NUMERICAL-ANALYSIS OF REDISTRIBUTION OF C HROMIUM AND CARBON DURING SOLIDIFICATION OF PRIMARY AUSTENITE IN FE-CR-C ALLOY

The redistribution of chromium and carbon during solidification of pri mary austenite was evaluated for Fe-Cr-C alloys by a finite difference method. In the calculation, the diffusion of chromium and carbon were estimated in both solid and liquid phases. The equilibrium partition was assumed at the interface between solid and liquid, though the part ition coefficients of chromium and carbon varied depending on the allo y contents of liquid phase. EPMA analysis was also made on Fe-10.84%Cr -0.95%C and Fe-5.34%Cr-0.92%C alloy specimens solidified at a cooling rate, of 0. 167 K/s to reveal the chromium and carbon distribution in primary austenite. The comparison of experimental values with the calc ulated ones revealed the diffusion of chromium in austenite was very s low and resulted in the microsegregation, while carbon diffused comple tely and exhibited uniform distribution in austenite. The partition co efficient of chromium decreased gradually with the increase in the fra ction of solid, f(S), and that of carbon changed little until f(S) = 0 . 7 and then gradually decreased. These changes in partition coefficie nts remarkably influenced the redistribution of elements.