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Enhancing strength and plasticity by pre-introduced indent-notches in Zr36cu64 metallic glass:A molecular dynamics simulation study

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Journal of Materials Science & Technology 2020年第8期36卷 119-125页

作者： Shidong Feng Lin Li k.c.chan Lei Zhao Limin Wang Riping Liu State key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao066004China Advanced Manufacturing Technology Research centre Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic University999077Hong KongChina Department of Metallurgical and Materials Engineering The University of AlabamaTuscaloosaAL35487USA

The deformation behavior in Zr36 cu64 metallic glasses with pre-introduced indent-notches has been studied by molecular dynamics simulation at the atomic *** indent-notches can trigger the formation of densely-packed clusters composed of solid-like atoms in the indent-notch affected *** denselypacked clusters are highly resistant to the nucleation of shear ***,there is more tendency for the shear bands to nucleate outside the indent-notch affected zone,which enlarges the deformation region and enhances both the strengthening effect and the plastic deformation *** indent-notched MGs,when determining the initial yielding level,there is a competition process occurring between the densely-packed clusters leading to the shear band formation outside the indent-notch affected zone and the stress-concentration localizing deformation around the notch *** the indent-notch depth is small,the stress-concentration around the notch root plays a dominant role,leading to the shear bands initiating from the notch root,reminiscence of the *** the indent-notch depth increases,there are many densely-packed clusters with high resistance to deformation in the indent-notch affected zone,leading to the shear band formation from the interface between the indent-notch affected zone and the *** research findings provide a feasible means for improving the strength and the plasticity of metallic glasses at room temperature.

关键词： Metallic glass Notch Shear band Microstructure Molecular dynamics simulation

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Laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy with significantly enhanced wear resistance

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Journal of Materials Science & Technology 2022年第15期110卷 43-56页

作者： Jiasi Luo Wanting Sun Ranxi Duan Wenqing Yang k.c.chan Fuzeng Ren Xu-Sheng Yang Department of Industrial and Systems Engineering Advanced Manufacturing Technology Research CentreThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China The Hong kong Polytechnic University Shenzhen Research Institute Shenzhen 518060China

Heterogeneous gradient nanostructured metals have been shown to achieve the strength-ductility synergy, thus potentially possessing the enhanced tribological performance in comparison with their homogeneous nanograined counterparts. In this work, a facile laser surface remelting-based surface treatment technique is developed to fabricate a gradient nanostructured layer on a TiZrHfTaNb refractory highentropy alloy. The characterization of the microstructural evolution along the depth direction from the matrix to the topmost surface layer shows that the average grain size in the ~100 μm-thick gradient nanostructured layer is dramatically refined from the original ~200 μm to only ~8 nm in the top surface layer. The microhardness is therefore gradually increased from ~240 HV in matrix to ~650 HV in the topmost surface layer, approximately 2.7 times. Noticeably, the original coarse-grained single-phase bodycentered-cubic TiZrHfTaNb refractory high-entropy alloy is gradually decomposed into TiNb-rich bodycentered-cubic phase, TaNb-rich body-centered-cubic phase, ZrHf-rich hexagonal-close-packed phase and TiZr Hf-rich face-centered-cubic phase with gradient distribution in grain size along the depth direction during the gradient refinement process. As a result, the novel laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy demonstrates the significantly improved wear resistance, with the wear rate reducing markedly by an order of magnitude, as compared with the as-cast one. The decomposed multi-phases and gradient nanostructures should account for the enhanced wear resistance. Our findings provide new insights into the refinement mechanisms of the laser-treated refractory high-entropy alloys and broaden their potential applications via heterogeneous gradient nanostructure engineering.

关键词： Laser surface treatment Refractory high-entropy alloy Gradient nanostructure Wear resistance High-resolution transmission electron microscopy

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critical transitions in the shape morphing of kirigami metallic glass

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Journal of Materials Science & Technology 2021年第2期61卷 204-212页

作者： D.X.Han L.Zhao S.H.chen G.Wang k.c.chan Advanced Manufacturing Technology Research center Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HornKowloonHong KongChina School of Mechanical Engineering Hefei University of TechnologyHefei230009China Laboratory for Microstructures Institute of MaterialsShanghai UniversityShanghai200444China

kirigami, the ancient Japanese paper cutting technique, has been applied to achieve high stretchability and low energy loss of designed metallic glass. Despite the exploration of the underlying deformation mechanism of kirigami-inspired structures from the energy point of view, the morphable responses of the kirigami patterns and the origin of the kirigami response are yet to be fully understood. This study reveals the mechanical driven-forms of the kirigami structure with the corresponding deformation stages. Based on the beam deflection theory, the elastic buckling behavior of kirigami metallic glass is manifested and a critical force prediction model is developed. Moreover, a force concentration parameter is introduced in the rigid-plastic deformation stage, predicting the nominal ultimate force. The kirigami-inspired facture force is firstly proposed. The findings of these models are in good agreement with the experimental sizedependent kirigami responses, and expected to provide significant insights into the understanding of the deformation behavior and the design of kirigami metallic glasses.

