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| 1 | Microstructural evolution and defect formation in a powder metallurgy nickel-based superalloy processed by selective laser melting显示文摘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)route.The microstructural features and defects were systematically investigated both prior to and after heat treatment and compared with the PM counterpart.Both 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 mechanism.Columnar grains oriented along building direction were ubiquitous,corresponding to strong<001>fiber texture.Solidification cell structures and melt pools are pervasive and noγ'precipitates were detected at about 10 nm scale before heat treatment.After supersolvus solution and two-step aging treatments,high volume fractionγ'precipitates emerged and their sizes and morphologies were comparable to those in PM alloy.<001>texture is relieved and columnar grains tend to become more equiaxed due to static recrystallization process and grain boundary migration events.Significant annealing twins formed in SLM alloy and are clarified as a consequence of recrystallization.Our 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. | Hongyu Wu Dong Zhang Biaobiao Yang Chao Chen Yunping Li Kechao Zhou Liang Jiang Ruiping Liu | 2020 | Journal of Materials Science & Technology2020，36，1： | 4 |
| 2 | Improving Densification and Mechanical Properties of FeAl/TiC Composites by Addition of Ni显示文摘FeAl/TiC composites were fabricated by hot pressing blended elemental powders. The effects of Ni-doping on thedensification and mechanical properties of the composites were studied. Results show that the density of the com-posites decreases with the content of TiC increasing, and the addition of Ni significantly improves the densificationprocess by enhancing mass transfer in the bonding phase. The mechanical properties of the composites are closelyrelated with their porosity. Besides increasing the density of the composites, the addition of Ni improves the mechan-ical properties by other three effects: solution-strengthening the bonding phase, strengthening the FeAl-TiC interfaceand increasing ductile fracture in FeAl phase. | Yong LIU, Fengxiao LIU, Baiyun HUANG, Kechao ZHOU, Yuehui HE and Zhihong TANGNational Key Lab for P/M, Central South University, Changsha 410083, China | 2003 | Journal of Materials Science & Technology2003，19，1： | 4 |
| 3 | Porous tantalum structure integrated on Ti6Al4V base by Laser Powder Bed Fusion for enhanced bony-ingrowth implants:In vitro and in vivo validation显示文摘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 drawbacks.However,the scaffolds obtained are unsatisfactory.In 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 substrate.Mechanical testing revealed that the novel scaffolds were biomechanically compatible,and the interfacial bonding strength was as high as 447.5 MPa.In vitro biocompatibility assay,using rat bone marrow mesenchymal stem cells(r-BMSCs),indicated that the novel scaffolds were biocompatible.Alkaline phosphatase and mineralized nodule determination demonstrated that the scaffolds favored the osteogenic differentiation of r-BMSCs.Moreover,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 bone.Overall,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. | Pengfei Lei Hu Qian Taomei Zhang Ting Lei Yihe Hu Chao Chen Kechao Zhou | 2022 | Bioactive Materials2022，7，1： | 3 |
| 4 | Processing TiAl-Based Alloy by Elemental Powder Metallurgy显示文摘TiAl-based alloys with various compositions (including Ti-48Al, Ti-47Al-2Cr-2Nb, Ti-47Al-2Cr- 2Nb-0.2B and Ti-47Al-3Cr, in mole fraction) had been prepared by elemental powder metallurgy (EPM). The results have shown that the density of the prepared Ti-48Al alloy increases with increasing hot pressing temperature up to 1300℃. The Ti-48Al alloy microstructure mainly consisted of island-like Ti3Al phase and TiAl matrix at hot pressing temperature below 1300℃, however, coarse a2/r lamellar colonies and r grains appeared at 1400℃. It has also indicated that the additions of elemental Cr and B can refine the alloy microstructure. The main microstructural inhomogeneity in EPM TiAl-based alloys was the island-like a2 phase or the aggregate of a2/r lamellar colony, and such island-like structure will be inherited during subsequent heat treatment in (a+r) field. Only after heat treatment in a field would this structure be eliminated. The mechanical properties of EPM TiAl-based alloys with various compositions were tested, and the effect of alloy elements on the mechanical properties was closely related to that of alloy elements on the alloy microstructures. Based on the above results, TiAl-based alloy exhaust valves were fabricated by elemental powder metallurgy and diffusion joining. The automobile engine test had demonstrated that the performance of the manufactured valves was very promising for engine service. | Yong LIU, Baiyun HUANG, Yuehui HE and Kechao ZHOU (National Key Laboratory for Powder Metallurgy, Central South University of Technology, Changsha 410083, China) | 2000 | Journal of Materials Science & Technology2000，16，6： | 3 |
