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Segregation enabled outstanding combination of mechanical and corrosion properties in a FecrNi medium entropy alloy manufactured by selective laser melting

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Journal of Materials Science & technology 2022年第4期99卷 207-214页

作者： Heng Duan Bin liu Ao Fu Junyang He tao Yang c.t.liu Yong liu State Key Lab of Powder Metallurgy Central South UniversityChangsha 410083China Max-Planck-Institut für Eisenforschung Max-Planck-βe 1Düsseldorf 40237Germany Department of Materials Science and Engineering City University of Hong KongHong KongChina Department of Mechanical Engineering City University of Hong KongHong KongChina

Selective laser melting(SLM)has the advantage in preparing supersaturated solid solutions due to its unique thermal field and high solidification *** this study,a face-centered cubic single-phase FecrNi medium entropy alloy(MEA)with an ultrahigh cr content(~35 at.%)was additively manufactured by *** as-built MEA shows a hierarchical microstructure of coarse columnar grains and submicron dislocation cell structures,where the cell boundaries are probed segregated with cr and c and decorated with nano *** appearance of these dislocation barriers results in an excellent combination of strength(σ_(0.2)=745 MPa,σ_(UtS)=1007 MPa)and ductility(ε_(f)=31%).the current MEA also shows a superb corrosion resistance with a corrosion current density of 0.06μA cm^(−2) in 3.5 wt.%Nacl solution,which is far lower than that of 316 *** high content of solutioned cr in the MEA ensures sufficient cr supply to form an integrated cr_(2)O_(3) passive film,and the large number of cell boundaries acting as the diffusion channels lead to the fast formation of a stable passive film over the alloy surface.

关键词： Selective laser melting Microsegregation Strength Ductility corrosion resistance

Structure Heterogeneity in Metallic Glass: Modeling and Experiment

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Journal of Materials Science & technology 2014年第6期30卷 560-565页

作者： H.B.Ke J.F.Zeng c.t.liu Y.Yang centre for Advanced Structural Materials Department of Mechanical and Biomedical EngineeringCity University of Hong Kong

Despite the great efforts dedicated to metallic glasses （MGs）, their structure still remains a mystery to be understood. With comparison to the existing mJciomechanical models, such as the free-volume and shear transformation zone （StZ） models, we first discuss in this article our recently proposed ＇core-shell＇ model, which contains a solid-like matrix and liquid-like inclusions. this serves as the theoretical basis to understand the structural heterogeneity in MGs in our analytical framework. After that, a scanning ultrafast nanoindentation technique is used to map out the structure heterogeneity in a Zr-based bulk metallic glass （BMG）. With these ongoing research efforts, we hope that more research work could be stimulated in the pursuit of the structure-property relation in MGs.

关键词： Metallic glass Structure heterogeneity Nanoindentation core-shell model

Off-stoichiometry-guided design of high-strength chemically complex intermetallic-based alloys with outstanding ductility

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Journal of Materials Science & technology 2023年第29期160卷 28-33页

作者： Bo Xiao Jixun Zhang Shaofei liu Yilu Zhao Lianyong Xu c.t.liu tao Yang Department of Materials Science and Engineering Mechanical Behavior Division of Shenyang National Laboratory for Materials ScienceCity University of Hong KongHong KongChina center for Advanced Nuclear Safety and Sustainable Development City University of Hong KongHong KongChina Hong Kong Institute for Advanced Study City University of Hong KongHong KongChina School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China School of Materials Science and Engineering Tianjin UniversityTianjin 300350China

*** the lasting drive for improved energy efficiency in power gen-eration encourages the innovative design of advanced structural materials with superb mechanical properties[1-6].Among these materials,ordered intermetallic alloys[7-9],as a unique class of metallic materials,have drawn increasing concern from both the scientific and industrial communities due to their intriguing high-temperature properties,strong chemical binding,and low atomic mobility[10,11].However,in light of the insufficient number of slip systems and/or intrinsically weak grain boundary(GB),they are usually brittle at ambient temperature,severely hindering their practical use in engineering systems[12].Previous studies reported that the change in alloy stoichiometry has a significant beneficial effect on the ductility of intermetallic *** instance,liu et al.

