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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/s.Thereby,the phase formation was characterized via advanced in-situ highenergy X-ray diffraction.It has been found that the evolving kinetic constraints can be used as a tool to deliberately alter the crystalline phase formation.This 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 property-profile.Consequently,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

Synthesis of YAG∶Ce^(3+) Phosphor by Polyacrylamide Gel Method and Promoting Action of α-Al_2O_3 Seed Crystal on phase formation

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Journal of Rare Earths 2005年第5期23卷 517-520页

作者：李永绣李颖毅闵宇霖吴燕利程昌明周雪珍辜子英 Research Center for Rare Earths & Micro/Nano Functional Materials Nanchang University Nanchang 330047 China

YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.

关键词： YAG ： Ce^3 ＋ phosphor polyacrylamide gel α-Al2O3 seed crystal phase formation rare earths

Effect of wheel speed on phase formation and magnetic properties of (Nd_(0.4)La_(0.6))-Fe-B melt-spun ribbons

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Journal of Rare Earths 2018年第11期36卷 1179-1183页

作者： Liang Wang Jiang Wang Maohua Rong Guanghui Rao Huaiying Zhou School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology Guilin 541004China

The effect of wheel speed on phase formation and magnetic properties of （Ndo.4La0.6）lsFeTzsBzs and （Ndo.4La0.6）13.4Fe79.9B6.7 ribbons prepared by melt-spinning method was investigated experimentally. Based on X-ray diffraction results, all melt-spun ribbons consist of the main phase with the tetragonal 2：14：1 type structure and the minor α-Fe phase. Magnetic measurements show the maximum magnetic energy product （（BH）max） and the remanence （Mr） increases firstly and then decreases with the increase of wheel speed, while the coercivity （Hci） increases, resulting from the variation of the average volume fraction of the ^-Fe phase and the average grain size in the melt-spun ribbons. Using Henkel plots, the interaction between the 2：14：1 phase and the ^-Fe phase in the melt-spun ribbons was analyzed and the intergranular exchange coupling is manifested. Optimal magnetic properties of Hci - 7.27 kOe, Mr - 90.94 emu/g and （BH）max -- 12.10 MGOe are achieved in the （Ndo.4La0.6）lsFeTzsBT.s ribbon with the wheel speed of 26 m/s. It indicates that magnetic properties of Nd-Fe-B melt-spun ribbons with highly abundant rare earth element La can be improved by optimizing alloy composition and preparation process.

关键词： Nd-La-Fe-B ribbons phase formation Melt-spinning Magnetic properties Rare earths

Metallurgical Microstructure Complexity in the Electron Beam Welding (EBW) Joint of Ti6246

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Journal of Minerals and Materials Characterization and Engineering 2024年第2期12卷 100-111页

作者： Daniel Moreno Yohanan Nachmana Roei Saraga Tal Rokah Denis Panchenco Michael Mansano Elinor Itzhaky Moshe Shapira Beth Shemesh Engines LTD FAA & EASA Beth Shemesh Israel

Electron Beam Welding (EBW) is employed to both melt and unite materials, influencing their thermal history and subsequently determining the microstructure and properties of the welded joint. Welding Titanium alloys involves undergoing local melting and rapid solidification, subjecting the material to thermal stresses induced by a thermal expansion coefficient of 9.5 × 10 m/m°C. This process, reaching range temperatures from the full melting alloy to room temperature, results in phase formation dictated by the thermodynamic preferences of the alloyed elements, posing a significant challenge. Recent efforts in simulation and calculations have been undertaken elsewhere to address this challenge. This study focuses on a joint of two plates with differing cross-sectional areas, influencing heat transfer during welding. This report presents a case study focusing on the metallurgical changes observed in the microstructure within the welded zone, emphasizing alterations in the cooling rate of the welded joint. The investigation utilizes optical metallography, Vickers’s Hardness testing, and SEM (scanning electron microscopy) to comprehensively characterize the observed changes in addition to heat transfer simulation of the welded zone.

