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Mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding
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作者 Zongan Luo Xin Zhang +3 位作者 Zhaosong Liu Hongyu Zhou Mingkun Wang Guangming Xie 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第8期1890-1899,共10页
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile... This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum,and the tensile specimens fractured at the matrix after exceeding 1 Pa.Non-equilibrium grain boundaries were formed at the hot-rolled interface,and a large amount of Mg_(2)Si particles were linearly precipitated along the interfacial grain boundaries(IGBs).During subsequent heat treatment,Mg_(2)Si particles dissolved back into the matrix,and Al_(2)O_(3) film remaining at the interface eventually evolved into MgO.In addition,the local IGBs underwent staged elimination during HRB,which facilitated the interface healing due to the fusion of grains at the interface.This process was achieved by the dissociation,emission,and annihilation of dislocations on the IGBs. 展开更多
关键词 6061 Al alloy hot-roll bonding VACUUM mechanical properties interfacial grain boundaries
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Temperate Stutzerimonas Phage Encoding Toxin-Antitoxin System Genes Represents a Novel Genus
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作者 ZHANG Hong GUO Ruizhe +14 位作者 GAO Chen ZHENG Kaiyang XIONG Yao DONG Yue LIU Yundan WANG Ziyue CHEN Ying WANG Hongmin SHAO Hongbing SUNG Yeong Yik MOK Wen Jye WONG Li Lian MCMINN Andrew WANG Min LIANG Yantao 《Journal of Ocean University of China》 SCIE CAS CSCD 2024年第4期1087-1101,共15页
Stutzerimonas have been extensively studied due to their remarkable metabolic and physiological diversity.However,research on its phages is currently limited.In this study,we isolated a novel double-stranded DNA(dsDNA... Stutzerimonas have been extensively studied due to their remarkable metabolic and physiological diversity.However,research on its phages is currently limited.In this study,we isolated a novel double-stranded DNA(dsDNA)phage,vB_SstM-PG1,from the marine environment that infects Stutzerimonas stutzeri G1.Its dsDNA genome is 37204 bp long with a G/C content of 64.14%and encodes 54 open reading frames.The phage possesses a tail packaging structure that is different from known Stutzerimonas stutzeri phages and exhibits structural protein characteristics similar to those of temperate phages.In addition,two genes of toxin-antitoxin system,including YdaS_antitoxin and HEPN_SAV_6107,were found in the vB_SstM-PG1 genome and play important roles in regulating host growth and metabolism.With phylogenetic tree and comparative genomic analysis,it has been determined that vB_SstM-PG1 is not closely related to any phages previously identified in the GenBank database.Instead,it has a connection with enigmatic,uncultured viruses.Specifically,the vB_SstM-PG1 virus exhibits an average nucleotide identity of over 70%with six uncultivated viruses identified in the IMG/VR v4 database.This significant finding has resulted in the identification of a novel viral genus known as Metabovirus. 展开更多
关键词 Stutzerimonas vB_SstM-PG1 Metabovirus temperate phage genomic and phylogenetic analysis
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Variations and determinants of tissue carbon concentration of 32 sympatric temperate tree species
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作者 Jun Pan Jing Zhang +8 位作者 Xingchang Wang Xiuwei Wang Qi Wang Yankun Liu Yulong Liu Yunfei Diao Xiankui Quan Chuankuan Wang Xiaochun Wang 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第6期62-72,共11页
Plant carbon(C)concentration is a fundamental trait for estimating C storage and nutrient utilization.However,the mechanisms of C concentration variations among different tree tissues and across species remains poorly... Plant carbon(C)concentration is a fundamental trait for estimating C storage and nutrient utilization.However,the mechanisms of C concentration variations among different tree tissues and across species remains poorly understood.In this study,we explored the variations and determinants of C concentration of nine tissues from 216 individuals of 32 tree species,with particular attention on the effect of wood porosity(i.e.,non-porous wood,diffuse-porous wood,and ring-porous wood).The inter-tissue pattern of C concentration diverged across the three