Dispersion of fine primary inclusions of MgO and ZrO2 in Fe-10 mass Pct Nialloy and the solidification structure

The homogeneous dispersion of primary inclusions of MgO and ZrO2 was studie d in an Fe-10 mass pet Ni alloy as a function of the holding time at 1873 K and the cooling rate. The spatial size distribution was estimated from the planar size distribution obtained in a cross section by applying the Schwa rtz-Saltykov transformation. It was found that the content of insoluble Mg or Zr estimated from the size distribution agreed with that obtained from c hemical analysis. The influence on the solidification macrostructure such a s columnar dendrite, equiaxed dendrite, and globular crystal of dissolved M g or Zr and inclusion particles having the mean diameter of roughly 1 mu m was investigated. The area fraction of globular crystals in the Mg deoxidat ion decreased with increasing dissolved Mg content (>30 mass ppm) in the pr esence of MgO particles. In the Zr deoxidation, however, globular crystals were only observed in the presence of ZrO2 particles without respect to the presence of dissolved Zr.