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Shock compression and spallation damage of high-entropy alloy Al_(0.1)CoCrFeNi

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journal of Materials Science & Technology 2022年第33期128卷 1-9页

作者： N.B.Zhang j.xu Z.D.Feng y.F.Sun j.y.Huang x.j.Zhao x.H.yao S.Chen L.Lu S.N.Luo Key Laboratory of Advanced Technologies of Materials Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China The Peac Institute of Multiscale Sciences Chengdu 610031China Department of Engineering Mechanics South China University of TechnologyGuangzhou 510641China

Shock compression and spallation damage of a face-center cubic phase high-entropy alloy(HEA)Al_(0.1)CoCrFeNi were investigated via plate impact experiments along with free surface velocity *** samples were characterized with transmission electron microscopy and electron backscatter *** Hugoniot equation of state and spall strength at different impact strengths were *** exists a power-law relation between spall strength and strain *** spall strength of Al_(0.1)CoCrFeNi HEA is about 50%higher than those of previously studied HEAs and comparable to those widely applied structural stainless steels at the same shock *** glide and stacking faults are the important deformation mechanisms in the Al_(0.1)CoCrFeNi *** are only observed at high shock *** in the Al_(0.1)CoCrFeNi HEA is ductile in *** are nucleated preferentially in grain interiors,and the intragranular voids show a strong dependence on grain boundary misorientation and peak stress.

关键词： Al_(0.1)CoCrFeNi High-entropy alloy Hugoniot Spall damage Microstructure

Nano-phase transformation of composite precipitates in multicomponent Al-Mg-Si(-Sc)alloys

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journal of Materials Science & Technology 2022年第15期110卷 216-226页

作者： S.B.Wang C.F.Pan B.Wei x.Zheng y.x.Lai j.H.Chen Key Laboratory of LCR Materials and Devices of yunnan Province National Center for International Research on Photoelectric and Energy MaterialsSchool of Materials and EnergyYunnan UniversityKunming 650091China Collaborative Innovation Center of Renewable Energy Materials and Department of Physics Guangxi UniversityNanning 530004China Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc ***,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many ***,using atomic-scale transmission electron microscopy and atomic-resolution spectroscopy,we have revealed the microstructural differences between two age-hardened Al-0.5Mg-0.4Si(wt.%)alloys with and without *** first significant effect of Sc-addition on the precipitation microstructure of the Al-Mg-Si-Sc alloy is that Sc-atoms may distribute at theβ"-precipitate/Al-matrix interface and therefore accelerate aging kinetics at the initial stage of *** second significant effect of Sc-addition is that in the transition from theβ"-hardened peak-age stage to theβ′-hardened late stage,Sc-atoms can greatly improve the stability of transitionalβ"/B'/β′composite precipitates by entering the B'-substructures and/or locating at the precipitate/Al *** such Sc-atoms effectively suppressβ"toβ'transformation and cross-sectional coarsening of bothβ"and composite precipitates,leading to much finer precipitate needles with smaller diameter but much larger length,as compared with those precipitate needles formed in the alloy without ***,the alloy with Sc-addition exhibits a much better thermal stability than that without Sc.

关键词： Al alloy Strengthening mechanism Phase transition Transmission electron microscopy

Towards the diffusion source cost reduction for NdFeB grain boundary diffusion process

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journal of Materials Science & Technology 2020年第1期36卷 50-54页

作者： H.x.Zeng Z.W.Liu j.S.Zhang x.F.Liao H.y.yu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China

Aiming at improving the performance/cost ratio in grain boundary diffusion process(GBDP),the critical RE containing Pr-Al-Cu alloy,less expensive RE containing La-Al-Cu alloy and non-RE Al-Cu alloy were employed as the diffusion *** preliminary results show that the coercivity was successfully enhanced from 1000 kA/m to 1695,1156 and 1125 kA/m by Pr70Al20Cu10,La70Al20Cu10 and Al75Cu25(at.%) alloys diffusion,respectively,due to the formation of(Nd,Pr)-Fe-B,La2 O3 and c-Nd2 O3 phases respectively,after *** is also found that the corrosion resistance can be improved by Al-Cu diffusion due to the positive effects of Al and Cu elements in grain *** present results demonstrated the various coercivity enhancement mechanisms for the GBDP based on different diffusion sources,and provided feasible solutions for cost reduction of GBDP and NdFeB production by saving RE resource.

