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Achieving high hetero-deformation induced(HDI)strengthening and hardening in brass by dual heterostructures

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Journal of materials Science & technology 2022年第3期98卷 244-247页

作者： X.t.Fang Z.K.Li y.F.Wang M.Ruiz X.L.ma H.y.Wang y.Zhu R.Schoell C.Zheng D.Kaoumi y.t.Zhu Department of materials Science and Engineering North Carolina State UniversityRaleighNC 27695USA Key Laboratory for Anisotropy and texture of materials of Ministry of Education Northeastern UniversityShenyang 110819China School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China Department of materials Science and Engineering Texas A and M UniversityCollege StationTX 77840USA Department of Mechanical and Aerospace Engineering North Carolina State UniversityRaleighNC 27695USA Department of Nuclear Engineering North Carolina State UniversityRaleighNC 27695USA Science and technology on thermostructural Composite materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China

Heterostructured materials,defined as materials that contain multiple zones with dramatically different flow stresses,have the potential to push the envelope of the strength-ductility of metals and alloys beyond what can be obtained conventionally[1–3].A prominent example is the heterogeneous lamella ti that is as strong as its ultrafine-grained ti,while as ductile as the coarsegrained ti[4].

关键词： grain strengthening deformation

Extending the Relational Model to Deal withProbabilistic Data

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Journal of Computer Science & technology 2000年第3期15卷 230-240页

作者：马宗民 ZHANG W.J ma W.y CityUniversityofHongKong KowloonHongKongP.R.China

According to the soundness and completeness of information in databases, the expressive form and the semantics of incomplete information are discussed in this paper. On the basis of the discussion, the current studies on incomplete data in relational databases are reviewed. In order to represent stochastic uncertainty in most general sense in the real world, probabilistic data are introduced into relational databases. An extended relational data model is presented to express and manipulate probabilistic data and the operations in relational algebra based on the extended model are defined in this paper.

关键词： incomplete information uncertain information extended relational model probabilistic data relational algebra

High-Speed Friction Stir Welding of t6-treated B4Cp/6061Al Composite

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 67-74页

作者： y.Z.Li y.N.Zan Q.Z.Wang B.L.Xiao Z.y.ma Key Laboratory of Nuclear materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and technology of China Shenyang 110016China

t6-treated 20 wt% B4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. the macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(NZ) of the joints, the B4 C particles were broken up and uniformly redistributed. the NZ exhibited lower hardness than the base metal(BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

Effect of post-bond heat treatment on the microstructure and high temperature mechanical property of a tLP bonded γ'-strengthened co-based single crystal superalloy

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Journal of materials Science & technology 2021年第21期80卷 244-258页

作者： S.y.Wang y.Sun C.y.Cui X.F.Sun y.Z Zhou y.M.ma H.L.An Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Harbin Welding Institute China Academy of Machinery Science and TechnologyHarbin 150028China

Post-bond heat treatment(PBHt) applied to a transient liquid phase(tLP) bonding joint is an effective approach to remove the brittle borides and improve its ***,we proposed two types of PBHt strategies to obtain a tLP bonded γ'-strengthened Co-based single crystal superalloy,and the microstructural characteristics and tensile properties of the two heat treated joints were compared to identify the optimal PBHt *** evolution of the brittle boride in the joint after the PBHt was studied by using in-situ *** experimental results allowed to provide a theoretic model to quantitatively evaluate the distribution of the brittle phase after the optimal PBHt and analyze the joint fractures to understand the failure *** obtained results revealed that a post-bond solid solution treatment performed to the joint at a high temperature(over 1275℃) could decrease the area fraction of the boride from 7.2 % to 1.4 % and increase the elongation from 1.9 % to 7.8 %.this work emphasizes the relevance of solid solution temperature when a PBHt strategy is applied.

关键词： transient liquid phase(tLP) γ'-strengthened co-based single crystal superalloy Heat treatment sequence Brittle boride tensile property

Modulators for terahertz Communication: the Current State of the Art

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Research 2019年第1期2019卷 895-916页

作者： Z.t.ma Z.X.Geng Z.y.Fan J.Liu H.D.Chen College of Science Minzu University of ChinaBeijing 100081China School of Information Engineering Minzu University of ChinaBeijing 100081China State Key Laboratory for Integrated Optoelectronics Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China

With the increase of communication frequency,terahertz(tHz)communication technology has been an important research feld;particularly the terahertz modulator is becoming one of the core devices in tHz communication *** modulation performance of a tHz communication system depends on the characterization of tHz *** modulators based on diferent principles and materials have been studied and ***,they are still on the way to practical application due to low modulation speed,narrow bandwidth,and insufcient modulation ***,we review the research progress of tHz modulator in recent years and evaluate devices critically and *** focus on the working principles such as electric,optical,optoelectrical,thermal,magnetic,programmable metamaterials and nonlinear modulation methods for tHz wave with semiconductors,metamaterials,and 2D materials(such as graphene,molybdenum disulfde,and tungsten disulfde).Furthermore,we propose a guiding rule to select appropriate materials and modulation methods for specifc applications in tHz communication.