关键词： intermetallic ductility alloys

Low temperature Environmental Embrittlement in Ordered Intermetallics

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Journal of Materials Science & technology 1993年第4期9卷 235-247页

作者： N.S.Stoloff c.t.liu Department of Materials Engineering Rensselaer Polytechnic Institute.TroyNew YorkUSA Metals and ceramics Division Oak Ridge National LaboratoryOak RidgeTennesseeUSA

A comprehensive review of low temperature environmental embrittlement in intermetallics is pres- ented. Moisture and hydrogen are shown to severely embrittle many intermetallics, including iron, nickel and titanium aluminides. the roles of composition, microstructure and external test variables are emphasized. Several methods to reduce or avoid embrittlement are described.

关键词： environmental embrittlement ordered intermetallics alleviation

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

Phase stability in high entropy alloys:Formation of solid-solution phase or amorphous phase

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Progress in Natural Science:Materials International 2011年第6期21卷 433-446页

作者： Sheng GUO,c.t.liu center of Advanced Structural Materials,MBE Department, city University of Hong Kong,Kowloon,Hong Kong,china center of Advanced Structural Materials MBE Department City University of Hong Kong Kowloon Hong Kong China

the alloy design for equiatomic multi-component alloys was rationalized by statistically analyzing the atomic size difference,mixing enthalpy,mixing entropy,electronegativity,valence electron concentration among constituent elements in solid solutions forming high entropy alloys and amorphous *** solution phases form and only form when the requirements of the atomic size difference,mixing enthalpy and mixing entropy are all *** most significant difference between the solid solution forming high entropy alloys and bulk metallic glasses lies in the atomic size *** rules provide valuable guidance for the future development of high entropy alloys and bulk metallic glasses.

关键词： high entropy alloys amorphous alloys bulk metallic glasses phase stability solid solution

Rational design of chemically complex metallic glasses by hybrid modeling guided machine learning

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npj computational Materials 2021年第1期7卷 1242-1251页

作者： Z.Q.Zhou Q.F.He X.D.liu Q.Wang J.H.Luan c.t.liu Y.Yang Department of Mechanical Engineering College of EngineeringCity University of Hong KongKowloonHong KongChina college of Mechatronics and control Engineering Shenzhen UniversityShenzhenChina Laboratory for Structures Institute of Materials ScienceShanghai UniversityShanghaiChina Department of Materials Science and Engineering College of EngineeringCity University of Hong KongKowloonHong KongChina Department of Advanced Design and System Engineering College of EngineeringCity University of Hong KongChina

the compositional design of metallic glasses(MGs)is a long-standing issue in materials science and ***,traditional experimental approaches based on empirical rules are time consuming with a low *** this work,we successfully developed a hybrid machine learning(ML)model to address this fundamental issue based on a database containing~5000 different compositions of metallic glasses(either bulk or ribbon)reported since *** the prior works relying on empirical parameters for featurization of data,we designed modeling guided data descriptors in line with the recent theoretical models on amorphization in chemically complex alloys for the development of the hybrid classification-regression ML *** hybrid ML modeling was validated both numerically and *** importantly,it enabled the discovery of MGs(either bulk or ribbon)through the ML-aided deep search of a multitude of quaternary to scenery alloy *** computational framework herein established is expected to accelerate the design of MG compositions and expand their applications by probing the complex and multi-dimensional compositional space that has never been explored before.

