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Journal of Materials Science & Technology 2016年第12期32卷 1326-1331页

作者： Zhen Tan Lu Wang yunfei xue Xingwang Cheng Long Zhang School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 China National Key Laboratory of Science and Technology on Materials under Shock and Impact Beijing 100081 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post *** above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous *** milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous ***,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.

关键词： Amorphous powder Thermal stability Heat treatment Mechanical alloying Transmission electron microscopy

Dynamic Tensile Property of Zr-based Metallic Glass/Porous W Phase Composite

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Journal of Materials Science & Technology 2010年第10期26卷 908-913页

作者： yunfei xue Lu Wang Huanwu Cheng Fuchi Wang Haifeng Zhang Aiming Wang School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The dynamic tensile deformation and fracture behavior of the Zr-based metallic glass/porous W phase composite were investigated at room temperature by means of the Split Hopkinson Tension Bar （SHTB）.It was found that the composite exhibited no appreciable macroscopic plastic deformation prior to catastrophic fracture and the fracture surface was perpendicular to the axial *** micro cracks were observed along the interface between W grains or the interface between the metallic glass phase and the W *** electron microscopy （SEM） observations revealed that vein-like patterns,dimple-like patterns and substantive ridge-like structures were the typical fracture morphologies on the fracture surface for the metallic glass phase and the morphology of the W phase is a mixture of intergranular and transgranular *** on those results referred above,the dynamic tensile deformation and fracture mechanism of the Zr-based metallic glass/porous W phase composite were discussed in detail.

关键词： Metallic glasses Porous W Composite Dynamic tension Fracture behavior

Ultrashort-time liquid phase sintering of high-performance fine-grain tungsten heavy alloys by laser additive manufacturing

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Journal of Materials Science & Technology 2021年第31期90卷 30-36页

作者： Shangcheng Zhou Yao-Jian Liang Yichao Zhu Benpeng Wang Lu Wang yunfei xue School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

Liquid phase sintering(LPS)is a proven technique for preparing large-size tungsten heavy alloys(WHAs).However,for densification,this processing requires that the matrix of WHAs keeps melting for a long time,which simultaneously causes W grain coarsening that degenerates the *** work develops a novel ultrashort-time LPS method to form bulk high-performance fine-grain WHAs based on the principle of laser additive manufacturing(LAM).During LAM,the high-entropy alloy matrix(Al_(0.5)Cr_(0.9)FeNi_(2.5)V_(0.2))and W powders were fed simultaneously but only the matrix was melted by laser and most W particles remained solid,and the melted matrix rapidly solidified with laser moving away,producing an ultrashort-time LPS processing in the melt pool,i.e.,laser ultrashort-time liquid phase sintering(LULPS).The extreme short dwell time in liquid(-1/10,000 of conventional LPS)can effectively suppress W grain growth,obtaining a small size of 1/3 of the size in LPS ***,strong convection in the melt pool of LULPS enables a nearly full densification in such a short sintering *** with LPS WHAs,the LULPS fine-grain WHAs present a 42%higher yield strength,as well as an enhanced susceptibility to adiabatic shear banding(ASB)that is important for strong armor-piercing capability,indicating that LULPS can be a promising pathway for forming high-performance WHAs that surpass those prepared by conventional LPS.

关键词： Tungsten heavy alloy Laser additive manufacturing Liquid phase sintering

Thermal Residual Stresses in W Fibers/Zr-based Metallic Glass Composites by High-energy Synchrotron X-ray Diffraction

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Journal of Materials Science & Technology 2015年第2期31卷 159-163页

作者： Xinqiang Zhang yunfei xue Haifeng Zhang Huameng Fu Zhengbin Wang Zhihua Nie Lu Wang School of Materials Science and Engineering Beijing Institute of Technology National Key Laboratory of Science and Technology on Materials under Shock and Impact School of Materials Science and EngineeringBeijing Institute of Technology Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Thermal residual stresses in W fibers/Zr-based metallic glass composites were measured by in situ high energy synchrotron X-ray diffraction(HEXRD). The W fibers for the composites were 300,500,and 700 m m in diameter,respectively. Coaxial cylinder model(CCM) and finite element model(FEM) were employed to simulate the distribution of thermal residual stress,respectively. HEXRD results showed that the selected diameters of W fiber had little influence on the value of thermal residual stresses in the present composites. Thermal residual stresses simulated by CCM and FEM were in good agreement with HEXRD measured results. In addition,FEM results exhibited that thermal residual stress concentrated on interface between the two phases and area where the two W fibers were the closest ones to each other.