关键词： Grain boundary diffusion Cost reduction Coercivity Microstructure Corrosion resistance

LOW TEMPERATURE THERMODyNAMIC STUDy OF THE STABLE AND METASTABLE PHASES OF SILVER

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Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 355-362页

作者： x.B. Li y.Q. xie y.Z. Nie H.j. Peng Research Center of Advanced Materials Xiangtan University Xiangtan 411105 China School of Material Science and Engineering University Changsha 410083 China Central South

The low temperature thermodynamics of the stable phase of silver was assessed by the polynomial model and Debye model from the experimental data available in the literature. By means of the constrained non-linear least squares curve fitting arithmetic, two sets of parameter values were determined. The expression of the thermodynamic functions cp（T） and G（T）-H （298.15K） at 0-298.15K were presented. Only the low temperature thermodynamics of the metastable phase of silver can be extrapolated by the Debye model The expression of the thermodynamic functions cp（T） at 0- 298.15K was presented.

关键词： silver thermodynamic heat capacity SGTE (Scientific Group Thermodata Europe)

STUDy ON NANOMETER ZINC PARTICLES FABRICATED By GAS EVAPORATION METHOD

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 161-168页

作者： A.A.A.Saleh x.j.Zhai y.C.Zhai y.Fu A.L.Zhang School of Materials and Metallurgy Northeastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004China

Nanometer Zn particles with mean diameters 12-100nm made by evaporating its powders in argon gas were studied mainly by x-ray diffraction and electron microscopy. They are collected at various distances and those factors influencing the mean particle size were studied. The optimal synthetic conditions were obtained, i.e., evaporation temperature is 1200℃; argon flow rate is 0.4m3/h; amount of powder charged is 3g; distance from evaporation source is 10cm. It was found that the size of particles was governed by argon flow rate, evaporation temperature, amount of metal charged and distance from the source. The size increases remarkably with distance in the space where no metal vapor exists. This implies that the crystallites grow by coalescence. Electron micrographs and diffraction patterns are reproduced to show the size, shape and state of oxidations. Nanoparticles with definite crystal habits were sometimes observed among those with irregular ones.

关键词： gas evaporation method nanometer Zn xRD TEM

Oxidation behavior and microstructural evolution of FeCoNiTiCu five-element high-entropy alloy nanoparticles

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journal of Materials Science & Technology 2024年第10期177卷 133-141页

作者： H.Bai R.Su R.Z.Zhao C.L.Hu L.Z.ji y.j.Liao y.N.Zhang y.x.Li x.F.Zhang Key Laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang110819China Institute of Advanced Magnetic Materials College of Materials and Environmental EngineeringHangzhou Dianzi UniversityHangzhou310012China

High-entropy alloys(HEAs)have attracted extensive attention ascribed to their unique physical and chemical properties induced by the cocktail ***,their oxidation behaviors,in particular at nanoscale,are still lack because of multi-element complexity,which could also be completely differ-ent from the bulk *** this work,we synthesized FeCoNiTiCu five-element HEA nanopar-ticles(NPs)with uniform elemental distribution by arc-discharging approach,and further investigated their oxidation behaviors at 250 ℃,and 350 ℃.The morphology,structure and element distribution of NPs were analyzed by transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS)and electron energy loss spectroscopy(EELS).The surface oxidation in FeCoNiTiCu NPs during the high-temperature process can induce nanoscale pores at core/shell interfaces by Kirkendall effect,and even the eventual coalescence into a single ***,the oxidation states of NPs with diameters(d)varying from 60 to 350 nm were analyzed in detail,revealing two typical configurations:hollow(dyolk-shell structures(d>150 nm).The experimental results were complemented by first-principles calculations to investigate the diffusion behaviors of five elements,evidencing that the surface oxidation strongly alters the surface segregation preferences:(1)in the initial stage,Cu and Ni appear to prefer segregating on the surface,while Co,Ti and Fe tend to stay in the bulk;(2)in the oxidation process,Cu prefers to stay in the center,while Ti segregates to the surface ascribed to the reduced po-tential *** study gives new insights into oxidation of nanoscale HEA,and also provides a way for fabrication of high-entropy oxides with controllable architectures.