关键词： Metamaterial kirigami metallic glass critical load Size effect Beam deflection

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Micro-scaled plastic yielding and shear-banding dynamics in metallic glasses

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Journal of Materials Science & Technology 2023年第21期152卷 237-246页

作者： D.X.Han G.Wang Q.Wang R.Feng X.D.Ma k.c.chan c.T.Liu Institute of Materials Shanghai UniversityShanghai 200444China Department of Industrial and Systems Engineering The Hong Kong Polytechnic UniversityHong KongChina Neutron Scattering Division Oak Ridge National LaboratoryOak RidgeTN 37831United States Department of Material Science and Engineering College of Science and EngineeringCity University of Hong KongHong KongChina center for Advanced Structural Materials College of Science and EngineeringCity University of Hong KongHong KongChina

Shear-banding behavior in metallic glasses plays a key role in the operation of plastic deformation,which is associated with yield *** a micro-scale,the shear-banding behavior must be affected by many factors from the test machine and the ***,in this study,comprehensively considering a machine compliance,a geometry imperfection of micro-pillar,and a substrate sink-in the machine-sample-substrate system,we developed a plastic-strength model at a micrometer scale in this study,which is evidenced by the microscale compressive properties of 18 kinds of metallic *** the-oretical model provides a guidance for the elastic limits and shear-banding dynamics of metallic glasses at the micro-scale,which can be applicable to characterize the microscale deformation behavior of other amorphous materials.

关键词： Metallic glasses Shear-banding dynamics Micro-compression Plastic deformation

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Structural changes ofαPhase in Furnace cooled Eutectoid Zn-Al Based Alloy

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Journal of Materials Science & Technology 2007年第3期23卷 347-352页

作者： Y.H.Zhu k.c.chan G.k.H.Pang T.M.Yue W.B.Lee Advanced Manufacturing Technology Research center Department of Industrial and Systems Engineering The Hong Kong Polytechnic University Hong Kong China Department of Applied Physics The Hong Kong Polytechnic University Hong Kong China

Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FcZA22 alloy during ageing at 170℃. One was the hcp transitional α＂ m phase which aooears as directional rods and the round precipitates. The other was the fcc α＇m phase. 〈101〉. The orientation relationship between the a phase and transitional phase α＇m was determined as （022）α＇m （fcc）//（022^-）α（fcc）, [1^-11]α＇m, （fcc）//[2^-33]α（fcc）. The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships.

关键词： Phase decomposition Microstructural evolution Zn-Al alloys

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cutting characteristics of Zr-Based Bulk Metallic Glass

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Journal of Materials Science & Technology 2015年第2期31卷 153-158页

作者： D.X.Han G.Wang J.Li k.c.chan S.To F.F.Wu Y.L.Gao Q.J.Zhai Laboratory for Microstructures Shanghai University Department of Industrial and System Engineering The Hong Kong Polytechnic University

cutting behavior exerts a considerable influence on the fabrication of bulk metallic glass(BMG) components. In this study,the influences of machining parameters(i.e.,depth of cutting,feed rate,and spindle rate) on the turned surface of a Zr-based BMG after observing the 3D morphologies of this surface were *** results showed that the influence of the spindle rate on the surface morphologies is more substantial as compared to the depth of cutting and the feed rate. Nanoscratch tests were conducted to further characterize the separation mechanism of the chips,which revealed that the chips are torn off the surface of a BMG because of inhomogeneous localized maximum shear stress.