关键词： Ti Alloys Welding phase formation Hardness Metallography

High-entropy intermetallics:from alloy design to structural and functional properties

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Rare Metals 2022年第6期41卷 1989-2001页

作者： Hang Wang Quan-Feng He Yong Yang Department of Mechanical Engineering City University of Hong KongHong Kong 999077China Department of Materials Science and Engineering.City University of Hong Kong Hong Kong 999077China Department of Advanced Design and System Engineering.City University of Hong Kong Hong Kong 999077China

Conventional intermetallics are strong but brit-tle.However,multi-principal element intermetallics,also termed as high-entropy intermetallics(HEIs)in the recent high-entropy alloy literature,are strong but malleable,some of which even show appreciable ductility and fracture toughness at room temperature.In this article,we provide a focused review on the recent researches on HEIs,from the fundamentals,such as the concept of HEIs,the formation rules to the structural and functional properties of HEIs.The results hitherto reported clearly show that the HEIs with distinct properties could be a promising material for future structural and functional applications.

关键词： Internetallics High-entropy alloys phase formation Mechanical properties Functional properies

Variant selection in laser powder bed fusion of non-spherical Ti-6Al-4V powder

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Journal of Materials Science & Technology 2023年第16期147卷 56-67页

作者： Mohammadreza Asherloo Ziheng Wu Julian E.C.Sabisch Iman Ghamarian Anthony D.Rollett Amir Mostafaei Department of Mechanical Materials and Aerospace EngineeringIllinois Institute of Technology10 W 32nd StreetChicagoIL 60616United States Materials Engineering Division Lawrence Livermore National Laboratory7000 East AveLivermoreCA 94550United States Samuel Roberts Noble Microscopy Laboratory University of OklahomaNormanOK 73019United States School of Aerospace and Mechanical Engineering University of OklahomaNormanOK 73019United States Department of Materials Science and Engineering Carnegie Mellon UniversityPittsburghPA 15213United States

The presence ofα/αon priorβ/βgrain boundaries directly impacts the final mechanical properties of the titanium alloys.Theβ/βgrain boundary variant selection of titanium alloys has been assumed to be unlikely owing to the high cooling rates in laser powder bed fusion(L-PBF).However,we hypothesize that powder characteristics such as morphology(non-spherical)and particle size(50–120μm)could affect the initial variant selection in L-PBF processed Ti-6Al-4V alloy by locally altering the cooling rates.Despite the high cooling rate found in L-PBF,results showed the presence ofβ/βgrain boundaryαlath growth inside two adjacent priorβgrains.Electron backscatter diffraction micrographs confirmed the presence ofβ/βgrain boundary variant selection,and synchrotron X-ray high-speed imaging observation revealed the role of the“shadowing effect”on the locally decreased cooling rate because of keyhole depth reduction and the consequentβ/βgrain boundaryαlath growth.The self-accommodation mechanism was the main variant selection driving force,and the most abundantα/αboundary variant was type 4(63.26°//[10553¯]).The dominance of Category IIαlath clusters associated with the type 4α/αboundary variant was validated using the phenomenological theory of martensite transformations and analytical calculations,from which the stress needed for theβ→αtransformation was calculated.

关键词： Variant selection phase formation Additive Manufacturing Hydride-dehydride powder Texture analysis Electron backscattered diffraction

Effect of alloying elements on microstructure, mechanical and damping properties of Cr-Mn-Fe-V-Cu high-entropy alloys

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Journal of Materials Science & Technology 2018年第11期34卷 2014-2021页

作者： Ruokang Song Fan Ye Chenxi Yang Sujun Wu School of Materials Science and Engineering Beihang University (BUAA)

A series of new Cr-Mn-Fe-V-Cu high-entropy alloys were prepared by arc melting and suction casting.It is found that with the addition of Cu, the structure of the alloys evolved from BCC ＋ BCC1 phases to BCC ＋ FCC phases. With increase of Cu, the volume fraction of the Cu-Mn-rich FCC phase increased, and the morphology of the FCC phase transformed from granular particles to long strips and blocks. Compared with other reported HEAs, the Cr-Mn-Fe-V-Cu HEAs exhibit a good balance between strength and ductility. The CrMn0.3 FeVCu0.06 alloy with granular FCC particles exhibits the highest compressive yield strength（1273 MPa） and excellent ductility（εf= 50.7%）. Quantitative calculations for different strengthening mechanisms demonstrate that dislocation and precipitate strengthening are responsible for high strength of the CrMn0.3 FeVCu0.06 alloy, while the solid solution strengthening effect is very low because of its small atomic-size difference. In addition, the CrMn0.3 FeVCu0.06 alloy exhibits good damping capacity due to its high dislocation and interface damping effects. Therefore, the dislocation density and distribution of FCC phase are the crucial factors for improvement of both mechanical properties and damping capacity of the HEAs.

