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Effect of Electromagnetic Frequency on Microstructures of Continuous Casting Aluminum Alloys

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Journal of Materials Science & Technology 2002年第5期18卷 401-403页

作者： BeijiangZHANG GuiminLU 等 KeylaboratoryofElectromagneticProcessingofMaterials MinistryofEducationSchoolofMaterialsandMetallurgyNortheasternUniversityShenyang110004China KeylaboratoryofElectromagneticProcessingofMaterials M

The relationship between electromagnetic frequency and microstructures of continuous casting aluminum alloys was studied. 7075 aluminum alloy ingot of 100 mm in diameter was produced by electromagnetic continuous casting process, the microstructures of as-cast ingot was examined by scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). The results showed that electromagnetic frequency greatly influenced segregation and microstructures of as-cast ingot, and product quality can be guaranteed by the application of a proper frequency. Electromagnetic frequency plays a significant role in solute redistribution; low frequency is more efficient for promoting solution of alloying elements.

关键词： Continuous casting Aluminum alloy Microstructure. Electromagnetic casting

Numerical Simulations of Equiaxed Dendrite Growth Using Phase Field Method

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Journal of Materials Science & Technology 2002年第1期18卷 51-53页

作者： YutuoZHANG WeichengPANG 等 InstituteofMetalResearch TheChineseAcademyofScienceShenyang110016China schoolofmaterialsandmetallurgy NortheasternUniversityShengyang110006China

The phase field method can be used to perform realistic numerical experiments on equiaxed dendrite growth in a metallic system. The equiaxed dendrite evolution during the solidification of a pure material was numerically simulated using the phase field model. The equiaxed dendrite growth in a two-dimensional square domain of undercooled melt (nickel) with four-fold anisotropy was simulated. The phase field model equation was solved using the explicit finite difference method on a uniform mesh. The formation of various equiaxed dendrite patterns was shown by a series of simulations, and the effect of anisotropy on equiaxed dendrite morphology was investigated.

关键词： Phase field method Dendritic growth Numerical simulation

A Coprecipitation Coating Synthesis of SiC/YAG Composites

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Journal of Materials Science & Technology 2004年第3期20卷 323-326页

作者： NingZHANG HongqiangRU XudongSUN QingkuiCAI schoolofmaterialsandmetallurgy NortheasternUniversityShenyang110004China MaterialsDepartment ShenyangUniversityShenyang110044China

The α-SiC in 0.5μm size powders were coated with Al_2O_3 and Y_2O_3 by a coprecipitation coating (CPC) method forfabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechanical mixing(MM) method for comparison. Two kinds of SiC/YAG composites were manufactured by pressureless sintering usingthe different powders, named CPC composite and MM composite thereafter respectively. It is shown that the CPCcomposite has the advantages of homogeneous distribution of YAG phase and of being sintered to high density ata low temperature, 100℃ lower than that of MM composite. The strength (573 MPa) and hardness (23.3 GPa) ofthe CPC composite are significantly higher than those (323 MPa and 13.5 GPa) of the MM composite, respectively.

关键词： Coprecipitation SiC/YAG composites Mechanical mixing method

Through Thickness Variation of Cross Shear Rolling Texture in Grain Oriented Silicon Steel

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Journal of Materials Science & Technology 2002年第6期18卷 519-521页

作者： GangLIU LiangZUO 等 ShenyangNationalLaboratoryforMaterialsScience InstituteofMetalReserachChineseAcademyofSciencesShenyang110016China schoolofmaterialsandmetallurgy NortheasternUniversityShenyang11

The texture inhomogeneity in cross shear rolled grain oriented Si steel was investigated by means of the through thickness texture analysis. For the chosen rolling reductions (55%, 66.5%) and mismatch speed ratios (1.0, 1.1, 1.3), the deformation textures in various thickness layers consist of three major components, i.e. strong γ-fiber, medium α-fiber and weak η-fiber, and they show an asymmetrical distribution throughout the thickness. The effect of reduction on the texture gradient is found to be more significant at and near the center layer; however, the effect of mismatch speed ratio is less important. In most cases, a strong {111} texture component appears in the subsurface layers, that may favour the formation of a sharp Goss texture during the subsequent annealing.

