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Formation of intermetallic phases in unrefined and refined AA6082 Al alloys investigated by using SEM-based ultramicrotomy tomography

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journal of Materials Science & Technology 2022年第25期120卷 118-128页

作者： j.M.Yu T.hashimoto h.T.li n.Wanderka Z.Zhang C.Cai X.l.Zhong j.Qin Q.P.Dong h.nagaumi X.n.Wang Shagang School of Iron and Steel and high-Performance Metal Structural Materials Research Institute Soochow UniversitySuzhou 215137China School of Materials The University of ManchesterSackville StreetManchester M139PLUK Chinalco Materials Application Research Institute Co.ltd. Beijing 102200China helmholtz-Zentrum Berlin Für Materialien und Energie Hahn-Meitner-Platz 1Berlin 14109Germany Key laboratory of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang 110819China

The spatial arrangement,distribution and morphology of Fe-bearing intermetallics in AA6082 alloys depends on the manufacturing process of the alloy and thus influences the macroscopic ***,the microstructure of a near industrial scale casting AA6082 Al alloy fabricated by:(a)direct chill casting,(b)Al-5 Ti-1 B grain refiner addition and(c)intensive melt shearing has been investigated by threedimensional visualization using SEM-based serial ultra microtomy *** formation sequence of phases in AA6082 alloys is generally categorized into four stages:formation ofα-Al grains,Fe-bearing intermetallics,Mg_(2)Si phase,and eutectic *** of three-dimensional visualization of the microstructure indicated that TiBparticles not only could nucleate Fe-bearingβ-intermetallics,but also could provide substrate for the formation of Fe-bearingα-intermetallics and Mg_(2)Si.A further deep analysis reveals that the essential condition for the formation of secondary phases such as Fe-bearing intermetallics and Mg_(2)Si phase is the build-up of a supersaturated solute front at theα-Al solid-liquid interface irrespective of the specific nucleation *** addition,the results indicate that grain refinement processing causes the severe interconnectivity of Fe-bearingα-***,the intensive melt shearing is a better manufacturing process because the intermetallics are more evenly distributed and refined than with the addition of the grain refiner,thereby improving the properties of the alloy.

关键词： Al-Si-Mg alloy Grain refinement Al-Fe-Si intermetallic phase Tomography Ultramicrotomy Mg2Si

Colloidal(Gd0.98nd0.02)2O3 nanothermometers operating in a cell culture medium within the first and second biological windows

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journal of Rare Earths 2020年第5期38卷 483-491页

作者： M.l.Debasu h.Oliveira j.Rocha l.D.Carlos Department of Physics CICECO-Aveiro Institute of MaterilsUniversidade de Aveiro3810-193AveiroPortugal Department of Chemistry CICECO-Aveiro Institute of MaterialsUniversidade de Aveiro3810-193AveiroPortugal Department of Biology CESAMLaboratory of Biotechnology and CytomicsUniversidade de Aveiro3810-193AveiroPortugal

non-contact,self-referenced and near-infrared luminescent nanothermometers have been recognized as emerging tools in the fields of nanomedicine and nanotechnology due to their great capability of precise temperature readout at the nanoscale and real-time deep-tissue ***,the development of multifunctional and biocompatible luminescent nanothermometers operating within the optically transparent biological windows with high thermal sensitivity(>2.0%/K)remains ***,we present(Gd0.98nd0.02)2O3 nanothermometers operated effectively within the first and second biological windows upon continuous-wave laser diode excitation at 808 *** thermometric parameters are defined by the relative changes in the emission intensities originating from the two Stark components of the 4 F3/2 level(R2 and R1)to the 4 I9/2(900-1000 nm),4 I11/2(1035-1155 nm)and 4 I13/2(1300-1450 nm)*** thermo metric parameters are evaluated for colloidal samples in a cell culture medium and powder samples,and the highest thermal sensitivity(2.18%/K at 298 K)is attained for the former in the first biological window(both the excitation and emission in the 800-965 nm range).The repeatability and temperature uncertainty are 99%and 1.2 K,*** nanothermometers are biocompatible with human MnT-1 melanoma and haCaT cells for 24 h of exposure and nanoparticle concentration up to 0.400 mg/ml,showing their potential for applications in nanomedicine,e.g.,intracellular imaging and temperature mapping.

