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Computer Modeling in Engineering & Sciences 2016年第4期111卷 303-333页

作者： M.Ohsaki T.Miyamura j.y.zhang Department of Architecture and Architectural Engineering Kyoto UniversityKyoto-Daigaku KatsuraNishikyoKyoto 615-8540Japan Department of Computer Science Nihon University1 NakagawaraTokusadaTamuraKoriyama 963-8642Japan Department of Architecture and Urban Design Nagoya City University2-1-10 Kita-ChigusaChigusaNagoya 464-0083Japan

A simple constitutive model,called semi-implicit model,for cyclic loading is proposed for steel materials used for structures such as building frames in civil *** constitutive model is implemented in the E-Simulator,which is a software package for large-scale seismic response *** constitutive relation is defined in an algorithmic manner based on the piecewise linear combined isotropic-kinematic *** rules are used for the first and subsequent loading states to incorporate characteristics such as yield plateau and Bauschinger effect of rolled mild steel *** optimization method is also presented for parameter identification from the results of cyclic and monotonic loading ***,the proposed model is readily applicable to practical elastoplastic analysis of building *** of the model is demonstrated in an example of a cantilever subjected to various types of cyclic loading.

关键词： Combined isotropic-kinematic hardening Piecewise linear hardening Steel material Parameter optimization Cyclic load

A strong and ductile NiCoCr-based medium-entropy alloy strengthened by coherent nanoparticles with superb thermal-stability

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journal of Materials Science & Technology 2023年第1期132卷 201-212页

作者： D.D.zhang j.Kuang H.Xue j.y.zhang G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we designed a novel NiCoCr-based medium-entropy alloy(MEA)strengthened by coher-ent L12-nanoparticles,i.e.,(NiCoCr)92 Al 6 Ta 2(at.%).The strengthening and deformation mechanisms of the material and the coarsening kinetics of the coherent precipitates were systematically *** results indicated that giant precipitation hardening and its synergy with other strengthening contributors confer on the aged material a yield strength as high as 1.0 ***,a unique particle-features-dependent plasticity mechanism was revealed in this *** is,the alloy with a lower volume frac-tion,denser distribution,and finer particles mainly deformed by dislocation planar slip,otherwise,stack-faults-mediated plasticity was favored,rationalized by the cooperative/competitive effect of stack-fault energy,spatial confinement,and applied ***,the coarsening behavior of precipitate fol-lowed a modified Lifshitz-Slyozov-Wagner(LSW)model,and the nanoparticles displayed remarkably su-perior thermal stability compared to most traditional superalloys and reported multicomponent *** superb coarsening resistance of precipitate originated from the coupled effect of intrinsic sluggish diffusion in multi-principal alloys and the dual-roles of Ta species as a precipitate *** work provides a new pathway to develop strong-yet-ductile multicomponent alloys as promising candidates for high-temperature applications.

关键词： Medium-entropy alloy Mechanical properties Precipitation hardening Deformation mechanisms Coarsening kinetics

Dual effect of Cu on the Al3Sc nanoprecipitate coarsening

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journal of Materials Science & Technology 2020年第2期37卷 38-45页

作者： y.H.Gao L.F.Cao j.Kuang j.y.zhang G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China International joint Laboratory for Light Alloys(Ministry of Education) Chongqing UniversityChongqing 400044China

It is generally considered that the Al3Sc nanoprecipitates are highly thermal stable,mainly due to quite slow Sc diffusion in theα-Al *** this paper,we demonstrate in an Al-Cu-Sc alloy that the Cu atoms have dual effect on the coarsening of Al3Sc *** the one hand,the Cu atoms with high diffusivity tend to accelerate the Al3Sc coarsening,which results from the Cu-promoted Sc *** the other hand,some Cu atoms will segregate at the Al3Sc/matrix interface,which further stabilizes the Al3Sc nanoprecipitates by reducing the interfacial *** between these two effects is tailored by temperature,which rationalizes the experimental findings that the coarsening kinetics of Al3Sc nanoprecipitate is greatly boosted at 300℃-overaging while significantly suppressed at 400℃-overaging.

关键词： Al alloys Precipitate coarsening Interfacial segregation Microstructural evolution

Achieving excellent strength-ductility synergy in twinned NiCoCr medium-entropy alloy via Al/Ta co-doping

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journal of Materials Science & Technology 2021年第28期87卷 184-195页

作者： D.D.zhang H.Wang j.y.zhang H.Xue G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049PR China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of ChinaChengdu610041PR China

