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Study of the Interface between Steel Insert and Aluminum Casting in EPC

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Journal of Materials Science & Technology 2008年第1期24卷 60-64页

作者： K.h.Choe K.S.Park B.h.Kang g.S.Cho K.Y.kim K.W.Lee M.h.kim A.Ikenaga S.Koroyasu Advanced Material Processing Team Korea Institute of Industrial Technology IncheonKorea Department of Materials Engineering Korea University of Technology and Education ChoongnamKorea Department of Materials Science and Engineering Inha University IncheonKorea Department of Metallurgy and Materials Science graduate School of Engineering Osaka Prefecture UniversityOsakaJapan Department of Mechanical and Precision Systems Teiko University UtsunomiyaJapan

The effective surface treatment method for steel insert composited with Al base metal by expendable pattern casting （EPC） process and the bonding interface between steel insert and Al base metal were *** was found that Zn plating on steel insert was effective on improving the bonding property between steel insert and Al base metal in EPC *** is thought to promote the formation of diffusion *** almost none content of Zn was observed in the boundary which had been plated on the steel insert.A diffusion layer consisting of Al,Si and Fe was formed at the insert/alloy interface and its hardness was higher than the steel insert as matter of course Al base *** layer turned out to be intermetallic compounds of Al-Si-Fe *** pouring temperature promoted the diffusion of Fe into Al alloy,so Fe content in intermetallic layers increased at higher pouring *** layer nearest to steel disappeared due to applied pressure.

关键词： Expendable pattern casting Insert casting Intermetallic compound Al-Si-Fesystem

Design of small-area multi-bit antifuse-type 1 kbit OTP memory

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Journal of Central South University 2009年第3期16卷 467-473页

作者：李龙镇 LEE J h kim T h JIN K h PARK M h hA P B kim Y h Department of Electronic Engineering Changwon National University Department of Computer Science and Technology Yanbian University

A multi-bit antifuse-type one-time programmable （OTP） memory is designed, which has a smaller area and a shorter programming time compared with the conventional single-bit antifuse-type OTP memory. While the conventional antifuse-type OTP memory can store a bit per cell, a proposed OTP memory can store two consecutive bits per cell through a data compression technique. The 1 kbit OTP memory designed with Magnachip 0.18 μm CMOS （complementary metal-oxide semiconductor） process is 34% smaller than the conventional single-bit antifuse-type OTP memory since the sizes of cell array and row decoder are reduced. And the programming time of the proposed OTP memory is nearly 50% smaller than that of the conventional counterpart since two consecutive bytes can be compressed and programmed into eight OTP cells at once. The layout area is 214 μm× 327 μ,, and the read current is simulated to be 30.4 μA.

关键词： multi-bit OTP programming time antifuse memory data compression

Design of logic process based low-power 512-bit EEPROM for UhF RFID tag chip

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Journal of Central South University 2010年第5期17卷 1011-1020页

作者：金丽妍 LEE J h kim Y h Department of Electronic Engineering Changwon National University

A 512-bit EEPROM IP was designed by using just logic process based *** limit the voltages of the devices within 5.5 V,EEPROM core circuits,control gate(Cg) and tunnel gate(Tg) driving circuits,DC-DC converters:positive pumping voltage(VPP=4.75 V) ,negative pumping voltage(VNN=4.75 V) ,and VNNL(=VNN/2) generation circuit were *** addition,switching powers Cg high voltage(Cg_hV) ,Cg low voltage(Cg_LV) ,Tg high voltage(Tg_hV) ,Tg low voltage(Tg_LV) ,VNNL_Cg and VNNL_Tg switching circuit were supplied for the Cg and Tg driving ***,a sequential pumping scheme and a new ring oscillator with a dual oscillation period were *** reduce a power consumption of EEPROM in the write mode,the reference voltages VREF_VPP for VPP and VREE_VNN for VNN were used by dividing VDD(1.2 V) supply voltage supplied from the analog block in stead of removing the reference voltage generators.A voltage level detector using a capacitive divider as a low-power DC-DC converter design technique was *** result shows that the power dissipation is 0.34μW in the read mode,13.76μW in the program mode,and 13.66μW in the erase mode.

