Ru element-induced recrystallization behavior in a fourth-generation Ni-based single crystal superalloy

The effect of 3 wt% Ru addition on the recrystallization behavior of a Ni-based single crystal superalloy was systematically investigated. The results revealed that Ru addition significantly promoted the microsegregation of Al and Ta elements into the interdendritic region during solidification, leading to an increased volume fraction of γ/γ′ eutectic from 6.67% in the Ru-free alloy to 9.5% in the 3Ru alloy. These enlarged eutectic regions, which exhibited lower deformation resistance than the dendrite cores, acted as preferential sites for strain concentration during indentation deformation, resulting in a larger deformation zone with higher dislocation density beneath the indentation in the 3Ru alloy. Upon subsequent heat treatment at 1315 °C, the recrystallization preferentially nucleated within these highly deformed γ/γ′ eutectic areas via the particle stimulated nucleation (PSN) mechanism. Consequently, the alloy with 3 wt% Ru additions exhibited a larger recrystallized area and coarser recrystallized grains compared to the Ru-free alloy. This work demonstrated that Ru addition promoted PSN-mediated recrystallization nucleation by increasing the γ/γ′ eutectic content at as-cast and enhancing deformation localization.