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Modified embedded-atom method interatomic potentials for Mg-Al-Ca and Mg-Al-Zn ternary systems

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Journal of Magnesium and Alloys 2021年第1期9卷 317-335页

作者： Hyo-Sun Jang Donghyuk Seol byeong-joo lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Al,Ca,and Zn are representative commercial alloying elements for Mg alloys.To investigate the effects of these elements on the deformation and recrystallization behaviors of Mg alloys,we develop interatomic potentials for the Al-Ca,Al-Zn,Mg-Al-Ca and Mg-Al-Zn systems based on the second nearest-neighbor modified embedded-atom method formalism.The developed potentials describe structural,elastic,and thermodynamic properties of compounds and solutions of associated alloy systems in reasonable agreement with experimental data and higher-level calculations.The applicability of these potentials to the present investigation is confirmed by calculating the generalized stacking fault energy for various slip systems and the segregation energy on twin boundaries of the Mg-Al-Ca and Mg-Al-Zn alloys,accompanied with the thermal expansion coefficient and crystal structure maintenance of stable compounds in those alloys.

关键词： 2NN MEAM Interatomic potential Mg-Al-Ca Mg-Al-Zn Atomistic simulation

A neural network model for high entropy alloy design

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npj Computational Materials 2023年第1期9卷 1734-1746页

作者： Jaemin Wang Hyeonseok Kwon Hyoung Seop Kim byeong-joo lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Graduate Institute of Ferrous and Energy materials Technology(GIFT) Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Center for Heterogenic Metal Additive Manufacturing Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Institute for Convergence Research and Education in Advanced Technology Yonsei UniversitySeoul 03722Republic of Korea Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

A neural network model is developed to search vast compositional space of high entropy alloys(HEAs).The model predicts the mechanical properties of HEAs better than several other models.It’s because the special structure of the model helps the model understand the characteristics of constituent elements of HEAs.In addition,thermodynamics descriptors were utilized as input to the model so that the model predicts better by understanding the thermodynamic properties of HEAs.A conditional random search,which is good at finding local optimal values,was selected as the inverse predictor and designed two HEAs using the model.We experimentally verified that the HEAs have the best combination of strength and ductility and this proves the validity of the model and alloy design method.The strengthening mechanism of the designed HEAs is further discussed based on microstructure and lattice distortion effect.The present alloy design approach,specialized in finding multiple local optima,could help researchers design an infinite number of new alloys with interesting properties.

关键词： alloy alloys microstructure

Activation of non-basalslip in multicomponent Mg alloy

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Journal of Magnesium and Alloys 2022年第2期10卷 629-642页

作者： Hyo-Sun Jang Jong-Kwan lee Antonio João Seco Ferreira Tapia Nack joon Kim byeong-joo lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Graduate Institute of Ferrous Technology Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Activating non-basalslip is a key method to improve room temperature ductility and formability of Mg alloys.However,the detailed criterion for activation of theslip in multicomponent Mg alloys,which can be utilized in commercial Mg alloys,requires further understanding.The present authors investigated the mechanism and criterion using a molecular statics simulation on dislocation behaviors in multicomponent Mg alloys.We found that if multicomponent Mg alloys have an equivalent dislocation binding intensity to associated binary Mg alloys that are optimized to minimize the critical resolved shear stress anisotropy and thus activate theslip,then the critical resolved shear stress anisotropy between slip systems of the multicomponent Mg alloys can also be minimized,resulting in activation of theslip.The activation is maximized in multicomponent Mg alloys when alloying a large amount of weak dislocation binding elements.It was confirmed through experiments that the multicomponent Mg alloys satisfying the above criterion show higher room-temperature tensile elongation and formability than other alloys.

关键词： Mg–Zn–Ca alloy Molecular statics simulation Ductility Formability

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy:an atomistic simulation study

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npj Computational Materials 2018年第1期4卷 662-670页

作者： Won-Mi Choi Yong Hee Jo Seok Su Sohn Sunghak lee byeong-joo lee Department of Material Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Although high-entropy alloys(HEAs)are attracting interest,the physical metallurgical mechanisms related to their properties have mostly not been clarified,and this limits wider industrial applications,in addition to the high alloy costs.We clarify the physical metallurgical reasons for the materials phenomena(sluggish diffusion and micro-twining at cryogenic temperatures)and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations(Monte Carlo,molecular dynamics and molecular statics).A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish diffusion.We predict that the hexagonal close-packed(hcp)structure is more stable than the face-centered cubic(fcc)structure at 0 K,which we propose as the fundamental reason for the micro-twinning at cryogenic temperatures.The alloying effect on the critical resolved shear stress(CRSS)is well predicted by the atomistic simulation,used for a design of non-equiatomic fcc HEAs with improved strength,and is experimentally verified.This study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

关键词： alloy alloying entropy

Effects of Craddition on Charpy impact energy in austenitic 0.45C-24Mn-(0,3,6)Cr steels

