Estimation of phase density and γ′ amount distribution of creep-ruptured nickel-base single crystal superalloy CMSX-2

The density of γ and γ′ phases and the distribution of γ′ amount in the typical dendritic regions of creep-ruptured CMSX-2 were calculated. The result shows that the density of the two phases decreases and the γ′ phase amount increases in the dendritic core, arm and interdendrite regions in sequence. The density of γ and γ′ phases decreases successively in the three typical dendritic regions with the increase of the test temperature (accompanied by the decrease of the externally applied stress). At higher levels of temperature and relatively lower levels of external stress, the gradient of the distribution of γ′ amount in the three dendritic regions becomes steeper as compared to the case of medium high levels of temperature and relatively higher levels of external stress. The γ′ phase amounts partitioned in separate dendritic regions are correlated with the creep rupture life of the alloy samples in the two extreme situations. It is shown that the lowest amount of the γ′ phase is partitioned into the dendritic core region corresponded to the shortest rupture life of the alloy sample, and the opposite is true when the highest amount of the γ′ phase is partitioned into the dendritic core region of the alloy sample.