关键词： Gd2O3 nd3^+-doped nanoparticles luminescent nanothermometry Thermal sensitivity Cytotoxicity of nanoparticles Rare earths

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

Systematic study of the dependence of magnetic and structural properties of nd2Fe14B powders on the average particle size

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journal of Rare Earths 2020年第9期38卷 961-968,I0002页

作者： j.F.Durán Perdomo G.A.Pérez Alcázar h.D.Colorado j.A.Tabares l.E.Zamora j.j.S.Garitaonandia Department of Physics University of ValleA.A.25360 CaliColombia Applied Physics II Department Basque Country University48080 BilbaoSpain

A systematic study of the magnetic and structural properties dependence on the particle size was *** this,commercial ndFeB powder was separated into five different mean particle sizes using ***,from the original powder,eleven samples were also produced by mechanical milling assisted by surfactant,using various milling times.A total of sixteen samples were studied by scanning electron microscopy(SEM),X-ray diffraction(XRD),vibrating sample magnetometry(VSM),and Mdssbauer spectrometry(MS).The particle sizes of the samples vary from the micrometer to the nanometer *** crystallite size decreases with decreasing particle *** result indicates that the nd2Fe14B phase is found in all the samples,and the presence of this phase is also corroborated by MS using six sextets for fitting their spectra,with an additional singlet corresponding to the nd1.1Fe4B4 *** mean hyperfine magnetic field increases with increasing particle size because the magnetic dipolar interaction between the magnetic moment of the particles increases with particle *** the VSM measurements the magnetic energy density(Bh)max values were calculated for different particle sizes,and their maximum value of 34.45 MGOe is obtained for the sample with the particle size of 60μm.

关键词： hard magnetic material XRD Mossbauer spectrometry Magnetization Particle size Rare earths

A COMPUTATIOnAl APPROACh FOR OPTIMAl COnTROl SYSTEMS GOVERnED BY PARABOlIC VARIATIOnAl InEQUAlITIES

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journal of Computational Mathematics 2003年第6期21卷 815-824页

作者： n.h.Sweilam l.F.Abd-Elal Department of Mathematics Faculty of Science Cairo University Giza-EgyptDepartment of Mathematics Faculty of Science Cairo University Giza-Egypt

Iterative techniques for solving optimal control systems governed by parabolic varia-tional inequalities are presented. The techniques we use are based on linear finite elements method to approximate the state equations and nonlinear conjugate gradient methods to solve the discrete optimal control problem. Convergence results and numerical experiments are presented.

关键词： Parabolic variational inequalities finite elements method nonlinear conjugate gradient methods.

A novel approach to enhance decrepitation temperature and reducibility of ultrafine iron ore concentrate pellets

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journal of Iron and Steel Research International 2024年第11期31卷 2622-2632页

作者： B.l.Wen Z.h.Fan j.X.li D.l.liu j.l.Yang School of Metallurgical Engineering Anhui University of TechnologyMa'anshan 243032AnhuiChina jianlong(liaoning)Energy Saving and Environmental Protection

Utilizing ultrafine iron ore concentrate for pellet production can expand domestic iron ore resources in China and promote the utilization of low-grade ***,a challenge arises with the low decrepitation temperature and reducibility in the preparation process of ultrafine iron ore concentrate *** address the challenge,a novel approach was proposed,which incorporated straw powder as an additive to enhance pellet porosity,thereby improving the decrepitation temper-ature and reducibility of ultrafine iron ore concentrate *** effect of varying proportions of straw powder(0.0-2.0%)on the characteristics of ultrafine iron ore concentrate pellets was *** indicate that at a 2.0%straw powder ratio,pellet decrepitation temperature notably rises from 380 to 540℃,while the reducibility index escalates from 25.7%to 48.1%.nevertheless,the addition of straw powder results in diminished drop strength,compressive strength of green pellets,and cold crushing strength of fired *** addition,enhanced pellet reducibility leads to exacerbated reduction swelling index and reduction degradation *** these effects,all parameters remain within an acceptable range.

