Effect of ruthenium on tensile properties of a single crystal Ni-based superalloy

The tensile properties of two single crystal Ni-based superalloys with and without added Ru (0 and 3 wt%) were investigated under a constant strain rate of 3.3×10 −4 /s at 20 °C, 760 °C, 800 °C and 1000 °C, respectively. The deformation mechanisms could be divided into two temperature regimes. From room temperature to 800 °C, the deformation mechanism is caused by the shearing of γ′ particles by anti-phase boundaries (APB) or stacking faults. At 1000 °C, the deformation mechanism is caused by the bypassing of γ′ particles by dislocations. At 20 °C and 800 °C, γ′ particles were sheared by APB. Due to smaller γ′ particles, the yield strength was decreased with addition of 3 wt% Ru. Additionally, work hardening is less pronounced in the alloy without Ru, hence the ultimate tensile strength was not decreased with the addition of 3 wt% Ru. At 760 °C, γ′ particles were sheared by stacking faults. Since the formation of stacking faults was promoted, the yield strength was decreased due to a 3 wt% Ru addition. However, the ultimate tensile strength was significantly increased when 3 wt% Ru was added. This is due to the markedly stronger work hardening caused by large numbers of stacking faults. At 1000 °C, deformation occurred by dislocations bypassing γ′ particles. Due to wider γ channels, the yield strength was decreased by 3 wt% Ru addition. Moreover, Alloy 3Ru has smaller γ′ particles and a volume fraction as well as less pronounced work hardening, so the ultimate tensile strength was decreased when 3 wt% Ru was added.