Correlation Between Radial Growth Rate of Cylindrical Solid and Time in Melt

The radial growth of δ-phase in Fe-0.15%C-0.8% Mn steel during solidification was in-situ observed under a high-temperature confocal scanning laser microscope (HTCSLM). The correlation between radial growth rate of cylindrical solid and time in melt was investigated, and the expression was deduced. The results indicate that the radius of cellular δ-phase rapidly enlarges at the beginning, and then the enlargement amplitude gradually declines. The variation of radial growth rate vs time is the same for each cellular δ-phase, and the radial growth rate of δ-phase rapidly declines to about 1.5 μm/s within 10 s at a cooling rate of 2.7 K/min, after that the growth rate slowly falls. The experimental data of the radial growth rate of cellular δ-phase are consistent with the calculation results for Fe-0.15%C-0.8% Mn steel.