关键词： Metallic glass W fiber diameter Thermal residual s

Discovery of Late Jurassic Sporopollen Assemblage from the Tamulangou Formation in the Hongqi Sag of the Hailar Basin,Inner Mongolia,China

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Acta Geologica Sinica(English Edition) 2020年第5期94卷 1718-1720页

作者： WAN Chuanbiao xue yunfei SUN Yuewu HOU Yanping JIN Yudong ZHANG Xin LI Ti Exploration and Development Research Institute of Daqing Oilfield Company Ltd. DaqingHeilongjiang 163712China Key Laboratory for Evolution of Past Life and Environment in Northeast Asian(Jilin University) Ministry of EducationChangchun 130026China

Objective The Hailar Basin is situated in the northwestern margin of the Jiamusi-Mongolia *** was a continent marginal basin to the south of the Mongolia-Okhotsk Ocean during the Jurassic and *** basement of the basin... 详细信息

关键词： Jurassic basin Basin

Simultaneously improved the strength and ductility of laser powder bed fused Al-Cr-Fe-Ni-V high-entropy alloy by hot isostatic pressing:Microcrack closure and precipitation strengthening

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Journal of Materials Science & Technology 2024年第13期180卷 55-68页

作者： Ziwei Liu Zhen Tan Dingyong He Zheng Zhou Xingye Guo Wei Shao Haihua Yao yunfei xue Li Cui Faculty of Materials and Manufacturing Beijing University of TechnologyBeijing 100124China Beijing Engineering Research Center of Eco-materials and LCA Beijing 100124China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

Hot isostatic pressing(HIP)is usually applied to reduce the defects including cracks and pores in the materials prepared by laser powder bed fusion(LPBF).In the present research,in order to improve the relative density and mechanical property,HIP was employed on the LPBF-processed Al-Cr-Fe-Ni-V high-entropy alloy(HEA)with microcracks and *** microstructure evolution and property improvement induced by HIP were *** the LPBF-processed HEA,the microcracks were caused by residual stress and element segregation,and these microcracks as well as the pores reduced significantly after HIP ***,HIP temperature has a more critical effect on the microcrack closure than the holding time,thus,microcracks and pores still existed after HIP-1 treatment(1273 K,8 h),while HIP-2 treatment(1473 K,4 h)could close the microcracks *** crack closure was attributed to the interfacial diffusion of the alloying element under high temperature accompanied by high pressure,and the degree of element diffusion at both interfaces of the cracks determined the bonding strength after crack *** temperatures at high pressure induced more adequate element diffusion and higher bonding *** above high temperature and high pressure also induced the growth of the L1_(2) phase and the precipitation of the B2 phase in ***,the tensile strength and elonga-tion of the LPBF-processed HEA after HIP-2 treatment were simultaneously enhanced(80.7%and 222.5%higher than that of LPBF-processed HEA,respectively).This could be attributed to the combined effect of microcrack/pore closure and precipitation *** strengthening effect of the B2 phase and L1_(2) phase accounted for 53%(dislocation by-pass mechanism)and 47%(dislocation shearing mechanism)of the total precipitation strengthening,respectively.

