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Microstructures, mechanical properties, and grease-lubricated sliding wear behavior of Cu–15Ni–8Sn–0.8Nb alloy with high strength and toughness

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Friction 2021年第5期9卷 1061-1076页

作者： Jinjuan CHENG Mincong MAO Xueping GAN Qian LEI zhou LI kechao zhou State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Materials Science and Engineering Central South UniversityChangsha 410083China

Alloys used as bearings in aircraft landing gear are required to reduce friction and wear as well as improve the load‐carrying capability due to the increased aircraft ***–15Ni–8Sn–0.8Nb alloy is well known for possessing good mechanical and wear properties that satisfy such *** this study,the microstructure,mechanical properties,and grease‐lubricated sliding wear behavior of Cu–15Ni–8Sn–0.8Nb alloy with 0.8 wt%Nb are *** nanoscale NbNi3 and NbNi2Sn compounds can strengthen the alloy through the Orowan strengthening mechanism.A Stribeck‐like curve is plotted to illustrate the relationship among friction coefficient,normal load,and sliding velocity and to analyze the grease‐lubricated *** wear rate increases with normal load and decreases with sliding velocity,except at 2.58 m/s.A wear mechanism map has been developed to exhibit the dominant wear mechanisms under various friction *** the normal load is 700 N and the sliding velocity is 2.58 m/s,a chemical reaction between the lubricating grease and friction pairs occurs,resulting in the failure of lubricating grease and an increase in wear.

关键词： Cu–15Ni–8Sn–0.8Nb alloy microstructure mechanical properties grease‐lubricated wear behavior

Advanced silicon nanostructures derived from natural silicate minerals for energy storage and conversion

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Green Energy & Environment 2022年第2期7卷 205-220页

作者： Hao Wan Wei Ma kechao zhou Yijun Cao Xiaohe Liu Renzhi Ma School of Chemical Engineering Zhengzhou UniversityZhengzhou450001China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China International Center for Materials Nanoarchitectonics(WPI-MANA) National Institute for Materials Science(NIMS)Namiki 1-1TsukubaIbaraki305-0044Japan

To effectively alleviate the ever-increasing energy crisis and environmental issues,clean and sustainable energy-related materials as well as the corresponding storage/conversion devices are in urgent ***(Si) with the second most elemental abundance on the crust in the form of silicate or silica(SiO_(2)) minerals,is an advanced emerging material showing high performance in energy-related fields(***,photocatalytic hydrogen evolution).For the improved performance in industry-scale applications,Si materials with delicate nanostructures and ideal compositions in a massive production are highly *** account of the reserve,low cost and diverse micro-nanostructures,silicate minerals are proposed as promising raw *** the article,crystal structures and the reduction approaches for silicate minerals,as well as recent progress on the as-reduced Si products for clean energy storage/conversion,are presented ***,some cutting-edge fields involving Si materials are discussed,which may offer deep insights into the rational design of advanced Si nanostructures for extended energy-related fields.

关键词： minerals massive silicate

EFFECT OF MICROSTRUCTURES ON CYCLIC-OXIDATION BEHAVIOUR OF TiAl ALLOY

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中国有色金属学会会刊：英文版 1996年第2期6卷 91-94页

作者： zhou kechao Huang Baiyun Qu Xuanhui He Yuehui Kong Gaoning Powder Metallurgy Research Institute Central South University of TechnologyChangsha 410083

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关键词： γ-TiAl oxidation microstructure morphology Al_(2)O_(3) oxide scale

The dynamic responses of lamellar and equiaxed nearβ-Ti alloys subjected to multi-pass cross rolling

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Journal of Materials Science & Technology 2020年第8期36卷 220-229页

作者： Wei Chen Hande Wang Y.C.Lin Xiaoyong Zhang Chao Chen Yaping Lv kechao zhou State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China

This work gives a comparison on the microstructural characteristics,textural discrepancies,and twinning behaviors of lamellar and equiaxed nearβ-Ti alloys during multi-pass cross rolling with a rolling reduction of 20%,50%and 80%.The results showed that the restoration mechanism of the alloy inβphase is strongly dependent on theαmorphologies,and in comparison,strain path has weaker influences on the grain refinement of theβ***,the texture intensities of bothαandβphases were weakened owing to the dynamic recrystallization(DRX)of the two phases in the equiaxed ***,with regard to the lamellar microstructure,dynamic recovery(DRV)of theβphase predominated,forming elongatedβ***,theαandβmatrix in lamellar microstructures obeyed the Burgers orientation relationship,which was gradually broken down until the final ***,the{1101}twinning exhibits a strong size *** the continuous DRX ofαphases,theα-twinning is suppressed owing to progressive grain *** activation ofβ-twinning,namely{332}?113?and{112}?111?,in nearβ-Ti alloys is heavily dependent on the deficientβ-stabilizing elements and the local stress *** findings provide an effective way to obtain ultra-fine grain microstructures of this alloy.

