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Microstructural Features and Mechanical Behaviors of Al_(0.5)Cr_(0.8)CoFeNi_(2.5)V_(0.2) High-Entropy Alloys Fabricated by Selective Laser Melting Technique

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Acta Metallurgica Sinica(English Letters) 2022年第10期35卷 1591-1606页

作者： Yao Yan Wei-Dong song Ke-Feng Li Kang Zhao Tong-Tong Sun kai-kai song Jian-Hong Gong Li-Na Hu Shenzhen Research Institute of Shandong University Shenzhen518057China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Guangdong Institute of Materials and Processing Guangdong Academy of SciencesGuangdong UniversityGuangzhou510650China School of Mechanical Electrical and Information EngineeringShandong UniversityWeihai264209China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan250061China

In this work,high strength and ductile Al_(0.5)Cr_(0.8)CoFeNi_(2.5)V_(0.2) high-entropy alloys(HEAs)were fabricated by the selective laser melting(SLM)technique.After orthogonal experiments,it was verified that a wide SLM processing parameter window can be used to produce crack-free samples for the investigated HEAs.All the printed HEA samples exhibit good densification higher than 98.3%.It was found that obvious epitaxial growth leads to the formation of the cylindrical and equiaxed ordered face-centered cubic(FCC)crystals,displaying the characteristics of sub-cylindrical and sub-cellular microstructures.The low-angle grain boundaries(LAGBs)prefer appearing around subgrain structures,while the high-angle grain boundaries(HAGBs)tend to form around coarse grains.Two HEA samples with high and low apparent densities were selected to observe their mechanical properties,which exhibit Vickers hardness higher than 263 HV and do not fail during compression.With increasing densification,the strength gradually rises.According to the engineering stress–strain curves during compression,the yield strength is higher than 530 MPa,while the strength near 40%engineering strain is larger than 1840 MPa.During deformation,a large density of dislocations becomes popular within subgrain structures together with the pre-existing dislocations from rapid solidification,leading to the formation of planar and cross slip bands.Within coarse cylindrical crystals,some deformation twins are also induced together with the appearance of a distinct copper-type texture during deformation.As a result,the as-printed samples display better mechanical properties than the as-cast counterpart.The present studies provide a very good HEA candidate for the SLM process,but more work should be conducted to achieve excellent comprehensive properties.

关键词： High-entropy alloys Selective laser melting Mechanical properties Microstructures

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Enhanced mechanical performance of gradient-structured CoCrFeMnNi high-entropy alloys induced by industrial shot-blasting

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Rare Metals 2023年第3期42卷 982-993页

作者： Ming-Zhi Zhang Kun Zhang kai-kai song Xiao-Yu Zou Wei-Dong song Ke-Feng Li Li-Na Hu Ze-Qun Zhang Jürgen Eckert Shenzhen Research Institute of Shandong University Shenzhen 518057China CAS Key Laboratory of Microgravity(National Microgravity Laboratory) Institute of MechanicsChinese Academy of SciencesBeijing100190China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Mechanical Electrical and Information EngineeringShandong UniversityWeihai 264209China Guangdong Institute of Materials and Processing Guangdong Academy of SciencesGuangzhou 510650China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China Erich Schmid Institute of Materials Science Austrian Academy of SciencesLeoben 8700Austria Department of Materials Science Montanuniversitat LeobenLeoben 8700Austria

In this study,CoCrFeMnNi high-entropy alloys(HEAs)with a surface gradient nanostructure were produced using industrial shot blasting,which improved their mechanical properties compared to the untreated alloy.The severely plastically deformed(SPD)surface layer had a multi-scale hierarchical structure with a high density of stacking faults,deformation nanotwins,and amorphous domains.The depth of the SPD layer steadily increased as the shot-blasting time increased.The differences in the microhardness and tensile strength before and after shotblasting demonstrated the significant effect of the SPD layer on the mechanical performance.The microhardness of the homogenized HEA was~5 GPa.In comparison,the maximum microhardness of the specimens after 20 min of shot blasting was~8.0 GPa at the surface.The yield strength also improved by 178%,and a large ductility of~36%was retained.Additional nanograin boundary,stacking fault,and twin strengthening within the gradientnanostructured surface layer caused the strength to increase.During tensile deformation,strain concentration began at the surface of the specimen and gradually spread to the interior.Thus,the gradient-nanostructured surface layer with improved strain hardening can prevent early necking and ensure steady plastic deformation so that high toughness is achieved.

关键词： High-entropy alloy Shot blasting Gradient structure Mechanical property Deformation mechanism

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Influence of Zn Addition on Microstructures and Martensitic Transformation in CuZr-based Alloys

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Journal of Iron and Steel Research(International) 2016年第1期23卷 31-36页

作者： kai-kai song Dian-yu WU Feng WAN Xiao-jun BAI Chong-de CAO Department of Physics School of ScienceNorthwestern Polytechnical University School of Mechanical Electrical &Information EngineeringShandong University(Weihai)

Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents（i.e.,7.0,10.0,and 14.0at.%）,the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature（M_s）decreases from（412±5）K to（329±5）K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons（i.e.,e_v/a and c_v）,respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.

