Grain-growth-inhibiting Effects of TiC and ZrC Precipitates in Fe–0.15~0.30mass%C Alloy

The crystallization and precipitation of TiC and ZrC in an Fe–0.05~0.30%C alloy have been studied from the measurement of particles located at interdendritic region and austenite grain boundaries. The particles and γ grains were observed with the samples quenched at 1673–1743 K and those for holding at 1673 K for 0–180 min. In an Fe–0.05~0.30%C–0.03%Ti alloy with soluble oxygen, the precipitation of Ti(O, C)x occurs at 0.15 and 0.30% C, while it does not at 0.05% C. The cross section area of particles increases with increasing carbon contents. In the case of TiC precipitation in an Fe–0.20%C–0.06~0.22%Ti alloy the particles at interdendritic region dissolve and re-precipitate at γ grain boundaries during holding at 1673 K for 0–120 min. The TiC particles at γ boundaries dissolve after 60 min, whereby resulting in the abnormal grain growth. In the case of ZrC precipitation in an Fe–0.20%C–0.02~0.27%Zr alloy, however, the ZrC particles at interdendritic region dissolve and continuously re-precipitate at γ grain boundaries up to 180 min, whereby resulting in the normal grain growth.