关键词： Nearβ-Ti alloys Multi-pass cross rolling Dynamic recrystallization {1101}Twinning β-twinning

Microstructural evolution and defect formation in a powder metallurgy nickel-based superalloy processed by selective laser melting

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Journal of Materials Science & Technology 2020年第1期36卷 7-17页

作者： Hongyu Wu Dong Zhang Biaobiao Yang Chao Chen Yunping Li kechao zhou Liang Jiang Ruiping Liu State Key Laboratory for Powder Metallurgy Powder Metallurgy Research InstituteCentral South UniversityChangsha 410083China State Key Laboratory of Nickel and Cobalt Resources Comprehensive Utilization Jinchang 737100China Yuanmeng Precision Technology(Shenzhen)Institute Shenzhen 518063China

In this study,the selective laser melting(SLM)technology has been employed to manufacture a nickelbased superalloy which was conventionally prepared through powder metallurgy(PM)*** microstructural features and defects were systematically investigated both prior to and after heat treatment and compared with the PM *** solidification cracking and liquation cracking were observed in the SLM specimen in which the grain misorientation and low melting point(γ+γ')eutectic played a vital role in their formation *** grains oriented along building direction were ubiquitous,corresponding to strongfiber *** cell structures and melt pools are pervasive and noγ'precipitates were detected at about 10 nm scale before heat *** supersolvus solution and two-step aging treatments,high volume fractionγ'precipitates emerged and their sizes and morphologies were comparable to those in PM alloy.texture is relieved and columnar grains tend to become more equiaxed due to static recrystallization process and grain boundary migration *** annealing twins formed in SLM alloy and are clarified as a consequence of *** results provide fundamental understandings for the SLM PM nickel-based superalloy both before and after heat treatment and demonstrate the potential to fabricate this group of alloys using SLM technology.

关键词： Nickel-based superalloy Selective laser melting Microstructure Defects Annealing twin

Improved dielectric constant and energy density of P(VDF-HFP)composites using NBT-xST(x=0,0.10,0.26)whiskers

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Journal of Advanced Dielectrics 2018年第6期8卷 80-88页

作者： Xuefan zhou Lu Wang Guoliang Xue kechao zhou Hang Luo Dou Zhangy State Key Laboratory of Powder Metallurgy Central South University Changsha Hunan 410083P.R.China

The high-performance energy-storage dielectric capacitors are increasingly important due to their wide applications in high power ***,we fabricated a novel P(VDF-HFP)-based capacitor with surface-modified NBT-xST(x?0,0.10,0.26)whiskers,denoted as Dop@NBT-xST/P(VDF-HFP).The influences of ST content,fillers’volume fraction and electric field on the dielectric properties and energy-storage performance of the composites were investigated *** results show that the dielectric constant monotonously increased with the increase of ST content and fillers’volume *** composite containing 10.0 vol%NBT-0.26STwhiskers possessed a dielectric constant of 39 at 1 kHz,which was 5.6 times higher than that of pure P(VDF-HFP).It was noticed that the D-E loops of the composites became thinner and thinner with the increase of ST *** to the reduced remnant polarization,the composite with 5.0 vol%NBT-0.26STwhiskers achieved a high energy density of 6.18 J/cm3 and energy efficiency of approximately 57%at a relatively low electric field of 200 kV/*** work indicated that NBT-0.26ST whisker is a kind of potential ceramic filler in fabricating the dielectric capacitor with high discharged energy density and energy efficiency.

关键词： P(VDF-HFP) NBT-xST whiskers dielectric composite dielectric constant energy storage

A Novel Method for Preparation of TaC Coating on C/C Composite Material

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Journal of Materials Science & Technology 2005年第3期21卷 381-385页

作者： Hanwei HE, kechao zhou and Xiang XIONG State Key Lab of Powder Metallurgy, Central South University, Changsha 410083, China Lab. of Powder Metallurgy Central South University Changsha 410083 China

A new method for preparation of TaC coating on C/C composite material is reported. The amorphous ethylate tantalum jellied as the precursor is prepared and spread densely on the surface of the C/C composite material so as to form a multilayer film. In a graphitization furnace the multilayer film is transformed into TaC coating at various temperatures. Ethylate tantalum film is characterized by FT-IR (Fourier transform infrared) spectra, XRD (X-ray diffraction) and SEM (scanning electron microscopy) and TaC coating is characterized by XRD and SEM. At 1200℃ the coating contained TaC and Ta2O5, and at above 1400℃ only TaC is formed. The coating formed at 1600℃ is a continuous stratum structure, and that formed at 1600℃ is a porous net structure. Analysis on thermodynamics and formation mechanism of TaC indicates that, after ethylate tantalum is decomposed, Ta2O5 is first produced and then transformed into Ta2C, and newly formed Ta2C is transformed into TaC by the sufficient C at last.

