Kinetic modeling of phase selection during non-equilibrium solidification of a tungsten–carbon system Original Research Article

A dynamic computational model developed within the context of the classical theory of phase evolution was applied to the W–C system to simulate the kinetics of phase selection during non-equilibrium solidification at 50%-C between the thermodynamically stable WC and the metastable WC1−x and W2C. The kinetic variables used in the model are directly obtained from the free energy formulations that characterize the stable and metastable equilibria amongst participating phases. The isothermal kinetic analysis suggests that at low to moderate undercoolings, thermodynamic stability prevails, while at deep undercoolings (∼1000 K) the crystallization of W2C completes faster than the more thermodynamically stable WC1−x and almost as fast as WC. The non-isothermal kinetic analysis suggests that thermodynamic stability prevails under moderate to high cooling rates (e.g. 104−106 K/s), however under ultra-high cooling rates (e.g. 108 K/s), the crystallization of WC1−x and W2C completes at nearly the same undercooling as that of WC.