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Microstructure and mechanical properties of hybrid fabricated 1Cr12Ni2WMoVNb steel by laser melting deposition

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Chinese Journal of Aeronautics 2013年第2期26卷 481-486页

作者： wang Yudai Tang Haibo Fang Yanli wang huaming Engineering Research Center of Ministry of Education on Laser Direct Manufacturing for Large Metallic Components School of Materials Science and Engineering Beihang University

Laser melting deposition was carried out to deposit a 1Cr12Ni2WMoVNb steel bar on a wrought bar of same material. Room-temperature tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample were evaluated, and microstructure, fracture surface morphology, and hardness profile were analyzed by an optical microscope （OM）, a scanning electron microscope （SEM）, and a hardness tester. Results show that the hybrid fabricated 1Cr12Ni2WMoVNb steel sample consists of laser deposited zone, wrought substrate zone, and heat affected zone （HAZ） of the wrought substrate. The laser deposited zone has coarse columnar prior austenite grains and fine well-aligned dendritic structure, while the HAZ of the wrought substrate has equiaxed prior austenite grains which are notably finer than those in the wrought substrate zone. Besides, austenitic transformation mechanism of the HAZ of the wrought substrate is different from that of the laser deposited zone during the reheating period of the laser deposition, which determines the different prior austenite grain morphologies of the two zones. Microhardness values of both the laser deposited zone and the HAZ of the wrought substrate are higher than that of the wrought substrate zone. Tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample are comparable to those of the wrought bar, and fracture occurs in the wrought substrate zone during the tensile test.

关键词： Heat affected zone Laser melting deposition Martensitic stainless steel Mechanical properties Metallic material Solid phase transformation

TWO-STAGE OCCLUDED OBJECT RECOGNITION METHOD FOR MICROASSEMBLY

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Chinese Journal of Mechanical Engineering 2007年第1期20卷 115-119页

作者： wang huaming ZHU Jianying Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

A two-stage object recognition algorithm with the presence of occlusion is presented for microassembly. Coarse localization determines whether template is in image or not and approximately where it is, and fine localization gives its accurate position. In coarse localization, local feature, which is invariant to translation, rotation and occlusion, is used to form signatures. By comparing signature of template with that of image, approximate transformation parameter from template to image is obtained, which is used as initial parameter value for fine localization. An objective function, which is a function of transformation parameter, is constructed in fine localization and minimized to realize sub-pixel localization accuracy. The occluded pixels are not taken into account in objective function, so the localization accuracy will not be influenced by the occlusion.

关键词： Object recogntion Local feature Sub-pixel Objective function

Analysis of the nutation and precession of the vortex core and the influence of operating parameters in a cyclone separator

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Chinese Journal of Chemical Engineering 2022年第6期35卷 1-10页

作者： Pan Zhang Guanghui Chen Weiwen wang Guodong Zhang huaming wang College of Electromechanical Engineering and Key Laboratory of Multiphase Flow Reaction and Separation Engineering of Shandong Province Qingdao University of Science and TechnologyQingdao 266069China College of Chemical Engineering Qingdao University of Science and TechnologyQingdao 266043China School of Naval Architecture and Electrical Engineering Zhejiang Ocean UniversityZhoushan 316022China

Vortices motion in the anisotropic turbulent flow of cyclones makes a vital impact on flow stability and collection ***,there remains a lack of clarity in the overall feature of vortices *** this work,a numerical analysis was conducted to clarify the complex motion of the vortex core in a cyclone *** validity of the numerical model was demonstrated by comparing the computational results with experimental data in the *** revealed by the results,the vortex core not only has a precession motion about the geometrical center axis but also does a nutation motion in the axial *** frequencies of the precession motions show two main *** the magnitudes of the precession and nutation motions have non-uniform distributions in the ***,the precession-nutation motions of the vortex cores exhibit a similar fluctuant pattern to the dust ring on the separator *** inlet gas velocity and the inlet solid loading show vital effects on the magnitudes and frequencies of precession and nutation motion.

关键词： Cyclone separator Precession vortex core Nutation motion Separation efficiency Numerical simulation Fluid mechanics

Performance Investigation of Cone Dielectric Elastomer Actuator Using Taguchi Method

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Chinese Journal of Mechanical Engineering 2011年第4期24卷 685-692页

作者： wang huaming ZHU Yinglong ZHAO Dongbiao LUAN Yunguang College of Mechanical and Electrical Engineering Nanjing University of Aeronautics andAstronautics Nanjing 210016 China State Key Laboratory of Robotics Shenyang Institute of Automation Chinese Academy of Science Shenyang 110016 China Engineering Institute of Engineering Corps PLA University of Science and Technology Nanjing 210007 China