porosity types;metabolically active tissues(foliage and fine roots,except for the foliage of ring-porous species)generally had higher C levels compared with inactive wood.The poor inter-correlations between tissue C concentrations indicated a necessity of measuring tissue-and specific-C concentrations.Carbon concentration for almost all tissues generally decreased from non-porous,to diffuse-porous and to ring-porous.Tissue C was often positively correlated with tissue(foliage and wood)density and tree size,while negatively correlated with growth rate,depending on wood porosity.Our results highlight the mediating effect of type of wood porosity on the variation in tissue C among temperate species.The variations among tissues were more important than that among species.These findings provided insights on tissue C concentration variability of temperate forest species. 展开更多
关键词 Carbon fraction Growth rate temperate tree species Tissue density Wood porosity
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Grouping tree species to estimate basal area increment in temperate multispecies forests in Durango,Mexico
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作者 Jaime Roberto Padilla-Martínez Carola Paul +2 位作者 Kai Husmann Jose Javier Corral-Rivas Klaus von Gadow 《Forest Ecosystems》 SCIE CSCD 2024年第1期1-13,共13页
Multispecies forests have received increased scientific attention,driven by the hypothesis that biodiversity improves ecological resilience.However,a greater species diversity presents challenges for forest management... Multispecies forests have received increased scientific attention,driven by the hypothesis that biodiversity improves ecological resilience.However,a greater species diversity presents challenges for forest management and research.Our study aims to develop basal area growth models for tree species cohorts.The analysis is based on a dataset of 423 permanent plots(2,500 m^(2))located in temperate forests in Durango,Mexico.First,we define tree species cohorts based on individual and neighborhood-based variables using a combination of principal component and cluster analyses.Then,we estimate the basal area increment of each cohort through the generalized additive model to describe the effect of tree size,competition,stand density and site quality.The principal component and cluster analyses assign a total of 37 tree species to eight cohorts that differed primarily with regard to the distribution of tree size and vertical position within the community.The generalized additive models provide satisfactory estimates of tree growth for the species cohorts,explaining between 19 and 53 percent of the total variation of basal area increment,and highlight the following results:i)most cohorts show a"rise-and-fall"effect of tree size on tree growth;ii)surprisingly,the competition index"basal area of larger trees"had showed a positive effect in four of the eight cohorts;iii)stand density had a negative effect on basal area increment,though the effect was minor in medium-and high-density stands,and iv)basal area growth was positively correlated with site quality except for an oak cohort.The developed species cohorts and growth models provide insight into their particular ecological features and growth patterns that may support the development of sustainable management strategies for temperate multispecies forests. 展开更多
关键词 temperate multispecies forests Cluster analysis Basal area increment Generalized additive models
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Instrumented oscillographic study on impact toughness of an axle steel DZ2 with different tempering temperatures
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作者 Shuo Liu Peng Zhang +6 位作者 Bin Wang Kaizhong Wang Zikuan Xu Fangzhong Hu Xin Bai Qiqiang Duan Zhefeng Zhang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第7期1590-1598,共9页
Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the... Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface. 展开更多
关键词 axle steel DZ2 tempering process impact toughness oscillographic impact test impact crack propagation carbides
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Characterization of W80Cu20 alloy sheet prepared by hot-rolling 被引量:3
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作者 Hu-Ping Guo Wen-Ge Chen Hui Zhang 《Rare Metals》 SCIE EI CAS CSCD 2013年第6期569-573,共5页
