Orientation-Dependent Characteristics for Residual Grains during Hot Deformation of Nickel-Based Alloy 925

In the present work, the orientation characteristics of residual grains during hot deformation of an age-hardening Ni-Fe-Cr alloy (Alloy 925) at different conditions were systematically analyzed through high-resolution electron back-scatter diffraction. Based on the measurement of the kernel average misorientation, the density of geometrical necessary dislocations (GNDs) was further calculated. The orientation-dependent deformation mechanism of the residual grains was also discussed using Schmid factor difference ratio (SFDR) analysis. The results show that the deformed microstructure features typical “necklace” structures. Many distorted twin boundaries can be observed within the residual grains at 950 °C. When the deformation temperature increases to 1150 °C, the volume fraction of dynamic recrystallization (DRX) increases, leading to the extensive formation of primary Σ3 twin boundaries. Additionally, the GNDs are widely distributed in the residual grains, while they are rare for the recrystallized grains. The maximum GND density value can be obtained at the interface of “soft–hard” grains. The GND density also increases at higher strain rates, and the number of DRX grains significantly affects the distribution of the GND density. Moreover, based on the calculations and SFDR analysis, it can be summarized that the {100} and {111} grains are prone to deform in the uniserial slip mode and the multiple slip mode, respectively.