关键词： Cross shear rolling Grain oriented Si steel Deformation texture

FORMATION OF GRADIENT COATING OF Fe-BASED ALLOY WITH RARE EARTHS BY PLASMA SURFACING

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 713-718页

作者： L.J.Shang A.Q.Sun J.F.Chen C.M.Zhang Q.K.Cai CollegeofMaterialsScienceandEngineering ShenyangPolytechnicUniversityShenyang110023China schoolofmaterialsandmetallurgy NortheasternUniversityShenyang110004China

A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3, Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.

关键词： rare earth plasma surfacing Fe-base alloy microstructure graded coating

Corrosion Behavior of SiC_p/2024 Al Matrix Composites in 3.5 wt pct Sodium Chloride

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Journal of Materials Science & Technology 2002年第3期18卷 261-263页

作者： ChunlinHE ZhimingSHI 等 schoolofmaterialsandmetallurgy NortheasternUniversityShenyang110004China InstituteofMetalResearch ChineseAcademyofSciencesShenyang110016China

The influences of the volume fraction and the particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024Al metal matrix composites in aerated 3.5 wt pct NaCl aqueous solution were investigated. The electrochemical behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy, and the general corrosion behavior of the composite was studied further by immersion tests. The results showed that the pitting susceptibility was about the same for the composite and the alloy. The corrosion potential was also independent of the SiC phase. The corrosion resistance for the composite decreased as the volume fraction increased or the particle size decreased.

关键词： SiCp/2024Al matrix composites Corrosion Pitting

Technique of Aluminum Alloy Composite by Inversion Casting

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Journal of Materials Science & Technology 2002年第2期18卷 187-188页

作者： NaLI JinglinWEN 等 InstituteofMetalRetalResearch ChineseAcademyofSciencesShenyang110016China schoolofmaterialsandmetallurgy NortheasternUniversityShenyang110006China

The influence of the temperature of liquid aluminum alloy, the dipping time in liquid alloy and the thickness of base strips on the solidified layer was studied during the process of producing aluminum alloy composite strips used in automobile radiator with inversion casting. It is concluded that there is welding as well as diffusion of alloying elements between the base strip and the coating. Experiments have proved that the base strip/coating interface has a good bonding. 4343 and 3003 are used in the test.

关键词： Composite aluminum Antomobile radiator Inversion casting

A New Thermodynamic Calculation Method for Binary Alloys: Part I: Statistical Calculation of Excess Functions

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Journal of Materials Science & Technology 2002年第3期18卷 237-241页

作者： XingqiuCHEN P.Rogl 等 schoolofmaterialsandmetallurgy NortheasternUniversityShenyang110004China InstitutfuerPhysikalischeChemie UniversitaetWienWahringerstrαβe42A-1090WienAusria

The improved form of the calculation formula for the activities of the components in binary liquid and solid alloys has been derived based on the free volume theory considering excess entropy and Miedema's model for calculating the formation heat of binary alloys. A calculation method of excess thermodynamic functions for binary alloys has been established, and the formulas of integral molar excess properties and partial molar excess properties for solid ordered or disordered binary alloys have been developed. The calculated results are in good agreement with the experimental values. Ag-Pb, Fe-Mn, Ag-Au and Co-Pt are taken for example in the research and analysis.

关键词： Binary alloy Thermodynamic Excess functions Enthalpy

INFLUENCE OF TIN ON THE HOT DUCTILITY OF A LOW-CARBON STEEL

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Acta Metallurgica Sinica(English Letters) 2003年第6期16卷 478-482页

作者： Z.X.Yuan J.Jia A.M.Guo D.D.Shen S.H.Song J.Liu schoolofmaterialsandmetallurgy WuhanUniversityofScienceandTechnologyWuhan430081China ResearchInstituteofWuhanIron＆SteelCompany Wuhan430080China

The influence of tin on the hot ductility of a 0.15wt%C steel is investigated using a continuous-casting thermal simulator with three cooling rates. Tin can apparently deteriorate the hot ductility of the steel. Non-equilibrium grain boundary segregation of tin occurs during cooling and plays an important role in reducing the hot ductility of the steel. There is a critical cooling rate for the Sn segregation being between 5 and 20K/s.

关键词： hot ductility non-equilibrium segregation steel grain boundary impurity