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In situ neutron diffraction unravels deformation mechanisms of a strong and ductile Fe Cr Ni medium entropy alloy

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Journal of Materials Science & Technology 2022年第21期116卷 103-120页

作者： L.Tang F.Q.Jiang J.S.Wróbel B.Liu S.Kabra R.X.Duan J.H.Luan Z.B.Jiao M.M.Attallah D.Nguyen-Manh B.Cai School of Metallurgy and Materials University of BirminghamB152TTUnited Kingdom Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Faculty of Materials Science and Engineering Warsaw University of Technologyul.Wołoska 141Warsaw 02-507Poland State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China Rutherford Appleton Laboratory ISIS FacilityDidcot OX110QXUnited Kingdom Department of Materials Science and Engineering City University of Hong KongKowloonHong KongChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina CCFE United Kingdom Atomic Energy AuthorityAbingdonOxfordshire OX143DBUnited Kingdom

We investigated the mechanical and microstructural responses of a high-strength equal-molar medium entropy FeCrNi alloy at 293 and 15 K by in situ neutron diffraction *** 293 K,the alloy had a very high yield strength of 651±12 MPa,with a total elongation of 48%±5%.At 15 K,the yield strength increased to 1092±22 MPa,but the total elongation dropped to 18%±1%.Via analyzing the neutron diffraction data,we determined the lattice strain evolution,single-crystal elastic constants,stacking fault probability,and estimated stacking fault energy of the alloy at both temperatures,which are the critical parameters to feed into and compare against our first-principles calculations and dislocation-based slip system *** density functional theory calculations show that the alloy tends to form shortrange order at room ***,atom probe tomography and atomic-resolution transmission electron microscopy did not clearly identify the short-range ***,at 293 K,experimental measured single-crystal elastic constants did not agree with those determined by first-principles calculations with short-range order but agreed well with the values from the calculation with the disordered configuration at 2000 *** suggests that the alloy is at a metastable state resulted from the fabrication *** view of the high yield strength of the alloy,we calculated the strengthening contribution to the yield strength from grain boundaries,dislocations,and lattice *** lattice distortion contribution was based on the Varenne-Luque-Curtine strengthening theory for multi-component alloys,which was found to be 316 MPa at 293 K and increased to 629 MPa at 15 K,making a significant contribution to the high yield *** plastic deformation,dislocation movement and multiplication were found to be the dominant hardening mechanism at both temperatures,whereas twinning and phase transformation were not *** is mainly due to the high stack

关键词： medium entropy alloy Multi-component alloy Cryogenic temperature Neutron diffraction

Probing deformation mechanisms of gradient nanostructured CrCoNi medium entropy alloy

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Journal of Materials Science & Technology 2020年第22期54卷 85-91页

作者： Jia Li Li Li Chao Jiang Qihong Fang Feng Liu Yong Liu Peter K.Liaw State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha410082China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN37996USA

The gradient nanostructured medium entropy alloys(MEAs) exhibit a good yielding strength and great plasticity. Here, the mechanical properties, microstructure, and strain gradient in the gradient nanostructured MEA CrCoNi are studied by atomic simulations. The strong gradient stress and strain always occur in the deformed gradient nanograined MEA CrCoNi. The origin of improving strength is attributed to the formation of the 9 R phase, deformation twinning, as well as the fcc to hcp phase transformation, which prevent strain localization. A microstructure-based predictive model reveals that the lattice distortion dependent solid-solution strengthening and grain-boundary strengthening dominate the yield strength,and the dislocation strengthening governs the strain hardening. The present result provides a fundamental understanding of the gradient nanograined structure and plastic deformation in the gradient nanograined MEA, which gives insights for the design of MEAs with higher strengths.

关键词： medium entropy alloy Gradient nanograined structure Atomic simulation Strengthening Deformation 9R phase Deformation twinning Phase transformation

Refined microstructure and enhanced mechanical properties of AlCrFe_(2)Ni_(2) medium entropy alloy produced via laser remelting

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Journal of Materials Science & Technology 2022年第4期99卷 18-27页

作者： Tianyi Han Yong Liu Mingqing Liao Danni Yang Nan Qu Zhonghong Lai Jingchuan Zhu School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China Center of Analysis and Measurement and Computing Harbin Institute of TechnologyHarbin 150001China

