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Nucleation mechanism of a nickel-base superalloy during dynamic recrystallization

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Acta Metallurgica Sinica(English Letters) 2011年第4期24卷 295-300页

作者： Shuai WANG Lei WANG Yang LIU GuohuaXU Beijiang ZHANG Guangpu ZHAO Key laboratory for Anisotropy and Texture of materials Northeastern University Shenyang 110819China high temperature materials Research Institute Central Iron and Steel Research Institute Beijing100081 China

Hot compression test was carried out at 1000 ~C to investigate the dynamic recrys- tallization nucleation mechanism of a nickel-base superalloy. It was found that the bulging of original grain boundaries was inhibited by carbides and deformation twins at the boundaries. Recrystallized nuclei evolved from the subgrains of dislocation re- configuration along original grain boundaries, and the growth of the potential nuclei was carried out by the coalescence of subgrains. The necklace structure of recrys- tallized grains along original grain boundaries was attributed to the strain gradient from grain boundary to grain interior.

关键词： Dynamic recrystallization Electron backscattering diffraction(EBSD) Transmission electron microscopy (TEM) Superalloy

Sub-solvus Cellular Recrystallization and P Phase Formation in a Single-Crystal Superalloy Containing Re

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Acta Metallurgica Sinica(English Letters) 2015年第1期28卷 72-76页

作者： Long-Chao Zhuo Ming Huang Ji-Chun Xiong Jia-Rong Li Jing Zhu The State Key laboratory of New Ceramics and Fine Processing Laboratory of Advanced Materials (MOE) School of Materials Science and Engineering National Center for Electron Microscopy in Beijing Tsinghua University Science and Technology on Advanced high temperature Structural materials laboratory Beijing Institute of Aeronautical Materials

Sub-solvus recrystallization behavior of a second-generation single-crystal superalloy has been studied by transmission electron microcopy and scanning transmission electron microcopy. Surface local stress facilitated cellular recrystallization accompanied with formation of twin structure and TCP phase of P during annealing at sub-solvus temperature of 1,100 °C. The precipitation of P phase is considered to be attributed to the coarsening of c0 phase in the recrystallized aggregates which lower the activation energy for atomic migration.

关键词： Nickel-based single-crystal superalloys Interfaces Recrystallization Twin boundary STEM

An in situ high-pressure X-ray diffraction experiment on hydroxyapophyllite

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Chinese Physics B 2013年第1期22卷 167-170页

作者：范大伟魏舒怡谢鸿森 Institute of Geochemistry of laboratory for high temperature & high Pressure Study of the Earth's Interior Chinese Academy of Sciences

The compression behavior of a natural hydroxyapophyllite is investigated up to about 10.01 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the high Pressure Experiment Station, Beijing Synchrotron Radiation Facility （BSRF）. Over this pressure range, no phase change or disproportionation is observed. The isothermal equation of state is determined for the first time. The values of zero-pressure volume V0, isothermal bulk modulus K0, and K0＇ refined with a third-order Birch-Mumaghan equation of state are V0 = 1276.3 ± 0.9 A3, K0 = 71± 3 GPa, and K0＇ = 8 ±1. Furthermore, we confirm that the values of linear compressibility β along the a and c directions of hydroxyapophyllite are elastically anisotropic.

关键词： hydroxyapophyllite X-ray diffraction equation of state high pressure

Low cycle fatigue behavior of micro-grain casting K4169 superalloy at room temperature

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Progress in Natural Science:materials International 2022年第6期32卷 693-699页

作者： Rui Liu Xitao Wang Pinpin Hu Chengbo Xiao Jinshan He Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Shandong Provincial Key laboratory for high Strength Lightweight Metallic materials Advanced Materials Institute Qilu University of Technology (Shandong Academy of Science) Science and Technology on Advanced high temperature Structural materials laboratory AECC Beijing Institute of Aeronautical Materials

The strain-controlled low cycle fatigue tests were carried out at 298 K for the newly developed micro-grain casting K4169 superalloy,and the cyclic stress response,deformation and fracture behaviors of the alloy were *** results show that the fatigue life of the alloy was increased by more than two times compared with other casting K4169 *** can be partly attributed to grain refinement impeding crack initiation and *** the strain amplitude was in plastic range(Δεt/2≥ 0.5%),the alloy displayed a short period of initial cyclic stability followed by cyclic softening to *** observing dislocation configurations,only a few dislocations moved around grain boundaries at initial cycles,leading to short cyclic ***,dislocations in the slip bands cut γ" phase continuously leading to cyclic *** the strain amplitude was in elastic range(Δεt/2 ≤ 0.4%),the alloy exhibited elastic deformation and the peak stress kept *** addition,the crack initiation site changed from the MC carbides to the persistent slip bands on surface with increasing strain amplitudes.

