Effect of Ru on tensile behavior and deformation mechanism of a nickel-based single crystal superalloy

Abstract

The effects of Ru on the tensile properties and deformation mechanism of the two alloys were investigated in detail at room temperature, 760 °C and 1100 °C. The microstructures of the two alloys after the tensile deformation were obtained via the TEM. Based on the microstructures, the increase of Ru further reduced the stacking faults energy at room temperature and 760 °C, which promoted the formation of stacking faults in the γ matrix and γ' phase. These stacking faults were seldom observed in the previous works. On the other hand, the slipping of dislocations was effectively hindered due to the stacking faults, which was contributed to tensile properties and work-hardening. Moreover, the dislocation pile-up groups were mainly shown on the γ/γ' interface of the alloy containing 2.5 wt % Ru at 760 °C, which was conducive to the work-hardening but harmful to the tensile properties. Hence, the yield strength and ultimate tensile stress were significantly improved with the increase of Ru at room temperature and 760 °C. The brittleness of the two alloys was improved with the increase of Ru at 760 °C due to the combined action of stacking faults, K–W locks, increase of the strength of γ' phase and high flow stress. Besides, the motion of the dislocations changed from cutting into the γ' phase to bowing out the γ' phase at 1100 °C. This movement mode of dislocations was promoted with the increase of Ru due to the wider γ matrix channels, which induced a slight decrease in tensile properties. Finally, the relation between deformation mechanisms and tensile behaviors was explained in detail according to the microstructures and tensile curves.