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Journal of Materials Science & Technology 2020年第15期47卷 21-30页

作者： Seok Gyu lee Bohee Kim Min Cheol Jo Kyeong-Min Kim Junghoon lee Jinho Bae byeong-joo lee Seok Su Sohn Sunghak lee Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang37673South Korea Steel Products Design Team Hyundai SteelDangjin31779South Korea Steel Products Research Group 1 Technical Research LaboratoriesPOSCOGwangyang57807South Korea Department of Materials Science and Engineering Korea UniversitySeoul02841South Korea

Effects of Cr addition(0,3,and 6 wt%) on Charpy impact properties of Fe-C-Mn-Cr-based steels were studied by conducting dynamic compression tests at room and cryogenic temperatures.At room temperature,deformation mechanisms of Charpy impacted specimens were observed as twinning induced plasticity(TWIP) without any transfo rmation induced plasticity(TRIP) in all the steels.At cryogenic temperature,many twins were populated in the Cr-added steels,but,interestingly,fine ε-martensite was found in the OCr steel,satisfying the Shoji-Nishiyama(S-N) orientation relationship,{111}γ//{0002}ε and γ//ε.Even though the cryogenic-temperature staking fault energies(SFEs) of the three steel were situated in the TWIP regime,the martensitic transformation was induced by Mn-and Cr-segregated bands.In the OCr steel,SFEs of low-(Mn,Cr) bands lay between the TWIP and TRIP regimes which were sensitively affected by a small change of SFE.The dynamic compressive test results well showed the relation between segregation bands and the SFEs.Effects of Cr were known as not only increasing the SFE but also promoting the carbide precipitation.In order to identify the possibility of carbide formation,a precipitation kinetics simulation was conducted,and the predicted fractions of precipitated M23C6 were negligible,0.4-1.1×10-5,even at the low cooling rate of 10℃/s.

关键词： Austenitic high-Mn steels Charpy impact energy Split Hopkinson pressure bar Twinning induced plasticity(TWIP) Transformation induced plasticity(TRIP) Stacking fault energy(SFE)

Body-centered-cubic martensite and the role on room-temperature tensile properties in Si-added SiVCrMnFeCo high-entropy alloys

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Journal of Materials Science & Technology 2021年第17期76卷 222-230页

作者： Yong Hee Jo Junha Yang Won-Mi Choi Kyung-Yeon Doh Donghwa lee Hyoung Seop Kim byeong-joo lee Seok Su Sohn Sunghak lee Center for High Entropy Alloys Pohang University of Science and TechnologyPohang 37673South Korea Department of Materials Science and Engineering Division of Advanced Materials SciencePohang University of Science and TechnologyPohang 37673South Korea Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 37673South Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841South Korea

We present a new class of metastable high-entropy alloys(HEAs),triggering deformation-induced martensitic transformation(DIMT)from face-centered-cubic(FCC)to body-centered-cubic(BCC),i.e.,BCC-DIMT.Through the ab-initio calculation based on 1 st order axial interaction model and combined with the Gibbs free energy calculation,the addition of Si is considered as a critical element which enables to reduce the intrinsic stacking fault energy(ISFE)in Si_xV_((9-x))Cr_(10)Mn_5 Fe_(46)Co_(30)(x=2,4,and 7 at.%)alloy system.The ISFE decreases from-30.4 to-35.5 mJ/m^(2)as the Si content increases from 2 to 7 at.%,which well corresponds to the reduced phase stability of FCC against HCP.The BCC-DIMT occurs in all the alloys via intermediate HCP martensite,and the HCP martensite provides nucleation sites of BCC martensite.Therefore,the transformation rate enhances as the Si content increases in an earlier deformation ra nge.However,the BCC-DIMT is also affected by the phase stability of FCC against BCC,and the stability is the highest at the Si content of 7 at.%.Thus,the 7Si alloy presents the moderate transformation rate in the later deformation range.Due to the well-controlled transformation rate and consequent strain-ha rdening rate,the 7Si alloy possesses the superior combination of strength and ductility beyond 1 GPa of tensile strength at room temperature.Our results suggest that the Si addition can be a favorable candidate in various metastable HEAs for the further property improvement.

