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Compositional complexity dependence of dislocation density and mechanical properties in high entropy alloy systems

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Progress in Natural Science:Materials International 2020年第4期30卷 545-551页

作者： P.Thirathipviwat G.Song j.Bednarcik U.Kühn T.Gemming K.Nielsch j.Han Leibniz Institute of Solid State and Materials Research (IFW Dresden) Frontier Research Center for Applied Atomic Sciences Ibaraki University Division of Advanced Materials Engineering and Institute for rare metals Kongju National University Institute of Physic Pavol Jozef Safarik University in Ko?ice Deutsches Elektronen-Synchrotron (DESY) Institute of Materials Science Technische Universit?t Dresden Institute of Applied Physics Technische Universit?t Dresden Korea Institute for Rare Metals Korea Institute of Industrial Technology (KITECH)

This study focuses on a quantitative analysis of dislocation accumulation after cold plastic deformation and mechanical properties of Fe Ni Co Cr Mn and Ti Nb Hf Ta Zr high entropy alloys(HEAs) which are single phase fcc and bcc solid solutions, respectively. In order to study the role of compositional complexity from unary to quinary compositions on dislocation accumulation and mechanical properties after plastic deformation, the single solid solution phase forming sub-alloys of the two HEAs were investigated. All studied samples revealed a large plastic deformability under cold-rotary swaging process by 85–90% area reduction without intermediate annealing. The dislocation density of all studied samples, determined by Williamson-Hall method on synchrotron X-ray diffraction patterns, were between 1014-1015m-2dependent on the alloy composition. The level of dislocation density after plastic deformation is not only affected by the number of constituent element but the lattice distortion and intrinsic properties in terms of stacking fault energy, modulus misfit, and melting point also impact the dislocation storage. The level of dislocation density determines the level of mechanical properties because of a resistance to dislocation motions. The hardness and yield compressive strength of the studied samples are proportional to the level of dislocation density.

关键词： High entropy alloys Dislocation density Synchrotron XRD Mechanical properties

Laser additive manufactured high-performance Fe-based composites with unique strengthening structure

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journal of Materials Science & Technology 2021年第30期89卷 242-252页

作者： Hongyu Chen Dongdong Gu Liang Deng Tiwen Lu Uta Kühn Konrad Kosiba College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components Nanjing University of Aeronautics and AstronauticsNanjing 210016China Leibniz IFW Dresden Institute for Complex MaterialsP.O.Box 270116D-01069 DresdenGermany

Steel matrix composites(SMCs),reinforced by ceramic particles,have received a consistent attention in recent *** conventional methods to prepare SMCs is generally challenging,and the mechanical properties of conventionally fabricated SMCs are *** this study,we successfully fabricated highperformance SMCs by laser powder bed fusion(LPBF)of a composite powder consisting of Fe-based alloy powder and submicron-sized WC *** effect of laser energy density on the phase formation,microstructural evolution,overall density and resulting mechanical properties of LPBF-fabricated composites was *** present results show that a novel Fe_(2)W_(4)C carbidic network precipitates in the solidified microstructure entailing segregations along the boundaries of cellular *** presence of this carbidic network hampers the growth of sub-grains even at elevated temperatures,and hence,stabilizes the grain size though prepared at a broad range of different energy *** exact distribution of the Fe_(2)W_(4)C carbides depends on the employed laser energy densities,as for instance they are more uniformly distributed at higher energy *** density of LPBF samples reaches the maximum value of 99.4%at 150 j/mm^(3).In this parameter set,high microhardness of~753 HV,compression strength of~3350 MPa and fracture strain of~24.4%are *** enhanced mechanical properties are ascribed to less metallurgical defects,higher volume fraction of the martensitic phase and increasing pile-up dislocations resulting from the pinning effect by Fe_(2)W_(4)C carbide.

