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Ultrastrong and ductile BCC high-entropy alloys with low-density via dislocation regulation and nanoprecipitates

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Journal of Materials Science & Technology 2022年第15期110卷 109-116页

作者： Xuehui Yan Peter K.liaw Yong Zhang Beijing Advanced Innovation Center of Materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing 100083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996United States of America

The high strength is a typical advantage of body-centered-cubic high-entropy alloys(BCC–HEAs).However,brittleness and weak strain-hardening ability are still their Achilles'***,extraordinary strength together with good tensile ductility are achieved in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(100-x)Al_(x) alloys(at.%,x=10 and 20)at room *** low densities of less than 6 g/cm^(3)are exhibited in these *** nanoprecipitates and diversifying dislocation motions are the keys to achieving such salient *** is worth noting that the tensile strength of 1.8 GPa in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(80)Al_(20)alloy is a record-high value known in reported BCC–HEAs,as well as a tensile strain over 8%.Furthermore,the maximum strain of~25%in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(90)Al_(10)alloy can challenge existing limit value,and is accompanied with a tensile strength of 1.2 *** current work does not only provide novel ultra-strong and tough structural materials with low density,but also sheds new light on designing BCC–HEAs with attractive performances and strain-hardening ability.

关键词： High-entropy alloys Mechanical properties Dislocation Nanoprecipitates Strain hardening

Structure design and property of multiple-basis-element(MBE)alloys flexible films

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Nano research 2022年第6期15卷 4837-4844页

作者： Hao Huang Peter K.liaw Yong Zhang Qinghai Provincial Engineering research Center of High Performance Light Metal Alloys and Forming Qinghai UniversityXining 810016China State Key Laboratory of Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996-2100USA Shunde Graduate School University of Science and Technology BeijingFoshan 528399China

A controlled wrinkled structure is a simple and effective approach to achieve unique properties and has been widely used in flexible *** this study,we reported a substrate prestrain method for fabricating wrinkle-structured Zr52Ti34Nb14 multiplebasis-element(MBE)alloy films as biocompatible *** in the film thickness and substrate prestraining enabled a precise control of the amplitude and wavelength of the wrinkled structures,ranging from micrometers to ***,owing to the flexibility of the wrinkled structures,the wrinkle-structure pattern could be adjusted by simply relaxing or further stretching of the substrate,leading to dynamically tunable transmittance and wetting *** result not only reveals Zr52Ti34Nb14 MBE alloy films as a potential flexible material,but also provides a new structural design approach for other MBE alloy systems.

关键词： multiple-basis-element alloy thin films microstructures optical transmission wetting behavior

A trend based investment decision approach using clustering and heuristic algorithm

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Science China(Information Sciences) 2014年第9期57卷 204-217页

作者： WU ChungMin CHOU ShengChun liaw HorngTwu Graduate Institute of Services and Technology Management National Taipei University of Technology Department of Information Management Shih Hsin University

This paper proposes a stock price trend clustering and trend investment decision model by using a genetic algorithm to search for optimal solutions and the best investment strategies for different stock price *** new price trend clustering model identifies three types of stock price movements:uptrends,sideways trends,and ***,trends discovered through stock price movements or technical indicator graphs are typically subjective and *** paper takes daily stock prices and trading volume data from the China Shanghai Stock Exchange Composite Index(SSECI)from January 2,1997 to August31,2012,to examine the performance of the proposed trend clustering *** proposed model is also compared to other popular stock market investment strategies to verify its *** result shows that the proposed trend clustering model correctly identifies three different trends in the stock ***,the trend investment strategy model developed by using genetic algorithm methodology performs better than other investment strategies,namely,Granville’s rule,the KD indicator strategy,the buys and holds strategy,and GMA rules,in both bull and bear market *** results prove the proposed new model to be a stable and valid investment strategy.