关键词： Ultrafine iron ore concentrate:Straw powder Green pellet quality Decrepitation temperature:Metallurgical property

hopf-flip bifurcation of high dimensional maps and application to vibro-impact systems

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Acta Mechanica Sinica 2005年第4期21卷 402-410页

作者： jianhua Xie Wangcai Ding E.h. Dowell l. n. Virgin Department of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China School of Mechanical Engineering Lanzhou Jiaotong UniversityLanzhou 730070 China School of Engineering.Duke University. Durham NC27708-0300USA

This paper addresses the problem of hopf-flip bifurcation of high dimensional maps. Using the center manifold theorem, we obtain a three dimensional reduced map through the projection technique. The reduced map is further transformed into its normal form whose coefficients are determined by that of the original system. The dynamics of the map near the hopf-flip bifurcation point is approximated by a so called “time-2τ^2 map” of a planar autonomous differential equation. It is shown that high dimensional maps may result in cycles of period two, tori T^1 （hopf invariant circles）, tori 2T^1 and tori 2T^2 depending both on how the critical eigenvalues pass the unit circle and on the signs of resonant terms＇ coefficients. A two-degree-of-freedom vibro-impact system is given as an example to show how the procedure of this paper works. It reveals that through hopf-flip bifurcations, periodic motions may lead directly to different types of motion, such as subharmonic motions, quasi-periodic motions, motions on high dimensional tori and even to chaotic motions depending both on change in direction of the parameter vector and on the nonlinear terms of the first three orders.

关键词： Maps Vibro-impact dynamics hopf-flip bifurcation Torus Chaos

healing Process of Casting Pores in a ni-based Superalloy by hot Isostatic Pressing

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journal of Materials Science & Technology 2015年第11期31卷 1151-1157页

作者： X.G.Zheng Y.-n.Shi l.h.lou Shenyang national laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Superalloy Division Institute of Metal Research Chinese Academy of Sciences

hot isostatic pressing （hIP） with a pressure of 180 MPa at a temperature of 1170 ℃ was introduced to an investment cast ni-based superalloy （Mgl） turbocharger blade to explore the healing process of casting pores generated during investment casting. Optical micrograph and scanning electron naicroscopy （SEM） observations indicate that eutectic pores are the main cast defects in the as-cast blade before hIP. These pores normally locate at the solidification front of γ/γ＇ eutectic with a size of a few micrometers to a few tens of micrometers. After hIP for 4 h, most of the pores were closed. Based on phase characteristics, these pores were healed by the formation of γ matrix with finer and irregular-shaped γ＇ precipitates. healing interface can be easily distinguished by SEM. line scan by using energy dispersive X-ray spectroscopy （EDS） reveals a much higher Ti and Al concentration in the healing interface. It is proposed that solute diffusion toward the casting pores during hIP results in the formation of γ, and the much higher concentration of γ＇-forming elements Al and Ti near the healing interface contributes to the precipitation of γ＇ in the healed region in the succeeding cooling process after hIP.

关键词： Superalloy hot isostatic pressing (hIP) healing

STUDY OF ThE X70 PIPElInE STEEl CORRODInG In 3.0wt% naCl SOlUTIOn USInG ElECTROChEMICAl IMPEDAnCE SPECTROSCOPY TEChnIQUE

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Acta Metallurgica Sinica(English letters) 2004年第6期17卷 907-911页

作者： l.j.Zhang Z.Zhang F.h.Cao j.Q.Zhang j.M.Wang C.n.Cao DepartmentofChemistry ZhejiangUniversityHangzhou310027China DepartmentofChemistry ZhejiangUniversityHangzhou310027China／／ StateKeyLaboratoryforCorrosionandProtectionofMetalsInstituteofMetalResearchTheChineseAcademyofSciencesSlaenyang110016China

The corrosion process of the X70 pipeline steel in 3.0wt% naCl solution were studied using polarization method, and the chronological characteristics during the entire polarization plot were investigated in detail using EIS technique. In the active region of X70 steel, such as 20mV potential bias applied on open circuit potential (OCP), the impedance spectra was comprised of three parts: a high-frequency capacitive loop, a middle-frequency capacitive loop and a low-frequency inductive component. When positive polarization potential increased, the capacitive loops at high and middle frequency range merged, and the inductive component at low frequency shrunk. At high positive polarization potential bias (500-800mV vs. OCP), the high-frequency capacitive loop and the low-frequency inductive loop exhibited as disheveled points due to the synergism of the inhomogeneity of the corroding material and the localized corrosion. The results were fitted utilizing the equivalent circuits to simulate the impedance spectra and to interpret the electrochemical features shown during the experiments.

关键词： X70 pipeline steel corrosion polarization EIS