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International journal of Minerals,Metallurgy and Materials 2011年第3期18卷 260-269页

作者： j. Ndalamo A.f. Mulaba-Bafubiandi B.B. Mamba Department of Chemical Technology University of Johannesburg Department of Extraction Metallurgy University of Johannesburg

The leaching of cobalt from four-mixed Co-Cu oxidized ores containing cobalt at levels ranging from 0.5wt% to 34wt% was studied and the results has been reported. Conventional dissolution of these oxidized Co-Cu ores with diluted H2SO4 and SO2 as a reducing agent resulted in a substantial improvement in the solution based recovery of cobalt. UV/visible spectroscopic analysis of the leached solu-tions indicated that the increased cobalt content in the solution was a result of flushing the acidified cobalt leaching solution with SO2. fur-thermore, UV/visible spectroscopy confirmed that as SO2 was flushed into the acidified leaching solution, Co3＋ bearing minerals were re-duced to the readily soluble Co2＋ bearing minerals, and this resulted in the increase of total cobalt in the collected solution. The mechanism of the reduction of Co3＋ to Co2＋ bearing minerals when SO2 is flushed during the leaching of mixed Co-Cu oxidized ores, including the stability trends of Co3＋, Co2＋, and Cu2＋ complexes, as shown by their UV/visible spectra, are also discussed.

关键词： cobalt metallurgy dissolution leaching reaction kinetics spectroscopic analysis

New methods to find solutions and analyze stability of equilibrium of nonholonomic mechanical systems

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Acta Mechanica Sinica 2018年第6期34卷 1136-1144页

作者： j.Chen Y.X.Guo f.X.Mei School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China School of Physics Liaoning UniversityShenyang 110000China

A large proportion of constrained mechanical systems result in nonlinear ordinary differential equations,for which it is quite difficult to find analytical *** initial motions method proposed by Whittaker is effective to deal with such problems for various constrained mechanical systems,including the nonholonomic systems discussed in the first part of this paper,where in addition to differential equations of motion,nonholonomic constraints *** final equations of motion for these systems are obtained in the form of corresponding power ***,an alternative,direct method to determine the initial values of higher-order derivatives(q)0,(q)0,…is proposed,being different from that of *** second part of this work analyzes the stability of equilibrium of less complex,nonholonomic mechanical systems represented by gradient *** discuss the stability of equilibrium of such systems based on the properties of the gradient *** advantage of this novel method is its avoidance of the difficulty of directly establishing Lyapunov functions aimed at such unsteady nonlinear ***,these theoretical considerations are illustrated through four examples.

关键词： Nonholonomic system Initial motions Gradient system Lyapunov function Stability

Operator Splitting for Three-Phase flow in Heterogeneous Porous Media

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Communications in Computational Physics 2009年第6期6卷 72-84页

作者： E.Abreu j.Douglas f.furtado f.Pereira Instituto Nacional de Matematica Pura e Aplicada RJ 22460-320Brazil Department of Mathematics Purdue UniversityWest LafayetteIN 47907-1395USA Department of Mathematics University of WyomingLaramieWY 82071-3036USA Department of Mathematics and School of Energy Resources University of WyomingLaramieWY 82071-3036USA

We describe an operator splitting technique based on physics rather than on dimension for the numerical solution of a nonlinear system of partial differential equations which models three-phase flow through heterogeneous porous *** model for three-phase flow considered in this work takes into account capillary forces,general relations for the relative permeability functions and variable porosity and permeability *** our numerical procedure a high resolution,nonoscillatory,second order,conservative central difference scheme is used for the approximation of the nonlinear system of hyperbolic conservation laws modeling the convective transport of the fluid *** scheme is combined with locally conservative mixed finite elements for the numerical solution of the parabolic and elliptic problems associated with the diffusive transport of fluid phases and the pressure-velocity *** numerical procedure has been used to investigate the existence and stability of nonclassical shock waves(called transitional or undercompressive shock waves)in two-dimensional heterogeneous flows,thereby extending previous results for one-dimensional flow *** experiments indicate that the operator splitting technique discussed here leads to computational efficiency and accurate numerical results.