关键词： clustering genetic algorithms stock trend investment strategy

High strength-superplasticity combination of ultrafine-grained ferritic steel:The significant role of nanoscale carbides

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Journal of Materials Science & Technology 2021年第24期83卷 131-144页

作者： J.W.Liang Y.F.Shen r.D.K.Misra P.K.liaw Key Laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang110004China The State Key Lab of rolling&Automation Northeastern UniversityShenyang110819China Laboratory for Excellence in Advanced Steel research University of Texas at El PasoTX79968USA Department of Materials Science and Engineering University of TennesseeKnoxvilleTN37996USA

There is currently a gap in our understanding of mechanisms that contribute to high strength and high plasticity in high strength UFG ferritic steel with nano-size Fe3 C carbides in situations that involve combination of various strain rates and high *** this regard,we describe the mechanistic basis of obtaining high strength-high plasticity combination in an ultrafine-grained(UFG)(~500±30 nm)ferritic steel with nano-size carbides,which sustained large plastic deformation,exceeding 100%elongation at a temperature significantly below 0.5 of the absolute melting point(Tm).To address the missing gap in our knowledge,we conducted a series of experiments involving combination of strain rate and temperature effects in conjunction with electron microscopy and atom probe tomography(APT).Strain rate studies were carried out at strain rates in the range of 0.0017-0.17 s^(-1)and at different temperatures from 25℃to 600℃.Dynamic recrystallization occurred at 600℃,resulting in a significant decrease in yield and tensile ***,the UFG ferritic steels had an advantage in tensile strength(UTS)and elongation-to-failure(εf)at 600℃,especially at strain rate of 0.0017 s^(-1),with high UTSof 510 MPa and excellent low temperature(rplasticity(εf=110%).These mechanical properties are significantly superior compared to similar type of steels at identical temperature.A mechanistic understanding of mechanical behavior of UFG ferritic steels is presented by combining the effect of strain rate,temperature,and nano-size carbides.

关键词： UFG ferritic steel Strain rate Temperature Nano-size precipitate Low temperature superplasticity

Gain Flattened raman Fiber Amplifier Using Parameter Optimization and DCF Fiber

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光学学报 2003年第S1期23卷 493-494页

作者： Shien-Kuei liaw Jy-Wang liaw Department of Electronic Engineering Taiwan University of Science and Technology No. 43 Section 4 Keelung Rd. Taipei 106 TaiwanAdvanced Research Division Chung-Hua Telecommunication Laboratory Yang-Mei 326 Taiwan

We investigate two configurations of raman fiber amplifier in the 1530-1570 nm region. The gain spectrum variation is decreased from 8.31 dB to 2.48 dB when appropriately adjust the individual two pumps and optical fi... 详细信息

关键词： DCF on be as nm than Gain Flattened raman Fiber Amplifier Using Parameter Optimization and DCF Fiber rFA that

Nanoscale fluctuation of stacking fault energy strengthens multi-principal element alloys

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Journal of Materials Science & Technology 2023年第27期158卷 218-225页

作者： Zongrui Pei Markus Eisenbach Peter K.liaw Mingwei Chen New York University New York 10012USA Oak ridge National Laboratory Oak RidgeTennessee 37831USA Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996USA Department of Materials Science and Engineering Johns Hopkins UniversityBaltimoreMaryland 21218USA Engineering and Hopkins Extreme Materials Institute Johns Hopkins UniversityBaltimoreMaryland 21218USA

Chemical randomness and the associated energy fluctuation are essential features of multi-principal ele-ment alloys(MPEAs).Due to these features,nanoscale stacking fault energy(SFE)fluctuation is a natural and independent contribution to strengthening ***,existing models for conventional alloys(i.e.,alloys with one principal element)cannot be applied to *** extreme values of SFEs required by such models are unknown for MPEAs,which need to calculate the nanoscale volume relevant to the SFE *** the present work,we developed an analytic model to evaluate the strengthening ef-fect through the SFE fluctuation,profuse in *** model has no adjustable parameters,and all parameters can be determined from experiments and ab initio *** model explains available experimental observations and provides insightful guidance for designing new MPEAs based on the SFE *** generally applies to MPEAs in random states and with chemical short-range order.

