The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the...The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life,especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores,eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.展开更多
Two experimental alloys containing diff erent contents of Ru were investigated to study the eff ect of Ru on the microstructural evolution during long-term thermal exposure.The increase in Ru promoted the formation of...Two experimental alloys containing diff erent contents of Ru were investigated to study the eff ect of Ru on the microstructural evolution during long-term thermal exposure.The increase in Ru promoted the formation of cubical,tiny,and evenγ′phase after full heat treatment.Moreover,the samples after full heat treatment were exposed at 1100℃ for diff erent time.Based on the classical model by Lifshitz,Slyozov,and Wagner,the coarsening ofγ′phase of the alloy containing 2.5 and3.5 wt.%Ru during the long-term aging was controlled by the interface reaction and diff usion,respectively.Theγ/γ′lattice misfi t was more negative with the increment of Ru addition,which induced the formation of stable raftedγ′phase in the alloy containing 3.5 wt.%Ru at the initiation of long-term aging.Besides,the increase in Ru reduced the diff usion coeffi cient,which could restrain theγ′phase coarsening.The lowerγ/γ′lattice misfi t of the alloy containing 2.5 wt.%Ru promoted the interface reaction,which induced the rapid coarsening ofγ′phase.Therefore,the increase in Ru improved the microstructural stability of the alloys.On the other hand,the raise of Ru induced"reverse partitioning"behavior,which was eff ective in suppressing the emergence of the topologically close-packed phase(TCP phase).The TCP phase occasionally occurred in the alloy containing 2.5 wt.%Ru,which was attributed to the high temperature and the supersaturation of theγmatrix.Moreover,the TCP phase was determined asμphase,which had a high concentration of Co,Re,Mo,and W.A sketch map describing the evolution of the TCP phase was also constructed.展开更多
Stress-rupture properties of a Ni-base Re-containing single-crystal superalloy with three orientations have been tested under 900℃/445 MPa.An obvious anisotropy of stress-rupture property is attributed to orientation...Stress-rupture properties of a Ni-base Re-containing single-crystal superalloy with three orientations have been tested under 900℃/445 MPa.An obvious anisotropy of stress-rupture property is attributed to orientation reliant deformation microstructure.The good strength in[001]orientation is attributed to the rapid multiplication of dislocations active in horizontal channels and laterγ'cutting via dislocations pair coupled with anti-phase boundary.The microtwin formation largely limits the strength and plasticity as a result of the continuous shearing acrossγ/γ'microstructure by{111}112 slip activated in[011]orientation.The property in[111]orientation results mainly from the lateral cross-slip movements of the screw dislocations within connected matrix channels as well as the precipitate shearing by coplanar dislocations.Microcracks all initially originate from the interdendritic micropores in three orientations.The critical temperature of stress-rupture anisotropy could be increased by a high level of refractory solutes especially Re.展开更多
Coarsening of cuboidal γ’ precipitates and relevant diffusion process in Ni-based single-crystal superalloy CMSX-4 were investigated at 1000,1020 and 1040℃ for specific times.The y’ coarsening kinetics followed a ...Coarsening of cuboidal γ’ precipitates and relevant diffusion process in Ni-based single-crystal superalloy CMSX-4 were investigated at 1000,1020 and 1040℃ for specific times.The y’ coarsening kinetics followed a cubic rate law with time and was presumably controlled by bulk diffusion of elements in y matrix.The associated diffusion activation energy was experimentally determined to be about 300 kJ/mol when it is considered the temperature-dependent thermo-physical parameters in modified Lifshitz-Slyozov-Wagner theory.The influence of temperature on γ/γ’ microstructure is briefly discussed based on pseudo-binary [Ni]-[Al] phase diagram.Interactions among elements can effectively raise the local vacancy formation and vacancy-atom exchange barriers close to γ-and γ’-partitioning elements,respectively.Thus,it can significantly reduce the inter-coupling migrations of atoms during the macroscopic cross-diffusion process associated with γ’ coarsening of Ni-based superalloys.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51571196, 51671188 and 5160119)Shenyang Science and Technology Project (No. 17-101-2-00)
文摘The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life,especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores,eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.