关键词： electrically erasable programmable read-only memory (EEPROM) logic process DC-DC converter ring oscillator sequential pumping scheme dual oscillation period radio frequency identification (RFID)

Effect of roll speed ratio on the texture and microstructural evolution of an FCC high-entropy alloy during differential speed rolling

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Journal of Materials Science & Technology 2022年第16期111卷 152-166页

作者： h.T.Jeong W.J.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

A very coarse-grained(335μm)Fe_(41)Mn_(25)Ni_(24)Co_(8)Cr_(2)high-entropy alloy with a single FCC phase was cold rolling to a 80%reduction in thickness using the differential speed rolling technique with various speed ratios(SRs)ranging between 1 and *** the SR was increased,the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear *** SR=4,the entire thickness of the sheet was covered with micro-shear bands,and ultrafine(sub)grains with a size of1.4μm were uniformly formed along the shear bands.A continuous dynamic recrystallization(CDRX)mechanism occurred during rolling,and a higher SR accelerated the CDRX *** conventional rolling(at SR=1),a brass{110}orientation texture with minor components of S{123}and Cu{112}orientations *** higher SRs,shear texture developed as the main type,while the development of rolling texture was *** microstructure at SR=4 obtained after annealing at973 K showed a fully recrystallized microstructure composed of a five times smaller grain size(4μm)with a higher intensity ofγfiber texture compared with that prepared by conventional *** samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after *** current results demonstrate that by using differential speed rolling with a high SR,one can achieve a significantly finer and more homogeneous microstructure,stronger shear texture,and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional *** strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening.

关键词： high entropy alloys Differential speed rolling Texture grain refinement Strength Severe plastic deformation

Microstructure tailoring of Al_(0.5)CoCrFeMnNi to achieve high strength and high uniform strain using severe plastic deformation and an annealing treatment

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Journal of Materials Science & Technology 2021年第12期71卷 228-240页

作者： h.T.Jeong W.J.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

Ultrafine-grained alloys fabricated by severe plastic deformation(SPD)have high strength but often poor uniform *** via high-ratio differential speed rolling(hRDSR)followed by an annealing treatment was applied to Al_(0.5)CoCrFeMnNi to design the microstructure from which both high strength and high uniform strain can be *** optimized microstructure was composed of an ultrafine-grained FCC matrix(1.7-2μm)with a high fraction of high-angle grain boundaries(61%-66%)and ultrafine BCC particles(with a size of 0.6-1μm and a volume fraction of8%-9.3%)distributed uniformly at the grain boundaries of the FCC *** the severely plastically deformed microstructure,the nucleation kinetics of the BCC phase was *** static recrystallization(CSRX)took place during the annealing process at 1273 *** of the BCC phase particles occurring concurrently with CSRX effectively retarded the grain growth of the FCC *** precipitation of the hard and brittleσphase was,however,*** annealed sample processed by hRDSR with the optimized microstructure exhibited a high tensile strength of over 1 gPa with a good uniform elongation of 14%-20%.These tensile properties are comparable to those of transformation-induced plasticity *** mechanisms of the severely plastically deformed alloy before and after annealing were identified,and each strengthening mechanism contribution was *** calculated results matched well with the experimental results.

关键词： high entropy alloys Severe plastic deformation Uniform ductility high strength Dual phase Annealing

grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe(41)Mn(25)Ni(24)Co8Cr2high entropy alloy

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Journal of Materials Science & Technology 2020年第7期42卷 190-202页

作者： h.T.Jeong W.J.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe(41)Mn(25)Ni(24)Co8 Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5μm),8.1μm and 590.2μ*** the temperature between 298 and773 K,the material with the large grain size of 590.2μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain *** material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%)due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement *** tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5μ*** deformation behavior of the Fe(41)Mn(25)Ni(24)Co8 Cr2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic *** activation energies for plastic flow for the materials with different grain sizes were similar as^199 kJ/*** predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation *** sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85%due to it