Alloying is an effective strategy to tailor microstructure and mechanical properties of metallic materials to overcome the strength-ductility trade-off *** this work,we combined a novel alloy design principle,*** pronounced solid solution hardening(SSH)based on the misfit volumes engineering,and simultaneously,architecting the ductile matrix based on the valence electron concentrations(VEC)criterion,to fulfill an excellent strength-ductility synergy for the newly emerging high/medium-entropy alloys(HEAs/MEAs).Based on this strategy,Al/Ta co-doping within NiCoCr MEA leads to an efficient synthetic approach,that is minor Al/Ta co-doping not only renders significantly enhanced strength with notable SSH effect and ultrahigh strain-hardening capability,but also sharply refines grains and induces abnormal twinning behaviors of(NiCoCr)_(92)Al_(6)Ta_(2) *** with the partially twinned NiCoCr MEA,the yield strength(σy)and ultimate tensile strength(σUTS)of fully twinned Al/Ta-containing MEA were increased by~102%to~600 MPa and~35%to~1000 MPa,respectively,along with good ductility beyond 50%.Different from the NiCoCr MEA with deformation twins(DTs)/stacking faults(SFs)dominated plasticity,the extraordinary strain-hardening capability of the solute-hardened(NiCoCr)_(92)Al_(6)Ta_(2) MEA,deactivated deformation twinning,originates from the high density of dislocation walls,microbands and abundance of *** abnormal twinning behaviors,i.e.,prevalence of annealing twins(ATs)but absence of DTs in(NiCoCr)_(92)Al_(6)Ta_(2) MEA,are explained in terms of the relaxation of grain boundaries(for ATs)and the twinning mechanism transition(for DTs),respectively.

关键词： Medium-entropy alloys Mechanical properties Solid solution hardening Twinning behavior Strength-ductility synergy

Designing hetero-structured ultra-strong and ductile Zr-2.5Nb alloys:Utilizing the grain size-dependent martensite transformation during quenching

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journal of Materials Science & Technology 2022年第30期125卷 198-211页

作者： S.y.Liu j.y.zhang j.Kuang X.y.Bao D.D.zhang C.L.zhang j.K.yang G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

To further improve the service performance of Zr-2.5Nb alloy worked as pressure tubes in pressurized heavy water reactors,more investigation about the microstructure and thermomechanical processing route of Zr-2.5Nb alloy need to be *** this work,a hetero-structured Zr-2.5Nb alloy was prepared by applying a novel *** analysis reveals that the alloy exhibits a grain sizedependent martensite substructure transition during post-rolling *** hetero-structure consists of equiaxed primaryαgrains and the lamellae groups containing both parallelα’dislocation martensite andα’twin *** with the previously reported Zr-Nb alloys,the present Zr-2.5Nb alloys manifest the highest yield strength(∼710 MPa),together with a high ultimate tensile strength(∼844 MPa)and good ductility(∼17.1%).The enhanced mechanical properties are found to arise from the properly controlled fraction/size of the two types of martensite,which not only significantly strengthens the alloy but also contributes to a stronger strain hardening.A model based on the grain-size-dependent critical resolved shear stress for dislocation slip and twinning has been proposed to explain theα’martensite substructures transition at a critical grain size dc=3.3μ*** this size,the critical resolved shear stress(CRSS)for twinning is higher than that for the***,theα’dislocation martensite is more favorable to ***,theα’twin martensite would exhibit a high *** present work indicates that making use of the grain size-dependent martensite transformation to tailor the heterostructure in Zr alloys is an effective strategy to overcome the strength–ductility trade-off in the material.

关键词： Zr-Nb alloys Heterogeneous structure Martensitic transformation Grain size Strength

Unusual He-ion irradiation strengthening and inverse layer thickness-dependent strain rate sensitivity in transformable high-entropy alloy/metal nanolaminates:A comparison of Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu vs Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu

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journal of Materials Science & Technology 2022年第21期116卷 199-213页

作者： y.F.Zhao H.H.Chen D.D.zhang j.y.zhang y.Q.Wang K.Wu G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical *** ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased *** to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation *** contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 *** this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion ***,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced *** unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.

关键词： High entropy alloy/metal nanolaminates Interfaces Irradiation hardening Strain rate sensitivity Size effects

Enhancing the high-temperature creep properties of Mo alloys via nanosized La_(2)O_(3) particle addition

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journal of Materials Science & Technology 2022年第35期130卷 53-63页

作者： P.M.Cheng C.yang P.zhang j.y.zhang H.Wang j.Kuang G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China School of Mechanical Engineering Chengdu UniversityChengdu 610106China