| 5 | Designing high-strength titanium alloy using pseudo-spinodal mechanism through diffusion multiple experiment and CALPHAD calculation显示文摘This study used the pseudo-spinodal mechanism to obtain the ultrafineαphase for designing highstrength titanium alloy.Diffusion 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 ultrafineαphase.CALPHAD 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 ultrafineαphase.The 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 elements.The deformation mechanism of the alloy is the dislocation slip of theαandβphases and the twin deformation of theαphase.The large number ofα/βinterfaces produced by the fineαphase is the main reason for limiting the ductility of the alloy.The use of the pseudo-spinodal mechanism combined with diffusion multiple experiments and CALPHAD is an effective method for designing high-strength titanium alloys. | Di Wu Libin Liu Lijun Zeng Wenguang Zhu Wanlin Wang Xiaoyong Zhang Junfeng Hou Baoliang Liu Jiafeng Lei Kechao Zhou | 2021 | Journal of Materials Science & Technology2021，，15： | 3 |
| 6 | The dynamic responses of lamellar and equiaxed nearβ-Ti alloys subjected to multi-pass cross rolling显示文摘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 theβmatrix.Therefore,the texture intensities of bothαandβphases were weakened owing to the dynamic recrystallization(DRX)of the two phases in the equiaxed microstructure.While,with regard to the lamellar microstructure,dynamic recovery(DRV)of theβphase predominated,forming elongatedβsubgrains.Besides,theαandβmatrix in lamellar microstructures obeyed the Burgers orientation relationship,which was gradually broken down until the final reduction.Lastly,the{1101}twinning exhibits a strong size effect.With the continuous DRX ofαphases,theα-twinning is suppressed owing to progressive grain refinement.The 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 concentration.These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy. | Wei Chen Hande Wang Y.C.Lin Xiaoyong Zhang Chao Chen Yaping Lv Kechao Zhou | 2020 | Journal of Materials Science & Technology2020，36，8： | 3 |
| 7 | A Novel Method for Preparation of TaC Coating on C/C Composite Material显示文摘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. | Hanwei HE, Kechao ZHOU and Xiang XIONG State Key Lab of Powder Metallurgy, Central South University, Changsha 410083, China | 2005 | Journal of Materials Science & Technology2005，21，3： | 3 |
| 8 | Microstructures, mechanical properties, and grease-lubricated sliding wear behavior of Cu–15Ni–8Sn–0.8Nb alloy with high strength and toughness显示文摘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 weights.Cu–15Ni–8Sn–0.8Nb alloy is well known for possessing good mechanical and wear properties that satisfy such requirements.In 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 investigated.The 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 mechanism.The 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 conditions.When 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. | Jinjuan CHENG Mincong MAO Xueping GAN Qian LEI Zhou LI Kechao ZHOU | 2021 | Friction2021，9，5： | 1 |
| 9 | Relationship be-tween lamellar α evolution and flow behavior during isothermaldeformation of Ti-5Al-5Mo-5V-1Cr-1Fe near β titanium alloy显示文摘 | Chao Li Xiaoyong Zhang Kechao Zhou | 2012 | Materials Science & Engineering A2012，558，： | 1 |
| 10 | Mi croscrateh behavior of copper-graphite composites 显示文摘 | Xiao Jinkun Zhang Lei Zhou Kechao | 2013 | Tribology International2013，57，： | 1 |
| 11 | Effects of in situ biomineralization on microstructural and mechanical properties of hydroxyapatite/polyethylene composites 显示文摘 | Huang Suping Zhou Kechao | 2006 | Journal of Applied Polymer Science2006，101，3： | 1 |
| 12 | Hot corrosion of a novel (Ni ,Co)O/ (Ni ,Co)Fe2O4 composite coating thermally converted form an electrodeposited Ni-Co-Fe2O3 composite coating 显示文摘 | Li Ma Kechao Zhou Zhiyou Li | 2011 | Corrosion Science2011，53，： | 1 |
| 13 | Microwave ab- sorption properties of carbon fibers with carbon coils of different morphologies (double microcoils and single nanocoils) grown on them显示文摘 | Lei Liu Pingge He Kechao Zhou | 2014 | Journal of Materials Science2014，49，： | 1 |
| 14 | Oxidation behaviors of electrodeposited nickel-cobalt coatings in air at 960℃ 显示文摘 | Zhou Kechao Ma Li Li Zhiyou | 2011 | Transactions of Nonferrous Metals Society of China2011，21，： | 1 |
| 15 | Factors affecting the lamellar spacing in two-phase Ti-AI alloys with fully lamellar microstructures 显示文摘 | Tang Jiancheng Huang Baiyun Zhou Kechao | 2001 | 36 (9) : 1737-17422001，36，9： | 1 |
| 16 | Porous hydroxyapatite ceramics fabricated by an ice-templating meth- od显示文摘 | ZHOU Kechao ZHANG Yan ZHANG Dou et at | 2011 | Scripta Mater2011，64，： | 1 |
| 17 | Synthesis and mi- crowave absorption properties of carbon coil-carbon fiber hybrid materials 显示文摘 | Liu Lei Zhou Kechao He Pingge | 2013 | Materials Letters2013，110，： | 1 |
| 18 | EffectofaddingmethodofCronmicrostructureandpropertiesofWCG9NiG2Crcementedcarbides 显示文摘 | ShiKaihua Zhou Kechao LiZhiyou etal | 2013 | IntJournalofReGfractoryMetalsandHardMaterials2013，38，： | 1 |
| 19 | Microwave ab- sorption properties of carbon fibers with carbon coils of different morphologies (double microcoils and single nanocoils) grown on them 显示文摘 | Liu Lei He Pingge Zhou Kechao | 2014 | J Mater Sci2014，49，： | 1 |
| 20 | EFFECT OF MICROSTRUCTURES ON CYCLIC-OXIDATION BEHAVIOUR OF TiAl ALLOY显示文摘EFFECTOFMICROSTRUCTURESONCYCLIC-OXIDATIONBEHAVIOUROFTiAlALLOYZhouKechao;HuangBaiyun;QuXuanhui;HeYuehui;KongGaoning(PowderMeta... | Zhou Kechao Huang Baiyun Qu Xuanhui He Yuehui Kong Gaoning | 1996 | 中国有色金属学会会刊:英文版1996，6，2： | 1 |
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