关键词： C/C composite TaC coating Ethylate tantalum

Porous tantalum structure integrated on Ti6Al4V base by Laser Powder Bed Fusion for enhanced bony-ingrowth implants:In vitro and in vivo validation

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Bioactive Materials 2022年第1期7卷 3-13页

作者： Pengfei Lei Hu Qian Taomei Zhang Ting Lei Yihe Hu Chao Chen kechao zhou Department of Orthopedic Surgery Hunan Engineering Research Center of Biomedical Metal and Ceramic ImplantsXiangya HospitalCentral South UniversityChangsha 410008China Department of Orthopedic Surgery The First Affiliated HospitalCollege of MedicineZhejiang UniversityChina State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China

Despite the widespread application of Ti6Al4V and tantalum(Ta)in orthopedics,bioinertia and high cost limit their further applicability,respectively,and tremendous efforts have been made on the Ti6Al4V-Ta alloy and Ta coating to address these ***,the scaffolds obtained are *** this study,novel high-interface-strength Ti6Al4V-based porous Ta scaffolds were successfully manufactured using Laser Powder Bed Fusion for the first time,in which porous Ta was directly manufactured on a solid Ti6Al4V *** testing revealed that the novel scaffolds were biomechanically compatible,and the interfacial bonding strength was as high as 447.5 *** vitro biocompatibility assay,using rat bone marrow mesenchymal stem cells(r-BMSCs),indicated that the novel scaffolds were *** phosphatase and mineralized nodule determination demonstrated that the scaffolds favored the osteogenic differentiation of ***,scaffolds were implanted into rabbits with femur bone defects,and imaging and histological evaluation identified considerable new bone formation and bone ingrowth,suggesting that the scaffolds were well integrated with the host ***,these results demonstrated good mechanical compatibility,biocompatibility,and osteointegration performance of the novel Ti6Al4V-based porous Ta scaffold,which possesses great potential for orthopedic clinical applications.

关键词： Tantalum Ti6Al4V Laser powder bed fusion Orthopedic scaffolds Osteointegration

Designing high-strength titanium alloy using pseudo-spinodal mechanism through diffusion multiple experiment and CALPHAD calculation

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Journal of Materials Science & Technology 2021年第15期74卷 78-88页

作者： Di Wu Libin Liu Lijun Zeng Wenguang Zhu Wanlin Wang Xiaoyong Zhang Junfeng Hou Baoliang Liu Jiafeng Lei kechao zhou State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Material Science and Engineering Central South UniversityChangsha 410083China School of Metallurgy and Environment Central South UniversityChangsha 410083China School of Metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055China School of Materials Science&Engineering North Minzu UniversityYinchuan 750021China Xi'an Trianlge Defence Incorporated Company Xi'an710089China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

This study used the pseudo-spinodal mechanism to obtain the ultrafineαphase for designing highstrength titanium *** multiple experiments were designed to find the composition range of TM-x Mo-y V alloy(TM:Ti-4.5 Al-2 Cr-2.5 Nb-2 Zr-1 Sn)for obtaining ultrafineα*** results confirm that when the alloy composition is located near the intersection of theαandβphase free energy curves,the alloy will undergo pseudo-spinodal transformation and obtain the ultrafineα*** designed TM-6 Mo-3 V alloy has a yield strength of 1411 MPa and an elongation of 6.5%.The strength of the alloy depends on the thickness,fraction of theαphase and the solid solution strengthening effect of the alloying *** deformation mechanism of the alloy is the dislocation slip of theαandβphases and the twin deformation of theα*** large number ofα/βinterfaces produced by the fineαphase is the main reason for limiting the ductility of the *** use of the pseudo-spinodal mechanism combined with diffusion multiple experiments and CALPHAD is an effective method for designing high-strength titanium alloys.

关键词： Pseudo-spinodal mechanism Alloy design CALPHAD Diffusion multiple Strengthening mechanism