Molybdenum(Mo) alloys with different La_(2)O_(3)particle additions(0.6,0.9,1.5 wt.%) were prepared by powder metallurgy to investigate the effect of La_(2)O_(3)particles on microstructural evolution and creep behavior of the *** Mo,annealed at 1500℃ for 1 h,presented a fully recrystallized microstructure characterized by equiaxed *** alloys doped with La_(2)O_(3)particles(Mo-La_(2)O_(3)alloys),on the other hand,exhibited fibrous grains elongated in the rolling direction of the *** contrast to the shape of the grains,the average grain size of the alloys was found to be insensitive to the addition of La_(2)O_(3)*** La_(2)O_(3)particles with diameters ranging from 65 to 75 nm were distributed within the grain *** creep tests showed that dislocation creep was the predominant deformation mode at intermediate creep rate(10^(-7)s^(-1)-10^(-4)s^(-1)) in the present *** creep stress exponent and activation energy were found to decrease with increasing temperature,particularly within the low creep rate regime(ys exhibited remarkably greater apparent stress exponent and activation energy than pure Mo.A creep constitutive model based on the interaction between particles and dislocations was utilized to rationalize the nanoparticle-improved creep *** was demonstrated that low relaxed efficiency of dislocation line energy,which is responsible for an enhanced climb resistance of dislocations,is the major creep strengthening mechanism in the Mo-La_(2)O_(3)*** addition,the area reduction and creep fracture mode of the Mo-La_(2)O_(3)alloys were found to be a function of the creep rate and temperature,which can be explained by the effect of the two parameters on the creep and fracture mechanisms.

关键词： Mo alloys Nanosized particles Creep strength Deformation and fracture

III-Nitride-Based Quantum Dots and Their Optoelectronic Applications

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Nano-Micro Letters 2011年第3期3卷 200-207页

作者： G.E.Weng A.K.Ling X.Q.Lv j.y.zhang B.P.zhang Department of Physics Laboratory of Micro-Nano Optoelectronics Xiamen University MEMS Research Center Xiamen University

During the last two decades, III-nitride-based quantum dots(QDs) have attracted great attentions for optoelectronic applications due to their unique electronic properties. In this paper, we first present an overview on the techniques of fabrication for III-nitride-based QDs. Then various optoelectronic devices such as QD lasers, QD light-emitting diodes(LEDs), QD infrared photodetectors(QDIPs) and QD intermediate band(QDIB) solar cells(SCs) are discussed. Finally, we focus on the future research directions and how the challenges can be overcome.

关键词： III-nitride-based quantum dots Lasers Light-emitting diods Infrared photodetectors Solar cells

Tuning the microstructure for superb corrosion resistance in eutectic high entropy alloy

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journal of Materials Science & Technology 2022年第14期109卷 197-208页

作者： S.Shuang Q.yua X.Gao Q.F.He j.y.zhang S.Q.Shi y.yang Department of Mechanical Engineering City University of Hong KongKowloon TongKowloonHong KongChina Department of Mechanical Engineering Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Department of Materials Science and Engineering City University of Hong KongKowloon TongKowloonHong KongChina

In this work,we demonstrate that the corrosion resistance of the FeCrNiCoNb_(0.5) eutectic high entropy alloy(EHEA)can be tuned by controlling the size of its eutectic *** microstructure refinement,the EHEA exhibits a superb corrosion resistance in 1 M NaCl in terms of a very low corrosion current density and an ultra-high transpassviation potential,which outperforms a variety of other HEAs and conventional metals and *** the fundamental level,the microstructure refinement results in a rapid formation of a thick and compact passive film with less Cl-adsorption on the EHEA,which results in significant enhancement in its corrosion *** outcome of our research provides important insights into the design of corrosion resistant chemically complex alloys.

关键词： Eutectic high entropy alloy Passivation Transpassivation potential Microstructure size

An insight into Mg alloying effects on Cu thin films:microstructural evolution and mechanical behavior

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journal of Materials Science & Technology 2020年第22期54卷 101-112页

作者： G.y.Li L.F.Cao j.y.zhang X.G.Li y.Q.Wang K.Wu G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an710049China International joint Laboratory for Light Alloys(Ministry of Education) College of Materials Science and EngineeringChongqing UniversityChongqing400044China Electron Microscopy Center of Chongqing University Chongqing UniversityChongqing400044China

How to design ultra-strong,light-weight Cu alloys is a long-term pursuit in materials community,which is technically superior and cost-effective for their promising energy-saving *** this work,we prepared Cu-Mg alloyed thin films to study light element Mg alloying effects on the microstructure,hardness and strain rate sensitivity(SRS) of nanocrystalline Cu thin *** the studied Mg concentrationrange spanning from 0 at.% to 16.8 at.%,both the grain size and the twin spacing decrease monotonously with increasing Mg composition while Cu-2.8 at.% Mg sample has the highest twin fraction of ~75%.A combined strengthening model was employed to quantify the Mg concentration-dependent hardness of nanotwinned(NT) Cu-Mg thin films,in which the grain/twin boundary facilitates strengthening while the solute Mg atoms induce *** the constant rate of loading tests and the nanoindentation creep tests uncover that compared with pure Cu samples,the NT Cu-Mg thin films manifest much lower SRS,particularly in the creep tests,owing to the activation of dynamic strain aging effects.

关键词： Cu-Mg thin films Microstructure evolution Creep tests Hardness Strain rate sensitivity