关键词： Micro-grain cast K4169 Low-cycle fatigue Cyclic softening Slip bands

Creep behavior and effect factors of a TiAl–Nb alloy at high temperature

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Progress in Natural Science:materials International 2021年第3期31卷 477-485页

作者： Shunke Zhang Sugui Tian Gengyu Li Ning Tian Fangwei Jin Huichen Yu Xiaoxia Lv Guangyan Wang Deyuan Li Shenyang University of Technology Guizhou University of Engineering Science Beijing Key laboratory of Aeronautical materials Testing and Evaluation Science and Technology on Advanced High Temperature Structural Materials Laboratory AVIC Beijing Institute of Aeronautical Materials

The effect of solution treatment on the microstructure and creep properties of forged TiAl-Nb alloys was *** results showed that the microstructure of forged alloy mainly consisted of γ/αlamellar colonies and fine equiaxed recrystallized γ/α*** the solution treatment the microstructure of the alloy transformed into a fully lamellar structure due to the lamellar colonies growth by consuming equiaxed *** with the forged alloy the creep life of the solution treated alloy at 800℃/220 MPa increased from 116 h to 339 *** better creep resistance may be attributed to the transform of fine equiaxed γ/αgrain to the lamellar colonies with serrated grain boundaries due to the solution *** deformation mechanism of the solution treated alloy during creep is considered to be dislocation slipping within the lamellar γ/αphases,and the dislocation movement may be hindered by the γ/αinterface and the formation of dislocation *** interaction of the dislocations with the tangles may increase the resistance of the dislocation motion and hence improve the creep resistance of the *** was found that during the creep of the forged alloys the cracks mainly initiated at the equiaxed grain,and in the solution treated alloy the cracks initiated at the grain *** creep continued the cracks propagated and connected to each other,leading to the damage and rupture of the forged and solution treated alloys.

关键词： Forged TiAl–Nb alloy Solution treatment Microstructure Creep Deformation and damage

DNS of a spatially evolving hypersonic turbulent boundary layer at Mach 8

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1408-1418页

作者： LIANG Xian LI XinLiang laboratory of high temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences

This paper reports the direct numerical simulation (DNS) for hypersonic turbulent boundary layer over a flat-plate at Ma∞ =8 with the ratio of wall-to-freestream temperature equal to 1.9, which indicates an extremely cold wall condition. It is primarily used to assess the wall temperature effects on the mean velocity profile, Walz equation, turbulent intensity, strong Reynolds analogy (SRA), and compressibility. The present high Mach number with cold wall condition induces strong compressibility effects. As a result, the Morkovin's hypothesis is not fully valid and so the classical SRA is also not fully consistent. However, some modified SRA is still valid at the far-wall region. It is also verified that the semi-local wall coordinate y* is better than conventional y+ in analysis of statistics features in turbulent boundary layer (TBL) in hypersonic flow.

关键词： DNS compressibility effects turbulent boundary layer

Numerical investigation on the thermal protection mechanism for blunt body with forward-facing cavity

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Science China(Technological Sciences) 2016年第7期59卷 1120-1129页

作者： LI XinDong HU ZongMin JIANG ZongLin State Key laboratory of high temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences

Numerical experiments are carried out using the standard hypersonic ballistic-type model(HB-2) to investigate the effect of forward-facing cavity on the aerodynamic heating. A general concept is proposed which utilizes the flow disturbances generated passively in the nosed subsonic region to weaken the detached shock wave. Several aspects are mainly studied, including shock shape and standoff distance, surface heat flux and pressure, flowfield feature and cooling mechanism. The numerical results indicate that shock strength and standoff distance increase with an increase in the L/D ratio of the cavity. Interestingly, a bulge structure of the detached shock associated with a deep cavity is observed for the first time. Local surface heat flux and pressure around the concave nose are much lower respectively than those at the stagnation point of the baseline model. In addition, both surface heat and pressure reductions are proportional to the L/D ratio. A negative heating phenomenon may occur in the vicinity of a sharp lip or on the base wall of a deep cavity. If the L/D ratio exceeds 0.7, the detached shock appears as a self-sustained oscillation which can be referred to as the cooling mechanism.

关键词： hypersonic flow aerodynamic heating thermal protection system forward-facing cavity

Development of the detonation-driven expansion tube for orbital speed experiments

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Science China(Technological Sciences) 2015年第4期58卷 695-700页

作者： JIANG Zong Lin WU Bo GAO Yun Liang ZHAO Wei HU Zong Min State Key laboratory of high-temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences

The hypersonic flow at orbital speeds is a fundamental issue for the ground tests of aerospace *** detonation-driven high-enthalpy expansion tube(JF16 expansion tube)was developed to investigate re-entry physics.A forward detonation cavity(FDC)driver was applied in the JF16 expansion tube to create stable driving *** sound speed ratio of the detonated to test gas was examined to minimize the magnitude of test flow *** acceleration section length,incident shock decay and diaphragms thickness were investigated in detail to obtain optimal operation *** visualization was also carried out with schlieren system to demonstrate the test flow stability and the effective test *** data showed that the test flow with a velocity of 8.3 km/s and a total enthalpy up to 40 MJ/kg can be generated successfully and the test duration lasts for more than 50μs.

关键词： detonation driver shock-expansion tube high-enthalpy flow test flow

Flux pinning evolution in multilayer Pb/Ge/Pb/Ge/Pb superconducting systems

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Chinese Physics B 2023年第3期32卷 491-496页

作者：高礼鑫张晓珂张安蕾肖祁陵陈飞葛军饴 materials Genome Institute Shanghai UniversityShanghai 200444China Shanghai Key laboratory for high temperature Superconductors Shanghai UniversityShanghai 200444China Zhejiang laboratory Hangzhou 311100China

Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex–vortex interactions,including the competing one in the recently proposed type-1.5 ***,potential candidate that can be used to study the multicomponent superconductivity is ***,we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent *** additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting *** magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic *** vortex phase diagram and the optimum critical current density have been ***,a second magnetization effect is observed,and is attributed to the upper layer,which provides the weak pinning sites to localize the flux *** pinning behaviors switches to the mixed type with the increase of the insulting layer *** results open a new perspective to the study and related applications of the multilayer superconducting systems.

关键词： multilayer superconducting film competing interaction flux pinning mechanism