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Effects of Heat Treatment on Surface Recrystallization and Stress Rupture Properties of a Fourth-Generation Single-Crystal Superalloy after Grit Blasting

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Acta Metallurgica Sinica(English Letters) 2017年第7期30卷 614-620页

作者： zhen-xue shi shi-Zhong Liu Xiao-Guang Wang Jia-Rong Li Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China

The specimens of a fourth-generation single-crystal superalloy were grit-blasted and heat-treated in vacuum at 1100, 1150, 1200, 1250 and 1300 °C for 4 h, respectively. Then, the microstructure and the stress rupture properties of the recrystallized alloy were investigated at 1150 °C/120 MPa. The results showed that a cellular recrystallization occurred in the surface layer after heating at 1100, 1150 and 1200 °C for 4 h. An equiaxed recrystallization formed as the specimen was heat-treated at 1300 °C for 4 h, while a mixed recrystallization occurred in the specimen heat-treated at 1250 °C for 4 h. The recrystallized depth clearly increased with a rise of the heat treatment temperature. The stress rupture life continuously decreased with a rise of the heat treatment temperature up to 1250 °C. Although the overall stress rupture life reduced to different degrees, the stress rupture life of specimen after heat treatment at 1300 °C was relatively high and intermediate between those of specimens treated at 1150 and 1200 °C. The fact that the stress rupture life reduced to different degrees after heat treatment can be attributed to the recrystallization of the surface layer and to the microstructure evolution of the interior of the specimen. The small γ’ phase precipitated again after heat treatment at 1300 °C for 4 h. So,the stress rupture life was relatively longer than that after heat treatment at 1200 or 1250 °C although the equiaxed recrystallization formed in the surface layer.

关键词： Single-crystal superalloy Heat treatment Recrystallization Stress rupture properties

Effects of Ru on the microstructure and phase stability of a single crystal superalloy

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International Journal of Minerals,Metallurgy and Materials 2012年第11期19卷 1004-1009页

作者： zhen-xue shi Jia-rong Li shi-zhong Liu Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical MaterialsBeijing 100095China

Two experimental single crystal superalloys, the Ru-free alloy and the Ru-containing alloy with [001 ] orientation, were cast in a directionally solidified furnace, while other alloying element contents were kept unchanged. The effects of Ru on the microstructure and phase stability of the single crystal superalloy were investigated, y＇ directional coarsening and rafting were observed in the Ru-free alloy and Ru-containing alloy after long-term aging at 1070~C for 800 h. Needle-shaped o topologically close packed （TCP） phases precipitated and grew along the fixed direction in both the alloys. The precipitating rate and volume fraction of TCP phases decreased significantly by adding Ru. The compositions ofy and y＇ phases measured using an energy-dispersive X-ray spectroscope （EDS） in transmission electron microscopy （TEM） analysis showed that the addition of Ru lessened the partition ratio of TCP forming elements, Re, W and Mo, and decreased the satu- ration degrees of these elements in y phase, which can enable the Ru-containing alloy to be more resistant to the formation of TCP phases. It is indicated that the addition of Ru to the Ni-based single crystal superalloy with high content of the refractory alloying element can enhance phase stability.

关键词： superalloys nickel alloys single crystals ruthenium microstructure phase stability

Tensile Behavior of the Second Generation Single Crystal Superalloy DD6

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Journal of Iron and Steel Research International 2015年第8期22卷 738-742页

作者： zhen-xue shi shi-zhong LIU Jian YU Jia-rong LI Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

Tensile properties of the second generation single crystal superalloy DD6 were investigated from 20 ℃ to 1 100 ℃. Microstructure evolution and fracture mechanism were examined by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the tensile strength decreases slightly with increasing temperature from 20 ℃ to 400 ℃. The tensile strength of the alloy increases with the increase of temperature from 400 ℃ to 800 ℃. Above 800 ℃, the yield strength of the alloy decreases greatly with increasing temperature. The elongation and contraction of area almost present opposite tendency in contrast to changes of the tensile strength. At lower and intermediate temperature （from 20 ℃ to 850 ℃）, the tensile fracture mechanism shows quasi-cleavage mode, while at high temperature （980 ℃ and 1 100 ℃）, it is dimple mode. The γ＇ precipitate morphology still maintains cubic after tensile fracture at lower and intermediate temperature. The γ＇ phase changes into rectangular solid at high temperature. The γ＇ phase is sheared by anti-phase boundary （APB） or stacking faults at lower and intermediate temperature. At high temperature, dislocations overcome γ＇ through by-passing mechanism.