关键词： Operator splitting three-phase flow heterogeneous porous media central differencing schemes mixed finite elements

fatigue Properties Improvement of Low-Carbon Alloy Axle Steel by Induction Hardening and Shot Peening:A Prospective Comparison

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1343-1356页

作者： G.C.Chu f.Z.Hu X.j.jin Y.Zhang Q.Wang j.P.Hou Z.f.Zhang Shi-Changxu Innovation Center for Advanced Material Institute of Metal ResearchChinese Academy of SciencesShenyang 110016.China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Manshan Iron and Steel Co. Ltd.Maanshan 243000China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Baowu Group Masteel Rail Transit Materials Technology Company Limited Maanshan 243000China

fatigue fracture is the major threat to the railway axle, which can be avoided or delayed by surface strengthening. In this study, a low-carbon alloy axle steel with two states was treated by surface induction hardening and shot peening, respectively, to reveal the mechanism of fatigue property improvement by microstructure characterization, microhardness measurement, residual stress analysis, roughness measurement, and rotary bending fatigue tests. The results indicate that both quenching and tempering treatment can effectively improve the fatigue properties of the modified axle steel. In addition, induction hardening can create an ideal hardened layer on the sample surface by phase transformation from the microstructure of ferrite and pearlite to martensite. By comparison, shot peening can modify the microstructure in surface layer by surface severe plastic deformation introducing a large number of dislocation and even cause grain refinement. Both induction hardening and shot peening create compressive residual stress into the surface layer of axle steel sample, which can effectively reduce the stress level applied to the metal surface during the rotary bending fatigue tests. On the whole, the contribution of induction hardening to the fatigue life of axle steel sample is better than that of the shot peening, and induction hardening shows obvious advantages in improving the fatigue life of axle steel.

关键词： Surface strengthening Induction hardening Shot peening Axle steel fatigue property improvement

Remarkably high fracture toughness of HfNbTaTiZr refractory high-entropy alloy

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journal of Materials Science & Technology 2022年第28期123卷 70-77页

作者： X.j.fan R.T.Qu Z.f.Zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nano Science and Technology Institute University of Science and Technology of ChinaSuzhou 215132China

High-entropy alloys(HEAs)with face-centered cubic(fCC)phase such as CoCrfeMnNi or CoCrNi generally exhibit ultra-high fracture toughness but relatively low *** contrast,body-centered cubic(BCC)HEAs often display higher strengths,but the few reports on fracture toughness measurement demonstrate low toughness *** we show that the BCC HfNbTaTiZr refractory HEA,which possesses a combination of high strength,good tensile ductility and excellent high-temperature properties,also exhibits a remarkably high fracture *** using the"single specimen"compliance method for j-integral measurement according to the ASTM E1820–17 standard,its fracture toughness K_(jIC)was experimentally determined to be 210 MPa m^(1/2),which renders this HEA among the toughest metallic *** excellent damage tolerance makes the HEA promising for applications as high-temperature structural materials such as in aerospace field.

关键词： High-entropy alloys BCC structure fracture toughness j-integral

Thermal and structural properties of Nd2O3-doped calcium boroaluminate glasses

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journal of Rare Earths 2016年第5期34卷 521-528页

作者： j.D.M.Dias G.H.A.Melo T.A.Lodi j.O.Carvalho P.f.facanha filho M.j.Barboza A.Steimacher f.Pedrochi Centro de Ciencias Sociais Saude e TecnologiaUniversidade Federal do Maranhao-Imperatriz MA Instituto federal de Educaceo Ciencia e Tecnologia do Maranhao Campus Imperatriz-Imperatriz-MA Instituto federal de Educacao Ciencia e Tecnologia do Tocantins Campus Araguaina-Araguaina-TO

Nd^3＋ doped CaO-Al2O-B2O3-Caf2 glasses were prepared by conventional melt-quenching technique,and their structural and thermal properties were *** amorphous nature of these samples was confirmed by X-ray diffraction（XRD）.The measured density showed an increase with Nd2O3 doping,at the expense of *** spectra presented changes with addition of Nd2O3,which indicated that the network structure of the glasses studied presented various borate groups,such as tetraborates,metaborates,ortho-borates and pyroborates *** N4 values calculated from fTIR spectra revealed that incorporation of Nd2O3 into glass network converted the structural units from BO4 to *** the analysis of DTA curves,we verified that Tg increased with the addition of Nd2O3;it was similar to the behavior caused by modifier oxides in the structure of borate *** that,the calculated glass stability Tx–Tg for doped samples presented a decrease if compared to the undoped *** heat and thermal conductivity did not present significant changes with Nd2O3 concentration,up to 2.30 mol.%.The results of density,DTA,Raman and fTIR reinforced the idea that Nd2O3 acted as network modifier.

