Kinetics of creep damage accumulation induced by a room-temperature plastic deformation introduced during processing of AM1 Ni-based single crystal superalloy

During the manufacturing process of Ni-based single crystal superalloy components, unexpected plastic deformation can be introduced in the material at different stages. A room-temperature plastic deformation was introduced to AM1 superalloy in between solution and aging heat treatments to mimic one case of unintentional plastic deformation. Our previous study revealed that the prior plastic deformation causes faster precipitation coarsening in the vicinity of the slip bands and decreases creep life, especially at temperatures above 950 degrees C. In this study, microstructures of creep ruptured and creep interrupted specimens were further analyzed to understand the origin of the early creep failure induced by plastic deformation. The results show that the plastic deformation enhances the nucleation and growth of deformation-pores during aging treatments. During creep deformation, the microstructure coarsened bands act as creep damage accumulating path for further void growth. Local stress concentration around coarsened voids activates recrystallization at the very last stage of the creep failure.