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Selective laser melting of Al–8.5Fe–1.3V–1.7Si alloy: Investigation on the resultant microstructure and hardness

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Chinese Journal of Aeronautics 2015年第2期28卷 564-569页

作者： zheng lijing Liu Yingying Sun Shaobo Zhang Hu School of Materials Science and Engineering Beihang University

This article presents the microstructure and hardness variation of an Al 8.5Fe-1.3V 1.7Si （wt%, FVS0812） alloy after selective laser melting （SLM） modification. Three zones were distinguished across the melting pool of the SLM-processed FVS0812 alloy： the laser melted zone （LMZ）, the melting pool border, and the heat affected zone （HAZ） in the previously deposited area around the melting pool. Inside the LMZ, either an extremely fine cellular-dendritic structure or a mixture zone of the α-Al matrix and nanoscale Al12（Fe,V）3Si particles appeared. With a decreased laser beam scanning speed, the cellular-dendritic structure zone within the LMZ shrank significantly while the mixture zone expanded. The α-Al and Al12（Fe,V）3Si mixture zone was also observed in the HAZ, but another phase, submicron θ-Al13Fe4 particles with rectangular or hexagonal shapes, formed along the melting pool border. Microhardness tests indicated that the hardness of the SLM-processed FVS0812 samples far exceeded that of the as-cast FVS0812 alloy.

关键词： Al-Fe-V-Si alloys Hardness Melting pool Microstructure Selective laser melting

Microstructural evolution of a PM TiAl alloy during heat treatment in α+γ phase field

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Rare Metals 2012年第5期31卷 424-429页

作者： SU Meike zheng lijing LANG Zebao YAN Jie ZHANG Hu School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

In this study, the effect of temperatures and cooling rates of heat treatment on the microstructure of a powder metallurgy (PM) Ti-46Al-2Cr-2Nb-(B,W) (at.%) alloy was studied. Depending on the cooling rate and temperature, the different structures were obtained from the initial near-γ (NG) microstructures by heat treatment in the α+γ field. The results show that the microstructures of samples after furnace cooling (FC) consist primarily of equiaxed γ and α 2 grains, with a few grains containing lamellae. Duplex microstructures consist mainly of γ grains and lamellar colonies were obtained in the quenching into another furnace at 900°C (QFC) samples. However, further increasing of the cooling rate to air cooling (AC) induces the transformation of α→α_2 and results in a microstructure with equiaxed γ and α_2 grains, and no lamellar colonies are found.

关键词： γ-TiAl-based alloys powder metallurgy heat treatment duplex structure phase volume fractions

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混凝土材料动态破坏过程的近场动力学模拟

新型建筑材料 2024年第6期51卷 20-25,41页

作者：郑立静宁晓骏彭一昆明理工大学云南昆明650504

采用黏弹性近场动力学方法,根据混凝土单轴强度J准则类比得到近场动力学键伸长率的动态断裂准则。通过对骨料下的填充混凝土板、梁等构件进行模拟,探究了不同的加载速率下,骨料对裂纹形态及裂纹扩展路径的影响。结果表明,加载速率越大,... 详细信息

采用黏弹性近场动力学方法,根据混凝土单轴强度J准则类比得到近场动力学键伸长率的动态断裂准则。通过对骨料下的填充混凝土板、梁等构件进行模拟,探究了不同的加载速率下,骨料对裂纹形态及裂纹扩展路径的影响。结果表明,加载速率越大,混凝土中填充的骨料断裂度也越大。动态断裂J准则能准确描述混凝土在动态荷载下的破坏形态,该方法为混凝土的损伤防治工程提供了指导依据。

关键词：近场动力学动态断裂准则混凝土破坏动态荷载三点弯曲

Permutation polynomials x~(2k+1+3)+ax2k+2+bx over F_(22k) and their differential uniformity

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Science China(Information Sciences) 2020年第10期63卷 255-257页

作者： Jie PENG lijing zheng Chunsheng WU Haibin KAN Mathematics and Science College Shanghai Normal University School of Mathematics and Physics University of South China Department of Mathematics Lianyungang Normal University Shanghai Key Laboratory of Intelligent Information Processing School of Computer ScienceFudan University Fudan-Zhongan Joint Laboratory of Blockchain and Information Security Shanghai Blockchain Engineering Research Center Shanghai Institute for Advanced Communication and Data Science Shanghai Institute of Intelligent Electronics & Systems