关键词： Bulk metallic glass Ultra-precision machining Surf

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锆基块体非晶及非晶基复合材料在过冷液态区的形变行为

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中国科学（G辑） 2008年第4期38卷 471-476页

作者：谌祺柳林 k.c.chan 华中科技大学材料成形与模具技术国家重点实验室武汉430074 Department of Industrial and System Engineering The Hong Kong Polytechnic UniversityHong KongChina

利用电弧熔炼/水冷铜模吸铸技术制备了块体非晶合金(Zr_75-cu_25)_78.5Ta_4Ni_10A_l7.5和第二相形态为颗粒状的块体非晶基复合材料(Zr_75cu_25)_74.5Ta_8Ni_10A_l7.5.利用Instron力学性能实验机研究了块体非晶和复合材料在过冷液态区内... 详细信息

利用电弧熔炼/水冷铜模吸铸技术制备了块体非晶合金(Zr_75-cu_25)_78.5Ta_4Ni_10A_l7.5和第二相形态为颗粒状的块体非晶基复合材料(Zr_75cu_25)_74.5Ta_8Ni_10A_l7.5.利用Instron力学性能实验机研究了块体非晶和复合材料在过冷液态区内的单向压缩变形行为.结果表明:两种材料在过冷液态区内的形变行为都强烈依赖于温度和变形速率.随着应变速率的增加,两种材料的流变特征都由牛顿流变转变为非牛顿流变.用基于自由体积模型的过渡态理论(transition state theory)对两种材料的压缩形变行为进行了阐释和比较.

关键词：块体非晶合金复合材料过冷液态压缩变形自由体积

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consortium for the Human Information and Neurocognitive Endophenotype (cHINE) in china's Mainland: An example from neurological soft signs for neuropsychiatric disorders

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chinese Science Bulletin 2011年第32期56卷 3409-3415页

作者： chan Raymond c k Neuropsychology and Applied cognitive Neuroscience Laboratory Key Laboratory of Mental Health Institute of Psychology Chinese Academy of Sciences

Increasing efforts to identify alternate expressions of neuropsychiatric disorders that are broader than the DSM or IcD diagnostic criteria needed to diagnose them reflects a growing consensus that multidimensional expressions of neuropsychiatric disorders may advance the search for underlying etiological or modulatory factors. Endophenotypic research can be considered to be one of the most promising strategies to bridge the gap between genomic complexity and the phenotypic heterogeneity observed in neuropsychiatric disorders. However, the majority of endophenotype studies were limited to our western counterparts, very little has been done and initiated by scholars in china's Mainland. In this paper, we urge the need to establish a potential central consortium for endophenotypes to study neuropsychiatric disorders in china's Mainland. In particular, we illustrate a potential example of neurological soft signs in following the steps for building the consortium.

关键词：精神障碍中国大陆神经茅根信息人力多维表达式 IcD

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Status and prospects for symmetric organic redox flow batteries

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Journal of Energy chemistry 2025年第1期100卷 125-143页

作者： Md Al Raihan c.Adam Dyker Department of chemistry University of New Brunswick

As environmental concerns from fossil fuel consumption intensify, large-scale energy storage becomes imperative for the integration of renewable sources like wind, hydro, and solar with the electrical *** flow batteries, particularly those employing organic molecules, are positioned as a key technology for this purpose. This review explores the growing field of symmetric organic redox flow batteries(ORFBs) within this context. Unlike traditional asymmetric designs based on unique active materials for each electrode, symmetric ORFBs involve a single bipolar species for both electrodes. This review highlights the benefits of a symmetric design, and categorizes five distinct classes of organic bipolar molecules used in both aqueous and non-aqueous solvents. By providing a comprehensive overview of their cell cycling and performance characteristics, the strengths and weaknesses of the diverse categories of bipolar molecules are highlighted for both solvent systems, as are opportunities for future development. This should guide new research directions and advance the development of practical symmetric ORFBs.

关键词： Redox flow battery Symmetric battery Organic battery Aqueous electrolyte Non-aqueous electrolyte

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Structural changes of a Tropical cyclone during Landfall: β-plane Simulations

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Advances in Atmospheric Sciences 2010年第5期27卷 1143-1150页

作者： k.c.SZETO Johnny c.L.chan School of Energy and Environment City University of Hong Kong

This study investigated the effects of landfall on the structure of a tropical cyclone （Tc）. Numerical simulations were performed using the Weather Research and Forecasting Model on a β-plane. Two landfall experiments, one with an east–west and another with a north–south oriented coastline, were performed. Similar to previous studies on an f-plane, large-scale flows in the low-to-middle troposphere were modified due to friction. A pair of counter rotating gyres was found, which was shown to be consistent with the slight deffection of the Tc relative to the control experiment without land. compared to previous f-plane simulations, because of the inherent asymmetries due to the β-gyres, the large-scale pattern of flows and convergences/divergences related to friction were found to depend on coastline orientations. On the other hand, regardless of the coastline orientation, convergences were found to be stronger to the left for both cases near landfall, as in previous f-plane simulations. Such a convergence pattern subsequently induced a change in convection and rainfall at the eyewall.

关键词： tropical cyclone landfall numerical simulations

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