关键词： High-entropy alloy phase formation Mechanical properties Damping capacity

CuZr-based bulk metallic glass and glass matrix composites fabricated by selective laser melting

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Journal of Materials Science & Technology 2021年第22期81卷 139-150页

作者： Liang Deng Long Zhang Konrad Kosiba RenéLimbach Lothar Wondraczek Gang Wang Dongdong Gu Uta Kühn Simon Pauly Leibniz IFW Dresden Institute for Complex MaterialsHelmholtzstraße 20D-01069DresdenGermany Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China Otto Schott Institute of Materials Research University of JenaFraunhoferstraße 6D-07743 JenaGermany Laboratory for Microstructure Institute of MaterialsShanghai UniversityShanghai200444China College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing210016China University of Applied Sciences Aschaffenburg Würzburger Straße 45D-63743AschaffenburgGermany

Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.

关键词： Selective laser melting CuZr-based glass Bulk metallic glass matrix composites phase formation Mechanical properties

New DySrAlO_4 Compound Synthesis and formation Process Correlations for LnSrAlO_4(Ln=Nd,Gd,Dy) Series

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Acta Metallurgica Sinica(English Letters) 2016年第5期29卷 450-456页

作者： E.A.Tugova New Inorganic Materials Laboratory Ioffe Institute

For the first time, DySrA104 of K2NiF4-type structure was synthesized. The parameters of DySrA104 ele- mentary unit cell are determined as follows： a = 0.368 （4） nm, c = 1.229 （2） nm, V = 0.166 （4） nm3. The research of the complex aluminates ZnSrA104 （Ln = Nd, Gd, Dy） solid-state process demonstrated the change of the formation mecha- nism among LnSrA104 （Ln = Nd, Gd, Dy） series from DySrA104 oxide. The performed analysis provided a possibility to realize why chemists couldn＇t get DySrA104 for a long period of time.

关键词： Rare earths Oxide materials K2NiF4-type structure Solid-state reactions phase formation

High-entropy carbide ceramics: a perspective review

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Tungsten 2021年第2期3卷 131-142页

作者： Zhe Wang Zhong-Tao Li Shi-Jun Zhao Zheng-Gang Wu College of Materials Science and Engineering and Hunan Province Key Laboratory for Spray Deposition Technology and Application Hunan UniversityChangsha 410082China Department of Mechanical Engineering City University of Hong KongHong Kong 999077China

High-entropy carbide ceramics(HECCs)exhibited a series of property superiority,such as high hardness,high oxidation resistance and adjustable range of thermal conductivity,making them great candidates for structural materials used in extreme service conditions.However,current HECC-related reports can only provide limited guidance for the design of HECC materials with promising properties and stable structure or for their high-quality fabrication.To fill this gap,we proposed in the current review that integrated efforts should be taken in the following three aspects to advance the design and fabrication of high-performance HECCs.First,the rule for the single-phase formation needs to be theoretically identified using high-throughput density functional theory calculations(HTDFT)and a highly accurate predictive model for rapid compositional design warrants establishment through the combination of HTDFT and machine-learning studies.In parallel with the compositional design,the lack of theoretical foundation and guidance for the synthesis of highly dense and highly pure HECC materials necessitates extensive studies focusing on the principle for the synthesis of HECC pre-alloy powders and on the powder densification mechanisms during high-temperature sintering.Moreover,great attentions are to be paid to the mechanistic understandings on the mechanical,oxidation and thermal conduction behaviors of HECC materials;for example,the toughening and strengthening mechanisms of HECC materials could be elucidated through discerning the"HECC composition-stacking fault energy distribution/bonding state-dislocation behavior"correlations.

关键词： High-entropy carbide ceramics phase formation Mechanical property Oxidation behavior Thermal conduction Fabrication