关键词： Nanoscale energy fluctuation Staking fault energy Chemical short-range order Multi-principal element alloy Mechanism

Array Waveguide Grating Based Fiber Lasers

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光学学报 2003年第S1期23卷 -页

作者： Shien-Kuei liaw Department of Electronic Engineering Taiwan University of Science and Technology No. 43 Sec. 4 Keelung Rd. Taipei 106 Taiwan

Two array waveguide grating (AWGs) based fiber ring lasers are experimentally demonstrated. Either of them achieves wavelength discrete tuning of 32 nm, or yields simultaneously lasing up to four channels with -7 dBm ... 详细信息

关键词： AWG in be as Array Waveguide Grating Based Fiber Lasers of dBm have for

A Brief review of High Entropy Alloys and Serration Behavior and Flow Units

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Journal of Iron and Steel research International 2016年第1期23卷 2-6页

作者： Yong ZHANG Jun-wei QIAO Peter K.liaw State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Laboratory of Applied Physics and Mechanics of Advanced Materials College of Materials Science and EngineeringTaiyuan University of Technology Department of Materials Science and Engineering University of Tennessee

Multicomponent alloys with high entropy of mixing,e.g.,high entropy alloys（HEAs）and/or multiprincipal-element alloys（MEAs）,are attracting increasing attentions,because the materials with novel properties are being developed,based on the design strategy of the equiatomic ratio,multicomponent,and high entropy of mixing in their liquid or random solution ***,HEAs with the ultrahigh strength and fracture toughness,excellent magnetic properties,high fatigue,wear and corrosion resistance,great phase stability/high resistance to heat-softening behavior,sluggish diffusion effects,and potential superconductivity,etc.,were *** HEAs can even have very high irradiation resistance and may have some self-healing effects,and can potentially be used as the first wall and nuclear fuel cladding *** behaviors and flow units are powerful methods to understand the plastic deformation or fracture of *** methods have been successfully used to study the plasticity of amorphous alloys（also bulk metallic glasses,BMGs）.The flow units are proposed as：free volumes,shear transition zones（STZs）,tension-transition zones（TTZs）,liquid-like regions,soft regions or soft spots,*** flow units in the crystalline alloys are usually dislocations,which may interact with the solute atoms,interstitial types,or substitution ***,the flow units often change with the testing temperatures and loading strain rates,e.g.,at the low temperature and high strain rate,plastic deformation will be carried out by the flow unit of twinning,and at high temperatures,the grain boundary will be the weak area,and play as the flow *** serration shapes are related to the types of flow units,and the serration behavior can be analyzed using the power law and modified power law.

关键词： high entropy alloy bulk metallic glass serration behavior flow unit

Chemical short-range-order induced multiscale strengthening in refractory medium entropy alloys

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Acta Mechanica Sinica 2024年第6期40卷 41-49页

作者： Weizheng Lu Yang Chen Jia Li Peter K.liaw Qihong Fang State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha410082China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN37996USA

High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SrO).However,the complex role of SrO on mechanical properties from nano-scale to meso-scale is still challenging so ***,we study the strengthening mechanism and deformation behavior in a model body-centered-cubic HfNbTa MEA by using atomic-scale molecular dynamics,micro-scale dislocation dynamics,and meso-scale crystal plasticity finite *** SrO inhibits dislocation nucleation at the atomic scale,improving the flow *** SrO-induced ultrastrong local stress fluctuation greatly improves the micro-scale dislocation-based strength by the significant dislocation forest ***,the Ta-rich locally ordered structure leads to an obvious heterogeneous strain and stress partitioning,which forms a strong strain gradient in the adjacent grain interiors and contributes to the strong back-stress-induced strain hardening.

关键词： High/medium entropy alloys Multiscale strengthening Chemical short-range order