Gamma prime stability and its influence on tensile behavior of a wrought superalloy with different Fe contents

Gamma prime (gamma') stability and its influence on tensile behavior of a newly developed wrought superalloy with various Fe contents was studied both experimentally and thermodynamically. The results show that the gamma'-solvus temperature is higher and gamma-gamma' lattice mismatch is bigger in the alloy with the lower Fe content. During long-term thermal exposure at 650-750 degrees C, the coarsening behavior of gamma' precipitates follows Ostwald ripening kinetics and the lower Fe content can decrease the coarsening rate of gamma' precipitates due to the increase of the activation energy for gamma' coarsening. Moreover, the lower Fe content can retard the transformation from gamma' to eta phase. The tensile properties of the alloys with different Fe contents are almost same after standard heat treatment. However, after thermal exposure, the decrease of tensile strength in the alloy with lower Fe content is less than that of the alloys with higher Fe content due to the improvement of gamma' stability.