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Journal of Materials Science & Technology 2006年第3期22卷 291-294页

作者： Rongfa CHEN dunwen zuo Min WANG Department of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Mechanical Engineering Yangzhou University Yangzhou 225009 China

The compact oxide on the surface of SiCp/Al metal matrix composite （SiCp/Al MMC） greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface of SiCp/Al MMC by plasma erosion. Cu/Ni/Cu film of 5μm in thickness was prepared by magnetron sputtering method on the clean bonding surface in the same vacuum chamber, which was acted as an interlayer in transient liquid phase （TLP） bonding process. Compared with the same thickness of single Cu foil and Ni foil interlayer, the shear strength of 200 MPa was obtained using Cu/Ni/Cu film interlayer during TLP bonding, which was 89.7% that of base metal. In addition, homogenization of the bonding region and no particle segregation in interfacial region were found by analysis of the joint microstructure. Scanning electron microscopy （SEM） was used to observe the micrograph of the joint interface. The result shows that a homogenous microstructure of joint was achieved, which is similar with that of based metal.

关键词： SiCp/Al MMC Magnetron sputtering Cu/Ni/Cu film Transient liquid-phase(TLP) bonding

A review of friction stir joining of SiCp/Al composites

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Chinese Journal of Aeronautics 2020年第3期33卷 792-804页

作者： Lisheng zuo Xianrui ZHAO Zeyang LI dunwen zuo Hongfeng WANG College Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Naval Architecture&Ocean Engineering Jiangsu Maritime InstituteNanjing 211170China

SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace,automotive industry and other *** to the huge difference in performance between SiC particles and matrix alloys,traditional fusion welding methods are difficult to meet the join requirements of SiCp/Al *** stir joining(friction stir welding),as a solid phase joining process,has been proved to be a new technology with fine prospect in joining SiCp/Al composites compared with fusion welding *** some progress has been made in recent years,there are still full of *** this paper,the research status of friction stir joining of SiCp/Al composites in recent years is expatiated,including the weldability of SiCp/Al composites,the macrostructure and the microstructure of joints,mechanical properties of joints,and tool wear and ***,the existing challenges of friction stir joining of SiCp/Al composites are summarized and the future development directions are prospected.

关键词： Friction stir joining Mechanical properties Microstructure SiCp/Al composites Tool wear

Forces and Stresses During Friction Stir Joining of 2024 Aluminum Alloy

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第2期33卷 237-242页

作者： Deng Yongfang zuo dunwen Song Bo College of Mechanical & Electrical Engineering Nanjing University of Aeronautics and Astronautics Institute of Engineering and Research Jiangxi University of Science and Technology

An attempt is made to measure three direction forces using octagonal ring dynamometer in the 2024 aluminum alloy friction stir joining(FSJ)process.A test is made to measure the specific area stress and stress distributions in the specific area of the workpiece are *** workpiece stresses in the FSJ process are analyzed by numerical simulation *** is found that,in the downward stage of the process,feed force and lateral force in the tool are small,almost zero,and the maximum axial force can reach *** the stable joining stage,the forces acting on the tool become *** with the low speed,high feed speed results in small feed force and small lateral force,but large feed force in the stable joining *** stresses in three directions of feed direction,direction that perpendicular to butt face and direction perpendicular to the surface are *** simulation stress value of measure point is *** and numerical simulation can authenticate each *** experimental stress values and numerical simulation stress values are credible.

关键词： friction stir joining(FSJ) force stress 2024 aluminum alloy

Microstructure and Oxidation Behaviors of Nano-particles Strengthened NiCoCrAlY Cladded Coatings on Superalloys

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Chinese Journal of Mechanical Engineering 2010年第3期23卷 297-304页

作者： WANG Hongyu zuo dunwen CHEN Xinfeng YU Shouxin GU Yuanzhi Jiangsu Provincial Key Laboratory of Precision and Micro-manufacturing Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China School of Mechanical Engineering Jiangsu University Zhenjiang 212013 China

Nano-particles which can largely improve the microstructure and oxidation resistance of materials are often used as a strengthening component in metal matrix composites. However, few studies were reported on its application in the bond coat of duplex structure thermal barrier coating（TBC）. Three kinds of NiCoCrAlY coatings strengthened by different nano-particles with the same addition （1%, mass fraction） were prepared by the laser cladding technique on Ni-based superalloy substrates, aiming to study the effects of the nano-particles on microstructure and oxidation resistance of NiCoCrAlY coatings （the bond coat of the duplex structure thermal barrier coatings）. Scanning electron microscope （SEM）, X-ray diffractometer（XRD） and thermogravimetry were employed to investigate their morphologies, phases and cyclic oxidation behaviors in atmosphere at 1 050℃, compared with the coating without nano-particles. With the addition of nano-particles, the growth pattern of the grains at the interface changed from epitaxial growth to non-epitaxial growth or part-epitaxial growth; slender dendrites were broken and cellularized; cracks and pores were restrained; and the oxidation weight-gain and the stripping resistance of the oxide scale were improved as well. Among the three kinds of nano-particles, the SiC nano-particles showed the most improvement on microstructure, while the CeO2 nano-particles were insufficient, but its effects on the oxidation resistance are the same as those of the SiC nano-particles. Based on the discussions of the influence mechanism, it is believed that CeO2 nano-particles would show better improvement than SiC nano-particles if the proper amount is added and the proper preparation technique of micro-nanometer composite powders is adopted, with the synergistic action of nanometer effect and reactive element effect.

