Estimation of gamma and gamma ' phase compositions in typical regions of original dendrite structure of nickel-base single crystal superalloy CMSX-2

Formulae for partitioning ratio (R-i) and corresponding partitioning coefficients, (P-gamma)(i) and (P-gamma')(i), of alloying elements in superalloys are derived. Chemical compositions in typical dendritic regions (dendrite core, dendrite arm and interdendrite) of as-heat treated, undeformed and creep-rupture samples of CMSX-2 are measured with the aid of EDAX method. Atomic fractions of gamma and gamma' phases in the typical dendritic regions are calculated with the partitioning coefficient method. The characteristic compositions of alloying element partitioning in the gamma and gamma' phases of the regions and their relations to the rupture lives of the samples investigated are analyzed.