Dear editor,A polynomial f（x）∈Fq[x] is called a permutation polynomial （PP） over the finite field Fq if the associated mapping f:c （?） f（c） from Fq to itself is bijective.A PP f is called a complete permutation polynomial if f（x）+x is a *** over finite fields of even characteristic have wide applications,including cryptography,coding theory,and communication *** many block ciphers with substitution-permutation network structure,the substitution box is usually a PP over F_(22k)for some positive integer *** resist the differential attacks,the differential uniformity of this

关键词： Finite fields Permutation polynomial Binomial Trinomial Differential uniformity

Formation Mechanisms of Rudstones and Their Effects on Reservoir Quality in the Shulu Sag, Bohai Bay Basin, Eastern China

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Journal of Earth Science 2017年第6期28卷 1095-1108页

作者： Xufeng Liu lijing zheng Zaixing Jiang Xiangxin Kong School of Energy Resources China University of Geosciences Key Laboratory of Petroleum Resources Research Institute of Geology and Geophysics Chinese Academy of Sciences

Based on observations made on cores and cuttings from several wells in the lowermost part of the third member of the Shahejie Formation, several rock types, specifically clast-supported rudstone, matrix-supported rudstone, mixed-source rudstone, calcisiltite/calcarenite, massive calci- lutite and laminated calcilutite, have been identified in the Shulu sag. According to the sedimentary structures and distribution characteristics of these rocks, the carbonate breccias fall into two cate- gories, based on their origins： one formed by fan-delta channel sedimentation, whereas the other formed by earthquake-induced slump fan deposition. Clast-supported rudstone and matrix- supported rudstone are the main lithologies deposited by braided rivers in the fan delta plain and front, of which the pore space is mainly dissolution pores within gravels and tectonic fissures. Clast- supported rudstone, matrix-supported rudstone and mixed-source rudstone are the main lithologies of the earthquake-induced slump fans. These carbonate breccias developed along with soft-sediment deformation structures, which are interpreted as seismites and are widely distributed in the sag, in which intercrystalline pores, intergranular pores and fissures created from diagenetic shrinkage are developed. The two kinds of rudstones have different reservoir characteristics and oil/gas testing re- suits. The rudstones generated in the fan delta have higher porosity and permeability, as well as bet- ter oil/gas testing results. Thus, they are key targets for petroleum exploration.

关键词： rock type formation mechanism depositional model reservoir quality Shulu sag

Corrosion resistance of carbon ion-implanted M50NiL aerospace bearing steel

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Progress in Natural Science:Materials International 2017年第5期27卷 615-621页

作者： Fangfang Wang Chungen Zhou lijing zheng Hu Zhang School of Materials Science and Engineering Beihang University

The effect of carbon implantation on the corrosion behavior of M50NiL aerospace bearing steel through surface modification was investigated. X-ray photoelectron spectroscopy, Auger electron spectroscopy and X-ray diffraction were used to analyze the composition and structure of the carbon-implanted layer. The corrosion properties of the untreated and carbon ion-implanted samples were evaluated by potentiodynamic curves and electrochemical impedance spectroscopy, which were carried out in 3.5% NaCl solution. Ion implantation of carbon in the M50NiL bearing steel yielded a distinct decrease of the corrosion current densities and an obvious increase of the polarization resistance. The experimental results indicated that the content of chromium oxide in the passive film increased with carbon implantation and that the intergranular corrosion was suppressed in the carbon-implanted sample. Better corrosion protection was observed in the carbon ion implantation sample.

