Effect Of Long-term Aging On Microstructure And Mechanical Properties Of DD5 Nickel-based Single Crystal Superalloy

DD5 alloy is a second-generation single crystal superalloy independently developed by China and is the main material of turbine blades for aerospace engines.The single crystal superalloy turbine blades are subjected to high temperature and complex stress for a long time in the service process.Therefore,it is necessary to study the effect of long-term aging on the mechanical properties of DD5 alloy.By means of heat treatment,long-term aging and creep properties measuring of the alloys,the?'phase morphology,carbide morphology and TCP phase evolution of the DD5 alloy during the as-cast,heat-treated and long-term aging processes were investigated,and the variation of the dislocation networks during long-term aging and the effect of long-term aging on creep performance.The experimental results show that the as-cast microstructure of DD5 single crystal superalloy is a typical dendritic structure,and the interdendritic region contains different morphology eutectic structure and a few carbides.After the full heat treatment,the eutectic structure is eliminated,and the?'phase between dendritic regions and interdendritic regions tends to be consistent and distributes in a regular cubic form at the same time.During the aging at 1000?and 1100?,the longer the aging time,the higher the aging temperature,the greater the growth rate of the?phase,and the greater the coarsening rate of the?'phase in the interdendritic regions.M₂₃C₆ type carbides mainly precipitated during the aging at 1000?,and M₆C type carbides mainly precipitated during the aging at 1100?.During the aging at1000?,the amount of?phase increases with the prolongation of aging time.During the aging at 1100?,the amount of?phase increases first and then decreased with the prolongation of aging time.During the aging at 1100?,the density of the interface dislocation network is getting larger and larger with the prolongation of aging time,and different types of interface dislocation networks formed by dislocation reaction,and the?/?mismatch becomes larger and larger.After aging at 1100°C for 500h,the creep life of the alloy under different conditions decreased significantly.Severe coarsening of the?'phase,cubic coherent structure destruction,and the increase of the TCP phases are the main reasons for the decrease in creep properties of the alloy.After aging at 1000°C for 500 h,a large amount of M₂₃C₆ type carbides precipitated in interdendtitic region during creep under different conditions.The precipitated M₂₃C₆ type carbides are in coherent with the?'phase,and the creep lives of the alloy are significantly improved.