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Chinese Journal of Mechanical Engineering 2024年第1期37卷 203-214页

作者： Xiaokang Huang Xiaoyong Tian Qi Zhong Shunwen He Cunbao Huo Yi Cao Zhiqiang Tong Dichen Li State Key Laboratory of Manufacturing Systems Engineering Xi’an Jiaotong UniversityXian 710049China

Improvement of fabrication efficiency and part performance was the main challenge for the large-scale Powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment.

关键词： Powder bed fusion Efficiency Large-scale Spot size Heat-affected zone(HAZ)

Comparison of microstructure and mechanical behavior of Ti-35Nb manufactured by laser Powder bed fusion from elemental powder mixture and prealloyed powder

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Journal of Materials Science & Technology 2022年第10期105卷 1-16页

作者： J.C.Wang Y.J.Liu S.X.Liang Y.S.Zhang L.Q.Wang T.B.Sercombe L.C.Zhang School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia School of Engineering M050The University of Western Australia35 Stirling HighwayCrawleyPerthWA 6009Australia Northwest Institute for Nonferrous Metal Research Xi’an 710016China State Key Laboratory of Metal Matrix Composites School of Material Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Although different types of powder feedstock are used for additive manufacturing via laser Powder bed fusion(L-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock.This work investigated the microstructure,phase composition,melt pool morphology,and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental powder mixture.The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in theα/βmatrix,resulting from the unstable melt pool during the melting of the powder mixture.By contrast,parts produced from prealloyed powder display a homogeneous microstructure withβandαphases,owing to the full melting of prealloyed powder,therefore,a more stable melt pool to achieve a homogeneous microstructure.The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility(about 10 times that of the counterparts using mixed powder),attributed to the high homogeneity in microstructure and chemical composition,strong interface bonding,relatively low oxygen content,and the existence of a large amount ofβphase.This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.

关键词： Titanium-niobium Powder bed fusion Additive manufacturing Melt pool stability Microstructure Mechanical properties

High-accuracy calibration for multi-laser Powder bed fusion via in situ detection and parameter identification

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Advances in Manufacturing 2022年第4期10卷 556-570页

作者： Qi Zhong Xiao-Yong Tian Xiao-Kang Huang Zhi-Qiang Tong Yi Cao Di-Chen Li State Key Laboratory of Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an710049People’s Republic of China

Multi-laser Powder bed fusion(ML-PBF)adopts multiple laser-scanner systems to increase the build envelope and build speed,but its calibration is an iterative and time-consuming process.In particular,multiple large-scale scan fields have a complex distortion in the overlap area,challenging the calibration process.In this study,owing to the enormous workload and alignment problems in the calibration of multiple scan fields,a novel calibration system is designed in this study to realize in situ auto-detection of numerous laser spots in the build chamber to ensure high efficiency and accuracy.Moreover,because the detectable area could not cover the entire build area and the detection data still contained errors,a virtual laser-scanner system was established by identifying the assembly defects and galvo nonlinearities of the ML-PBF system from the detection data,which served as the system's controller to improve calibration accuracy.The multi-field alignment error was less than 0.012%,which could avoid the intersection and separation of scan paths in multi-laser scanning and therefore meet the requirements for high-precision ML-PBF.Finally,the reliability of the method was verified theoretically using principal component analysis.

关键词： Powder bed fusion Multi-laser technology Galvo calibration Assembly defects System identification

3D particle tracking velocimetry for the determination of temporally resolved particle trajectories within laser Powder bed fusion of metals

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International Journal of Extreme Manufacturing 2019年第3期1卷 96-105页

作者： Eric Eschner Tobias Staudt Michael Schmidt Institute of Photonic Technologies Friedrich-Alexander-Universität Erlangen-NürnbergKonrad-Zuse-Str.3/5D-91052ErlangenGermany Graduate School in Advanced Optical Technologies Friedrich-Alexander-Universität Erlangen-NürnbergPaul-Gordan-Str.6D-91052ErlangenGermany

Within this work,we present a system for the measurement of the three-dimensional(3D)trajectories of spatters and entrained particles during laser Powder bed fusion(L-PBF)of metals.It is comprised of two ultrahigh-speed cameras and a reconstruction task specific processing reconstruction algorithm.The system enables an automated determination of 3D measures from the trajectories of a large number of tracked particles.Ambiguity evolving from an underdetermined geometrical situation induced by a two-camera setup is resolved within the tracking using a priori knowledge of L-PBF of metals.All processing steps were optimized to run on a graphics processing unit to allow the processing of large amounts of data within an appropriate time frame.The overall approach was validated by a comparison of the measurement results to synthetic images with a known 3D ground truth.