关键词： High-entropy alloy Nanoparticles Oxidation Kirkendall effect Exchange bias effect

STUDy OF ExPLOSIVE VAPORIZATION OF LD11R ALUMINUMALLOy DURING ELECTRON BEAM DEEP PENETRATION

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Acta Metallurgica Sinica(English Letters) 2000年第6期13卷 1119-1124页

作者： Wang, y.j. jia, S.j. Liu, F.j. Chen, x.F. NKL of EDB process. Technol. Beijing 100024 China

High-power-density electron beam with single pulse was performed on the LD11R aluminum alloy. The electron beam was focused on three typical positions. For each case, the distribution of the solute concentration at the cavity bottom solid-liquid interface was investigated by using the 'rapidly fixing' method. The interaction of the beam and solute atoms was analyzed. A new mechanism of explosive vaporization was proposed based on the present results. The occurrence of this explosive vaporization source was discussed.

关键词： Electron beam welding Vaporization

RESEARCH ON THE EVALUATION METHOD OF FRICTION AND LUBRICATION IN DEEP DRAWING

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 439-445页

作者： D.N.He x.F.yin H.Z.Thao D.Lv x.y.Ruan j.L.Cheng j.y.jiang Shanghai j.ao Tong University National Die&Mold CAD E.R.CShanghai 200030China Shanghai Vopkswagen Automotive Company Ltd. Shanghai 201805China

The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other plastic process. The common test methods in laboratories are analyzed. It shows that though all those test methods can test the friction coefficient, the probe test method is most suitable for the research of friction and lubrication and the process in deep drawing, for this method is identical with the actual work condition either from the test principle or deformation status of the blank. Last the successful application in the deep drawing simulator newly developed the the probe method are intro- duced in detail.

关键词： deep drawing probe test method friction and lubrication evaluation method

Nonlinear Transient Response of Functionally Graded Material Sandwich Doubly Curved Shallow Shell Using New Displacement Field

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Acta Mechanica Solida Sinica 2018年第1期31卷 108-126页

作者： Z.N.Li y.x.Hao W.Zhang j.H.Zhang College of Mechanical Engineering Beijing Information Science and Technology University College of Mechanical Engineering Beijing University of Technology

In this paper, the nonlinear transient dynamic response of functionally graded material （FGM） sandwich doubly curved shell with homogenous isotropic material core and functionally graded face sheet is analyzed using a new displacement field on the basis of Reddy＇s third-order shear theory for the first time. The equivalent material properties for the FGM face sheet are assumed to obey the rule of simple power law function in the thickness direction. Based on Reddy＇s theory of higher shear deformation, a new displacement field is developed by introducing the secant function into transverse displacement. Four coupled nonlinear differential equations are obtained by applying Hamilton＇s principle and Galerkin method. It is assumed that the FGM sandwich doubly curved shell is subjected to step loading, air-blast loading, triangular loading, and sinusoidal loading, respectively. On the basis of double-precision variable- coefficient ordinary differential equation solver, a new program code in FORTRAN software is developed to solve the nonlinear transient dynamics of the system. The influences of core thickness, volume fraction, core-to-face sheet thickness ratio, width-to-thickness ratio and blast type on the transient response of the shell are discussed in detail through numerical simulation.

关键词： New displacement fields Functionally graded materials Sandwich doubly curvedshell Blast load Nonlinear transient response