Kinetic modeling of phase selection during non - equilibrium 48 solidification of a tungsten – carbon system

53 Abstract 54 A dynamic computational model developed within the context of the classical theory of phase evolution was applied 55 to the W–C system to simulate the kinetics of phase selection during non-equilibrium solidification at 50%-C between 56 the thermodynamically stable WC and the metastable WC1 x and W2C. The kinetic variables used in the model are 7 directly obtained from the free energy formulations that characterize the stable and metastable equilibria amongst 58 participating phases. The isothermal kinetic analysis suggests that at low to moderate undercoolings, thermodynamic 59 stability prevails, while at deep undercoolings ( 1000 K) the crystallization of W2C completes faster than the more 60 thermodynamically stable WC1 x and almost as fast as WC. The non-isothermal kinetic analysis suggests that thermo61 dynamic stability prevails under moderate to high cooling rates (e.g. 10 10 K/s), however under ultra-high cooling 62 rates (e.g. 10 K/s), the crystallization of WC1 x and W2C completes at nearly the same undercooling as that of WC. 63  2001 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.