DD6 single crystal superalloy specimens were prepared by spiral crystal selection method. After standard heat treatment the long term aging at 980 ℃ was performed for 2000 h. The influences of the microstructural evolution and mechanical properties of DD6 single crystal superalloy after long term aging at 980 ℃ were studied. The results show that with the prolongation of long term aging time, the size of γ' phase in the alloy increases. After long term aging for 2000 h, the size of γ' phase is about 1 μm, and there is no TCP phase precipitation, which shows that DD6 alloy has good microstructural stability. The stress rupture life of sample after long term aging for 2000 h is 180.16 h at 980 ℃/243 MPa, which is 56.3% of heat treated state, and 144.42 h at 1070 ℃/130 MPa, which is 35.31% of heat treated state. The fracture mode is microvoid coalescence fracture. The tensile strength and yield strength of the alloy after long term aging for 2000 h are reduced by 5.55% and 5.88% at 760 ℃, and 11% and 10.59% at 980 ℃, respectively.
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