Dielectric elastomer actuator （DEA） show promise for mechatronic applications due to the advantages of dielectric elastomer, such as lightweight, flexible, low cost, high strain, etc, and many configurations of DEAs have been demonstrated. As a kind of linear actuator, cone DEAs are studied in some laboratory prototypes due to easy manufacturing, however, their performance have not been exploited fully. Based on the working principle of DEA, a four-bar linkage mechanism is designed to provide negative stiffness preload, which can increase displacement output of actuator （outer diameter 100 mm） to 17 mm. Three cone actuating units are assembled in parallel to enhance the maximum force output to 5.07 N. Loading experiments of actuator in forward and backward strokes are performed, the experimental results show that backward stroke has stronger actuating capability than forward stroke, accordingly application of actuator is recommended. Four factors rather than applied voltage, i.e., number of actuating units, pre-stretch ratio, inner diameter, and outer diameter, are determined as influencing factors for Taguchi method. Then the performance objectives of actuator, i.e., displacement output, maximum force output, and maximum work in backward stroke, are investigated based on L9（34） Taguchi orthogonal design. The mean signal-to-noise （S/N） ratio based on the larger-the-better criterion is calculated according to the acquired displacement and force output. Analytical results show that outer diameter has the most significant influence on displacement output, and maximum force out and work output are influenced most by number of actuating units. Inner diameter also has an important effect on the performance objectives of actuator, while pre-stretch ratio has the least influence. The proposed performance investigation is helpful for the design and application of cone actuator in mechatronic system.

关键词： dielectric elastomer actuator performance objective Taguchi method

Formation of face-centered cubic titanium in laser surface re-melted commercially pure titanium plate

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Journal of Materials Science & Technology 2018年第5期34卷 767-773页

作者： Zhuo Li Xu Cheng Jia Li huaming wang national engineering laboratory of additive manufacturing for large metallic components school of materials science and engineeringbeihang university Beijing 100191 China

Micron-scale face-centered cubic titanium phase（named as δ phase） were noticed in the re-melted zone of laser surface re-melted commercially pure titanium *** morphology,sub-structure,orientation and distribution of δ phase were investigated by scanning electron microscopy,electron back-scattered diffraction and transmission electron *** kind formation processes of δ phase were put forward based on the *** first one is α＇→δ transformation which takes place in single α＇grains and leads to the orientation relationship {001}δ//{0001}α＇〈 110 〉 δ//〈 112^-0 〉α＇.The second one is β→α＇＋ δ transformation which takes place at α＇/α＇interfaces and leads to the orientation relationship{001}δ//{11^-0}β〈110〉 δ//〈111〉β.The third one is another kind of β→α＇＋ δ transformation that takes place at α＇/α＇interfaces and leads to the orientation relationship{11^-1}δ//{11^-0}β〈 110 〉 δ//〈 111 〈 β.It is believed that the transformations of δ phase are stress assistant ones and in the present investigation,the phase transformation stress of β→α＇transformation acts as the assistant driving force for the formation of δ phase.

关键词： Pure titanium Laser surface re-melt Martensitic phase transformation Face centered cubic Electron back-scattered diffraction

Microstructures and tensile properties of laser cladded AerMet100 steel coating on 300M steel

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Journal of Materials Science & Technology 2018年第4期34卷 643-652页

作者： Jian Liu Jia Li Xu Cheng huaming wang National Engineering Laboratory of Additive Manufacturing for Large Metallic Components School of Materials Science and EngineeringBeihangUniversityBeijing 100191China

A layer ofAerMet100 steel was coated on the surface of forged 300 M steel using laser cladding technique. The chemical compositions, microstructures, hardness and tensile properties of this AerMet100[300 M material were systematically investigated. Results show that the composition of the AerMet100 clad layer is macroscopically homogeneous, and a compositional transition zone with width of 150 μm is observed between the clad layer and heat affected zone. Microstructures in transition zone transform from the fine needle-like bainite in 300 M steel to the lath tempered martensite in AerMet100 clad layer. Microstructures in heat affected zone also gradually change from the thick plate bainite and blocky retained austenite （unstable heat affected zone） to fine needle-like bainite and film-like austenite （stable heat affected zone） due to different thermal cycle processes. Thick plate bainite together with blocky retained austenite in unstable heat affected zone reduce the strength and ductility of AerMet100/300 M material. However, the tensile specimens, consisting of clad layer and stable heat affected zone, show slightly inferior mechanical properties to 300 M steel. Ductile fracture exists in AerMet100 clad layer while quasi-cleavage fracture occurs in the stable heat affected zone.