关键词： high-temperature protective coating nano-particle microstructure cyclic oxidation laser cladding

Joining Force of Heterogeneous Titanium Alloy in Linear Friction Welding Process

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第3期33卷 370-374页

作者： Wang Hongfeng zuo dunwen Wang Jianli Song Weiwei College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics College of Mechanical and Electrical Engineering HuangShan University

A dynamometer was designed and manufactured to measure the joining force in the linear friction welding *** error percentages of the dynamometer in the upset(x)and vibration(y)directions were 0.9% and 0.75%,*** cross-sensitivity range of the dynamometer was 1.2%—3.3% in the two *** precision level satisfies the requirements of the dynamometer *** joining force of the TC17 and TC11 heterogeneous titanium alloys in the linear friction welding process was used to test the manufactured *** test results showed that the upset force was large,but the vibration force showed a smaller change in TC11 during the linear friction welding *** addition,the upset and vibration forces of the linear friction welding were greater with a short welding time than those with a long welding time.

关键词： heterogeneous titanium alloy linear friction welding dynamometer upset force vibration force

New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 377-383页

作者： ZHANG Guixiang ZHAO Yugang ZHAO Dongbiao zuo dunwen YIN Fengshi College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics School of Mechanical Engineering Shandong University of Technology

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidif

关键词： iron-based SiC composite powder gas atomization and rapid solidification spherical composite magnetic abrasive magnetic abrasive finishing(MAF)

Numerical Calculation and Experimental Research on Residual Stresses in Precipitation-hardening Layer of NAK80 Steel for Shot Peening

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Chinese Journal of Mechanical Engineering 2011年第3期24卷 439-445页

作者： MIAO Hong zuo dunwen WANG Min ZHANG Ruihong WANG Hongfeng Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Mechanical Engineering Yangzhou University Yangzhou 225000 China

Shot peening can improve fatigue strength of materials by creating compressive residual stress field in their surface layers,and offers a protection against crack initiation and propagation,corrosion,*** fatigue fracture and stress corrosion cracking of NAK80 steel parts are improved *** there lacks in-depth research in which the beneficial effect of the residual stress may be offset by the surface damage associated with shot peening,especially in terms of the research on the effective control of shot peening *** order to obtain the surface residual stress field of NAK80 steel after shot peening,the samples are shot peened by pneumatic shot peening machine with different *** residual stress in the precipitation-hardening layer of NAK80 steel is measured before and after a shot peening treatment by X-ray diffraction *** order to obtain true residual stress field,integral compensation method is used to correct *** setting up analytical model of the residual stress in the process of shot peening,the surface residual stress is calculated after shot peening,and mentioning the reason of errors occurred between calculated and experimental residual stresses,which is mainly caused by the measurement error of the shoot arc *** the same time,micro hardness,microstructure and roughness in the precipitation-hardening layer of NAK80 steel before and after shot peening were measured and surveyed in order to obtain the relation between shot peening strength and surface quality in the precipitation-hardening *** results show that the surface quality of NAK80 steel is significantly improved by shot peening *** over peening effect is produced when the shot peening intensity is too high,it is disadvantageous to improve sample＇s surface integrity,and leading to reduce the fatigue *** arc high value of optimal shot peening is 0.40 mm,the surface quality is the best,and the depth of residual stress in the precipit

关键词： shot peening residual stress precipitation-hardening layer surface quality

Diamond Film Synthesis with a DC Plasma Jet:Effect of the Contacting Interface between Substrate and Base on the Substrate Temperature

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Journal of Materials Science & Technology 2007年第4期23卷 495-498页

作者： Rongfa CHEN dunwen zuo Feng XU Duoseng LI Min WANG Department of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Mechanical Engineering Yangzhou University Yangzhou 225009 China

The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC （direct current） plasma jet. The effects of the solid contacting area,conductive materials and fixing between the substrate and the base were investigated without affecting the other parameters. Experimental results indicated that the preferable solid contacting area was more than 60% of total contacting areal; the particular Sn-Pb alloy was more suitable for conducting heat and the concentric fixing ring was a better setting for controlling the substrate temperature. The result was explained in terms of the variable thermal contact resistance at the interface between substrate and base. The diamond films were analyzed by scanning electron microscopy （SEM） for morphology, X-ray diffraction （XRD） for the intensity of characteristic spectroscopy and Raman spectroscopy for structure.

关键词： Diamond film Substrate temperature Contacting interface DC arc plasma jet

Optimization of Polishing Parameters with Taguchi Method for LBO Crystal in CMP

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Journal of Materials Science & Technology 2009年第5期25卷 703-707页

作者： Jun Li Yongwei Zhu dunwen zuo Yong Zhu Chuangtian Chen Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Beijing Center for Crystal Research ＆ of Sciences Beijing 100080 China Development Technical Institute of Physics and Chemistry Chinese Academy

Chemical mechanical polishing （CMP） was used to polish Lithium triborate （LiB3O5 or LBO） crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate （MRR） and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are： pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are： pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.

关键词： Chemical mechanical polishing (CMP) Lithium triborate (LBO) crystal Material removal rate (MRR) Surface roughness Taguchi method

Low Cycle Fatigue and Strengthening Mechanism of Cold Extruded Large Diameter Internal Thread of Q460 Steel

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Chinese Journal of Mechanical Engineering 2016年第3期29卷 556-563页

作者： MIAO Hong MEI Qing YUAN Jingyun ZHENG Zaixiang JIN Yifu zuo dunwen College of Mechanical Engineering Yangzhou University College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.

关键词： large diameter internal thread cold extrusion low cycle fatigue strengthening fatigue resistance