The γ/γ＇ microstructure of a Re-containing Ni-based single crystal super alloy after a two-step aging was studied using scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and scanning tra...The γ/γ＇ microstructure of a Re-containing Ni-based single crystal super alloy after a two-step aging was studied using scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and scanning transmission electron microscopy （STEM）.The crystals were grown by the floating zone （FZ） method.Both cuboidal and spherical γ＇ precipitates were formed after a two-step aging.The size of the cuboidal γ＇ phases first increased and then decreased with the extension of the second-step aging time.Re,Co and Cr strongly concentrated in the γ phase whereas Ni and Al enriched in the γ＇ phase.Thermodynamic calculation by JMatPro was performed to explain the experimental observations.展开更多
An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a ...An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.展开更多
The decay of the neutron-rich erbium isotope <sup>175</sup>Er is studied by using the reaction<sup>176</sup>Yb（n,2p）<sup>175</sup>Er.A partial decay scheme is proposed on the basi...The decay of the neutron-rich erbium isotope <sup>175</sup>Er is studied by using the reaction<sup>176</sup>Yb（n,2p）<sup>175</sup>Er.A partial decay scheme is proposed on the basis of X-γ and γ-γ coincidencemeasurements,taking into account eight observed gamma rays.A ground rotational band is as-signed to <sup>175</sup>Tm.Some systematic behaviors of 1/2+[411] ground rotational bands in odd-Athulium are described.The experimental and calculated decoupling parameters of these bandsare compared.展开更多
The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With th...The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With the aid of computer,the regressives expression derived from the experimental results are Tδ(℃) = T4 -21.2[Cr] +15.8[Ni]-223. Vδ(%)=0.715 exp 0.015(T-Tδ).展开更多
High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 . At the low spin states, the yrast coll...High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 . At the low spin states, the yrast collective structure built on the νh11/2-1 multiplet shows a transitional shape with γ ≈ 32° according to calculations of the triaxial rotor-plus-particle model. Three collective oblate bands with γ ～-60° at the high spin states were identified for the first time. A band crossing is observed around ω ～0.4 MeV in one oblate band based on the 25/2-level.展开更多
Based on analysis of three alloys with various Re contents, the effects of Re on the interfacial structure characteristic and interfacial dislocations ofγ/γ' in single crystal superalloys were investigated. A hi...Based on analysis of three alloys with various Re contents, the effects of Re on the interfacial structure characteristic and interfacial dislocations ofγ/γ' in single crystal superalloys were investigated. A high resolution transition electron microscopy (HRTEM) technique was used to detect the structure characteristic ofγ/γ' interface. The interfacial dislocations ofγ/γ' were analyzed with TEM. The results show that as Re content increases, the interfaces ofγ/γ' become orderly, the atomic arrangements at interfaces are more uniform, the number of mismatch dislocations increases and transition areas betweenγandγ' phases become narrow. That Re changes the interfacial structure promotes the formation of dense, regular and homogeneous interfacial dislocation networks in short time during creep at 1 100℃and 140 MPa, which results in strengthenedγ/γ' interface at elevated temperature.展开更多
The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete v...The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was foundthat the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand,less than -0.6% negative lattice misfit can promote the binding strength of γ/γ′ interface. On the other hand, the totalbonding strength of γ/γ′ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must becarefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structuralstability of γ/γ′interface when one designs a new Ni-base single crystal superalloy.展开更多
The as-cast microstructure, element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated. The results show that the severe element segregation leads to the complicated p...The as-cast microstructure, element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated. The results show that the severe element segregation leads to the complicated precipitations at the inter-dendritic region, including η-Ni3(Ti, Nb), eutectic(γ + γ’) and Laves, which shows the characteristics of both Ti, Al-strengthened and Nb-strengthened alloys. Differential thermal analysis, heating and quenching tests reveal the solidification sequence as follows: Liquids →γ matrix →(Nb, Ti)C →η-Ni 3(Ti, Nb) →eutectic( γ+γ’) → Laves. The melting points are between 1250 and 1260 °C for(Nb, Ti)C, between 1200 and 1210 °C for η phase, between 1180 and 1190 °C for eutectic(γ+γ’) and Laves. γ’ initially precipitates from matrix at 1150 °C and achieves the maximum precipitation at 1130 °C. According to the microstructure evolution captured during solidification and composition analysis by an energy dispersive spectrometer and electron probe microanalyzer,(Nb, Ti)/Al ratio is put forward to explain the formation of η-Ni3(Ti, Nb) and eutectic( γ+γ’). The solidification of γ matrix increased the Nb, Ti concentration in the residual liquids, so the high(Nb, Ti)/Al ratio would result in the formation of η-Ni3(Ti, Nb); the precipitation of the phase consumed Nb and Ti and decreased the(Nb, Ti)/Al ratio in the liquid, which led to the precipitation of eutectic(γ + γ’). Laves formed by the sides of η-Ni3(Ti, Nb) and in front of the eutectic( γ + γ’) after Al, Ti were further depleted by the two phases and Cr, Co, Mo were rejected to liquids.展开更多
基金Project(08dj1400402) supported by the Major Program for the Fundamental Research of Science and Technology Committee of the Shanghai Municipality,ChinaProject(09ZZ16) supported by Innovation Program of Shanghai Municipal Education Committee,China
文摘The γ/γ＇ microstructure of a Re-containing Ni-based single crystal super alloy after a two-step aging was studied using scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and scanning transmission electron microscopy （STEM）.The crystals were grown by the floating zone （FZ） method.Both cuboidal and spherical γ＇ precipitates were formed after a two-step aging.The size of the cuboidal γ＇ phases first increased and then decreased with the extension of the second-step aging time.Re,Co and Cr strongly concentrated in the γ phase whereas Ni and Al enriched in the γ＇ phase.Thermodynamic calculation by JMatPro was performed to explain the experimental observations.