关键词： CuZr-based alloy Zn microstructure phase transition rapid solidification

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Effect of pre-existing shear bands on mechanical properties and serration behaviors in bulk metallic glasses

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Journal of Iron and Steel Research(International) 2017年第4期24卷 402-410页

作者： Xu-dong Yuan Sheng-hai Wang kai-kai song Xiao-liang Han Yu-sheng Qin Dong-fang Li Xue-lian Li Bo song Hui Xing Li Wang School of Mechanical Electrical &Information EngineeringShandong University(Weihai) School of Science Northwestern Polytechnical University

Pre-existing（multiple）shear bands were introduced into the ductile Zr56Co28Al16 and Zr65Ni10Cu15Al10bulk metallic glasses（BMGs）through the lateral-deformation,respectively.It was found that the pre-exiting shear bands can further enhance the compressive plasticity of ductile BMGs.According to the serration analysis on the plastic deformation of the as-cast and the pre-deformed samples,the serration events in the stress-strain curves during deformation display a self-organized critical（SOC）behavior.Compared with the as-cast BMGs,a larger power-law scaling exponent calculated based on serrated flow behaviors becomes larger for the pre-deformed BMGs,implying that the shear banding stability of BMGs is effectively enhanced.This should be caused by the pronounced interactions of shear bands during plastic deformation for the pre-deformed BMGs.However,by introducing a large amount of multiple shear bands into the glassy matrix,it also becomes easier for shear bands to propagate along the pre-existing shear bands,leading to a lower cut-off elastic energy density for the pre-deformed BMGs.More multiple shear bands with stronger interactions for the pre-deformed BMGs could provide a larger chance to activate the shear-band cracking but less local elastic energies are remained for the subsequent crack-linking.

关键词： Bulk metallic glass Shear band Serration Ductility Pre-deformation

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Adaptive Consensus of Uncertain Multi-Agent Systems With Unified Prescribed Performance

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IEEE/CAA Journal of Automatica Sinica 2024年第5期11卷 1310-1312页

作者： Kun Li kai Zhao Yongduan song The authors are with the School of Automation Chongqing UniversityChongqing 400044China

Dear Editor,An adaptive consensus control algorithm for uncertain multi-agent systems(MAS),capable of guaranteeing unified prescribed performance,is presented in this letter.Unlike many existing prescribed performance related works,the developed control exhibits some features.Firstly,a distributed prescribed time observer is introduced so that not only each follower is able to estimate the leader’s signal within a predetermined time,but also the control design for each agent is independent with its neighbors.

关键词： agent prescribed Uncertain

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Random Forest-Based Fatigue Reliability-Based Design Optimization for Aeroengine Structures

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Computer Modeling in Engineering & Sciences 2024年第7期140卷 665-684页

作者： Xue-Qin Li Lu-kai song School of Energy and Power Engineering Beihang UniversityBeijing100191China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityKowloonHong Kong999077China Research Institute of Aero-Engine Beihang UniversityBeijing100191China

Fatigue reliability-based design optimization of aeroengine structures involves multiple repeated calculations of reliability degree and large-scale calls of implicit high-nonlinearity limit state function,leading to the traditional direct Monte Claro and surrogate methods prone to unacceptable computing efficiency and accuracy.In this case,by fusing the random subspace strategy and weight allocation technology into bagging ensemble theory,a random forest(RF)model is presented to enhance the computing efficiency of reliability degree;moreover,by embedding the RF model into multilevel optimization model,an efficient RF-assisted fatigue reliability-based design optimization framework is developed.Regarding the low-cycle fatigue reliability-based design optimization of aeroengine turbine disc as a case,the effectiveness of the presented framework is validated.The reliabilitybased design optimization results exhibit that the proposed framework holds high computing accuracy and computing efficiency.The current efforts shed a light on the theory/method development of reliability-based design optimization of complex engineering structures.

关键词： Random forest reliability-based design optimization ensemble learning machine learning

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Mobile Crowdsourcing Task Allocation Based on Dynamic Self-Attention GANs

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Computers, Materials & Continua 2024年第4期79卷 607-622页

作者： kai Wei song Yu Qingxian Pan School of Computer and Control Engineering Yantai UniversityYantai264005China School of Computer and Information Science Southwest UniversityChongqing400715China

Crowdsourcing technology is widely recognized for its effectiveness in task scheduling and resource allocation.While traditional methods for task allocation can help reduce costs and improve efficiency,they may encounter challenges when dealing with abnormal data flow nodes,leading to decreased allocation accuracy and efficiency.To address these issues,this study proposes a novel two-part invalid detection task allocation framework.In the first step,an anomaly detection model is developed using a dynamic self-attentive GAN to identify anomalous data.Compared to the baseline method,the model achieves an approximately 4%increase in the F1 value on the public dataset.In the second step of the framework,task allocation modeling is performed using a twopart graph matching method.This phase introduces a P-queue KM algorithm that implements a more efficient optimization strategy.The allocation efficiency is improved by approximately 23.83%compared to the baseline method.Empirical results confirm the effectiveness of the proposed framework in detecting abnormal data nodes,enhancing allocation precision,and achieving efficient allocation.