关键词： alloy glasses metallic

tailoring nanoprecipitates for ultra-strong high-entropy alloys via machine learning and prestrain aging

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Journal of Materials Science & technology 2021年第10期69卷 156-167页

作者： tao Zheng Xiaobing Hu Feng He Qjngfeng Wu Bin Han chen Da Junjie Li Zhijun Wang Jincheng Wang Ji-jung Kai Zhenhai Xia c.t.liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China center for Advanced Nuclear Safety and Sustainable Development City University of Hong KongHong KongChina Institute of Atomic and Molecular Science.Shaanxi University of Science and technology Xi'an710021China Department of Material Science and Engineering College of Science and EngineeringCity University of Hong KongHong KongChina Department of Materials Science and Engineering University of North TexasDentonTXUSA center for Advanced Structural Materials Department of Mechanical EngineeringCollege of Science and EngineeringCity University of Hong KongHong KongChina

the multi-principal-component concept of high-entropy alloys(HEAs) generates numerous new *** them,nanoscale precipitated HEAs have achieved superior mechanical properties and shown the potentials for structural ***,it is still a great challe nge to find the optimal alloy within the numerous *** to now,the reported nanoprecipitated HEAs are mainly designed by a trialand-error approach with the aid of phase diagram calculations,limiting the development of structural *** the current work,a novel method is proposed to accelerate the development of ultra-strong nanoprecipitated *** the guidance of physical metallurgy,the volume fraction of the required nanoprecipitates is designed from a machine learning of big data with thermodynamic foundation while the morphology of precipitates is kinetically tailored by prestrain *** a proof-of-principle study,an HEA with superior strength and ductility has been designed and systematically *** newly developed γ’-strengthened HEA exhibits 1.31 GPa yield strength,1.65 GPa ultimate tensile strength,and 15% tensile *** probe tomography and transmission electron microscope characterizations reveal the well-controlled high γ’ volume fraction(52%) and refined precipitate size(19 nm).the refinement of nanoprecipitates originates from the accelerated nucleation of the γ’ phase by prestrain aging.A deeper understanding of the excellent mechanical properties is illustrated from the aspect of strengthening mecha ***,the versatility of the current design strategy to other precipitation-hardened alloys is discussed.

关键词： High-entropy alloys Machine learning Prestrain aging Mechanical properties Strengthening mechanisms

Enhanced helium ion irradiation tolerance in a Fe-co-Ni-cr-Al-ti high-entropy alloy with L12 nanoparticles

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Journal of Materials Science & technology 2023年第12期143卷 169-177页

作者： Y.L.Zhao F.L.Meng t.Yang J.H.Luan S.F.liu G.M.Yeli W.t.Lin W.H.liu X.J.liu c.t.liu J.J.Kai School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China School of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Department of Materials Science and Engineering Mechanical Behavior Division of Shenyang National Laboratory for Materials ScienceCity University of Hong KongHong KongChina Department of Mechanical Engineering City University of Hong KongHong KongChina Institute of Nuclear&New Energy technology Tsinghua UniversityBeijing 100084China

L12-strengthened high entropy alloys(HEAs)with excellent room and high-temperature mechanical prop-erties have been proposed as promising candidates as structural materials for advanced nuclear ***,knowledge about their radiation response is fairly *** the present work,a novel HEA with a high density of L12 nanoparticles was irradiated with He ion at 500°*** electron microscope(tEM)and atom probe tomography(APt)were employed to study the evolution of mi-crostructural stability and radiation-induced *** to the single-phase FecoNicr HEA,the main microstructural features were numerous large faulted dislocation loops and helium *** the irradiation resistance of the present L12-strengthened HEA is much improved in terms of reduced bubble size,which could be attributed to the considerable He trapping efficiency of the coherent pre-cipitate/matrix interface and the enhanced capability of the interface for damage elimination when the matrix channel width is *** analysis revealed that an inverse-Kirkendall-mechanism-dominated radiation-induced segregation(RIS)occurs around bubbles,where a significant co enrichment and Ni de-pletion can be clearly *** addition,the competing dynamics of ballistic mixing and elemental clustering that raised from the irradiation-enhanced diffusion in a highly supersaturated matrix,along with the low precipitation nucleation barrier due to the small lattice misfit,lead to a dynamical pre-cipitation dissolution and re-precipitation appears under *** a promising phenomenon is expected to promote a potential self-healing effect and could in turn provide a sustainable irradiation tolerance over the operational lifetime of a reactor.

关键词： L12 nanoparticles High-entropy alloy Helium bubble Phase stability Radiation-induced segregation