关键词： modulator communication narrow

Effect of Carbon Nanotube Orientation on Mechanical Properties and thermal Expansion Coefficient of Carbon Nanotube-Reinforced Aluminum matrix Composites

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 901-908页

作者： Z.y.Liu B.L.Xiao W.G.Wang Z.y.ma School of materials Science and Engineering Dalian University of Technology Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences School of Mechanical Engineering Liaoning Shihua University

Carbon nanotube-reinforced 2009Al （CNt/2009Al） composites with randomly oriented CNts and aligned CNts were fabricated by friction stir processing （FSP） and FSP-rolling, respectively. the CNt/2009A1 composites with aligned CNts showed much better tensile properties at room temperature and elevated temperature compared with those with the randomly oriented CNts, which is mainly attributed to larger equivalent aspect ratio of the CNts and avoidance of preferential fracture problems. However, much finer grain size was not beneficial to obtaining high strength above 473 K. the aligned CNts resulted in tensile anisotropy, with the best tensile properties being achieved along the direction of CNt aligning. As the off-axis angle increased, the tensile properties were reduced due to the weakening of the load transfer ability. Furthermore, aligned CNts resulted in much lower coefficient of thermal expansion compared with randomly oriented CNts.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Coefficient of thermalexpansion Friction stir processing

tensile Strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum matrix Composites Fabricated by Powder Metallurgy Combined with Friction Stir Processing

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Journal of materials Science & technology 2014年第7期30卷 649-655页

作者： Z.y.Liu B.L.Xiao W.G.Wang Z.y.ma Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences Dalian University of technology Liaoning Shihua University

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube （CNt） reinforced AI （CNt/AI） and 6061AI （CNt/6061AI） composites. Microstructural observations indicated that CNts were uniformly dispersed in the matrix in both CNt/AI and CNt/6061AI composites. Mg and Si elements tended to segregate at CNt-AI interfaces in the CNt/6061AI composite during artificial aging treatment. the tensile properties of both the AI and 6061AI were increased by CNt incorporation. the electrical conductivity of CNt/AI was decreased by CNt addition, while CNt/6061AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Electrical properties Friction stir processing

Fabrication of large-bulk ultrafine grained 6061 aluminum alloy by rolling and low-heat-input friction stir welding

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Journal of materials Science & technology 2018年第1期34卷 112-118页

作者： C.y.Liu B.Qu P.Xue Z.y.ma K.Luo M.Z.ma R.P.Liu Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Key Laboratory of New Processing technology for Nonferrous Metal & materials Ministry of Education Guilin University of Technology Guangxi Key Laboratory of Universities for Clean Metallurgy and Comprehensive Utilization of Nonferrous Metal Resources Guilin University of Technology State Key Laboratory of Metastable materials Science and technology Yanshan University

In this study, the ultrafine grained （UFG） 6061 Al alloys fabricated by cold rolling were friction stir welded （FSW） with different rotation rates under both air cooling and rapid cooling in water. Low-heat-input parameters of 400 rpm rotation rate in water （400-Water） could effectively inhibit the coarsening of recrystallized grains, reduce the precipitation rate, and retain more dislocations of the UFG 6061 Al parent metal. 400-Water joint showed high lowest-hardness value, narrow low-hardness zone, and high tensile strength, attributing to the effect of dislocation, grain boundary, solid-solution, and precipitation hardening. this work provides an effective strategy to fabricate large-sized bulk UFG AI alloy by cold rolling with large deformation and low-heat-input FSW.

关键词： Aluminum alloys Ultrafine grained materia Friction stir welding Mechanical properties

StUDy ON tHE tHERMODyNAMICS OF CuO/Al IN SItU Al_2O_3 REINFORCED Al matRIX COMPOSItES

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 732-740页

作者： y.ma y.Hao S.Z.Kou X.N.Lu StateKeyLab.ofAdvancedNonferrousmaterials LanzhouUniversityofTechnologyLanzhou730050China

Based on the experiment and the thermodynamics analysis for CuO/Al system, it is founded that the compounding reaction of CuO/Al under low temperature is available. the general equation of adiabatic temperature of the system is set up, and the influence of resultant concentration and temperature on adiabatic temperature is theoretically analyzed. the values of heat effect of CuO/Al system under different temperature are also caculated.

关键词： composites in situ thermodynamics CuO Al exothermic dispersion