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Tailoring precipitation/properties and related mechanisms for a high-strength aluminum alloy plate via low-temperature retrogression and re-aging processes

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Journal of Materials Science & Technology 2022年第25期120卷 15-35页

作者： L.G.Hou H.Yu Y.W.Wang L.You Z.B.He C.M.Wu D.G.Eskin L.Katgerman L.Z.Zhuang J.S.Zhang State Key Laboratory for Advanced Metals&Materials University of Science&Technology BeijingBeijing 100083China BCAST Brunel University LondonKingston LaneUxbidge Middlesex UB83PHUnited Kingdom Institute of mineral resources Chinese Academy of Geological SciencesBeijing 100037China Nanjing Advanced Transportation Equipment New Technology Research Institute Nanjing 211800China Tomsk State University Tomsk634050Russian Federation Katgerman Aluminium Technology van Beuningenlaan 102334CC LeidenNetherlands Department of Materials Science and Engineering Delft University of TechnologyMekelweg 22628CD Delftthe Netherlands

The retrogression and re-aging(RRA)processes,aimed mainly at tailoring intergranular precipitates,could significantly improve the corrosion resistance(i.e.,stress corrosion cracking resistance)without considerably decreasing the strength,which signifies that an efficient control of the size,distribution and evolution of intergranular and intragranular precipitates becomes critical for the integrated properties of the(mid-)thick high-strength Al alloy plates.Compared to RRA process with retrogression at200℃ (T77),this study investigated the impact of a modified RRA process(MT77)with lower retrogression temperatures(155-175℃ )and first-stage under-aging on the properties of a high-strength AA7050 Al alloy,in combination with detailed precipitate characterization.The study showed that the strength/microhardness of the RRA-treated alloys decreased with raising retrogression temperature and/or prolonging retrogression time,along with the increased electrical conductivity.The rapid responsiveness of microstructure/property typical of retrogression at 200℃ was obviously postponed or decreased by using MT77 process with longer retrogression time that was more suitable for treating the(mid-)thick plates.On the other hand,higher retrogression temperature facilitated more intragranularηprecipitates,coarse intergranular precipitates and wide precipitate free zones,which prominently increased the electrical conductivity alongside a considerable strength loss as compared to the MT77-treated alloys.With the preferred MT77 process,the high strength approaching T6 level as well as good corrosion resistance was achieved.However,though a relatively homogeneous through-thickness strength was obtained,some small discrepancies of properties between the central and surface areas of an 86-mm thick 7050 Al alloy plate were observed,possibly related to the quenching sensitivity.The precipitate evolution and mechanistic connection to the properties were discussed and reviewed for high-strength Al alloys along with suggestions for further R

关键词： Aluminum alloy Heat treatment Precipitation Strength Grain boundary

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The frequency-dependent polarization switching in nanograined BaTiO_(3) films under high-strength electric field

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International Journal of Smart and Nano Materials 2023年第2期14卷 155-169页

作者： Ming-Ran Zhang Yu Su Department of Mechanics School of Aerospace EngineeringBeijing Institute of TechnologyBeijingP.R.China Department of Mechanical Engineering Quzhou UniversityQuzhouP.R.China

The polarization reorientation in ferroelectric nanomaterials under high-strength AC electric fields is intrinsically a frequency-dependent process.However,the related study is not widely seen.We report a phase-field investigation regarding the dynamics of polarization switching and the electromechanical characteristics of a polycrystalline BaTiO_(3) nanofilm under applied frequency from 0.1 to 80 kHz.The grain boundaries and the in-plane strains are considered in the model.The obtained hysteresis and butterfly loops exhibit a remarkable variety of shapes with the changing frequency.The underlying mechanism for the observed frequency-dependent physical properties was discussed via domain structure-based analysis.In addition,we examined the influence of the kinetic coefficient in the Ginzburg-Landau equation as well as the influence of the electric-field amplitude to the frequency dependency.It was found that a higher value of kinetic coefficient or field amplitude tends to enhance the mobility of polarization switching and to transform high-frequency characteristics to low-frequency ones.