Multi-pass hot-rolling technique was used to fabricate W80Cu20 alloy,and its properties were characterized in this paper.Results show that the W-Cu alloy sheets with a thickness of 0.5 mm and a relative density of99.8... Multi-pass hot-rolling technique was used to fabricate W80Cu20 alloy,and its properties were characterized in this paper.Results show that the W-Cu alloy sheets with a thickness of 0.5 mm and a relative density of99.87%can be successfully made using this new technique at 800℃.In hot-rolling process,Cu phases are closely surrounded by W particles under the rolling stress to form a network microstructure,thus making significant increase in electrical and thermal conductivity up to53.00%and 24.44%,respectively.Transverse and longitudinal hardness of the W–Cu sheets significantly increase due to the enhanced densification and deformation strength.Similar to that of the raw materials,three fracture types were observed in the hot-rolled materials,i.e.,ductile fracture of Cu binding phases,trans-granular fracture of W phases,and W–W interfacial fracture. 展开更多
关键词 hot-rolling W-Cu alloy PROPERTIES Fracture morphology SHEET
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Numerical simulation on microstructural evolution during multipass hot-rolling of aluminum alloys 被引量:1
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作者 张辉 杨立斌 +1 位作者 彭大暑 林高用 《中国有色金属学会会刊:英文版》 CSCD 2001年第2期230-234,共4页
Numerical simulation on microstructural evolution during multipass hot rolling of aluminum alloys was performed by using DEFORM TM software and incorporating Zener Hollomon parameter Z . The distributions of equivalen... Numerical simulation on microstructural evolution during multipass hot rolling of aluminum alloys was performed by using DEFORM TM software and incorporating Zener Hollomon parameter Z . The distributions of equivalent stress, equivalent strain, equivalent strain rate and temperature, as well as the distribution of recrystallization fraction through the thickness of deformed specimen during multipass hot rolling of 5182 aluminum alloy, were all calculated. The results agree well with the metallographic examination of the deformed specimen on Gleeble 1500. [ 展开更多
关键词 5182 ALUMINUM alloy multipass hot-rolling MICROSTRUCTURAL evolution FEM numerical simulation
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Scheduling problem for hot-rolling seamless steel tube production 被引量:1
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作者 HUO Jiazhen~(1)),LILin~(1,2)) and LI Hu~(1)) 1) School of Economics and Management TongJi University,Shanghai 20009,China 2) School of Business,East China University of Science and Technology,Shanghai 200237,China 《Baosteel Technical Research》 CAS 2010年第S1期95-,共1页
Taking the seamless tube plant of Baoshan Iron & Steel Complex in China as the background,we analyze the characters of hot rolling seamless steel tube:multi varieties,low volume,complicated production process,flex... Taking the seamless tube plant of Baoshan Iron & Steel Complex in China as the background,we analyze the characters of hot rolling seamless steel tube:multi varieties,low volume,complicated production process,flexible production routes.Then integrated scheduling problem for hot rolling seamless steel tube production is studied,which covers two key points;order-grouping problem and solution method for flowshop/jobshop scheduling problem.On the basis of these two problems,integrated scheduling decision system is developed.The design idea,function flow sheet,data processing method,and functional module of visualized human-computer interactive scheduling system implemented in seamless steel tube plant of Shanghai Baoshan Iron & Steel Complex are described into detail.Compared with manual system,the performance of system shows the applicability and superiority in several criteria. 展开更多
关键词 hot-rolling seamless steel tube production scheduling problem order-grouping problem decision system
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Microstructural evolution in Al-Zn eutectoid alloy by hot-rolling
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作者 Toshiaki MANAKA Goroh ITOH +1 位作者 Yoshinobu MOTOHASHI Takaaki SAKUMA 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第7期2107-2111,共5页
