Stress Rupture Properties and Fracture Behavior of DD6 Single Crystal Superalloy

The stress rupture properties, fracture behavior and microstructure evolution of the second generation single crystal superalloy DD6 at different conditions were investigated. The results show that the alloy has excellent stress rupture properties. The fracture mechanism of stress rupture of the alloy at 760°C/785MPa, 760°C/750MPa and 760°C/720MPa shows quasi-cleavage mode and the fracture mechanism at 980°C/250MPa, 1070°C/160MPa and 1100°C/140MPa shows dimple mode, while the fracture mechanism at 850°C/550MPa shows quasi-cleavage and dimple mixture mode. Only a little change in the morphology of γ′ phase occurred at 760°C/750MPa. The γ′ rafts form at temperature above 760°C and the thickness of rafts increases with increasing temperature. The dislocation shear mechanism including stacking fault formation is operative at lower temperature and high stress. The dislocation by-passing mechanism occurs to form networks at γ/γ′ interface under the condition of high temperature and lower stress.