文摘An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.
基金The project supported by the National Natural Scierice Foundation of Chinathe Chinose Academy of Sciences
文摘The decay of the neutron-rich erbium isotope <sup>175</sup>Er is studied by using the reaction<sup>176</sup>Yb（n,2p）<sup>175</sup>Er.A partial decay scheme is proposed on the basis of X-γ and γ-γ coincidencemeasurements,taking into account eight observed gamma rays.A ground rotational band is as-signed to <sup>175</sup>Tm.Some systematic behaviors of 1/2+[411] ground rotational bands in odd-Athulium are described.The experimental and calculated decoupling parameters of these bandsare compared.
文摘The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With the aid of computer,the regressives expression derived from the experimental results are Tδ(℃) = T4 -21.2[Cr] +15.8[Ni]-223. Vδ(%)=0.715 exp 0.015(T-Tδ).
基金Supported by National Natural Science Foundation of China (10575057, 10775078)Major State Basic Research Development Program (2007CB815005)Special Program of Higher Education Science Foundation (20070003149)
文摘High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 . At the low spin states, the yrast collective structure built on the νh11/2-1 multiplet shows a transitional shape with γ ≈ 32° according to calculations of the triaxial rotor-plus-particle model. Three collective oblate bands with γ ～-60° at the high spin states were identified for the first time. A band crossing is observed around ω ～0.4 MeV in one oblate band based on the 25/2-level.
文摘Based on analysis of three alloys with various Re contents, the effects of Re on the interfacial structure characteristic and interfacial dislocations ofγ/γ' in single crystal superalloys were investigated. A high resolution transition electron microscopy (HRTEM) technique was used to detect the structure characteristic ofγ/γ' interface. The interfacial dislocations ofγ/γ' were analyzed with TEM. The results show that as Re content increases, the interfaces ofγ/γ' become orderly, the atomic arrangements at interfaces are more uniform, the number of mismatch dislocations increases and transition areas betweenγandγ' phases become narrow. That Re changes the interfacial structure promotes the formation of dense, regular and homogeneous interfacial dislocation networks in short time during creep at 1 100℃and 140 MPa, which results in strengthenedγ/γ' interface at elevated temperature.
文摘The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was foundthat the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand,less than -0.6% negative lattice misfit can promote the binding strength of γ/γ′ interface. On the other hand, the totalbonding strength of γ/γ′ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must becarefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structuralstability of γ/γ′interface when one designs a new Ni-base single crystal superalloy.
文摘The as-cast microstructure, element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated. The results show that the severe element segregation leads to the complicated precipitations at the inter-dendritic region, including η-Ni3(Ti, Nb), eutectic(γ + γ’) and Laves, which shows the characteristics of both Ti, Al-strengthened and Nb-strengthened alloys. Differential thermal analysis, heating and quenching tests reveal the solidification sequence as follows: Liquids →γ matrix →(Nb, Ti)C →η-Ni 3(Ti, Nb) →eutectic( γ+γ’) → Laves. The melting points are between 1250 and 1260 °C for(Nb, Ti)C, between 1200 and 1210 °C for η phase, between 1180 and 1190 °C for eutectic(γ+γ’) and Laves. γ’ initially precipitates from matrix at 1150 °C and achieves the maximum precipitation at 1130 °C. According to the microstructure evolution captured during solidification and composition analysis by an energy dispersive spectrometer and electron probe microanalyzer,(Nb, Ti)/Al ratio is put forward to explain the formation of η-Ni3(Ti, Nb) and eutectic( γ+γ’). The solidification of γ matrix increased the Nb, Ti concentration in the residual liquids, so the high(Nb, Ti)/Al ratio would result in the formation of η-Ni3(Ti, Nb); the precipitation of the phase consumed Nb and Ti and decreased the(Nb, Ti)/Al ratio in the liquid, which led to the precipitation of eutectic(γ + γ’). Laves formed by the sides of η-Ni3(Ti, Nb) and in front of the eutectic( γ + γ’) after Al, Ti were further depleted by the two phases and Cr, Co, Mo were rejected to liquids.
