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Bulk nanocrystalline W-Ti alloys with exceptional mechanical properties and thermal stability

Journal of Materials Science & Technology 2022年第19期114卷 16-28页

作者： H.X.Xue X.C.Cai B.R.Sun X.Shen C.C.Du X.J.Wang T.T.Yang S.W.Xin T.D.Shen Clean Nano Energy Center State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China CSSC 723rd Research Institute China State Shipbuilding Corporation LimitedYangzhou 225000China

nanocrystalline(NC)W metals and alloys often exhibit higher radiation tolerance and strength than their coarse-grained counterparts.However,their thermal stability is low,making it difficult to achieve bulk NC W metals and alloys by consolidation using conventional techniques such as pressure-less sintering,hot-explosive-compaction sintering,and spark plasma sintering.Here we report the synthesis and mechanical properties of bulk NC W_(100-x)Ti_(x)(x=10 at.%-30 at.%)alloys prepared by consolidating mechanically alloyed NC powders under a high-temperature/high-pressure condition.Adding 20 at.%-30 at.%Ti largely improves the sinterability of NC W-Ti alloy powders.The room-temperature microhardness and compressive yield strength of consolidated bulk NC W_(80)Ti_(20) alloy are∼16.9 and 6.0 GPa,respectively,which are mainly caused by grain boundary strengthening and significantly higher than those of previously reported W and W alloys.The ultimate compressive strength of bulk NC W_(80)Ti_(20) measured between 900 and 1100°C deceases with increasing temperature.This behavior can be explained by the activation of Rachinger grain boundary sliding.No grain growth is observed in bulk NC W_(80)Ti_(20) after compression at 1000°C.Theoretical calculation suggests that it is the segregation of Ti at grain boundaries that decreases the specific grain boundary free energy and makes the NC W_(80)Ti_(20) alloy thermodynamically stable.

关键词： nanocrystalline W-Ti alloys Segregation Grain boundary energy Strength Hardness

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Grain-refining fabrication of nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy ceramics by ultra-high pressure sintering

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Journal of Materials Science & Technology 2023年第36期167卷 205-212页

作者： Zhangtian Wu Wei Ji Jinyong Zhang Yanan Yuan Ji Zou Weimin Wang Zhengyi Fu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Hubei Longzhong Laboratory Wuhan University of Technology Xiangyang Demonstration ZoneXiangyang 441000China

As an important A_(2)B_(2)O_(7)-type ceramic,(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy pyrochlore pos-sesses promising properties such as high melting point,high chemical durability,and low thermal conductivity.However,the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization.It usually needs long-term high-temperature soaking to achieve full density,but with inevitable grain growth.In this work,dense and grain-refined nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramics were prepared with ultra-high pressure sintering(UHPS)method under 10 GPa at a low temperature of 800℃.The densification behavior,microstructure evo-lution,and properties of the UHPS-ed samples were then investigated.The grain size of as-prepared(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramic was only 151 nm,which is 40%smaller than that of raw pow-der.In addition,it exhibited advantageous properties including both high hardness and aqueous durabil-ity.Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.

关键词： High-entropy ceramics Ultra-high pressure sintering Grain refining nanocrystalline Plastic deformation

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Ultra-strong and thermally stable nanocrystalline CrCoNi alloy

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Journal of Materials Science & Technology 2022年第11期106卷 1-9页

作者： Peng Gao Shuo Sun Heng Li Ranming Niu Shuang Han Hongxiang Zong Hao Wang Jianshe Lian Xiaozhou Liao School of Aerospace Mechanical&Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

Grain refinement to the nanocrystalline regime is the most effective way to strengthen materials but this often deteriorates the grain-size thermal stability and plasticity. Here we manufactured a nanocrystalline face centred cubic Cr Co Ni medium entropy alloy with columnar grains via magnetron sputtering. Compression of CrCoNi pillars with diameters of ~1 μm revealed a record high yield strength of ~5 GPa for pillars with face centred cubic structures and engineering plastic strain of > 30%. The alloy possessed an outstanding grain-size thermal stability even at 1073 K. Both nanocrystalline grain size and a high density of nanotwins/stacking faults are critical to the exceptional yield strength. Deformation twinning, grains refinement during deformation, grain boundary sliding and random grain orientation all contribute to the large plasticity. The outstanding thermal stability is attributed to the sluggish diffusion effect and the low energy of twin boundaries.

