δ/δ Grain Boundary Movement in Fe-0. 2%C-0. 8%Cr During Solidification Process

The moving process of delta/delta grain boundary during the solidification process of Fe-0. 2%C-0. 8%Cr has been observed in-situ with confocal scanning laser microscope (CSLM), and the establishment of delta/delta grain boundary, the moving mode, the moving speed and the influence of correlative factor were explored in detail. The results showed that the clear grain cannot be formed when delta phase merged during solidification process of the steel if the actual cooling rate was 0. 045 degrees C. s(-1). The delta/delta grain boundary with shape of flat will be formed if there is no essential conjunction between delta phase in a long period of time. The movement of delta grain boundary cross point drives other delta/delta grain boundaries to move. The moving process is not stable, and the moving rate variation ranges from 0. 12 to 1. 65 mu m . s(-1). Temperature of the system is the chief factor for influencing the moving rate of delta/delta grain boundary during the solidification. When the temperature fluctuation of system appears, the solidified grain boundary is re-melted, which results in the catastrophic fluctuation of moving rate for delta/delta grain boundary. When the solidification process reaches its end, the average moving rate of delta/delta grain boundary is quicker than that of L/delta interface. The coarsening rate of crystal grain in the melt is slower than that of solidified solid phase crystal grain.