The Al-Zn eutectoid alloy has been widely known as a typical superplastic metallic material, where fine-grained microstructure is usually obtained by heat treatment. Recently, thermo-mechanical controlled process has ... The Al-Zn eutectoid alloy has been widely known as a typical superplastic metallic material, where fine-grained microstructure is usually obtained by heat treatment. Recently, thermo-mechanical controlled process has also been reported to provide a fine-grained microstructure. In the present study, Al-Zn alloy ingots of 20 mm in thickness were homogenized and hot-rolled to a thickness of 2 mm under three processes: 1) the specimen was air-cooled after homogenization and hot-rolled; 2) the specimen was water-quenched after homogenization and hot-rolled; 3) the specimen was immediately hot-rolled after homogenization. Microstructural observation showed that, in processes l and 3, lamellar microstructure was formed after homogenization, and became fragmented to fine-grained microstructure as the hot roiling process proceeded. In process 2, fine-grained microstructure without lamellar microstructure was attained throughout the hot-rolling process. A minimum grain size of 1.6 μm was obtained in process 3. Tensile tests at room temperature showed that the elongation to failure was the largest in process 3. 展开更多
关键词 aluminum-zinc alloy eutectoid microstructure control hot-rolling superplastic material
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Deep learning for predictive mechanical properties of hot-rolled strip in complex manufacturing systems 被引量:2
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作者 Feifei Li Anrui He +5 位作者 Yong Song Zheng Wang Xiaoqing Xu Shiwei Zhang Yi Qiang Chao Liu 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第6期1093-1103,共11页
Higher requirements for the accuracy of relevant models are put throughout the transformation and upgrade of the iron and steel sector to intelligent production.It has been difficult to meet the needs of the field wit... Higher requirements for the accuracy of relevant models are put throughout the transformation and upgrade of the iron and steel sector to intelligent production.It has been difficult to meet the needs of the field with the usual prediction model of mechanical properties of hotrolled strip.Insufficient data and difficult parameter adjustment limit deep learning models based on multi-layer networks in practical applications;besides,the limited discrete process parameters used make it impossible to effectively depict the actual strip processing process.In order to solve these problems,this research proposed a new sampling approach for mechanical characteristics input data of hot-rolled strip based on the multi-grained cascade forest(gcForest)framework.According to the characteristics of complex process flow and abnormal sensitivity of process path and parameters to product quality in the hot-rolled strip production,a three-dimensional continuous time series process data sampling method based on time-temperature-deformation was designed.The basic information of strip steel(chemical composition and typical process parameters)is fused with the local process information collected by multi-grained scanning,so that the next link’s input has both local and global features.Furthermore,in the multi-grained scanning structure,a sub sampling scheme with a variable window was designed,so that input data with different dimensions can get output characteristics of the same dimension after passing through the multi-grained scanning structure,allowing the cascade forest structure to be trained normally.Finally,actual production data of three steel grades was used to conduct the experimental evaluation.The results revealed that the gcForest-based mechanical property prediction model outperforms the competition in terms of comprehensive performance,ease of parameter adjustment,and ability to sustain high prediction accuracy with fewer samples. 展开更多
关键词 hot-rolled strip prediction of mechanical properties deep learning multi-grained cascade forest time series feature extraction variable window subsampling
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Optimization technology of scheduling for hot-rolling mill
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作者 HUANG Kewei and DU Bin Automation Division,Research Institute,Baoshan Iron & Steel Co.,Ltd.,Shanghai 201900,China 《Baosteel Technical Research》 CAS 2010年第S1期96-,共1页