关键词： Medium entropy alloy CrCoNi nanocrystalline In-situ microscopy Mechanical properties Thermal stability

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Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition

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Journal of Materials Science & Technology 2022年第20期115卷 29-39页

作者： Junjie Wang Zongde Kou Shu Fu Shangshu Wu Sinan Liu Mengyang Yan Zhiqiang Ren Di Wang Zesheng You Si Lan Horst Hahn Xun-Li Wang Tao Feng Herbert Gleiter Institute of Nanoscience School of Material Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China Institute of Nanotechnology Karlsruhe Institute of TechnologyKarlsruhe 76021Germany Department of Physics City University of Hong KongHong KongChina Center for Neutron Scattering Shenzhen Research InstituteCity University of Hong KongShenzhen 518057China

In the current work,the BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy(nc-HEA)with ultrahigh hardness was formed by nanoscale diffusion-induced phase transition in a nanocomposite.First,a dual-phase Al/CoCrFeNi nanocrystalline high-entropy alloy composite(nc-HEAC)was prepared by a laser source inert gas condensation equipment(laser-IGC).The as-prepared nc-HEAC is composed of well-mixed FCC-Al and FCC-CoCrFeNi nanocrystals.Then,the heat treatment was used to trigger the interdiffusion between Al and CoCrFeNi nanocrystals and form an FCC-AlCoCrFeNi phase.With the increase of the annealing temperature,element diffusion intensifies,and the Al Co Cr Fe Ni phase undergoes a phase transition from FCC to BCC structure.Finally,the BCC-AlCoCrFe Ni bulk nc-HEA with high Al content(up to 50 at.%)was obtained for the first time.Excitingly,the nc-HEAC(Al-40%)sample exhibits an unprecedented ultra-high hardness of 1124 HV after annealing at 500℃ for 1 h.We present a systematic investigation of the relationship between the microstructure evolution and mechanical properties during annealing,and the corresponding micro-mechanisms in different annealing stages are revealed.The enhanced nanoscale thermal diffusion-induced phase transition process dominates the mechanical performance evolution of the nc-HEACs,which opens a new pathway for the design of high-performance nanocrystalline alloy materials.

关键词： High-entropy alloy nanocrystalline Composites Diffusion-induced phase transition Mechanical Inert gas condensation

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ITO纳米晶-植物纤维复合材料的电阻式压力传感器

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中国科学:材料科学(英文版) 2023年第10期66卷 3922-3930页

作者：夏亿劼黄鹏举林心铭吴鲁超李珂高晨溟钟高余 School of Mechanical Engineering University of Shanghai for Science and TechnologyShanghai 200093China Department of Materials Science Fudan UniversityShanghai 200433China

可穿戴电子设备因其在机器人触觉、人机交互和脉搏测试等领域具有潜在应用而引起广泛关注.作为一种可穿戴电子设备,柔性压力传感器应该是环保的,而且制造成本低.基于纤维素纸的压力传感器由于其优良的特性,如轻质、无毒或低毒、可降解... 详细信息

可穿戴电子设备因其在机器人触觉、人机交互和脉搏测试等领域具有潜在应用而引起广泛关注.作为一种可穿戴电子设备,柔性压力传感器应该是环保的,而且制造成本低.基于纤维素纸的压力传感器由于其优良的特性,如轻质、无毒或低毒、可降解性和柔韧性,而引起了人们的关注.在此,我们报道了一种基于铟锡氧化物(ITO)纳米晶体和植物纤维复合材料的电阻式触觉传感器.该压力传感器具有宽的检测范围(0-100 kPa)、高灵敏度(464.88 kPa^(-1))、快速的响应时间(6.93 ms)和恢复时间(7.18 ms)以及良好的加载/卸载稳定性.我们还展示了该压力传感器用于脉搏测试、呼吸监测、语音识别等各种人体运动检测.结果表明,ITO纳米晶-植物纤维复合材料压力传感器在智能可穿戴电子产品中显示出巨大应用潜力.

关键词： pressure sensors piezoresistance nanocrystalline composite

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Unveiling the grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy

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Journal of Materials Science & Technology 2022年第32期127卷 98-107页

作者： Shuo Sun Yang Yang Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys.