关键词： High-entropy alloy Laser powder bed fusion Hot isostatic pressing Crack closure Precipitation strengthening

Solid-State Hydrogen Storage Properties of Ti-V-Nb-Cr High-Entropy Alloys and the Associated Effects of Transitional Metals(M=Mn,Fe,Ni)

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1113-1122页

作者： Bo Cheng Yunkai Li Xiaoxi Li Huibin Ke Liang Wang Tangqing Cao Di Wan Benpeng Wang yunfei xue Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing314019China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing100081China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing100081China Department of Mechanical and Industrial Engineering Norwegian University of Science and Technology7491TrondheimNorway

Recently,high-entropy alloys(HEAs)designed by the concepts of unique entropy-stabilized mechanisms,started to attract widespread interests for their hydrogen storage *** with body-centered cubic(BCC)structures present a high potential for hydrogen storage due to the high hydrogen-to-metal ratio(up to H/M=2)and vastness of *** many studies reported rapid absorption kinetics,the investigation of hydrogen desorption is missing,especially in BCC *** have investigated the crystal structure,microstructure and hydrogen storage performance of a series of HEAs in the Ti-V-Nb-Cr *** types of TiVCrNb HEAs(Ti_(4)V_(3)NbCr_(2),Ti_(3)V_(3)Nb2Cr_(2),Ti_(2)V_(3)Nb_(3)Cr_(2))with close atomic radii and different valence electron concentrations(VECs)were designed with single BCC phase by CALPHAD *** three alloys with fast hydrogen absorption kinetics reach the H/M ratio up to ***,Ti_(4)V_(3)NbCr_(2)alloy shows the hydrogen storage capacity of 3.7 wt%,higher than other HEAs ever *** dehydrogenation activation energy of HEAs’hydride has been proved to decrease with decreasing VEC,which may be due to the weakening of alloy atom and H ***,Ti_(4)V_(3)NbCr_(2)M(M=Mn,Fe,Ni)alloys were also synthesized to destabilize *** addition of Mn,Fe and Ni lead to precipitation of Laves phase,however,the kinetics did not improve further because of their own excellent hydrogen *** increasing the content of Laves phase,there appear more pathways for hydrogen desorption so that the hydrides are more easily dissociated,which may provide new insights into how to achieve hydrogen desorption in BCC HEAs at room temperature.

关键词： High-entropy alloy Hydrogen storage CALPHAD Hydride stability Hydrogen sorption kinetics

Dynamic recrystallization-induced temperature insensitivity of yield stress in single-crystal Al1.2CrFeCoNi micropillars

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Science China(Technological Sciences) 2021年第1期64卷 11-22页

作者： HUANG RuiRui ZHANG Qian ZHANG Xuan LI JianGuo CAO TangQing YAO JiaHao xue yunfei GAO HuaJian LI XiaoYan Center for Advanced Mechanics and Materials Applied Mechanics LaboratoryDepartment of Engineering MechanicsTsinghua UniversityBeijing 100084China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Mechanical and Aerospace Engineering College of EngineeringNanyang Technological UniversitySingapore 639798Singapore Institute of High Performance Computing A*STARSingapore 138632Singapore

High-entropy alloys, a new class of metallic materials, exhibit excellent mechanical properties at high temperatures. In spite of the worldwide interest, the underlying mechanisms for temperature dependence of mechanical properties of these alloys remain poorly understood. Here, we systemically investigate the mechanical behaviors and properties of Al_(1.2)CrFeCoNi(comprising a body-centered cubic phase) and Al_(0.3)CrFeCoNi(comprising a face-centered cubic phase) single-crystal micropillars with three orientations([100], [110], and [111]) at temperatures varying from 300 to 675 K by using in situ compression of micropillars inside a scanning electron microscope. The results show that the yield stresses of Al_(1.2)CrFeCoNi micropillars are insensitive to temperature changes, and their flow stresses and work hardening rates increase slightly with increasing temperature from 300 to550 K, which differs from the typical temperature dependence of yield/flow stresses in metals and alloys. In contrast,Al_(0.3)CrFeCoNi micropillars exhibit typical thermal softening. Furthermore, it is found that the Al_(1.2)CrFeCoNi micropillars exhibit a transition from homogenous deformation to localized deformation at a critical temperature, while the Al_(0.3)CrFeCoNi micropillars always maintain a well-distributed and fine slip deformation. Detailed transmission electron microscopy analyses reveal that dynamic recrystallization(involving dislocation tangles, and formation of dislocation cell structures and sub-grains)plays a key role in the observed temperature insensitivity of the yield stress and increasing flow stress(and work hardening rate)with increasing temperature in the Al_(1.2)CrFeCoNi micropillars, and that thermally activated dislocation slip leads to thermal softening of the Al_(0.3)CrFeCoNi micropillars. The differences in deformation modes and temperature dependence of the mechanical properties between Al_(1.2)CrFeCoNi and Al_(0.3)CrFeCoNi essentially originate from the d

