Phase-field simulation of non-isothermal phase separation in rapidly quenched Co-Cu melts

Abstract

Analysis of phase separation under non-isothermal conditions in undercooled molten Co-Cu droplets has been performed theoretically. The calculated microstructure length scales agree with the Cahn-Hilliard (CH) and Langer-Bar-on-Miller (LBM) models, and experimental data. At moderate cooling rates Vc∼102-103 K/s, the wave length λm(t) of the fastest growing mode increases in time (∂λm/∂t>0) in exact correspondence with the isothermal LBM model. At high Vc∼104 K/s, λm slowly changes in time (∂λm/∂t∼0) in agreement with the non-isothermal CH model. At very high Vc∼105-108 K/s, initial decrease of λm (∂λm/∂t<0) is first predicted. Then λm achieves its maximum value in time (∂λm/∂t=0) and starts to increase (∂λm/∂t>0) at the later stage. The revealed effect is examined and theoretically explained.