The tensile property tests of DD6 single crystal superalloy were performed at 25°C, 760°C and 980°C in air. Detailed microstructure evolution was carried out on the alloy to illuminate the γ phase and dislocation structure after tensile fracture by scanning electron microscope and transmission electron microscopy. The results show that the alloy has the maximum tensile strength and the minimum plasticity at 760°C. DD6 alloy has the same anomalous yield strength behavior with other single crystal superalloys. The γ phase hasve a little extension in the stress orientation after tensile fracture at 25°C. The γ phase morphology still maintains cubic after tensile fracture at 760°C. The γ phase is no longer cubic and changes into rectangular solid in the specimen tensile ruptured at 980°C. The vertical γ matrix becomes thinner and horizontal γ matrix becomes thicker slightly. The γ phase is no longer cubic and changes into rectangular solid. High density dislocations are present in the matrix channels and a lot of superlattice stacking faults are seen within γ phases in the sample tested at 25°C. A large quantities of superlattice stacking faults within γ phase and a lot of dislocations tangling in matrix channel are all present in the sample tested at 760°C. The dislocation networks have homogeneously formed at γ/γ interface in the sample tested at 980°C.
Microstructure evolution and deformation mechanism of a [111]-oriented nickel-based single-crystal superalloy during high-temperature creep