关键词： Powder bed fusion laser image processing additive manufacturing high-speed imaging 3D particle velocimetry

Understanding the Rayleigh instability in humping phenomenon during laser Powder bed fusion process

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International Journal of Extreme Manufacturing 2022年第1期4卷 85-92页

作者： Wenxuan Zhang Wenyuan Hou Luc Deike Craig Arnold Department of Chemical and Biological Engineering Princeton UniversityPrincetonNJ 08544United States of America Princeton Institute for the Science and Technology of Materials Princeton UniversityPrincetonNJ 08544United States of America Department of Mechanical and Aerospace Engineering Princeton UniversityPrincetonNJ 08544United States of America High Meadows Environmental Institute Princeton UniversityPrincetonNJ 08544United States of America

The periodic undulation of a molten track’s height profile in laser-based Powder bed fusion of metals(PBF-LB/M)is a commonly observed phenomena that can cause defects and building failure during the manufacturing process.However a quantitative analysis of such instabilities has not been fully established and so here we used Rayleigh–Plateau theory to determine the stability of a single molten track in PBF-LB/M and tested it with various processing conditions by changing laser power and beam shape.The analysis discovered that normalized enthalpy,which relates to energy input density,determines whether a molten track is initially unstable and if so,the growth rate for the instability.Additionally,whether the growth rate ultimately yields significant undulation depends on the melt duration,estimated by dwell time in our experiment.

关键词： additive manufacturing Powder bed fusion dual lasers undulation humping

Development and Evaluation of Multiscale Fiber-reinforced Composite powders for powder-bed fusion Process

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Chinese Journal of Mechanical Engineering(Additive Manufacturing Frontiers) 2023年第2期2卷 43-53页

作者： Zhihao Wang Meixin Zhou Heye Xiao Shangqin Yuan Institute of Intelligence Material and Structure Unmanned System Research InstituteNorthwestern Polytechnical UniversityXi’an710072China State IJR Center of Aerospace Design and Additive Manufacturing School of Mechanical EngineeringNorthwestern Polytechnical UniversityXi’an710072China Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design MIIT ChinaNorthwestern Polytechnical UniversityXi’an710072China Singapore Centre for 3D Printing School of Mechanical and Aerospace EngineeringNanyang Technological UniversitySingapore639798Singapore

The development of multiscale fiber-reinforced composite powders is an effective way to improve the mechanical properties and functionality of additively manufactured parts.Herein,a novel thermally induced precipitation process is proposed for preparing multiscale fiber-reinforced powders.A systematic evaluation was conducted to explore the main factors influencing powder morphology,powder flow,and microstructure.In the powder-forming mechanism,the polymer matrix is coated on the microfiber,and a film of carbon nanotubes covers the powder surface,which is promoted by heterogeneous nucleation.The composite powders comprised polyamide 12,carbon fiber(CF),and carbon nanotubes,which have been successfully applied in Powder bed fusion processes including selective laser sintering(SLS).Smooth flow and powder deposition were observed,and the composite components obtained via SLS were well-fabricated using the optimized process parameters.A CF loading ratio of up to 66.7 wt%and homogeneous fiber distribution within the matrix were successfully achieved.

关键词： Fiber-reinforced composite powder Multi-scale fibers Powder bed fusion Selective laser sintering

High-fidelity Modeling of Multilayer Building Process in Electron Beam Powder bed fusion:Build-quality Prediction and Formation-Mechanism Investigation

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Chinese Journal of Mechanical Engineering(Additive Manufacturing Frontiers) 2023年第3期2卷 69-83页

作者： Chaochao Wu Pu Xie Muhammad Qasim Zafar Haiyan Zhao State Key Laboratory of Tribology Department of Mechanical EngineeringTsinghua UniversityBeijing100084China School of Mechanical Engineering and Automation Fuzhou UniversityFuzhou350108China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing100084China Department of Aeronautics and Astronautics Stanford UniversityPalo Alto94305United States

High-fidelity simulations of Powder bed fusion(PBF)additive manufacturing have made significant progress over the past decade.In this study,an efficient two-dimensional frame was developed for simulating the electron beam PBF process with hundreds of tracks for the direct prediction of the build quality.The applicable parameter range of the developed model was determined by comparing the heat transfer with that in three-dimensional cases.Subsequently,powder deposition and selective melting were coupled for a continuous simulation of the multilayer process.Three powder deposition models were utilized to generate random powder particles,and their effects on the packing structure and the resultant simulated build quality were investigated.The predicted build quality was validated using experimental results from independent studies.By reproducing the building process,the defect development mechanism in a multilayer process was revealed for the coalescence behaviors of randomly distributed powder particles,which also confirmed the importance of simulation at the high-fidelity powder scale.The effects of key process parameters during multilayer and multi-track processes on the build quality were systematically investigated.In particular,the formation statuses of all tracks during the simulated building process were recorded and analyzed statistically,which provided crucial information on the printing process for understanding the building mechanism or performing uncertainty analysis.