关键词： Laser additive manufacturing Laser powder bed fusion Steel matrix composite Microstructures Mechanical properties

Achieving exceptional wear resistance in a crack-free high-carbon tool steel fabricated by laser powder bed fusion without pre-heating

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journal of Materials Science & Technology 2023年第25期156卷 1-19页

作者： Konrad Kosiba Daniel Wolf Matthias Bönisch Kai Neufeld Ruben Hühne Tobias Gustmann jozef Bednarčík Hongyu Chen Xiaoliang Han Volker Hoffmann Lukas Beyer Uta Kühn Sergio Scudino Lars Giebeler julia K.Hufenbach Leibniz Institute for Solid State and Materials Research (IFW) Dresden E.V. Helmholtzstr. 20Dresden 01069Germany Department of Materials Engineering KU LeuvenKasteelpark Arenberg 44bus 2450Leuven 3001Belgium Department of Condensed Matter Physics Institute of PhysicsP.J. Safarik University in KosicePark Angelinum 9Kosice 04154Slovakia Institute of Experimental Physics Slovak Academy of ScienceWatsonova 47Kosice 040 01Slovakia Key Laboratory of Impact and Safety Engineering of Ministry of Education of China Ningbo UniversityNingbo 315211China TU Bergakademie Freiberg Institute of Materials ScienceGustav-Zeuner-Str. 5Freiberg 09599Germany

Laser powder bed fusion(LPBF)for the fabrication of dense components used for tooling applications,is highly *** stresses,which evolve in the additively manufactured part,are inherent to LPBF *** additional stress contribution in high-carbon steels arises from the austenite-to-martensite phase transformation,which may eventually lead to cracking or even *** an alternative to pre-heating the base plate,which is not striven by industry,lowering the martensite content which forms in the part,is essential for the fabrication of dense parts by LPBF of high-carbon tool steels which are then adapted to *** this study,a successful strategy demonstrates the processing of the Fe85Cr4Mo1V1W8C1(wt%)high-carbon steel by LPBF into dense parts(99.8%).The hierarchical microstructure consists of austenitic and martensitic grains separated by elemental segregations in which nanoscopic carbide particles form a network.A high density of microsegregation was observed at the molten pool boundary ultimately forming a *** LPBF-fabricated steel shows a yield strength,ultimate compressive stress,and total strain of 1210 MPa,3556 MPa,and 27.4%,*** mechanical and wear performance is rated against the industrially employed and highly wear-resistant 1.2379 tool steel taken as the *** its lower macro-hardness,the LPBF steel(58.6 HRC,0.0061 mm^(3) Nm^(-1))shows a higher wear resistance than the reference steel(62.6 HRC,0.0078 mm^(3) Nm^(-1)).This behavior results from the wear-induced formation of martensite in a microscale thick layer directly at the worn surface,as it was proven via high-energy X-ray diffraction mapping.

关键词： Additive manufacturing Laser powder bed fusion Steel Wear TRIP

Microstructural Evolution and Mechanical Behaviour of Metastable Cu-Zr-Co Alloys

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journal of Materials Science & Technology 2014年第6期30卷 584-589页

作者： S.Pauly K.Kosiba P.Gargarella B.Escher K.K.Song G.Wang U.Kühn j.Eckert IFW Dresden Institut für Komplexe Materialien HelmholtzstraBe 20D-01069 Dresden Germany Laboratory for Microstructures Shanghai University TU Dresden Institut für WerkstoffwissenschaftD-01062 Dresden Germany

Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.

关键词： Bulk metallic glasses Microstructural evolution Mechanical behaviour

Phase formation of a biocompatible Ti-based alloy under kinetic constraints studied via in-situ high-energy X-ray diffraction

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Progress in Natural Science:Materials International 2020年第3期30卷 432-436页

作者： Konrad Kosiba André Rothkirch junhee Han Liang Deng Benjamin Escher Gang Wang Uta Kühn jozef Bednarcik Leibniz IFW Dresden Institute for Complex Materials DESY Photon Science 3. Korea Institute of Industrial Technology (KITECH) Korea Institute for Rare Metals 4. Fraunhofer Institute for Photonic Microsystems IPMS Department of Engineering 5. Laboratory for Microstructures Institute of Materials Shanghai University 6. J. Safarik University in Kosice Institute of Physics Department of Condensed Matter Physics

The biocompatible Ti40Cu34Pd14Zr10Sn2bulk metallic glass was rapidly heated,also known as flash-annealed,at varying heating rates up to 1579 K/***,the phase formation was characterized via advanced in-situ highenergy X-ray *** has been found that the evolving kinetic constraints can be used as a tool to deliberately alter the crystalline phase *** novel processing route permits to select phases to crystallize to a predefined fraction and,thus,to potentially design the microstructure of materials according to a specified ***,flash-annealing poses a unique synthesis route to design materials with,for instance,good biomechanical compatibility.

