IN THE MAR-M247 SYSTEM

Elemental segregation behavior was examined in the as-solidified microstructures of six directionally-solidified MAR-M247-derivative alloys with variations in the C, Hf, and Ta levels. Elemental segregation patterns were determined from elemental contour maps of dendritic cross-sections generated from electron microprobe data. Hf, Ta, Ti, and Al were found to segregate to the liquid, W and Co segregated to the solid, and MO, Cr, and Ni did not segregate consistently to one phase during solidification. Initial distribution coefficients were calculated as the ratio of dendrite core composition to bulk alloy composition. Average distribution coefficients were determined from constructed solid composition profiles as a function of fraction solidified using a Scheil-type analysis. The distribution coefficients did not vary between the six alloys for a given element; mean values of the average distribution coefficients were found to be 0.12 for Hf, 0.77 for Ta, 0.73 for Ti, 0.94 for Al, 1.23 for W, and 1.07 for Co.