关键词： single crystal superalloy DD6 tensile behavior microstructure evolution

Forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy

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Rare Metals 2018年第5期37卷 399-406页

作者： Xiao-Dai Yue Jia-Rong Li Xiao-Guang Wang zhen-xue shi Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

The forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy were investigated. The microstructures were observed with optical microscope （OM） and field emission microscope （FEM） after homogenization-solution heat treated at 1328℃ and 1350 ℃ for 2 h, 6 h and 9 h. Results indicate that when heat treated at 1328 ℃, pores appear at the interface of eutectic and matrix at first and then leave in the matrix with the shrink of eutectic. When heat treated at 1350 ℃, incipient melting happens at first, and some of them have a pore in the center. After that, with the homogenization-solution process, incipient melting microstructure fades away gradually. By analyzing the results with thermodynamics and kinetics methods, it is concluded that some pores nucleate during directional solidification and then become larger and visible during homogenization-solution heat treatments; some pores are generated by incipient melting, yet such pores are difficult to be distinguished from other pores; imbalanced elements cross-diffusion induces to the forming and growing of pores too, and such imbalanced diffusion also plays an important part on the growth of all preexisting pores.

关键词： Single crystal superalloy Pore Homogenization Solution Heat treatment Incipient melting

Effect of cellular recrystallization on tensile properties of a nickel-based single crystal superalloy containing Re and Ru

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Journal of Iron and Steel Research International 2017年第10期24卷 1059-1064页

作者： zhen-xue shi shi-zhong Liu Xiao-dai Yue Li-jie Hu Wan-peng Yang Xiao-guang Wang Jia-rong Li Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical MaterialsBeijing 100095China

A nickel-based single crystal superalloy containing Re and Ru was cast in a directional solidification *** single crystal specimens after standard heat treatment were grit blasted with different pressures and then heat treated at 1100°C for 4 hunder vacuum *** evolution of recrystallized microstructure and its effect on the tensile properties at 850 and 980°C were *** heat treatment,the cellular microstructure was observed,and the thickness of the cellular recrystallization zone increases with the increase in grit blasting *** appearance of the cellular structure undermines the tensile *** the tensile strength and elongation decrease with increasing the thickness of the cellular *** recrystallized grain boundaries can act as the channels for the crack initiation and propagation during tensile *** low bearing capacity of recrystallized layers and the local stress concentration resulting from the notch effect of cracking were the main reasons for the decrease of tensile properties.

关键词： Single crystal superalloy Cellular recrystallization Tensile property Microstructure Fracture morphology

Design and Gait Planning of a Worm-inspired Metameric Robot for Pipe Crawling

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Journal of Bionic Engineering 2024年第3期21卷 1265-1277页

作者： Yu Liu Qingbiao shi zhen Chen Pen-Tung Sah Institute of Micro-Nano Science and Technology Xiamen UniversityXiamen361102China

The earthworm has been attracted much attention in the research and development of biomimetic robots due to their unique locomotion mechanism,compact structure,and small motion *** paper presents a new design and prototype of a worm-inspired metameric robot with a movement pattern similar to that of *** robot consists of multiple telescopic modules connected in series through joint *** telescopic module mimics the contraction and elongation motion modes of the earthworm segments.A kinematic and dynamic analysis is conducted on the telescopic module,and an input torque calculation method is provided to ensure sufficient friction between the robot and the pipe *** gait modes of the prototype robot for straight and turning locomotion are introduced,and these modes are extended to robots constructed by different numbers of telescopic *** addition,a method is proposed to increase the friction between the robot and the pipe wall in the aforementioned gait modes without changing the robot structure,thereby improving the robot’s motion ability in *** theoretical model of gait modes has also been validated through gait *** findings of this paper would provide a useful basis for the design,modeling,and control of future worm inspired robots.

关键词： Bio-inspired robot Spatial linkage mechanism Kinematics model Peristaltic locomotion

Electroacupuncture Promotes Angiogenesis in Mice with Cerebral Ischemia by Inhibiting miR-7

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Chinese Journal of Integrative Medicine 2024年第6期30卷 543-550页

作者： YU Qian SHU shi JU Xin-yao PENG Wei REN xue-qi SI Shu-han SONG shi-zhen XIE xue-yun FANG Bang-jiang ZHOU Shuang School of Acupuncture-Moxibustion and Tuina Shanghai University of Traditional Chinese MedicineShanghai201203China College of Basic Medicine Shanghai University of Traditional Chinese MedicineShanghai201203China Department of Emergency Longhua HospitalShanghai University of Traditional Chinese MedicineShanghai200032China