To establish the rolling plan of cold-rolling flattening set is very complicated,it is restrained by several constraints of rolling schedule.Operator's subjective and other human factors also affect the rationalit... To establish the rolling plan of cold-rolling flattening set is very complicated,it is restrained by several constraints of rolling schedule.Operator's subjective and other human factors also affect the rationality of plan arrangement seriously.Its result causes many abuses such as overusing transition strip,high-frequent roller switching,no-fully utilization of rollers,low arrangement rate of the plan.Therefore,we have initially developed a practical optimization model of rolling plan and schedule,which could be established and optimized by computer automatically,and a dynamic alignment module which have friendly UI according to the experience of operators.They have greatly enhanced the system usability.This system takes full advantage of relationship between the roller roughness and the rolling weight,reasonably arranges rolling based on different roughness demand,effectively enhances the use factor of roller and the smooth quality of steel string coil. A practical and effective scheduling optimization algorithm and rolling scheduling optimization applications system was developed based on the study of mixed hot rolling scheduling optimization model of carbon steel,stainless steel,stainless steel and carbon steel cross-rolling.The online application indicates that the model and algorithm is designed reasonable,practical and effective.This model system can significantly improve the scheduling efficiency and quality and it's also very positive in reducing heating energy consumption,enhancing the volume of units rolling plan,and optimizing the production of hot-rolled unit organization and planning and scheduling. 展开更多
关键词 hot-rolling SCHEDULING MODELING application system developing
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Three-dimensional assessment of movement patterns of Sichuan snub-nosed monkeys affected by habitat structure in temperate forests
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作者 Hai-Tao Yang Shun Li +8 位作者 Rong Hou Wen-Tao Song Yan-Wen Fu Yong-Bo Li Xiao-Wei Wang Gang He Colin A.Chapman Qing-Hua Guo Bao-Guo Li 《Zoological Research》 SCIE CAS CSCD 2023年第2期361-365,共5页
DEAR EDITOR,Movement patterns can reflect species-specific characteristics of individuals and animal groups at a given scale. Accurate three-dimensional(3D) assessment can quantify the relationship between movement pa... DEAR EDITOR,Movement patterns can reflect species-specific characteristics of individuals and animal groups at a given scale. Accurate three-dimensional(3D) assessment can quantify the relationship between movement patterns of an animal and its unique habitat. Here, we evaluated the effects of habitat structure on movement patterns of the golden snub-nosed monkey(Rhinopithecus roxellana). We used airborne light detection and ranging(LiDAR) to map the 3D structure of the temperate forest in the Qinling Mountains(Shaanxi, China). 展开更多
关键词 HABITAT movement temperATE
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Numerical Simulation of Stress Field in Physical Tempering Process of Flat Soda Lime Silica Glass
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作者 刘超英 HE Dongsheng +4 位作者 OU Yingchun HE Feng HAO Lizi XU Shaokun MA Juanrong 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2023年第1期20-30,共11页
Based on the analysis of different theory for glass tempering process,the“structural theory”with stress relaxation and structural relaxation effects was selected to investigate the tempering of flat glass quantifica... Based on the analysis of different theory for glass tempering process,the“structural theory”with stress relaxation and structural relaxation effects was selected to investigate the tempering of flat glass quantificationally.The geometrical model with small size and non-homogeneous mesh were considered to build the finite element models according to the characteristics of stress field.The tempering process of flat glass with12 mm thickness was calculated with the verified finite element model.The transient and permanent stress of the central area,edge and corner end of the flat glass are obtained and analyzed.From the calculation results of basic case,the transient tensile stress at the upper surface of the central area,the center point of edge,the edge of edge,the edge of corner were 14.30,18.94,40.76 and 34.75 MPa,respectively.The transient tensile stress at these points were dangerous to promote the glass to break during the tempering.In addition,the point at the diagonal line of symmetry plane in the thickness direction,which is 14 mm from corner,has the maximum permanent tensile stress about 70.01 MPa in the flat glass after tempering.Thus,it is indicated that the corner is the weakest region in the tempered glass. 展开更多