关键词： Mobile crowdsourcing task allocation anomaly detection GAN attention mechanisms

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Emerging interactively stretchable electronics with optical and electrical dual-signal feedbacks based on structural color materials

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Nano Research 2024年第3期17卷 1837-1855页

作者： Jialin Wang kai Zhao Changqing Ye Yanlin song School of Materials Science and Engineering Suzhou University of Science and TechnologySuzhou 215009China Key Laboratory of Green Printing Institute of ChemistryChinese Academy of SciencesBeijing 100190China

The booming development of wearable devices has aroused increasing interests in flexible and stretchable devices.With mechanosensory functionality,these devices are highly desirable on account of their wide range of applications in electronic skin,personal healthcare,human–machine interfaces and beyond.However,they are mostly limited by single electrical signal feedback,restricting their diverse applications in visualized mechanical sensing.Inspired by the mechanochromism of structural color materials,interactively stretchable electronics with optical and electrical dual-signal feedbacks are recently emerged as novel sensory platforms,by combining both of their sensing mechanisms and characteristics.Herein,recent studies on interactively stretchable electronics based on structural color materials are reviewed.Following a brief introduction of their basic components(i.e.,stretchable electronics and mechanochromic structural color materials),two types of interactively stretchable electronics with respect to the nanostructures of mechanochromic materials are outlined,focusing primarily on their design considerations and fabrication strategies.Finally,the main challenges and future perspectives of these emerging devices are discussed.

关键词： stretchable electronics structural color materials interactive sensing mechanochromism dual-signal feedbacks

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Jellyfish bio-inspired Fe@CNT@CuNC derived from ZIF-8 for cathodic oxygen reduction

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Nano Research 2024年第4期17卷 2352-2359页

作者： kai Cheng Zequan Liu Demin Jiang Min song Yuqiao Wang Research Center for Nano Photoelectrochemistry and Devices School of Chemistry and Chemical EngineeringSoutheast UniversityNanjing 211189China Yangtze River Delta Carbon Neutrality Strategy Development Institute Southeast UniversityNanjing 210096China School of Energy and Environment Southeast UniversityNanjing 210096China

Biomimetics provides guidance to design and synthesize advanced catalysts for oxygen reduction reaction in microbial fuel cells(MFCs).Herein,jellyfish-inspired Fe clusters on carbon nanotubes connected with CuNC(Fe@CNT@CuNC)were designed and prepared by using zeolitic imidazolate framework(ZIF)-8 precursors to imitate the organic texture and function of jellyfish.The antibacterial effect of Cu^(+)ions depressed the growth of cathode biofilm to ensure rapid mass transport.Fe clusters and CuNC connected by CNTs accelerated the electron transfer from Fe to CuNC.The optimization of oxygen adsorption was caused by electron redistribution between sites of Fe and Cu.Jellyfish-like catalysts achieved a half-wave potential of 0.86 V and onset potential of 0.95 V vs.reversible hydrogen electrode(RHE).MFCs gained the maximum power density of 1600 mW·m^(-2) after 500 h measurement.This work provides insights into the special design of advanced catalysts based on bio-inspiration and biomimetics.

关键词： bio-inspiration oxygen reduction reaction antibacterial ability microbial fuel cells density functional theory(DFT)rational design

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Hematuria after nocturnal exercise of a man: A case report

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World Journal of Clinical Cases 2024年第5期12卷 1025-1028页

作者： Ming-Jian Bai song-Tao Yang Xue-kai Liu Department of Clinical Laboratory Aerospace Center HospitalBeijing 100049China Department of Nephrology Aerospace Center HospitalBeijing 100049China

BACKGROUND A man experienced multiple episodes of macroscopic hematuria following nocturnal exercise.Urinary stones and tumors were considered the two most likely causes.The patient had two hobbies:Consuming health care products in large quantities and engaging in late-night running.CASE SUMMARY Health care products contain a large amount of calcium phosphate,and we hypothesize that this could induce the formation of small phosphate stones.After exercise,the urinary system is abraded,resulting in bleeding.The patient was advised to stop using the health care products.Consequently,the aforementioned symptoms disappeared immediately.However,the patient resumed the above two habits one year later;correspondingly,the macroscopic hematuria reap-peared.CONCLUSION This finding further confirmed the above inference and allowed for a new avenue to determine the cause of the patient’s hematuria.

关键词： Hematuria Health care products Exercise Case report

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