关键词： Ferroelectric nanograin Grain boundary phase field frequency dependence

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Solute Segregation to grain Boundaries in Al: A First-Principles Evaluation

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Acta Metallurgica Sinica(English Letters) 2022年第9期35卷 1572-1582页

作者： Jiawei Tang Yiren Wang Yong Jiang Jiangang Yao Hao Zhang National Key Laboratory for Powder Metallurgy School of Materials Science and EngineeringCentral South UniversityChangsha410083China School of Materials Science and Engineering Yantai Nanshan UniversityYantai265713China Jiangsu Haoran Spray Forming Alloy Co. LtdZhenjiang212009China

Solute-induced Grain boundary(GB) strengthening is eff ective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their potential eff ects on GB binding have been systematically investigated from fi rst-principles energetics. The low-energy Σ3(111) and Σ11(113) are immune to vacancy segregation, while high-energy Al GBs, such as Σ13(320), Σ9(221), Σ5(210), and Σ5(310), can attract both vacancies and solutes. Under-sized elements(Ni, Fe, Co, Cu) and similar-sized elements(Si, Zn, Ag, and Ti) prefer interstitial or vacancy sites at the GB interface, while over-sized elements(Mg, Zr, Sc, Er) tend to substitute Al or vacancy-neighboring sites at the GB interface. Segregated vacancies weaken GBs. Under-sized Ni, Co, Cu, similar-sized Ti, and over-sized Zr, Er, can directly enhance Al GBs, while similar-sized Ag and over-sized Mg reduce the GB binding strength. Solute strengthening or weakening eff ects tend to be always mitigated, more or less, by GB-segregated vacancies.

关键词： Al alloy Grain boundary Segregation Vacancy Solute First-principles

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Advanced development of grain boundaries in TMDs from fundamentals to hydrogen evolution application

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Chinese Chemical Letters 2024年第5期35卷 117-129页

作者： Ziyang Yin Lingbin Xie Weinan Yin Ting Zhi Kang Chen Junan Pan Yingbo Zhang Jingwen Li Longlu Wang College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology) Nanjing University of Posts&Telecommunications(NJUPT)Nanjing 210023China Institute of Advanced Materials(IAM)&Institute of Flexible Electronics(Future Technology) Nanjing University of Posts&Telecommunications(NJUPT)Nanjing 210023China

Grain boundary(GB),as a kind of lattice defect,widely exists in two-dimensional transition metal dichalcogenides(2D TMDs),which has complex and diverse influences on the physical/chemical properties of 2D TMDs.GBs are universally considered to be a double-edged sword,although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality,certain structure-oriented applications could be realized based on its unique properties.In this review,we first detailed the atomic structure characteristics of GBs and the corresponding techniques,then we systematically summarized the methods of introducing GBs into 2D TMDs.Next,we expounded unique electrical,mechanical,and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure.Moreover,the application of GB structure in hydrogen evolution reaction(HER)is also discussed.In the end,we make a conclusion and put forward outlooks,hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.

关键词： Grain boundary Transition metal dichalcogenides Two-dimensional materials Hydrogen evolution reaction Dislocation Molybdenum disulfide

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Copper-tetracyanoquinodimethane-derived copper electrocatalysts for highly selective carbon dioxide reduction to ethylene

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Nano Research 2022年第9期15卷 7910-7916页

作者： Xuewei Huang Dawei Wang Shuhao Yan Pengfei An Jianyu Han Zhiyu Guo Xinwei Li Zhongjun Chen Lin Chang Siyu Lu Zhiyong Tang Green Catalysis Center and College of ChemistryZhengzhou UniversityZhengzhou 450001China Henan Institute of Advanced Technology Zhengzhou UniversityZhengzhou 450001China CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049China

As one of the most promising CO_(2)utilization techniques,electrochemical CO_(2)reduction has recently received considerable attention.Cu is a unique electrocatalyst that can convert CO_(2)to value-added multi-carbon chemicals.Nevertheless,Cu catalysts are always limited by the poor selectivity and stability.Here,we report that using copper-tetracyanoquinodimethane(CuTCNQ)derived Cu nanoparticles as efficient electrocatalysts for conversion of CO_(2)to ethylene characteristic with high selectivity and stability,showing 56%Faradaic efficiency(FE)to C2H4 at−1.3 V vs.reversible hydrogen electrode(RHE).Upon the electrochemical CO_(2)reduction,CuTCNQ slowly reconstructs to Cu nanoparticles with abundant grain boundaries and residual Cu+on the surface.Theoretical calculation and operando characterization disclose that both as-formed Cu nanoparticle grain boundaries and residual Cu+endow the catalyst with high selectivity toward ethylene.Furthermore,during the reconstruction of CuTCNQ to Cu nanoparticles,the grain boundaries Cu surface is slowly refreshed by continual addition of Cu atoms,thus inhibiting the surface passivation and guaranteeing the electrocatalytic stability.

