A fourth generation single crystal(SC)nickel based cast superalloy DD15 with 1%Ru,3%Ru,5%Ru was prepared using vacuum induction single crystal furnace in order to optimize the properties and cost of DD15 alloy.The exp...A fourth generation single crystal(SC)nickel based cast superalloy DD15 with 1%Ru,3%Ru,5%Ru was prepared using vacuum induction single crystal furnace in order to optimize the properties and cost of DD15 alloy.The exposure experiment of three alloys was conducted at 1100℃for 1000 h.The stress rupture properties tests were performed at 1100℃temperature and 137 MPa pressure.The composition optimization of Ru element in DD15 alloy had been studied.It was found that the alloys with different Ru contents all consist of cuboidalγ′phase embedded coherent inγphase.Theγ′phase of the alloy all has a size of about 300-500 nm and a volume content of more than sixty percent.The dimension ofγ′precipitates is reduced and uniform with increase of Ru content.Ru element can reduce the distribution ratio of high melting point element,so the microstructural stability is enhanced with Ru content increasing.No topologically close-packed(TCP)phase precipitated in the 5%Ru alloy even after 1000 h exposure.The stress rupture life of the alloy is significantly improved as Ru content rising.The raft breadth decreases slightly as Ru content increases.The specimen with 1%Ru and 3%Ru exhibits the presence of TCP phases and without TCP phases precipitated in fracture specimen with 5%Ru.The density and integrity ofγ/γ′interfacial dislocation network increase as Ru content of the alloy rises.展开更多
According to more recent work, the Wilshire equations have shown good prediction accuracy in a wide range of materials and stress-temperature conditions, particularly in extrapolation of short term results to long ter...According to more recent work, the Wilshire equations have shown good prediction accuracy in a wide range of materials and stress-temperature conditions, particularly in extrapolation of short term results to long term predictions. In the current paper, this methodology was further developed for modeling anisotropic creep characteristics （i.e. minimum creep strain /~n, stress rupture life q and time to a specified strain t~） of four typical Ni-based directionally solidified （DS） and single crystal （SC） superalloys, where a simple orientation factor related to the ultimate tensile strength （UTS） was introduced. The application of these simplistic approaches showed that the anisotropic creep characteristics in a wide range of stress-temperature conditions can be accurately simulated. Meanwhile, during the application of the modified Wilshire equations, break points occurring at the specified stress levels agree well with the transition of creep deformation mechanisms occurring in different stress regions, which provides confidence for using this method.展开更多
基金Sponsored by the National Science and Technology Major Project(Grant No.2017-VI-0002-0071)。
文摘A fourth generation single crystal(SC)nickel based cast superalloy DD15 with 1%Ru,3%Ru,5%Ru was prepared using vacuum induction single crystal furnace in order to optimize the properties and cost of DD15 alloy.The exposure experiment of three alloys was conducted at 1100℃for 1000 h.The stress rupture properties tests were performed at 1100℃temperature and 137 MPa pressure.The composition optimization of Ru element in DD15 alloy had been studied.It was found that the alloys with different Ru contents all consist of cuboidalγ′phase embedded coherent inγphase.Theγ′phase of the alloy all has a size of about 300-500 nm and a volume content of more than sixty percent.The dimension ofγ′precipitates is reduced and uniform with increase of Ru content.Ru element can reduce the distribution ratio of high melting point element,so the microstructural stability is enhanced with Ru content increasing.No topologically close-packed(TCP)phase precipitated in the 5%Ru alloy even after 1000 h exposure.The stress rupture life of the alloy is significantly improved as Ru content rising.The raft breadth decreases slightly as Ru content increases.The specimen with 1%Ru and 3%Ru exhibits the presence of TCP phases and without TCP phases precipitated in fracture specimen with 5%Ru.The density and integrity ofγ/γ′interfacial dislocation network increase as Ru content of the alloy rises.
基金supported by the National Natural Science Foundation of China(Grand No.NSFC 51275023)the Innovation Foundation of BUAA for PhD Graduates(Grand No.YWF-14-YJSY-49)
文摘According to more recent work, the Wilshire equations have shown good prediction accuracy in a wide range of materials and stress-temperature conditions, particularly in extrapolation of short term results to long term predictions. In the current paper, this methodology was further developed for modeling anisotropic creep characteristics （i.e. minimum creep strain /~n, stress rupture life q and time to a specified strain t~） of four typical Ni-based directionally solidified （DS） and single crystal （SC） superalloys, where a simple orientation factor related to the ultimate tensile strength （UTS） was introduced. The application of these simplistic approaches showed that the anisotropic creep characteristics in a wide range of stress-temperature conditions can be accurately simulated. Meanwhile, during the application of the modified Wilshire equations, break points occurring at the specified stress levels agree well with the transition of creep deformation mechanisms occurring in different stress regions, which provides confidence for using this method.