关键词： Ultrahigh strength steel Laser cladding Microstructures Heat affected zone Tensile properties

Additive manufacturing of magnesium matrix composites: Comprehensive review of recent progress and research perspectives

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Journal of Magnesium and Alloys 2023年第2期11卷 425-461页

作者： Chenghang Zhang Zhuo Li Jikui Zhang Haibo Tang huaming wang Ningbo Institute of Technology Beihang UniversityNingbo315800China National Engineering Laboratory of Additive Manufacturing for Large Metallic Components Beihang University37 Xueyuan RoadBeijingChina Research Institute for Frontier Science Beihang University37 Xueyuan RoadBeijingChina Research Center on Laser Direct Manufacturing for Large Critical Metallic Component Beihang University37 Xueyuan RoadBeijingChina

The magnesium matrix composites(MMCs) formed by introducing reinforcements to magnesium alloys overcome the limitations of the mechanical properties to a certain extent, presenting unique and excellent properties that any component does not have, such as high specific stiffness and specific strength, good dimensional stability, outstanding shock absorption performance, excellent electromagnetic shielding and hydrogen storage characteristics, etc. As an emerging manufacturing technology, additive manufacturing(AM) is based on the design of threedimensional(3D) data model to obtain 3D objects through layer-by-layer processing, which possesses the advantages of short manufacturing cycle, high material utilization rate, high degree of design freedom, excellent mechanical properties and the ability to fabricate complex structural components. Combining the high stiffness and high strength properties of MMCs and the technical advantages of AM forming complex structural parts with high performance, the prepared AM MMCs have huge potential advantages and broad application prospects in new high-tech industries such as automobile, aerospace, consumer electronics and biomedicine, etc. This paper reviews the research progress in the field of AM MMCs, mainly introduces the main AM technologies, including selective laser melting(SLM), electron beam selective melting(EBSM), laser engineered net shaping(LENS) and wire and arc additive manufacturing(WAAM). The formation mechanism and control methods of the typical defects including balling effect, porosity, poor fusion, loss of alloy elements and cracks produced during AM are discussed. The main challenges of AM MMCs are proposed from the aspects of composition design and the preparation of powder raw material. The relationship between the microstructure and mechanical properties, corrosion performance and biocompatibility of AM MMCs are elaborated in detail. The application potential of AM MMCs in various fields at present and in th

关键词： Magnesium matrix composites Additive manufacturing Defects Microstructure Properties

Effects of microstructure on fatigue crack propagation behavior in a bi-modal TC11 titanium alloy fabricated via laser additive manufacturing

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Journal of Materials Science & Technology 2019年第2期35卷 403-408页

作者： Yafei wang Rui Chen Xu Cheng Yanyan Zhu Jikui Zhang huaming wang National Engineering Laboratory of Additive Manufacturing for Large Metallic Components Beihang University School of Materials Science and Engineering Beihang University School of Aeronautic Science and Engineering Beihang University

In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser additive manufacturing(LAM) TC11 alloy with a special bi-modal microstructure are investigated. The results indicate that the alloy presents a special bi-modal microstructure that comprises a fork-like primary α(αp) phase surrounded by a secondary α colony(αs) in the α phase matrix after the heat treatment is completed. The samples demonstrate a fast crack growth rate with larger da/d N values through the equiaxed grain sample versus across the equiaxed-columnar grain sample at low K values(<13.8). The differences that are observed between the crack propagation behaviors(in the crack initiation stage) of the samples can be mostly attributed to the different size and morphology of the αp lamellae and αscolony within the grains in the equiaxed and columnar grain regions rather than the grain boundaries. The cracks prefer to grow along the α/β boundary with a smooth propagation route and a fast propagation rate in the equiaxed grain region, where the αpand α clusters have a large ***, in the columnar grain region, small and randomly distributed αplamellae generate a zigzagshaped propagation path with a reduction in the da/d N value. Additionally, the change in the size of the αp lamellae in the equiaxed grains(heat affected bands, HAB) is also observed to influence the propagation behavior of the crack during the crack initiation stage.

关键词： Laser additive manufacturing TC11 titanium alloy Microstructure Fatigue crack propagation path Fatigue crack growth rate

MC CARBIDE FLOATATION IN A HOT CORROSION RESISTANT SINGLE CRYSTAL Ni-BASE SUPERALLOY DURING DIRECTIONAL SOLIDIFICATION

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Acta Metallurgica Sinica(English Letters) 1992年第1期5卷 66-68页

作者： wang huaming TANG Yajun ZHANG Jinghua ZHANG Zhiya HU Zhuangqi Inst of Metal Research Acad Sinica Shenyang China

The floating phenomenon of MC carbide(TiC)in a hot corrosion resistant single crystal Ni-base superalloy was observed during planar and cellular interface directional *** explanation about the phenomenon is presented.

关键词： single crystal Ni-base superalloy MC carbide floating phenomenon directional solidification