关键词： Medium-entropy alloy nanocrystalline Nanoindentation Incipient plasticity Grain boundary

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A multi-component nanocrystalline FeCrV alloy with improved mechanical properties and excellent irradiation resistance

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Progress in Natural Science:Materials International 2022年第4期32卷 433-442页

作者： Tingting Li Sizhe Diao Pingping Liu Yong Zhang Qian Zhan School of Materials Science and Engineering University of Science and Technology Beijing Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

An equiatomic low-activated Fe Cr V ternary alloy was prepared by mechanical alloying and spark plasma sintering. The BCC solid solution alloy exhibited an excellent strength-ductility synergy properties, which was 1.85GPa compressive yield strength, 3.04 GPa fracture strength and more than 28% plasticity at room temperature.Even at an elevated temperature of 600°C, its yield strength was still more than 1 GPa, revealing a pronounced high temperature resistance. The Fe Cr V alloy had a homogeneous microstructure with high-density dislocations.A nanocrystalline characteristic was demonstrated and the average grain size was about 322 nm, leading to the improved mechanical properties. The strengthening mechanism was discussed in detail and the contributions of strengthening factors were calculated. The Fe Cr V alloy was irradiated up to 160 dpa with 2 Me V Au2+ions at 573K. The nanoindentation test was carried out to simply evaluate the hardening degree under such a high dose irradiation with heavy ions. The semi-quantitative analysis results show that Fe Cr V alloy has an excellent irradiation tolerance compared with pure Fe.

关键词： Mechanical properties nanocrystalline Strengthening mechanism Au 2+ irradiation Multi-component alloy Mechanical alloying

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nanocrystalline ZrO_2 preparation and kinetics research of phase transition

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Rare Metals 2012年第1期31卷 51-57页

作者： Wu, Wenwei Cai, Jinchao Wu, Xuehang Li, Yongni Liao, Sen School of Chemistry and Chemical Engineering Guangxi University Nanning 530004 China

The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O, and Na2CO3·10H2O as raw materials. The nanocrystalline ZrO2 was obtained by calcining the precursor. The precursor and its calcined products were characterized using TG/DTA, FT-IR, XRD, and SEM. The results showed that the precursor dried at 353 K was a zirconyl carbonate compound. When the precursor was calcined at 673 K for 150 min, highly crystallization ZrO2 with tetragonal structure (space group P42/nmc (137)) was obtained with a crystallite size of 24 nm. However, when the precursor was calcined at 1023 K for 150 min, highly crystallization ZrO2 with monoclinic structure (space group P21/c(14)) was obtained with a crystallite size of 20 nm. The mechanism and kinetics of the thermal process of the precursor were studied using DTA and XRD techniques. Based on the Kissinger and Arrhenius equation, the values of the activation energies associated with the thermal process of the precursor were determined to be 26.80 and 566.73 kJ·mol−1 for the first and third steps, respectively. The mechanism of ZrO2 phase transition from tetragonal to monoclinic structure is the random nucleation and growth of nuclei reaction.

关键词： inorganic compounds nanocrystalline thermal process kinetics solid-state reaction at low heat

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nanocrystalline high-entropy hexaboride ceramics enable remarkable performance as thermionic emission cathodes

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Fundamental Research 2023年第6期3卷 979-987页

作者： Mengdong Ma Xinyu Yang Hong Meng Zhisheng Zhao Julong He Yanhui Chu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510641China Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China

The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential,yet relevant studies have been rarely reported.In this work,we report nanocrystalline(La_(0.25)Ce_(0.25)Nd_(0.25)Eu_(0.25))B6 high-entropy rare-earth hexaboride(HEReB6-1)ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first time.The as-fabricated samples exhibited a highly dense(96.3%)nanocrystalline(94 nm)microstructure with major(001)fiber textures and good grain boundaries without any impurities,resulting in a remarkable mechanical,electrical,and thermionic emission performance.The results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures;these were greater than the average values of corresponding binary rare-earth hexaborides,such as a Vickers hardness of 23.4±0.6 GPa and a fracture toughness of 3.0±0.4 MPa•m^(1/2)at room temperature.More importantly,they showed high emission current densities at elevated temperatures,which were higher than the average values of the corresponding binary rare-earth hexaborides.For instance,the maximum emission current density reached 48.3 A•cm^(−2)at 1873 K.Such superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes.

关键词： High-entropy ceramics Hexaborides nanocrystalline Mechanical properties Thermionic emission

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Fabrication of C@MoxTi1-xO2-δ nanocrystalline with functionalized interface as efficient and robust PtRu catalyst support for methanol electrooxidation

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Journal of Energy Chemistry 2020年第1期29卷 7-14,I0001页

作者： Jialong Li Lei Zhao Xifei Li Sue Hao Zhenbo Wang MIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyNo.92 West-Da Zhi StreetHarbin 150001HeilongjiangChina Institute of Advanced Electrochemical Energy&School of Materials Science and Engineering Xi'an University of TechnologyXi'an 710048ShaanxiChina

A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.

关键词： Interface functionalization TiO2 nanocrystalline Mo doping Core–shell PtRu catalyst Methanol electrooxidation

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