检索结果-南通市图书馆

型壳加热温度对单晶高温合金显微组织及“雀斑”形成的影响

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2024年第4期34卷 1191-1203页

作者：王志成李嘉荣刘世忠杨万鹏王效光北京航空材料研究院先进高温结构材料重点实验室北京100095

利用所设计的阶梯试样进行定向凝固试验和模拟,研究定向凝固过程型壳加热温度对单晶高温合金铸件显微组织和“雀斑”形成的影响。分析糊状区的温度场及形貌。结果表明,升高型壳加热温度,一次和二次枝晶间距减小,糊状区液相的渗透率和对... 详细信息

利用所设计的阶梯试样进行定向凝固试验和模拟,研究定向凝固过程型壳加热温度对单晶高温合金铸件显微组织和“雀斑”形成的影响。分析糊状区的温度场及形貌。结果表明,升高型壳加热温度,一次和二次枝晶间距减小,糊状区液相的渗透率和对流通道的宽度降低,“雀斑”形成倾向性降低,“雀斑”宽度减小,“雀斑”区域枝晶碎片减少。此外,随着型壳加热温度的升高,糊状区液相冷却速率增加,糊状区熔体的冷却时间减少,液体流动对枝晶的破碎程度得到削弱,这进一步降低单晶高温合金铸件“雀斑”形成的倾向性。

关键词：单晶高温合金 “雀斑”形成型壳加热温度定向凝固数值模拟

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2006年第6期48卷 654-663页

作者： Xu-Li Tang Guo-Yi Zhou Shu-Guang liu De-Qiang Zhang shi-zhong liu Jiong Li Cun-Yu Zhou South China Botanical Garden the Chinese Academy of Sciences Guangzhou 510650 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China Science Applications International Corporation （ SAIC） US Geological Survey （ USGS） National Center for Earth Resources Observation and Science （EROS） Sioux Falls South Dakota 57198 USA

The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve （DNR） In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season （April-September） and with low rates In the cool dry season （October-March）. Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean （± SD） soil respiration rate In the DNR forests was （9.0 ± 4.6） Mg CO2-C/hm^2 per year, ranging from （6.1 ± 3.2） Mg CO2-C/hm^2 per year in early successional forests to （10.7 ± 4.9） Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.

关键词： Dinghushan Nature Reserve moisture sensitivity Q10 soil CO2 efflux soil respiration subtropical forests successional forests temperature sensitivity Tropic of Cancer.

Wintertime Arctic Sea-Ice Decline Related to Multi-Year La Niña Events

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第9期41卷 1680-1690页

作者： Wenxiu zhong Qian shi Qinghua YANG Jiping liu Song YANG School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityGuangzhou 510275China

Arctic sea ice has undergone a significant decline in the Barents-Kara Sea(BKS)since the late *** studies have shown that the decrease in sea ice caused by increased poleward moisture transport is modulated by tropical sea temperature changes(mainly referring to La Niña events).The occurrence of multi-year La Niña(MYLA)events has increased significantly in recent decades,and their impact on Arctic sea ice needs to be further *** this study,we investigate the relationship between sea-ice variation and different atmospheric diagnostics during MYLA and other La Niña(OTLA)*** decline in BKS sea ice during MYLA winters is significantly stronger than that during OTLA *** is because MYLA events tend to be accompanied by a warm Arctic-cold continent pattern with a barotropic high pressure blocked over the Urals ***,more frequent northward atmospheric rivers intrude into the BKS,intensifying longwave radiation downward to the underlying surface and melting the BKS sea ***,in the early winter of OTLA years,a negative North Atlantic Oscillation presents in the high latitudes of the Northern Hemisphere,which obstructs the atmospheric rivers to the south of *** infer that such a different response of BKS sea-ice decline to different La Niña events is related to stratospheric *** the rapid climate changes in the past,more frequent MYLA events may account for the substantial Arctic sea-ice loss in recent decades.

关键词： Arctic sea ice multi-year ENSO Ural blocking atmospheric river Barents-Kara Sea

X-ray-activated Bi^(3+)/Pr^(3+)co-doped LiYGeO_4 phosphor with UV and NIR dual-emissive persistent luminescence

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第5期42卷 955-961,I0005页

作者： Xianggui Yin Hongyun zhong Lin liu Junpeng shi Xia Sun Yun Zhang State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou350002China Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials Xiamen Institute of Rare Earth MaterialsHaixi InstituteChinese Academy of SciencesXiamen361021China Fujian Science and Technology Innovation Laboratory for Optoelectronic Information of China Fuzhou350108China

X-ray-activated luminescence materials have broad application prospects in photodynamic therapy of deep *** them,X-ray-activated persistent luminescence materials(PLMs)exhibiting multiple emission peaks have drawn extensive attention for the ir capacity to achieve a combination of bioimaging and therapeutic ***,we developed a novel PLM,LiYGeO_4:Bi^(3+),Pr^(3+),that simultaneously exhibits UV and NIR dual persistent luminescence(PersL)emissions after irradiation by *** material can be re peatedly excited by X-ray and emits similar lumine scence intensity every time,which shows good PersL *** addition,LiYGeO_4:Bi^(3+),Pr^(3+)exhibits photostimulated PersL properties by stimulation with a red light-emitting diode(LED)or NIR laser after long-term *** work provides a new choice of X-ray-excited PLMs with UV and NIR dual emission and the novel phosphor shows promise as a potential candidate for the integration of treatment and diagnosis of deep tumors.

关键词： Co-doping X-ray-activated Dual emissions Persistent luminescence Rare earths

A residual denoising and multiscale attention-based weighted domain adaptation network for tunnel boring machine main bearing fault diagnosis

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第8期67卷 2594-2618页

作者： zhong Tao QIN ChengJin shi Gang ZHANG ZhiNan TAO JianFeng liu ChengLiang State Key Laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

As a critical component of a tunnel boring machine(TBM),the precise condition monitoring and fault analysis of the main bearing is essential to guarantee the safety and efficiency of the TBM cutter ***,under conditions of strong noise and complex working environments,traditional signal decomposition and machine learning methods struggle to extract weak fault features and achieve high fault classification *** address these issues,we propose a novel residual denoising and multiscale attention-based weighted domain adaptation network(RDMA-WDAN)for TBM main bearing fault *** approach skillfully designs a deep feature extractor incorporating residual denoising and multiscale attention modules,achieving better domain adaptation despite significant domain *** residual denoising component utilizes a convolutional block to extract noise features,removing them via residual ***,the multiscale attention module uses a 4-branch convolution and 3 pooling strategy-based channel–spatial attention mechanism to extract multiscale features,concentrating on deep fault *** training,a weighting mechanism is introduced to prioritize domain samples with clear fault *** optimizes the deep feature extractor to obtain common features,enhancing domain adaptation.A low-speed and heavy-loaded bearing testbed was built,and fault data sets were established to validate the proposed *** experiments show that in noise domain adaptation tasks,proposed the RDMA–WDAN significantly improves target domain classification accuracy by 42.544%,23.088%,43.133%,16.344%,5.022%,and 9.233%over dense connection network(DenseNet),squeeze–excitation residual network(SE-ResNet),antinoise multiscale convolutional neural network(ANMSCNN),multiscale attention module-based convolutional neural network(MSAMCNN),domain adaptation network,and hybrid weighted domain adaptation(HWDA).In combined noise and working condition domain a

关键词： tunnel boring machine(TBM) main bearing fault diagnosis domain adaptation antinoise cross working RDMA-WDAN