关键词： reconstruction Grain boundary ethylene CO_(2)electroreduction

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Densely packed ultrafine SnO_(2) nanoparticles grown on carbon cloth for selective CO_(2) reduction to formate

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Journal of Energy Chemistry 2022年第8期31卷 159-166,I0005页

作者： Xuewan Wang Dan Wu Xiaomin Kang Jiujun Zhang Xian-Zhu Fu Jing-Li Luo Shenzhen Key Laboratory of Polymer Science and Technology Guangdong Research Center for Interfacial Engineering of Functional MaterialsCollege of Materials Science and EngineeringShenzhen UniversityShenzhen 518060GuangdongChina School of Materials Science and Engineering Wuhan Institute of TechnologyWuhan 430205HubeiChina Institute for Sustainable Energy College of SciencesShanghai UniversityShanghai 200444China

Electrochemical reduction of CO_(2) to fuels and chemicals is a viable strategy for CO_(2) utilization and renewable energy storage.Developing free-standing electrodes from robust and scalable electrocatalysts becomes highly desirable.Here,dense SnO_(2) nanoparticles are uniformly grown on three-dimensional(3D)fiber network of carbon cloth(CC)by a facile dip-coating and calcination method.Importantly,Zn modification strategy is employed to restrain the growth of long-range order of SnO_(2) lattices and to produce rich grain boundaries.The hybrid architecture can act as a flexible electrode for CO_(2)-to-formate conversion,which delivers a high partial current of 18.8 m A cm-2 with a formate selectivity of 80%at a moderate cathodic potential of-0.947 V vs.RHE.The electrode exhibits remarkable stability over a 16 h continuous operation.The superior performance is attributed to the synergistic effect of ultrafine SnO_(2) nanoparticles with abundant active sites and 3D fiber network of the electrode for efficient mass transport and electron transfer.The sizeable electrodes hold promise for industrial applications.

关键词： Densely packed SnO_(2)nanoparticles Grain boundary Defect site Flexible electrode Electrochemical reduction CO_(2)to formate conversion

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MOLECULAR DYNAMICS SIMULATION OF ENTROPY AND SURFACE TENSION FOR Grain boundary OF α-Fe

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Acta Mechanica Sinica 1991年第1期7卷 88-92页

作者： Jiaqiang, Ding Zhiying, Chen Institute of Mechanics Chinese Academy of Sciences Beijing

The Grain boundary is an interface and the surface tension is one of its important thermodynamic properties. In this paper, the surface tension of the Σ9 Grain boundary for α-Fe at various temperatures and pressures is calculated by means of Computer Molecular Dynamics (CMD). The results agree satisfactorily with the experimental data. It. is shown that the contribution of entropy to surface tension of Grain boundary can be ignored.

关键词： Grain boundary entropy surface tension computer molecular dynamics simulation α-iron

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Effect of hydrogen on deformation behavior of Alloy 725 revealed by in-situ bi-crystalline micropillar compression test

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Journal of Materials Science & Technology 2021年第8期67卷 243-253页

作者： Xu Lu Dong Wang Department of Mechanical and Industrial Engineering Norwegian University of Science and TechnologyNo-7491TrondheimNorway

Nickel-based Alloy 725 bi-crystalline micropillars with different types of grain boundaries(GBs)were compressed in hydrogen-free and in-situ hydrogen-charged conditions to investigate the hydrogen effect on the deformation behavior of the selected GBs.In the presence of hydrogen,the compressive stresses on the micropillars increase regardless of the GB type.It was proposed that this hydrogen-induced hardening behavior is the synergistic effect of hydrogen-enhanced dislocation multiplication and interactions,the pinning effect of hydrogen on dislocation motion,and hydrogen-enhanced lattice friction.Transmission electron backscatter diffraction(t-EBSD)results demonstrate that both low-angle GBs and high-angle GBs can effectively suppress dislocation transmission through the GBs,resulting in dislocations pile up along the GBs in the hydrogen-charged condition.In contrast,this behavior was not observed in the micropillars with twin boundaries.