关键词 nite element temperING stress relaxation structural relaxation compressive stress tensile stress
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Effect of low-temperature tempering on the mechanical properties of cold-rolled martensitic steel
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作者 ZHU Xiaodong XUE Peng LI Wei 《Baosteel Technical Research》 CAS 2023年第1期11-16,共6页
Cold-rolled martensitic steel is an important type of advanced high-strength steel for automobile production.With martensite as its primary microstructure constituent, martensitic steel possesses exceptional high stre... Cold-rolled martensitic steel is an important type of advanced high-strength steel for automobile production.With martensite as its primary microstructure constituent, martensitic steel possesses exceptional high strength despite its low alloy content.As the strength of cold-rolled martensitic steel increases, the martensite and carbon content also increases, leading to a decrease in bending properties and toughness.In this paper, the effect of various tempering parameters on the bending property and impact toughness of a quenched cold-rolled martensitic steel sheet was studied.It is found that after quenching, the ductility and impact toughness of the experimental steel are improved using low-temperature heat treatment.The optimal tempering conditions for ductility and toughness are analyzed. 展开更多
关键词 water quenching temperING ultrahigh strength martensitic steel sheet
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Trees species’ dispersal mode and habitat heterogeneity shape negative density dependence in a temperate forest
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作者 Lishunan Yang Daniel J.Johnson +5 位作者 Zhichun Yang Xiaochao Yang Qiulong Yin Ying Luo Zhanqing Hao Shihong Jia 《Forest Ecosystems》 SCIE CSCD 2023年第5期589-596,共8页
Conspecific negative density dependence(CNDD)is a potentially important mechanism in maintaining species diversity.While previous evidence showed habitat heterogeneity and species’dispersal modes affect the strength ... Conspecific negative density dependence(CNDD)is a potentially important mechanism in maintaining species diversity.While previous evidence showed habitat heterogeneity and species’dispersal modes affect the strength of CNDD at early life stages of trees(e.g.,seedlings),it remains unclear how they affect the strength of CNDD at later life stages.We examined the degree of spatial aggregation between saplings and trees for species dispersed by wind and gravity in four topographic habitats within a 25-ha temperate forest dynamic plot in the Qinling Mountains of central China.We used the replicated spatial point pattern(RSPP)analysis and bivariate paircorrelation function(PCF)to detect the spatial distribution of saplings around trees at two scales,15 and 50 m,respectively.Although the signal was not apparent across the whole study region(or 25-ha),it is distinct on isolated areas with specific characteristics,suggesting that these characteristics could be important factors in CNDD.Further,we found that the gravity-dispersed tree species experienced CNDD across habitats,while for wind-dispersed species CNDD was found in gully,terrace and low-ridge habitats.Our study suggests that neglecting the habitat heterogeneity and dispersal mode can distort the signal of CNDD and community assembly in temperate forests. 展开更多
关键词 BIODIVERSITY Conspecific negative density dependence Dispersal Replicated point patterns temperate forest Topographic habitat
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Effect of nitrogen content on the microstructure and mechanical properties of titanium-bearing nonquenched and tempered steel after hot forging
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作者 YU Dajiang GAO Jiaqiang ZHAO Sixin 《Baosteel Technical Research》 CAS 2023年第2期1-6,共6页