关键词： High-energy X-ray diffraction Flash-annealing Phase formation Metallic glass Biocompatible Ti alloy

GLOBAL ASYMPTOTIC STABILITY IN N-SPECIES NONAUTONOMOUS LOTKA-VOLTERRACOMPETITIVE SYSTEMS WITH DELAYS

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Acta Mathematica Scientia 2003年第2期23卷 208-218页

作者：徐瑞陈兰荪 M.A.j.Chaplain Department of Mathematics Mechanical Engineering College Institute of Mathematics Academia Sinica Department of Mathematics University of Dundee

A delayed n-species nonautonomous Lotka-Volterra type competitive system without dominating instantaneous negative feedback is investigated. By means of a suitable Lyapunov functional, sufficient conditions are derived for the global asymptotic stability of the positive solutions of the system. As a corollary, it is shown that the global asymptotic stability of the positive solution is maintained provided that the delayed negative feedbacks dominate other interspecific interaction effects with delays and the delays are sufficiently small.

关键词： Nonautonomous Lotka-Volterra competitive system finite and infinite delay global asymptotic stability Lyapunov functional

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从一项赛事到一个IP

电子竞技 2021年第6期 59-63页

作者： j.hn5 不详

2017年7月28日,当记者走出热闹的上海东方体育中心时,看到了一位特别的粉丝。顶着当时35℃的高温,他在场馆的门口徘徊了许久。直至成都AG超玩会的选手们走出来,他才垫起脚望着东方体育中心,含泪对他们说了一句"加油"。几乎没有人看到这... 详细信息

2017年7月28日,当记者走出热闹的上海东方体育中心时,看到了一位特别的粉丝。顶着当时35℃的高温,他在场馆的门口徘徊了许久。直至成都AG超玩会的选手们走出来,他才垫起脚望着东方体育中心,含泪对他们说了一句"加油"。几乎没有人看到这一幕,但从这一刻起,兑现了大部分承诺的KPL联盟开始有了新的目标。

关键词：体育中心赛事东方体育选手

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褪去的直播热潮,会留下一地狼藉么?

电子竞技 2017年第3期 80-81页

作者： j.hn5

在新年交替之际,不时传出对于电子竞技未来的预测。乐观也好,悲观也罢,改变确实在发生,未雨绸缪也总没有错。互联网的出现加快了商业运转的效率,在这些看似缥缈的预测成真之前,一些悄然发生的改变应该足以引起我们的重视。褪去的直播热... 详细信息

在新年交替之际,不时传出对于电子竞技未来的预测。乐观也好,悲观也罢,改变确实在发生,未雨绸缪也总没有错。互联网的出现加快了商业运转的效率,在这些看似缥缈的预测成真之前,一些悄然发生的改变应该足以引起我们的重视。褪去的直播热潮如果说2017年与2016年不同的一点,那就是在新年交替之际我们并没有听闻选手令人咂舌的身价,也没有看到直播平台对于头部内容的激烈抢夺。

关键词：电子竞技成真转换战略资本市场竞争程度腾讯令人于非潜在竞争者娱乐行业

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全民电竞的城市拼图

电子竞技 2021年第8期 40-44页

作者： j.hn5

引语:武汉斗鱼NBW和合肥EHOME两支民间战队已经站在了职业赛场的门口,第三届王者荣耀全国大赛将迎来最后的战役。再过几个小时,谁能鱼跃龙门将有最终的结果。四个月前,在武汉江汉路步行街的尽头,几百名参赛者聚在一起,以海选赛点为中心... 详细信息

引语:武汉斗鱼NBW和合肥EHOME两支民间战队已经站在了职业赛场的门口,第三届王者荣耀全国大赛将迎来最后的战役。再过几个小时,谁能鱼跃龙门将有最终的结果。四个月前,在武汉江汉路步行街的尽头,几百名参赛者聚在一起,以海选赛点为中心一圈圈向外排列。最外侧坐着休息的人甚至堵住了旁边武汉城市博物馆和中信银行的门口。

关键词：总决赛决赛阶段 BFG