A Co-free as-cast AlCrAlCrFe_(2)Ni_(2)medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this *** effect of laser remelting on the microstructure,phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrAlCrFe_(2)Ni_(2)*** laser remelting process resulted in a significant decrease of grain size from about 780μm to 58.89μm(longitudinal section)and 15.87μm(transverse section)and an increase of hardness from 4.72±0.293 GPa to 6.40±0.147 GPa(longitudinal section)and 7.55±0.360 GPa(transverse section).It was also found that the long side plate-like microstructure composed of FCC phase,ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC *** mechanical properties were evaluated by the derived stressstrain relationship obtained from nano-indentation tests *** results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa(longitudinal section)and 1647.2 MPa(transverse section)after *** individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated,including grain boundary strengthening,dislocation strengthening,solid solution strengthening and precipitation *** calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.

关键词： medium entropy alloy Laser remelting Microstructure Nano-indentation Strengthening mechanism

Dislocation me diate d dynamic tension-compression asymmetry of a Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy

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Journal of Materials Science & Technology 2023年第28期159卷 204-218页

作者： Ao Meng Xiang Chen Yazhou Guo Yiping Lu Yonghao Zhao Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian 116024China

Although tension-compression(T-C)asymmetry in yield strength was rarely documented in coarse-grained face centered cubic(FCC)metals as critical resolved shear stress(CRSS)for dislocation slip differs little between tension and compression,the T-C asymmetry in strength,i.e.,higher strength when loaded in compression than in tension,was reported in some FCC high entropy alloys(HEAs)due to twinning and phase transitions activated at high strain regimes in *** this paper,we demonstrate a reversed and atypical tension-compression asymmetry(tensile strength markedly exceeds compressive strength)in a non-equiatomic FCC Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy(MEA)under dynamic loading,wherein dislocation slip governs dynamic deformation without twins or phase *** asymme-try can be primarily interpreted as higher CRSS and more hard slip modes(lower average Schmid factor)activated in grains under dynamic tension than ***,larger strain rate sensitivity in dy-namic tension overwhelmingly contributes to the higher flow stress,thanks to the occurrence of more immobile Lomer-locks,narrower spacing of planar slip bands and higher dislocation *** finding may provide some insights into designing MEAs/HEAs with desired properties under extreme conditions such as blast,impact and crash.

关键词： medium entropy alloy Dynamic deformation Tension-compression asymmetry Slip trace analysis EBSD and TEM

Achieving ultra-high mechanical properties in metastable Co-free medium entropy alloy via hierarchically heterogeneous microstructure

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Journal of Materials Science & Technology 2024年第16期183卷 175-183页

作者： Qiuyu Gao Xinghua Zhang Shilin Feng Zhenhua Han Chen Chen Tan Wang Shaojie Wu Yongfu Cai Fushan Li Ran Wei School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China School of Chemical Engineering Zhengzhou UniversityZhengzhou 450001China School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048China

A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this *** recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging *** yield strength of the MEA at room temperature(298 K)and liquid nitrogen temperature(77 K)increased from∼910 MPa and∼1250 MPa in the annealed state,respectively,to∼1145 MPa and∼1520 MPa in the aged state,while the uniform elongation maintained more than 15%.The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mech-anisms,including fine grain,dislocation,precipitation,transformation-induced plasticity,stacking faults,and nano-twins.

关键词： medium entropy alloy Precipitation strengthening Heterogeneous microstructure Transformation-induced plasticity Mechanical properties

Revealing the Local Microstates of Fe–Mn–Al medium entropy alloy:A Comprehensive First-principles Study

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Acta Metallurgica Sinica(English Letters) 2021年第11期34卷 1492-1502页

作者： Ying Zhang William Yi Wang Chengxiong Zou Rui Bai Yidong Wu Deye lin Jun Wang Xidong Hui Xiubing Liang Jinshan Li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China CAEP Software Center for High Performance Numerical Simulation Beijing 100088China Defense Innovation Institute Academy of Military Sciences of the PLA of ChinaBeijing 100071China

entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional *** local chemical complexions,microstates and configurational transformations are essential to reveal the structure–property relationship,thus,to promote the development of advanced multicomponent *** the present work,effects of local lattice distortion(LLD)and microstates of various configurations on the equilibrium volume(V0),total energy,Fermi energy,magnetic moment(μMag)and electron work function(Φ)and bonding structures of the Fe–Mn–Al medium entropy alloy(MEA)have been investigated comprehensively by first-principles *** is found that theΦandμMag of those MEA are proportional to the V 0,which is dominated by lattice *** terms of bonding charge density,both the strengthened clusters or the so-called short-range order structures and the weakly bonded spots or weak spots are *** the presence of weakly bonded Al atoms implies a large LLD/mismatch,the Fe–Mn bonding pairs result in the formation of strengthened clusters,which dominate the local microstates and the configurational *** variations ofμMag are associated with the enhancement of the nearest neighbor magnetic Fe and Mn atoms,attributing to the LLD caused by Al atoms,the local changes in the electronic *** work provides an atomic and electronic insight into the microstate-dominated solid-solution strengthening mechanism of Fe–Mn–Al MEA.