关键词： Aerospace bearing steel Ion implantation Electrochemical test Corrosion resistance

基于F-score和二进制灰狼优化的肿瘤基因选择方法

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南京师大学报（自然科学版） 2024年第1期47卷 111-120页

作者：穆晓霞郑李婧河南师范大学计算机与信息工程学院河南新乡453007

针对肿瘤基因数据维度高、噪声多、冗余性高的现状,结合Spearman相关系数改进F-score算法,在此基础上优化二进制灰狼算法,提出了一种基于改进F-score和二进制灰狼算法的肿瘤基因选择算法.首先,考虑特征之间的相关性,计算每个特征的F-sc... 详细信息

针对肿瘤基因数据维度高、噪声多、冗余性高的现状,结合Spearman相关系数改进F-score算法,在此基础上优化二进制灰狼算法,提出了一种基于改进F-score和二进制灰狼算法的肿瘤基因选择算法.首先,考虑特征之间的相关性,计算每个特征的F-score值和特征之间的Spearman相关系数的绝对值;然后,计算权重系数得出各个特征的权重值,依据重要性进行排序,选出初选特征子集;最后,通过收敛因子的衰减曲线和初始化方法优化二进制灰狼算法,调整全局搜索和局部搜索所占比例,增强全局搜索能力并提高局部搜索速度,有效节省时间开销,提升特征选择的分类性能和效率,得到最优特征子集.在9个肿瘤基因数据集上测试所提算法,在分类准确率和筛选特征数目两个指标上进行仿真实验,并与4种其他算法进行对比,实验结果证明所提算法表现良好,可有效降低基因数据维度,并具有较好的分类精度.

关键词：肿瘤基因 Fisher-score Spearman 相关系数二进制灰狼优化算法特征选择

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Microstructure, Mechanical Properties and Oxidation Resistance of Nb-22Ti-14Si-2Hf-2Al-xCr Alloys

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Chinese Journal of Aeronautics 2012年第2期25卷 292-296页

作者： WANG Ligang JIA Lina CUI Renjie zheng lijing ZHANG Hu School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Nb-22Ti-14Si-2Hf-2Al-xCr （x=2, 6, 10, 14, 17 at%） alloys are prepared by arc-melting under argon atmosphere. Microstructural characteristics, mechanical properties and oxidation resistance of the arc-melted alloys are investigated. At 2 at% Cr content, the microstructure is composed of Nbss, Nb3Si and a small quantity of Nb5Si3, when the Cr contents increase, Nb3Si disappears. For the high Cr content （x ≥ 10 at%） alloys, besides the Nbss and Nb5Si3, Cr2Nb is also detected. With the increase of Cr content, the volume fractions of Cr2Nb and Nb5Si3 increase, while that of Nbss increases firstly and then begins to degrade when the Cr content is higher than 6 at%. For the alloy with 2 at% Cr, the room temperature fracture toughness is about 14.5 MPa·m1/2, but badly decreases to about 8.5 MPa·m1/2, when the Cr contents increase. Vickers hardness of Nbss tends to increase linearly from about 400 to 500, while that of silicides is not sensitive to Cr contents, about 950. The appearance of Cr2Nb phase significantly improves the high temperature oxidation resistance of the alloys with high Cr contents. The isothermal oxidation tests show that the oxidation kinetics of the alloys with various Cr contents follows parabolic oxidation kinetics.

关键词： arc-melted alloys Nb-Si alloys microstructure mechanical properties oxidation resistance

Primary Solidification Phase and Lamellar Orientation in Directionally Solidified Ti-45Al-7Nb Alloy

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Chinese Journal of Aeronautics 2012年第3期25卷 489-492页

作者： YAN Jie zheng lijing XIAO Zhixia YANG Lili ZHANG Hu Key Laboratory of Aerospace Advanced Materials and Performance of Ministry of Education School of Material Science and Engineering Beihang UniversityBeijing 100191China

Primary solidification phase and lamellar orientation are investigated in Ti-45Al-7Nb alloy at very high ratio of temperature gradient to growth rate （G/v） by a liquid-metal-cooled directionally solidified method. It shows that Ti-45Al-7Nb alloy solidifies with primary ct phase. Longitudinal （parallel to growth direction） microstructure shows that a dendrites in solid-liquid mushy zone are discontinuous and transverse mierostructure of a dendrites is worm-like feature. Growth direction of a phase is about 80° away from （0001）,a direction, and close to （1120） a direction. The corresponding lamellar orientation is aligned at the angle of about 10° to growth direction, which is consistent with a-dendrite growth direction according to Blackburn orientation relationship. Therefore, due to the altered growth direction of a phase, the lamellar orientation in Ti-45Al-7Nb alloy is controlled at the G/v ratio of 5 × 10^9 ***^-2.

关键词： metallic material titanium aluminides directional solidification crystal growth lamellar orientation