基金financially supported by the National Science and Technology Major Project(No.2017-VI-0002–0072)the National Key R&D Program of China(No.2017YFA0700704)+1 种基金the National Natural Science Foundation of China(Nos.51671188,51601192 and 51701210)the Youth Innovation Promotion Association,Chinese Academy of Sciences and State Key Lab of Advanced Metals and Materials Open Fund(No.2018-Z07)。
文摘Two experimental alloys containing diff erent contents of Ru were investigated to study the eff ect of Ru on the microstructural evolution during long-term thermal exposure.The increase in Ru promoted the formation of cubical,tiny,and evenγ′phase after full heat treatment.Moreover,the samples after full heat treatment were exposed at 1100℃ for diff erent time.Based on the classical model by Lifshitz,Slyozov,and Wagner,the coarsening ofγ′phase of the alloy containing 2.5 and3.5 wt.%Ru during the long-term aging was controlled by the interface reaction and diff usion,respectively.Theγ/γ′lattice misfi t was more negative with the increment of Ru addition,which induced the formation of stable raftedγ′phase in the alloy containing 3.5 wt.%Ru at the initiation of long-term aging.Besides,the increase in Ru reduced the diff usion coeffi cient,which could restrain theγ′phase coarsening.The lowerγ/γ′lattice misfi t of the alloy containing 2.5 wt.%Ru promoted the interface reaction,which induced the rapid coarsening ofγ′phase.Therefore,the increase in Ru improved the microstructural stability of the alloys.On the other hand,the raise of Ru induced"reverse partitioning"behavior,which was eff ective in suppressing the emergence of the topologically close-packed phase(TCP phase).The TCP phase occasionally occurred in the alloy containing 2.5 wt.%Ru,which was attributed to the high temperature and the supersaturation of theγmatrix.Moreover,the TCP phase was determined asμphase,which had a high concentration of Co,Re,Mo,and W.A sketch map describing the evolution of the TCP phase was also constructed.
基金financially supported by the National Key R&D Program of China(No.2017YFA0700704)the National Natural Science Foundation of China(No.51871221)the National Science and Technology Major Project(No.2017-VI-0002-0072)。
文摘Stress-rupture properties of a Ni-base Re-containing single-crystal superalloy with three orientations have been tested under 900℃/445 MPa.An obvious anisotropy of stress-rupture property is attributed to orientation reliant deformation microstructure.The good strength in[001]orientation is attributed to the rapid multiplication of dislocations active in horizontal channels and laterγ'cutting via dislocations pair coupled with anti-phase boundary.The microtwin formation largely limits the strength and plasticity as a result of the continuous shearing acrossγ/γ'microstructure by{111}112 slip activated in[011]orientation.The property in[111]orientation results mainly from the lateral cross-slip movements of the screw dislocations within connected matrix channels as well as the precipitate shearing by coplanar dislocations.Microcracks all initially originate from the interdendritic micropores in three orientations.The critical temperature of stress-rupture anisotropy could be increased by a high level of refractory solutes especially Re.
基金financially supported by the National Key R&D Program of China (No. 2017YFA0700704)the National Natural Science Foundation of China (No. 51871221)the National Science and Technology Major Project (No. 2017-VI-00020072)。
文摘Coarsening of cuboidal γ’ precipitates and relevant diffusion process in Ni-based single-crystal superalloy CMSX-4 were investigated at 1000,1020 and 1040℃ for specific times.The y’ coarsening kinetics followed a cubic rate law with time and was presumably controlled by bulk diffusion of elements in y matrix.The associated diffusion activation energy was experimentally determined to be about 300 kJ/mol when it is considered the temperature-dependent thermo-physical parameters in modified Lifshitz-Slyozov-Wagner theory.The influence of temperature on γ/γ’ microstructure is briefly discussed based on pseudo-binary [Ni]-[Al] phase diagram.Interactions among elements can effectively raise the local vacancy formation and vacancy-atom exchange barriers close to γ-and γ’-partitioning elements,respectively.Thus,it can significantly reduce the inter-coupling migrations of atoms during the macroscopic cross-diffusion process associated with γ’ coarsening of Ni-based superalloys.