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1
Content available Effect of Trace Elements (Co, Cr) on the Microstructure and Physical Properties of Al-Si-Cu-Mg-Fe Extruded Alloy
Ahn S. S., Sharief P., Lee C. H., Son H. T., Kim Y. H., Kim Y. C., Hong S., Hong S. J.
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 3
857--862
EN
Trace elements Co, Cr were added to investigate their influence on the microstructure and physical properties of Al-Si extruded alloy. The Co, Cr elements were randomly distributed in the matrix, forms intermetallic phase and their existence wereconfirmed by XRD, EDS and SEM analysis. With addition of trace elements, the microstructure was modified, Si particle size was reduced and the growth rate of β-(Al5 FeSi) phase limited. Compared to parent alloy, hardness and tensile strength were enhanced while the linear coefficient of thermal expansion (CTE) was significantly reduced by 42.4% and 16.05% with Co and Cr addition respectively. It is considered that the low CTE occurs with addition of Co was due to the formation of intermetallic compound having low coefficient of thermal expansion. The results suggested that Co acts as an effective element in improving the mechanical properties of Al-Si alloy.
2
Content available Surface Modification of Self-Consolidated Microporous Ti Implant Compacts Fabricated by Electro-Discharge-Sintering in Air
Jo Y. J., Yoon Y. H., Kim Y. H., Chang S. Y., Kim J. Y., Lee Y. K., Van Tyne C. J., Lee W. H.
Archives of Metallurgy and Materials
|
2017
|
Vol. 62, iss. 2B
1287--1291
EN
A single pulse of 0.75-2.0 kJ/0.7g of atomized spherical Ti powders from 300 mF capacitor was applied to produce a microporous Ti implant compact by electro-discharge-sintering (EDS). A solid core in the middle of the compact surrounded by a microporous layer was found. X-ray photoelectron spectroscopy was employed to study the surface characteristics of the EDS Ti compact and it revealed that Ti, C and O were the main constituents on the surface with a smaller amount of N. The surface was lightly oxidized and was primarily in the form of TiO2 resulting from the air oxidation during EDS processing. The lightly oxidized surface of the EDS compact also exhibited Ti nitrides such as TiN and TiON, which revealed that the reaction between air constituents and the Ti powders even in times as short as 128 msec.
3
Content available Spontaneous Formation of Titanium Nitride on the Surface of a Ti Rod Induced by Electro-Discharge-Heat-Treatment in an N2 Atmosphere
Lee W. H., Yoon Y. H., Kim Y. H., Lee Y. K., Kim J. Y., Chang S. Y.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 2B
1281--1285
EN
A single pulse of 2.0 to 3.5 kJ of input energy from a 450 mF capacitor was applied to a commercially pure Ti rod in a N2 atmosphere. The surface of the Ti rod transformed from TiO2 into titanium nitride in times as short as 159 msec, providing a bimodal morphology of the cross-section. A much higher value of hardness that was observed at the edge of the cross-section was attributed to nitrogen-induced solid-solution hardening that occurred during the electrical discharge process. The activation energy (Ea) for the diffusion process was estimated to be approximately 86.9 kJ/mol. Results show that the electrical discharge process is a possible potential method for the nitriding of Ti; advantages include a short processing time and control of the nitrided layer without dimensional changes.
4
Content available Self-Consolidation Mechanism of Ti5Si3 Compact Obtained by Electro-Discharge-Sintering Directly from Physically Blended Ti-37.5 At.% Si Powder Mixture
Chang S. Y., Cheon Y. W., Yoon Y. H., Kim Y. H., Kim J. Y., Lee Y. K., Lee W. H.
Archives of Metallurgy and Materials
|
2017
|
Vol. 62, iss. 2B
1299--1302
EN
Characteristics of electro-discharge-sintering of the Ti-37.5at.% Si powder mixture was investigated as a function of the input energy, capacitance, and discharge time without applying any external pressure. A solid bulk of Ti5Si3 was obtained only after in less than 129 μsec by the EDS process. During a discharge, the heat is generated to liquefy and alloy the particles, and which enhances the pinch pressure can condensate them without allowing a formation of pores. Three step processes for the self-consolidation mechanism during EDS are proposed; (a) a physical breakdown of oxide film on elemental as-received powder particles, (b) alloying and densifying the consolidation of powder particles by the pinch pressure, and (c) diffusion of impurities into the consolidated surface.
