diffusional growth and Ostwald ripening of the minority phase droplets are investigated numerically. The results demonstrate that the cooling rate during the nucleation period of the minority phase droplets has an overwhelmingly strong effect on the microstructure formation compared with the cooling rate after the nucleation period. Generally, the effect of the Ostwald ripening of the minority phase droplets is weak in an alloy cooled continuously all through the miscibility gap and the average radius of the minority phase particles shows an inverse square root dependence on cooling rate. An obvious coarsening of the minority phase droplets occurs and the exponential varies towards -1/3 only when the cooling rate decreases by more than two orders of magnitude after the nucleation of the precipitated droplets.