Effect Of Long Term Aging On Microstructure And Mechanical Properties Of Dd6 Single Crystal Superalloy

DD6 single crystal superalloy specimens were prepared by spiral crystal selection method. After standard heat treatment the long term aging at 980 degrees C 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 degrees C were studied. The results show that with the prolongation of long term aging time, the size of gamma' phase in the alloy increases. After long term aging for 2000 h, the size of gamma' phase is about 1 mu m, 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 degrees C/243 MPa, which is 56.3% of heat treated state, and 144.42 h at 1070 degrees C/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 degrees C, and 11% and 10.59 % at 980 degrees C, respectively.