关键词： medium entropy alloy Bonding charge density Magnetic moment Microstates

Twinning induced remarkable strain hardening in a novel Fe_(50)Mn_(20)Cr_(20)Ni_(10) medium entropy alloy

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Journal of Iron and Steel Research International 2021年第11期28卷 1463-1470页

作者： Ming-jie Qin Xi Jin Min Zhang Hui-jun Yang Jun-wei Qiao College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024ShanxiChina Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024ShanxiChina State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The microstructures and tension properties of Fe_(50)Mn_(20)Cr_(20)Ni_(10) medium entropy alloy(MEA)were investigated,which was produced by vacuum induction melting and subsequently was homogenized at 1200 C for 6 *** characterization shows the single-phase solid solution with face-centered cubic structure by means of transmission electron microscopy and scanning electron microscopy combined with energy disperse *** Fe-MEA has an ultimate tensile strength of 550±10 MPa and a high strain hardening exponent,n,of 0.41 as well as a higher ductility(60%)than those of CrMnFeCoNi *** single-phase solid solution deforms plastically via dislocations and *** boundaries associated with deformation twinning impede dislocation motion,enhancing the strain hardening *** article focuses on the insights into the concept of Fe-MEAs and provides a potential direction for the future development of high entropy alloys and MEAs.

关键词： medium entropy alloy alloy design Labusch model Twinning induced plasticity Strain hardening

High-throughput simulation combined machine learning search for optimum elemental composition in medium entropy alloy

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Journal of Materials Science & Technology 2021年第9期68卷 70-75页

作者： Jia Li Baobin Xie Qihong Fang Bin Liu Yong Liu Peter K.Liawc State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha410082.China State Key Laboratory of Powder Metallurgy.Central South University Changsha410083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN37996USA

In medium/high entropy alloys, their mechanical properties are strongly dependent on the chemicalelemental composition. Thus, searching for optimum elemental composition remains a critical issue to maximize the mechanical performance. However, this issue solved by traditional optimization process via "trial and error" or experiences of domain experts is extremely difficult. Here we propose an approach based on high-throughput simulation combined machine learning to obtain medium entropy alloys with high strength and low cost. This method not only obtains a large amount of data quickly and accurately,but also helps us to determine the relationship between the composition and mechanical *** results reveal a vital importance of high-throughput simulation combined machine learning to find best mechanical properties in a wide range of elemental compositions for development of alloys with expected performance.

关键词： medium entropy alloy Optimum elemental composition High-throughput simulation Machine learning

Chemical inhomogeneity inhibits grain boundary fracture:A comparative study in CrCoNi medium entropy alloy

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Journal of Materials Science & Technology 2023年第22期153卷 228-241页

作者： Fuhua Cao Yan Chen Hai-Ying Wang Lan-Hong Dai State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China

Grain boundary(GB)fracture is arguably one of the most important reasons for the catastrophic failure of ductile polycrystalline *** is of interest to explore the role of chemical distribution on GB defor-mation and fracture,as GB segregation becomes a key strategy for tailoring GB *** we report that the inhomogeneous chemical distribution effectively inhibits GB fracture in a model CoCrNi medium entropy alloy compared to a so-called‘average-atom’*** deformation kinematics combined with electronic behavior analysis reveals that the strong charge redistribution ability in chemical disor-dered CrCoNi GBs enhances shear deformation and thus prevents GB crack formation and *** on the GBs with different chemical components and chemical distributions suggest that not only disordered chemical distribution but also sufficient“harmonic elements”with large electronic flexibility contribute to improving the GB fracture *** study provides new insight into the influence mechanism of GB chemistry on fracture behavior,and yields a systematic strategy and criterion,from the atoms and electrons level,forward in the design of high-performance materials with enhanced GB fracture resistance.

关键词： Fracture Chemical inhomogeneity Grain boundary medium entropy alloy