关键词： Hydrogen Nickel-based alloy Micropillar compression Plastic deformation Grain boundary

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Effect of Gd addition on the superconducting properties of Ti-based V, Nb, Ta alloys

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Superconductivity 2023年第2期6卷 58-63页

作者： SK Ramjan LS.Sharath Chandra Rashmi Singh M.K.Chattopadhyay Free Electron Laser Utilization Laboratory Raja Ramanna Centre for Advanced TechnologyIndore 452013Madhya PradeshIndia Homi Bhabha National Institute Training School ComplexAnushakti NagarMumbai 400094MaharastraIndia Laser and Functional Materials Division Raja Ramanna Centre for Advanced TechnologyIndore 452013Madhya PradeshIndia

The critical current density(Jc)of the body centered cubic(bcc)V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix[S.Paul,et.al,IEEE Trans.Appl.Supercond.31,5(2021)].Very low solubility of Gd in other bcc elements like Ta and Nb is also well known[Jr.KA Gschneidner in Prog Sci Technol Rare Earths,vol.1,pp.222–258,1964&M Neuberger,et.al in Handbook of Electronic Materials,Vol 4,1972].We use these facts to find the effect of adding 1 at.%Gd into the Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys on the superconducting properties e.g.,the transition temperature(Tc),Jc,flux pinning force density(Fp)and the microstructure.In spite of Gd being ferromagnetic,the Tc in these alloys change only marginally(increase by 0.3 K in Ta0.4Ti0.6 and decrease by 0.15 K in Nb0.6Ti0.4 after Gd addition.The Jc(H?1 T,T=4 K)increases by 5 and 1.5 times respectively in the Gd containing Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys,which is quite small as compared to the increase observed in the V0.6Ti0.4(20 times)system.With Gd addition,the grain size reduces approximately by 65%and 10%respectively in Nb0.6Ti0.4 and Ta0.4Ti0.6.Our analysis indicates that grain boundaries are the major flux line pinning centres in these alloys and the role of Gd in increasing the Jc depends on the effectiveness of Gd in reducing the grain size.The Grain boundary density depends strongly on the distribution of Gd precipitates,which is quite different from each other for two alloy systems under study.Moreover,our results suggest that the addition of Gd to commercial Nb‐Ti(Nb0.37Ti0.63)alloy is a new promising route for achieving higher Jc values.

关键词： Critical current density Ferromagnetism Flux pinning Grain boundary

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Hierarchical-vortex polarization domain pattern in nano polycrystalline ferroelectric

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Journal of Advanced Dielectrics 2022年第4期12卷 30-35页

作者： Zhiyong Huang Qinan Li Yin Liang Xiaoqiao He Jiagang Wu Haidong Fan Xiaobao Tian School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065P.R.China Department of Mechanics Sichuan UniversityChengdu 610065P.R.China Department of Civil Engineering Sichuan UniversityChengdu 610065P.R.China Department of Architecture and Civil Engineering City University of Hong Kong Tat Chee AvenueKowloonHong Kong Department of Materials Science Sichuan UniversityChengdu 610065P.R.China

Domain pattern is the carrier of electromechanical property.A novel domain pattern will open a gate for ferroelectric nano device.A distinctive topological domain pattern termed as hierarchical vortex(Hvo)has been found in polycrystalline ferroelectric based on the first-principles-based atomistic method.The Hvo pattern displays a unique structure,which is a flux-closing vortex encircle an anti-vortex or a vortex and anti-vortex pair(VA).Each Hvo structure could be regarded as a single vortex to forming a vortex-anti-vortex pair with anti-vortex or forming a vortex-vortex array with the vortex.The mechanism of HVo obtained in polycrystalline ferroelectric has been found that the Grain boundary(GB)equals the domain wall when the first-order vortex is in the vortex.The HVo will open a new view of the domain topology pattern and its evolution.

关键词： Domain pattern hierarchical vortex polycrystalline Grain boundary self-consistent

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