关键词： high entropy alloy temperature insensitivity dynamic recrystallization micropillar deformation twin

Optimization of the Classic Transfer-Stacking Model Migration Algorithm: A Way to Solve Time-Varying Performance Degradation of Acute Kidney Injury Clinical Prediction Model

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Journal of Biosciences and Medicines 2021年第4期9卷 14-28页

作者： yunfei xue Department of Computer Science Jinan University Guangzhou China

Acute Kidney Injury (AKI) is one of the most common acute and critical illnesses in general wards and intensive care units. Its high morbidity and high fatality rate have become a major global public health problem. There are often serious lags in clinical diagnosis of AKI. Early diagnosis and timely intervention and effective care become critical. The use of electronic medical record data to build an AKI risk prediction model has been proven to help prevent the occurrence of AKI. However, in actual clinical applications, the distribution of historical data and new data will continue to vary over time, resulting in a significant decrease in the performance of the model. How to solve the problem of model performance degradation over time will be a core challenge for the long-term use of predictive models in clinical applications. Aiming at the above problems, this paper studies the classic Transfer-Stacking model migration algorithm. Aiming at the lack of this algorithm, such as the loss of a large amount of feature information of the target domain and poor fit when integrating the model of the target domain, the Accumulate-Transfer-Stacking algorithm is proposed to improve it. Improvements include: 1) Optimize the input vector and model integration algorithm of Transfer-Stacking’s target domain model. 2) Optimize Transfer-Stacking from a single-source domain model to a multi-source domain model. The experimental results show that for the improved algorithm proposed in this paper when the data is sufficient and insufficient, the average AUC value of the model on the data of subsequent years is 0.89 and 0.87, and the average F1 Score value is 0.45 and 0.36. Moreover, this method is significantly better than the unimproved Transfer-Stacking algorithm and baseline method, and can effectively overcome the problem of data distribution heterogeneity caused by time factors.

关键词： Acute Kidney Injury Electronic Medical Record Risk Prediction Transfer Learning

Experimental and numerical study on the dynamic shear banding mechanism of HfNbZrTi high entropy alloy

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Science China(Technological Sciences) 2022年第8期65卷 1808-1818页

作者： SONG Wei-Li MA Quan ZENG QingLei ZHU ShengXin SUI MingBin CAO TangQing QI Wei CHEN YinQiang YU XiaoQi xue yunfei CHEN Hao-Sen Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Lightweight Multi-Functional Composite Materials and Structures Beijing 100081China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Faculty of Civil Engineering and Mechanics Jiangsu UniversityZhenjiang 212013China

High-entropy alloys(HEAs) have attracted considerable attention in recent years because of their unique mechanical *** this work, the mechanism of dynamic shear banding(also called adiabatic shear bands, ASBs) in a BCC HEA HfNbZrTi was investigated combining dynamic experiments and numerical simulations. The temperature evolution during dynamic shear banding, which has been believed to play a dominant role during ASB formation in the literature, was measured using high-speed infrared thermal detectors synchronized with a split Hopkinson pressure bar system. The dynamic mechanical behavior of the BCC HEA was described using the Johnson-Cook model accompanied by damage accumulation. The process of ASB formation,considering potential contributions from thermal softening and damage softening, was numerically investigated by controlling the activation of each softening mechanism separately. Based on the results of experimental observation and numerical analysis,dynamic shear banding in this BCC HEA is proposed to be dominated by damage softening, and thermal softening only plays a secondary role, which differs from the thermal-softening-dominated ASB formation in typical FCC HEAs such as the Cantor alloy.

关键词： adiabatic shear band high entropy alloys damage softening thermal softening