Objective To observe the angiogenesis effect of electroacupuncture(EA)at Shuigou acupoint(GV 26)in the treatment of cerebral ischemia,and explore the value of miRNA-7(miR-7)in *** First,48 mice were randomly divided into sham operation,middle cerebral artery occlusion(MCAO)model,and EA treatment *** 9 mice were divided into carrier control group,miR-7 knockout group and miR-7 overexpression group(n=3 each group).Finally,20 mice were divided into model and carrier control group,model and miR-7 knockout group,EA treatment and carrier control group and EA treatment and miR-7 overexpression group,with 3–6 mice in each *** MCAO model was established in the MCAO and EA *** deficit score and 2,3,5-triphenyltetrazolium chloride(TTC)staining were used to evaluate the severity of cerebral ***-eosin staining was used to describe basic pathological *** was used to quantify cerebral microvessel ***-time PCR and Western blot were used to detect the expression of miR-7 and its downstream target genes Krüppel-like factor 4/vascular endothelial growth factor(KLF4/VEGF)and angiopoietin-2(ANG-2)in the ischemic cerebral *** After EA,neurological deficit scores and infarction volumes decreased,and the density of cerebral microvessels *** the MCAO group,miR-7 expression was higher than that in the sham group(P<0.01).After EA at GV 26,miR-7 expression decreased(P<0.01)and the expression of downstream target genes KLF4/VEGF and ANG-2 increased as compared with the MCAO group(P<0.01).After EA combined with overexpression of miR-7,the expression of downstream target genes KLF4/VEGF and ANG-2 decreased compared to the control EA group(P<0.01).After miR-7 knockdown,the expression of KLF4/VEGF and ANG-2 increased(P<0.05 or P<0.01).Conclusions EA could promote angiogenesis in MCAO mice likely by inhibiting the expression of miR-7 and relieving inhibition of downstream target genes KLF4/VEG

关键词： electroacupuncture cerebral ischemia miRNA-7 angiogenesis Shuigou(GV 26) acupuncture points

Assessment of climate damage in China based on integrated assessment framework

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Advances in Climate Change Research 2024年第1期15卷 124-133页

作者： Jie LIU Xiang-zhen shi Li YANG Chang-Yi LIU Jin-Cheng WANG Rui-Min ZHU xue-Li shi Qiu-Feng LIU International Business School Shanxi Normal UniversityXi'an 710062China University of Chinese Academy of Social Sciences Bejing 102488China School of Economics and Management Xinjiang UniversityUrumqi 830046China Global Energy Interconnection Development and Cooperation Organization(GEIDCO) Bejing 100031China Hubei Enshi College Enshi 445099China CMA Earth System Modeling and Prediction Centre China Meteorological AdministrationBeijing 100081China National Climate Centre China Meteorological AdministrationBeijing 100081China

Developing a localized and consistent model framework for climate loss and damage assessment is crucial for the policy-making of climate change mitigation and *** study introduces a comprehensive,multidisciplinary Integrated Assessment Model(IAM)framework for evaluating climate damage in China,utilizing BCC-SESM climate model and FUND sectoral climate damage model under the SSP2-RCPs *** a bottom-up approach,the research estimates climate damage across eight major sectors,recalibrates sectoral climate damage functions and parameters for China,and elucidates distinctions among direct climate loss,market climate loss,and aggregate climate *** findings reveal that the total climate damage function for China follows a quadratic pattern in response to temperature *** 2050,the estimated climate damage is projected to be 5.4%,5.7%,and 8.2%of GDP under RCP2.6,RCP4.5,and RCP8.5,***,both direct and market climate losses are projected to remain below 2%of GDP by 2050,while the aggregate climate loss could reach as high as 8.2%,which is predominantly attributed to non-market *** a sectoral perspective,under the RCP8.5 scenario,human health damage constitutes the largest share(61.9%)of the total climate loss by 2050,followed by sea-level rise damage(18.6%).This study sheds lights on the adaptation policy that should attach importance to the non-market sectors,particularly focusing on human health and sea-level rise.

关键词： Climate loss and damage Integrated assessment model(IAM) FUND model Representative concentration pathways(RCPs)scenario BCC-SESM

Amino acids TORC(talk)to anabolism through uncharged tRNA

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Science China(Life Sciences) 2024年第8期67卷 1775-1776页

作者： zhen-zhen Ma shi-Min Zhao The Obstetrics&Gynecology Hospital of Fudan University State Key Laboratory of Genetic EngineeringShanghai Key Laboratory of Metabolic Remodelling and HealthFudan UniversityShanghai 200090China

Anabolism is essential for proliferation as well as to replenish dysfunctional macromolecules in *** to that both substantial building blocks and energy are required for anabolism,cells must double check whether these prerequisites are met before deciding to start *** acids are building blocks of protein synthesis,their sufficiency in cells is closely monitored by several mechanisms,which all are linked to protein synthesis.

关键词： synthesis. synthesis deciding