关键词： Powder bed fusion Electron beam melting Numerical simulation High-fidelity model Formation mechanism Build quality Defect

Additive manufacturing of metallic glasses and high-entropy alloys:Significance,unsettled issues,and future directions

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Journal of Materials Science & Technology 2023年第9期140卷 79-120页

作者： Haishun Liu Dengfeng Yang Qi Jiang Yangyang Jiang Weiming Yang Lin Liu Lai-Chang Zhang School of Materials Sciences and Physics China University of Mining and TechnologyXuzhou 221116China State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Material Processing and Die&Mould Technology and School of Materials Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

As two kinds of well-known prominent high-performance alloys,metallic glasses(MGs)and high-entropy alloys(HEAs)have attracted increasing attention.Most of them contain multiple alloying components,demonstrate intriguing microstructures,and exhibit excellent properties;however,their unique performances are closely dependent on the fabrication process,although they are limited due to the need for rapid solidification during fabrication.On the other hand,additive manufacturing(AM)can be used to fabricate complex parts via rapid solidification,thus saving materials.These advantages provide AM with a great possibility to produce MG and HEA materials with tunable microstructures therefore properties,and corresponding parts with complex geometries,large dimensions,and more functions.This paper provides a comprehensive and systematic overview of the manufacturing and properties of MGs and HEAs using AM techniques.The correlation between MGs and HEAs with conventional manufacturing meth-ods and the difficulties encountered are retrospectively discussed.Afterward,this review specifically focuses on the recent research advances in MGs and HEAs fabricated using AM technologies.Then,various properties of the AM-fabricated MGs and HEAs are discussed.Finally,the remaining issues and potential solutions,challenges,and future directions on the AM of MGs and HEAs are also presented.

关键词： Additive manufacturing Powder bed fusion Metallic glasses High-entropy alloys Research status

Plastic deformation of a Zr-based bulk metallic glass fabricated by selective laser melting

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Journal of Materials Science & Technology 2021年第1期60卷 139-146页

作者： L.Deng K.Kosiba R.Limbach L.Wondraczek U.Kühn S.Pauly IFW Dresden Institute for Complex MaterialsHelmholtzstraße 20D-01069DresdenGermany Otto Schott Institute of Materials Research University of JenaFraunhoferstraße 6D-07743JenaGermany University of Applied Sciences Aschaffenburg Würzburger Straße 45D-63743AschaffenburgGermany

Fully amorphous Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_(5) bulk metallic glass(BMG) samples with a relative density exceeding 98% were fabricated via selective laser melting(SLM).High fracture stresses of around1700 MPa and a reproducible plastic strain of about 0.5% were obtained for cylindrical SLM samples.The analysis of the observed serrations during compressive loading implies that the shear-band dynamics in the additively manufactured samples distinctly differ from those of the as-cast glass.This phenomenon appears to originate from the presence of uniformly dispersed spherical pores as well as from the more pronounced heterogeneity of the glass itself as revealed by instrumented indentation.Despite these heterogeneities,the shear bands are straight and form in the plane of maximum shear stress.Additive manufacturing,hence,might not only allow for producing large BMG samples with complex geometries but also for manipulating their deformation behaviour through tailoring porosity and structural heterogeneity.

关键词： Powder bed fusion Selective laser melting Bulk metallic glass Serrated flow Heterogeneity

3D Printing of Ceramic Biomaterials

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Engineered Regeneration

Engineered Regeneration 2022年第1期3卷 41-52页

作者： Michael Ly Sarah Spinelli Shayne Hays Donghui Zhu Department of Biomedical Engineering Stony Brook University100 Nicolls RdStony BrookNY 11794United States

Bioceramics are a popular class of materials used in biomedical applications due to their mechanical stability and biocompatibility.They exist in a variety of fields including hip joints for orthopedics,tooth fillings for dentistry,and scaffolds for tissue engineering;however,the standard processes currently used to manufacture these ce-ramic products can be time-consuming and costly.In response,current literature alternatively proposes additive manufacturing(3D printing)strategies to fabricate bioceramic materials in a cost-effective and efficient man-ner.Herein,we briefly cover five common processes and materials used in additive manufacturing bioceramics:fused deposition modeling,material jetting,binder jetting,Powder bed fusion,and vat photopolymerization.Fur-thermore,we discuss the potential of these 3D printed ceramic structures when applied to different biomedical technologies such as bone tissue scaffolds and structural implants.

关键词： Extrusion Binder jetting Material jetting Powder bed fusion Vat photopolymerization