The microstructure and mechanical properties of titanium(Ti)-bearing medium-carbon nonquenched and tempered steel with different nitrogen content before and after hot forging were investigated through smelting,forging... The microstructure and mechanical properties of titanium(Ti)-bearing medium-carbon nonquenched and tempered steel with different nitrogen content before and after hot forging were investigated through smelting,forging,and laboratory tests.The results show that the grain size of nonquenched and tempered steel was gradually refined,and the ferrite content gradually increased with an increase in nitrogen content.The grain size of the material with low nitrogen content increased abnormally,and its impact properties significantly decreased after hot forging.The grain size of nonquenched and tempered steel with higher nitrogen content was slightly larger than that before forging,and the tensile and yield strength increased,but the impact toughness was not significantly reduced.The Ti-bearing nonquenched and tempered steel showed better strength and toughness after hot forging with the addition of 0.010%0.015%nitrogen. 展开更多
关键词 nonquenched and tempered steel nitrogen content TITANIUM FORGING mechanical properties MICROSTRUCTURE
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Effect of quenching and tempering processes on properties and microstructure of G115 steel
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作者 WANG Tingting XU Songqian 《Baosteel Technical Research》 CAS 2023年第4期17-21,共5页
The novel martensitic heat-resistant steel G115 was designed for thick-section boiler components of ultra-supercritical(USC) power plants at 630-650 ℃.The impact of the quenching and tempering processes on the proper... The novel martensitic heat-resistant steel G115 was designed for thick-section boiler components of ultra-supercritical(USC) power plants at 630-650 ℃.The impact of the quenching and tempering processes on the properties and microstructure of G115 steel was explored.The samples that were quenched and tempered twice had a higher tensile strength at room temperature and 650 ℃,and the impact energy was significantly improved.The strength and impact energy increased in proportion to the increase in the first quenching temperature.The microstructure differences between the single and double quenched and tempered samples were examined using metallographic microscopy and scanning electron microscopy.The grain size of the double quenched and tempered samples was finer than that of the single quenched and tempered samples, and the tempered martensite lath is more visible, as are the carbides and other precipitates, which are finer and more uniformly distributed.As the first quenching temperature increased, the grains became coarser but more uniform. 展开更多
关键词 G115 quenching and tempering tensile properties MICROSTRUCTURE
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Tempered分数阶微分方程Nagumo型唯一解
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作者 黄洪鸿 《理论数学》 2023年第11期3254-3261,共8页
本文重点讨论Tempered分数阶微分方程柯西问题Nagumo迭代近似值的唯一性和收敛性。首先把柯西问题转化成等价Volterra积分方程,证出解的唯一性。然后,运用迭代方法,我们将Nagumo型唯一性和迭代近似值序列扩展到Tempered分数阶微分方程。
关键词 tempered分数阶算子 Nagumo型唯一性 迭代法
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中国主雨季极端小时降水时空分布和日变化特征 被引量:1
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作者 汪小康 崔春光 +1 位作者 刘柯 王晓芳 《气象》 CSCD 北大核心 2024年第4期393-406,共14页
基于国家级气象站逐小时降水资料,采用百分位阈值的极端降水定义方法,统计研究了中国1951—2021年4—10月小时降水时空分布和日变化特征。结果表明,中国主雨季极端降水阈值东南大、西北小,存在四个分别位于华南、环渤海、长江中下游和... 基于国家级气象站逐小时降水资料,采用百分位阈值的极端降水定义方法,统计研究了中国1951—2021年4—10月小时降水时空分布和日变化特征。结果表明,中国主雨季极端降水阈值东南大、西北小,存在四个分别位于华南、环渤海、长江中下游和四川盆地的大值区,随着极端性增强,北方小时降水阈值的增大较南方更显著,大值中心北移。月尺度上,小时降水的最高频次月份由南向北从5月推迟至8月,华西地区最晚(9—10月),随着极端性增强,最高频次月份由6月、7月推迟到7月、8月,且地区差异减小。日变化特征上,全国范围内小时降水频次占比,呈现午后到夜间的谷峰主循环和后半夜到上午的次循环,且随着极端性增强,主循环振幅增大,次循环峰值减小。不同地理位置看,四川盆地的极端小时降水峰值时刻出现在凌晨,其他三个大值区则与全国平均较为一致,日变化振幅从南到北逐渐减小,西部最大。小时降水峰值时刻具有空间聚集的特征,夜间峰值主要集中在南方沿海和华北、东北,早晨—上午峰值集中在中部、东部、西南和西北部分地区,空间分布中出现的逐渐推迟和突变特征与海陆分布和大地形密切相关。小时降水峰值时刻空间占比与频次占比的日变化特征类似,均有上午峰值平缓、夜间峰值陡峭的特征,这是因为不同站点到达夜间峰值的时刻接近,而到达上午峰值的时刻不同;两者主要区别在随着极端性增强,频次占比夜间主峰值显著增大,而峰值时刻空间占比主峰值几乎不变,这是因为频次的变化主要是由同一些站点上的次数变化导致,而非不同站点之间的差异。 展开更多
关键词 极端小时降水 百分比阈值 时空分布 日变化
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回火温度对易焊接80 kg级高强钢组织和力学性能的影响 被引量:1
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作者 刘丹 陈杰 +1 位作者 靳东 张青学 《热加工工艺》 北大核心 2024年第10期124-129,共6页
研究了不同回火温度对80 kg级直接淬火钢组织和性能的影响。结果表明:直接淬火钢具有较高的强韧性组合和高温回火抗性,当回火温度在450~650℃时,试验钢仍然保持板条状马氏体的形状和位向,随着回火温度升高,板条发生粗化,伴随着残余奥氏... 研究了不同回火温度对80 kg级直接淬火钢组织和性能的影响。结果表明:直接淬火钢具有较高的强韧性组合和高温回火抗性,当回火温度在450~650℃时,试验钢仍然保持板条状马氏体的形状和位向,随着回火温度升高,板条发生粗化,伴随着残余奥氏体的分解和碳化物的析出和长大等过程。当回火温度为700℃时,试验钢发生较高程度的再结晶,性能明显恶化。当回火温度为650℃时,试验钢具有最佳的综合力学性能,屈服强度为795 MPa,抗拉强度为821 MPa,断后伸长率为20.6%,标准试样-20℃冲击功为195 J。 展开更多
关键词 高强钢 回火温度 显微组织 力学性能 易焊接
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