Deformation twinning in a wrought Ni-base superalloy at intermediate temperatures

To further investigate the deformation twinning mechanism in wrought Ni-base superalloys under intermediate-temperature loading, we analyzed a turbine disk alloy by using aberration-corrected transmission electron microscopy (TEM). The twinning process occurs in two distinct stages: (1) stochastic nucleation of twin embryos occurs along 111 planes within isolated γ′ phases; (2) extensive propagation across multiple γ′ phases and γ channels, forming elongated, linear microtwins. Notably, Co enrichment at twin boundaries promotes twin formation by reducing the local stacking fault energy. After propagating through the γ/γ′ phase boundary (PB), these boundaries can trap partial dislocations, arresting further twin growth and reducing the twin thickness. These findings provide key insights into the intermediate-temperature deformation twinning behavior of wrought Ni-base superalloys. • Stochastic nucleation and extensive propagation are identified as two stages of intermediate-temperature twin formation. • γ/γ′ phase boundaries restrain the twin growth by trapping partial dislocations. • Co segregation at stacking faults and twins promotes deformation twinning by reducing stacking fault energy.