Variation of Alloying Element Distribution and Microstructure due to Microsegregation in Ni-base Superalloy GTD 111

Segregation during solidification and homogenization during thermal exposure in GTD 111 were investigated. The microstructures of as-cast, standard heat-treated, and thermally exposed specimens were observed by SEM. A compositional analysis of each specimen was conducted by EDS. The dendrite core was enriched in W and Co, though lower levels of Ti and Ta were observed. An unexpected phase, in this case like the phase, was observed due to segregation near the eutectic in the standard heat-treated specimen. Segregation also induced microstructural evolution near the eutectic during the standard heat treatment. A quantitative analysis and microstructural observations showed that the thermal exposure at a high temperature enhanced the chemical homogeneity of the alloy.