关键词： High-entropy alloy(HEA) Deformation-induced martensitic transformation(DIMT) Phase stability Stacking fault energy(SFE)

Co-W和Al-W合金系统的修正嵌入原子势能的计算（英文）

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Transactions of Nonferrous Metals Society of China 2015年第3期25卷 907-914页

作者：董卫平陈铮 byeong-joo lee 浙江师范大学工学院金华321004 西北工业大学材料学院凝固国家重点实验室西安710072 Department of Materials Science and Engineering Division of Advanced Nuclear EngineeringPohang University of Science and Technology(POSTECH)Pohang 790-784Korea

采用半经验的第二近邻修正型嵌入原子理论的原子间作用势模型,基于已开发的Co,Al和W纯元素原子间作用势参数,拟合Co-W和Al-W二元合金系参数,得到Co-W和Al-W二元合金的原子间作用势及势能函数。Co-W和Al-W二元合金的势能参数主要是由晶... 详细信息

采用半经验的第二近邻修正型嵌入原子理论的原子间作用势模型,基于已开发的Co,Al和W纯元素原子间作用势参数,拟合Co-W和Al-W二元合金系参数,得到Co-W和Al-W二元合金的原子间作用势及势能函数。Co-W和Al-W二元合金的势能参数主要是由晶格参数、形成焓、熔点以及弹性常数等物理性能的实验结果来确定的。结果表明,该势能参数能准确地计算出Co-W和Al-W二元合金的基本物理性能。其中,晶格常数、形成焓、热稳定性能和弹性常数与实验结果及第一性能计算结果非常吻合,混合焓以及液态混合焓与相图计算结果很相符。同时,拟合的Co-W和Al-W二元合金势能参数很容易与已有的其他Co基二元势能参数结合,并广泛用于Co-Al-W系多元合金各种性能的计算,特别是对界面性能的研究很适用。

关键词：修正嵌入原子方法 Co-W系统 Al-W系统原子级模拟

Evolution of microstructure and tensile properties of cold-drawn hyper-eutectoid steel wires during post-deformation annealing

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Journal of Materials Science & Technology 2020年第6期41卷 1-11页

作者： Majid Jafari Chan-Woo Bang Jong-Chan Han Kyeong-Min Kim Seon-Hyeong Na Chan-Gyung Park byeong-joo lee Department of Materials Science and Engineering POSTECH Pohang 37673 South Korea

Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements,thereby affecting the materials’mechanical properties.Herein,we describe the evolution of microstructure and tensile strength of the as-drawn 3.45 GPa steel wire during post-deformation annealing for 30 min at 150-450℃.Annealing at 150℃raised the strength to 3.77 GPa by age-hardening through activation of dislocations pinning by carbon,while further temperature rising up to 450℃caused a severe loss of strength.It was proved that annealing at 300 and 450℃destabilizes the lamellar microstructure,promoting the formation of carbon-deficient(Fe,Mn,Cr)3 C-type cementite particles with preferentially rounded and partially faceted hetero-interfaces.Annealing at 450℃yielded the accumulation of Mn and Cr at the ferrite/particle interfaces,and their concentrations at the interfaces were dependent on the interface structure;i.e.,lower concentrations at rounded interfaces(formed through capillarity–driven coarsening of the spheroidized cementite),and higher concentrations at faceted interfaces(that are initially existing in the as-drawn state).Our proof-of-principle observations,supported by thermodynamic calculations and kinetic assessments,provide a pathway for understanding the changes in microstructural and tensile properties during manufacturing of the hyper-eutectoid steel wires.

关键词： Three-dimensional atom probe(3DAP) High resolution transmission electron microscopy(HRTEM) Nano-grained low-carbon steel Annealing Tensile behavior

Small but big leaps towards neuroglycomics:exploring N-glycome in the brain to advance the understanding of brain development and function

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Neural Regeneration Research 2024年第3期19卷 489-490页

作者： Boyoung lee Hyun joo An Center for Cognition and Sociality Institute for Basic Science(IBS)DaejeonSouth Korea Asia-Pacific Glycomics Reference Site DaejeonSouth Korea Graduate School of Analytical Science&Technology Chungnam National UniversityDaejeonSouth Korea

Glycosylation is a process that involves the addition of sugar moieties or glycans to different types of molecules,including proteins,lipids,and nucleic acids.Among these,protein glycosylation is one of the most prevalent forms of post-translational modification,playing a crucial role in biological complexity.With more than ten monosaccharides identified within mammalian brain cells and more than 1×1012 possible combinations,the heterogeneity of glycosylation is extensive(Conroy et al.,2021).The diversity of glycans and the complexity of their structures allow for a wide range of protein functions.N-glycans are one of the most abundant forms of glycans and are involved in various cellular functions.N-glycans can be added to proteins at specific sequons,Asn-X-Ser/Thr,and are classified into three main types in mature glycoproteins:high mannose,complex,and hybrid.High mannose N-glycans consist of 5-9 mannose residues linked to a chitobiose core and undergo processing into complex or hybrid forms in the Golgi apparatus(Varki et al.,2017).Complex N-glycans are more diverse and contain various branched structures such as antennae with fucose,galactose,and sialic acid residues.Hybrid N-glycans contain one or more complex branches in conjunction with an oligomannose branch(Fisher and Ungar,2016).Understanding the specific functions of these different types of N-glycans in protein regulation,folding,and function is an active area of research in the life sciences,including glycobiology.

关键词： functions function apparatus