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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of Materials Processing
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Journal DOI :
The Korean Society for Technology of Plasticity
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Volume & Issues
Volume 9, Issue 6 - Nov 2000
Volume 9, Issue 5 - Oct 2000
Volume 9, Issue 4 - Aug 2000
Volume 9, Issue 3 - Jun 2000
Volume 9, Issue 2 - Apr 2000
Volume 9, Issue 1 - Feb 2000
Volume 6, Issue 1 - 00 2000
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Dislocation Movement around an Inclusion during Plastically-Accommodated Creep at High Temperatures
Eiichi Sato ; Kazuhiko Kuribayashi ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 1~1
Abstract Plastically accommodated creep in an inclusion bearing material (particle-or discontinuous fiber-reinforced metal matrix composite) without any interfacial relaxation mechanisms has been examined. For a material with an elastic-viscoplastic matrix, the non-uniform strain rate in steady state creep is derived using Eshelby's solution for elastic strain outside an inclusion. The obtained creep strain increment is impotent and does not generate any additional internal stress. During this creep deformation, a dislocation comes in from one direction and goes out in another direction, so that no dislocation nor internal stress but a heterogeneous plastic strain remains in the material. The concrete trajectory of the dislocations climbing over a cylindrical inclusion is calculated and illustrated.
Shape Change of Liquid Particles Embedded in a Solid Matrix Caused by Plastic Deformation of a Cu-B₂O₃Alloy
Susumn Onaka ; Masaharu Kato ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 7~7
A copper alloy containing amorphous B₂O₃dispersed particles is made by internal oxidation of a dilute Cu-B solid-solution alloy. Although the B₂O₃ particles behave as plastically non-deformable particles at room temperature, these become liquid particles in the solid Cu matrix at high temperatures. Cu single crystals containing the B₂O₃ particles are tensile tested at high temperatures. The shape change of the liquid particles due to the plastic deformation of the Cu matrix is observed with electron imcroscopy. The occurrence of relaxation by the diffusion of the Cu atoms along the Cu/B₂O₃ interface affects the shape change. The kinetics of the diffusional relaxation is discussed on the basis of the results of observations of the particle shape.
The Effect of Mn on the Mechanical Behavior of Al Alloys
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 13~13
Manganese has been known to be an alloying element of Al alloys that contributes to uniform deformation. Recently, it was found that as the manganese content increases over 0.5 wt.% in such aluminum alloys as the 6000, and 7000 series alloys, both yield and ultimate tensile strength increase significantly without decreasing ductility. The added manganese forms a manganese dispersoid of
Mn. This dispersoid has an incoherent structural relationship with respect to the matrix, FCC, in retarding the motion of dislocations that increase strength. Once the dislocation is blocked by the dispersoid, it tends to change the slip system by means of cross-slip. This cross-slip allows the deformation to maintain uniformly good ductility. TEM observation has proven the above mentioned activities of dislocation by analyzing the characters of the dislocations around and away from the dispersoids. Adding manganese to aluminum alloys not only enhances tensile strength but also significantly improves low-cycle fatigue resistance. Corrosion resistance is also measurable improved by the addition of manganese. After extrusion, the recrystallization is also retarded so that a very small grain size is maintained, contributing to an improvement in the mechanical properties.
Alloy Design of Intermetallic Dispersion Strengthened Aluminum Systems by Mechanical Alloying for High Temperature Applications
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 17~17
Good interfacial bonding between the matrix and the second phase is very important and may be guaranteed by the low lattice mismatch between them. In this study, trialuminide intermetallics such tetragonal
with Al₃M (M=Ti, V, Zr) or cubic Ll₂ with
were chosen as second phases to be dispersed on the basis of MEAM (Modified Embedded Atom Method) simulations. Specific compositions were determined based on thermodynamic calculations. Alloys were mechanically alloyed using Al powders and intermetallic powders that were separately fabricated. Hot pressed samples under vacuum analyzed in terms of phase formation during heat treatment and were tested in compression at room temperature and 693K. Specimens showed enhanced strength with a yield strength of 800-920MPa at room temperature and 190-260MPa at 693K. Observation of no phase change during heat treatment indicated high thermal stability of the microstructure.
Fabrication of Al Alloys Reinforced with AIN Particles Formed by In-Situ Reaction
이곤배 ; 심호섭 ; 허성우 ; 조수연 ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 25~25
The tensile properties and microstructures of Al alloys reinforced with AIN particles formed by in-situ reaction under a nitrogen atmosphere were analyzed. It was found that AIN particle layers formed on the surface of the Al particles in the powder bed, which replaced the Mg₃N₂ coated layers through the reaction, Mg₃N₂+2Al→2AIN+3Mg. The tensile strength and 0.2% offset yield strength in the control alloys were significantly greater than those in commercial alloys. This increase was due to the fine AIN particles formed by the above in-situ reactions of the Mg₃N₂ formation and its decomposition into AIN.
Load Transfer Mechanism and Mechanical Properties of SiCw/Al Metal Matrix Composites
Ryu, Ho J. ; Hong, Soon H. ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 33~33
The load transfer mechanism and mechanical properties of SiC whisker reinforced aluminum matrix composites were investigated. A generalized shear-lag model was proposed to analyze the effects of the aspect ratio, misorientation angle and volume fraction of SiC whisker on the mechanical properties of SiCw/Al composites. A new concept on effective aspect ratio was suggested, combining the effects of aspect ratio and alignment of whiskers, to calculate the effective stress acting on the aluminum matrix in SiCW/Al composites. The magnitude and anisotropy of the yield strength of the SiCw/2124Al composite can be estimated more accurately by substituting the average aspect ratio with the effective aspect ratio based on the generalized shear-lag model. The SiCw/2124Al composite with the largest effective aspect ratio showed the lowest minimum creep rate which decreased with increasing effective aspect ratio of SiC whisker, but were found to be almost similar under the same effective stress acting on the Al matrix. It is suggested that the role of SiC whisker is to improve the mechanical properties by reducing the effective stress acting on the Al matrix in the SiCw/Al metal matrix composite.