关键词： high entropy alloys grain size high temperature deformation mechanism Tensile behavior grain boundary sliding

Effects of grain size and Al addition on the activation volume and strain-rate sensitivity of CoCrFeMnNi high-entropy alloy

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Journal of Materials Science & Technology 2023年第12期143卷 242-252页

作者： h.T.Jeong W.J.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The activation volume(V∗)and strain-rate sensitivity exponent(m)of CoCrFeMnNi and Al_(0.5)CoCrFeMnNi high entropy alloys(hEAs)with various grain sizes(ranging between 2.4 and 356μm)were measured at different strain rates and strain levels at room *** the strain rate decreased,the plastic strain decreased,and the grain size increased,V∗*** enhanced solid-solution strengthening by addition of aluminum decreased V∗.The hassen plot was modified to capture the grain-size depen-dence of V∗by considering the grain-size dependence of the dislocation *** the plastic strain increased,the strain rate decreased,and the grain size decreased,m *** behavior of m could be quantitatively predicted by using equations derived for the grain-size-dependent V∗and flow *** difference in the grain-size dependence of m between conventional face centered cubic(FCC)metals and FCC hEAs over the nanograin size range could not be explained in terms of a relatively large hall-Petch slope of the FCC hEAs compared with that of the FCC conventional metals,but was explainable in terms of a substantially higher probability of activation of grain-boundary diffusion-controlled grain-boundary-sliding mechanism at nanograin sizes in the FCC conventional metals than in the FCC hEAs.

关键词： grain size high entropy alloys Activation volume Strain-rate sensitivity Solid solution

Prospects of huygens’ Metasurfaces for Antenna Applications

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Engineering 2022年第4期8卷 21-26页

作者： george V.Eleftheriades Minseok kim Vasileios g.Ataloglou Ayman h.Dorrah Department of Electrical and Computer Engineering University of TorontoTorontoON M5S 3G8Canada

*** In recent years,there has been an intense research effort by the international community in the field of“artificial”electromagnetic materials,or“metamaterials.”Metamaterials are engineered structures that induce a tailored arrangement of magnetic and electric dipole moments when excited by an incident electromagnetic *** certain conditions,such as when the comprising unit cells are sub-wavelength,metamaterials can be homogenized and described in terms of macroscopic constitutive parameters such as permeability,permittivity,and refractive index.A summary of the early work on“artificial dielectrics”can be found in Ref.[1].In the over 20-year-old field of metamaterials,the desired macroscopic parameters correspond to extreme properties such as negative permittivity,negative permeability,and a negative refractive *** the most recognized metamaterial is that which realizes a negative refractive index,originally demonstrated at microwaves and based on a unit cellmade out of a split-ring resonator and a wire[2].In the engineering community,a transmission-line approach was developed for implementing metamaterials with significant advantages,such as reduced transmission losses and wider operating bandwidths[3,4].

关键词： refractive arrangement artificial

Optimization Study of the Efficient Spindle

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Journal of Thermal Science 2008年第3期17卷 243-246页

作者： Y.D.kim D.h.Chun M.S.Kang h.D.kim Korea Textile Machinery Research Institute School of Textiles Yeungnam University School of Mechanical Engineering Andong National University

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package of cheese stacked on a spindle made of a perforated tube. Spindles up to now, have been designed without considering the characteristics of dyeing liquid, focusing only on the geometric configuration which cause many problems such as lack of level dyeing. To improve the level dyeing and find the appropriate spindle configuration for the most effective dyeing process, this study examines the spindle flow-field in detail, using a computational method. Flow characteristics inside the spindle have been investigated with varying in porosity, porous diameter and the velocity of the flow. The results show that the total pressure of the flow through the spindle is used to overcome body force. The characteristics of the flow from the porous spindle could also be observed. Based on the results from this study, an effective spindle configuration for level-dyeing has been proposed.

关键词： Porosity Spindle Yarn Dyeing Computational Fluid Dynamics