Microsegregation behavior of alloying elements in single-crystal nickel-based superalloys with emphasis on dendritic structure

Directionally solidified single crystal of CMSX-4 superalloy was investigated to show the evolution of microsegregation and the effect of crystal orientations on the solute distribution. As the solidification proceeded, Al, Ti, Ta and Mo consistently segregated to the residual liquid, while Co, W and Re segregated to the solidified γ dendrite core. Cr did not exhibit a consistent segregation tendency to either side. Increasing the solid volume fraction resulted in increasing segregation levels of Al, Ti, Ta, Co, W and Re, whereas the segregation levels of Cr and Mo did not consistently change. For most of the alloying elements, the solute profiles of the same element were similar along the [100] and the [110] crystal orientations. For Al, Ti and Ta, the solute contents increased from the dendrite core towards its periphery. Re, W, and Co showed the opposite trend. For Mo and Cr, uniform distribution profiles were shown along the [100] orientation with increasing distance from the γ dendrite core towards its periphery, while a large variation in the solute contents of both elements was observed along the [110] orientation. The solutes across a typical dendrite distributed more homogeneously along the [100] orientation than those along the [110] orientation.