Development of Crystallographic Texture during Processing of Some Aluminide Based Aerospace Materials
R. K. Ray ; Satyam Suwas ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 39~39
Because of their lower specific weights, remarkably high strength and improved oxidation resistance, the aluminide-based intermetallic compounds are the candidates for substituting the rather heavy superalloys, at present used in compressors and turbines of aircraft engines. The ordered intermetallic compounds based on Ni₃Al and Ti₃Al have stimulated much interest due to their attractive and somewhat unusual properties. Thermomechanical processing constitutes an important route for forming these materials into suitable shapes for various applications. The processing route also influences the texture of the product, which in turn dictates the final properties. The present work summarises the evolution of textures during thermomechanical processing involving cold / hot rolling and subsequent annealing of a two phase Ni₃Al base and a two phase Ti₃Al base alloy.
Effects of Texture on the Etching Property of Fe-36% Ni Invar Sheets
Park, N. J. ; Kim, S. M. ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 51~51
In order to make a high quality color cathode ray tube, the influence of the texture on the etching property of an invar (Fe-36%Ni) shadow mask sheet has been studied. For the etching property, new values (
- value) are presented which are estimated with the intensity of the inverse pole figure for the normal direction of the sheet. Furthermore, for the decision of the etching property, RD-values which are calculated with ODF are suggested. A good etching property is obtained when the RD-value is more than 2.
Characterization of the Defect Found in Gold Decoration Layer of Bone China
Yoon, C. S. ; Im, D. H. ; Kim, C. K. ; Chung, Y. C. ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 57~57
We investigated the microstructure of the gold decoration layer of bone china to pinpoint the cause of the gold cracking occurring in the process of high quality bone china manufacturing. Through the cross-sectional TEM (transmission electron microscope) analysis it has been observed that SnO₂ crystals from the matting agent that lies underneath the gold have undergone abnormal growth. As the few SnO₂ crystals under the gold grow excessively, the matting oxide bursts through the gold layer resulting in the gold cracking in the bone china tableware. It is also found that the defects in the glossy gold area cause more serious detriment to the quality of the gold layer than do those in the matt gold area. From this study, we conclude that the control of the size distribution of SnO₂ crystals is very important to keep high quality in the gold layer of bone china.
Interfacial Characteristics and Magnetoresistive Properties of Reactively Sputtered Fe-Al₂O₃-Co Magnetic Tunnel Junctions
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 63~63
Magnetic tunnel junctions (MTJs) comprised of two magnetic metal layers separated by a thin insulating oxide layer have been prepared by rf sputtering onto thermally oxidized (100) silicon wafers at room temperature. The magnetic layers with thickness of ∼50 nm consisted of thin films of Fe and Co, and the material for the oxide barriers with thickness of ∼10 nm was Al₂O₃. The barriers were prepared by rf reactive sputtering from pure metallic Al sources in mixed argon-oxygen atmospheres. Pt/Al₂O₃/Pt tunnel junctions were also prepared to characterize the reactively sputtered Al₂O₃barriers. Auger electron spectroscopy was used in this study to characterize the interfacial structures of the junctions. A distinct nonlinear transport behavior, even at 300K, in Pt/Al₂O₃/Pt junctions has revealed that the reactively sputtered Al₂O₃ is a good barrier material for tunnel junctions. Magnetoresistive measurements were made perpendicular to the film plane on the MTJs for in-plane applied magnetic fields and the results were discussed in connection with interfacial structures of the MTJs.
Thermoelectric Properties of the 0.05 wt.% SbI₃-Doped n-Type Bi₂(
)₃ Alloy Fabricated by the Hot Pressing Method
이선경 ; 오태성 ; 현도빈 ; 황창원 ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 67~67
Thermoelectric properties of the 0.05 wt.% SbI₃-doped n-type Bi₂(
)₃ alloy, fabricated by hot pressing at temperatures ranging from 350℃ to 550℃, were characterized. The electron concentration of the alloy decreased as the hot pressing temperature increased due to the annealing-out of the excess Te vacancies. When hot pressed at 350℃, a figure-of-merit of 0.75×
/K was obtained due to the low Seebeck coefficient of -145 μV/K and relatively high electrical resistivity of 2.05 mΩ-cm. Upon increasing the hot pressing temperature, however, the figure-of-merit was improved mainly due to the increase of the Seebeck coefficient. A maximum figure-of-merit of 2.1×
/K was obtained by hot pressing at 550℃.
Preparation of Tungsten Powder by the Combustion of CaWO₄/Mg
Lee, J. H. ; Jung, J. C. ; I. P. Borovinskaya ; C. W. Won ; V. I. Vershinnikov ;
Transactions of Materials Processing, volume 6, issue 1, 2000, Pages 73~73
Tungsten powder was prepared by a Self-Propagating High-Temperature Synthesis(SHS) Process of a CaWO₄-Mg mixture. Mg vapor was discovered to significantly affect such combustion parameters as the combustion temperature(
), the combustion velocity(U), the relative mass change(Δm) and the relative elongation(Δh) of the sample. These effects could be reduced by decreasing the internal Ar pressure, sample density and reducing agent content. The oxygen content in tungsten was decreased by using 5% excess Mg; the carbon content was diminished when the combustion process occurred under
=0.1 MPa. The MgO and CaO in the product was leached with an HCl solution. Such parameters as combustion temperature(
), U, Δm, and milling time(τ) were found to affect the tungsten particle size and morphology.