关键词： Nd^3+ Nd^3+ doped glass borate glasses glass structure thermal properties rare earths

NUMERICAL SIMULATION Of COLUMNAR TO EQUIAXED TRANSITION fOR DIRECTIONALLY SOLIDIfIED Ti-44Al ALLOY

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Acta Metallurgica Sinica(English Letters) 2008年第2期21卷 146-156页

作者： K.f. Wang j.j. Guo G.f. Mi C. Y. Li H.Z. fu School of IVlaterials Science and Engineering Henan Polytechnic University Jiaozuo 454100 China School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

Solute diffusion controlled solidification model was applied to simulate the columnar to equiaxed transition （CET） during directional solidification of Ti-44Al alloy. The simulation results show that the solutal interactions from growing equiaxed grains play an important role on CET. The effects of the applied thermal gradient and pulling velocity, the equiaxed seed spacing and nucleation undercooling on the CET are investigated in the present simulation. The simulated results indicated that the columnar branch spacing depends not only on the thermal gradient and the pulling velocity, but also on number of the seeds. A spacing adjustment can occur through initiation of seeds that develop into new columnar grains. The dependence of the CET on the thermal gradient and pulling velocity, qualitatively agrees with the analytical CET model of Hunt,

关键词： Ti-44Al alloy Directional solidification columnar to equiaxedtransition (CET) Numerical simulation

Effects of rejuvenation heat treatment on microstructure and creep property of a Ni-based single crystal superalloy

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journal of Materials Science & Technology 2021年第1期60卷 206-215页

作者： K.j.Tan X.G.Wang j.j.Liang j.Meng Y.Z.Zhou X.f.Sun Superalloys Division Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Department of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

Both surface and internal microstructures of a second-generation Ni-based single crystal(SX) superalloy were studied after creep and rejuvenation heat treatment(RHT).It is indicated that the microstructures,such as the dislocation network,the γ phase and the γ' phase,can be recovered to those after the standard heat treatment(SHT).It is found that RHT affected zone(RAZ) formed at the surface is composed of theγ'-free layer,the transition layer and the recrystallization(RX),which are less than 20 μm in depth *** depth of the RAZ doesn't affect the properties of the *** morphology of γ' phase at the RAZ is related to the composition of the *** average creep life after RHT is close to the average life after *** is concluded that RHT could effectively repair SX parts and increase the total life of the sample after a damage by creep.

关键词： Superalloys Rejuvenation heat treatment Microstructure Creep property

Transient vibration of thin viscoelastic orthotropic plates

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Acta Mechanica Sinica 2011年第1期27卷 98-107页

作者： j.Soukup f.Vale j.Volek j.Skoilas jan Evangelista Purkyně University in ústí nad Labem Faculty of Production Technology and Management Department of Machinery and Mechanics Centre of Material Diagnostics Institute of Thermomechanics AS CR v.v.i Academy of Sciences Czech Republic

This article deals with solutions of transient vibration of a rectangular viscoelastic orthotropic thin 2D plate for particular deformation models according to flu¨gge and *** linear model,a general standard viscoelastic body,of the rheologic properties of a viscoelastic material was *** time and coordinate curves of the basic quantities displacement,rotation,velocity,stress and deformation are *** results obtained by an approximate analytic method are compared with numerical results for 3D plate generated by fEM application and with experimental investigation.

关键词： Transient vibration thin plate Orthotropic General viscoelastic standard solid.

PRECIPITATION BEHAVIOR Of M_(2)N IN A HIGH-NITROGEN AUSTENITIC STAINLESS STEEL DURING ISOTHERMAL AGING

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 95-101页

作者： f. Shi L.j. Wang W.f. Cui C.M. Liu School of Materials ＆ Metallurgy Northeastern UniversityShenyang 110004 China

The precipitation behavior of M2N and the microstructural evolution in a Cr-Mn austenitic stainless steel with a high nitrogen content of 0.43mass% during isothermal aging has been investigated using optical microscopy （ OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The aging treatments have led to the decomposition of nitrogen supersaturated austenitic matrix through discontinuous cellular precipitation. The precipitated cells comprise alternate lamellae of M2N precipitate and austenitic matrix. This kind of precipitate morphology is similar to that of pearlite. However, owing to the non-eutectoidic mechanism of the reaction, the growth characteristic of the cellular precipitates is different from that of pearlite in fe-C binary alloys. M2N precipitate in the cell possesses a hexagonal crystal structure with the parameters a = 0.4752nm and c = 0.4429nm, and the orientation relationship between the M2V precipitates and austenite determined from the SADP is [01^-10]M2N//[101]γ, [2^-1^-10]M2N//[010]γ.

关键词： austenitic stainless steel high nitrogen microstructureisothermal aging precipitation