5
Content available Self-Consolidation and Surface Modification of Mechanical Alloyed Ti-25.0 at.% Al Powder Mixture by Using an Electro-Discharge Technique
Chang S. Y., Jang H. S., Yoon Y. H., Kim Y. H., Kim J. Y., Lee Y. K., Lee W. H.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 2B
1293--1297
EN
Electrical discharges using a capacitance of 450 μF at 0.5, 1.0, and 1.5 kJ input energies were applied in a N2 atmosphere to obtain the mechanical alloyed Ti3Al powder without applying any external pressure. A solid bulk of nanostructured Ti3Al was obtained as short as 160 μsec by the Electrical discharge. At the same time, the surface has been modified into the form of Ti and Al nitrides due to the diffusion process of nitrogen to the surface. The input energy was found to be the most important parameter to affect the formation of a solid core and surface chemistry of the compact.
6
Content available High-temperature Oxidation Behavior and Kinetics of Forged 12Cr-MoVW Steel
Kim Y. H., Oak J.-J., Bae K.-C., Lee W-J., Park Y. H.
Archives of Metallurgy and Materials
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2017
|
Vol. 62, iss. 2B
1099--1104
EN
The oxidation kinetics of forged 12Cr-MoVW steel was investigated in an air (N2+O2) atmosphere at 873-1073 K (Δ50 K) using thermogravimetric analysis. The oxidized samples were characterized using X-ray diffraction, and the surface and cross-sectional morphologies were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The forged 12Cr-MoVW steel samples exhibited parabolic behavior and a low oxidation rate compared with their as-cast counterparts. A protective oxide layer was uniformly formed at relatively low temperature (≤973 K) for the forged samples, which thus exhibited better oxidation resistance than the as-cast ones. These oxides are considered solid-solution compounds such as (Fe, Cr)2O3.
7
Content available Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses
Oak J.-J., Kim Y. H., Bae K.-C., Park Y. H.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 2B
1081--1087
EN
The newly designed Ti-based bulk metallic glass (BMG) in which case of fracture behavior was observed 1990MPa to compressive strength with a wide plastic deformation around 7% after process of elastic deformation. This phenomenon can be compared with those of Ti-based alloys and other Ti-based BMGs and indicates high potential to be applied in use. It was evaluated the Ti-based BMG for thermal stability that the reduced glass parameters, ΔTx, Trg and γ, are 79K, 0.50 and 0.38, respectively. In addition, it reveals high activation energies for crystallization in which are estimated to Ex1 = 291.77 ±9.71 kJ/mol, Ex2 = 588.77 ±28.88 kJ/mol and Ex3 = 330.26 ±3.61 kJ/mol on kissinger plotting in this study.
8
Content available Effect of Fe Content on the Microstructure and Mechanical Properties of Ti-Al-Mo-V-Cr-Fe Alloys
Bae K.-C., Oak J.-J., Kim Y. H., Park Y. H.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 2B
1105--1108
EN
To investigate the effect of Fe content on the correlation between the microstructure and mechanical properties in near-b titanium alloys, the Ti-5Al-5Mo-5V-1Cr-xFe alloy system has been characterized in this study. As the Fe content increased, the number of nucleation sites and the volume fraction of the α phase decreased. We observed a significant difference in the shape and size of the α phase in the matrix before and after Fe addition. In addition, these morphological deformations were accompanied by a change in the shape of the α phase, which became increasingly discontinuous, and changed into globular-type α phase in the matrix. These phenomena affected the microstructure and mechanical properties of Ti alloys. Specimen #2 exhibited a high ultimate tensile strength (1071 MPa), which decreased with further addition of Fe.
9
Effect of occupational health nursing practice on musculoskeletal pains among hospital nursing staff in South Korea
Kim Y. H., Jung M.- H.
International Journal of Occupational Safety and Ergonomics
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2016
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Vol. 22, No. 2
199--206
EN
Objective. The purpose of this study was to identify whether occupational health nursing variables serve as the contributing factors to musculoskeletal pains (MSP). Methods. A self-administered questionnaire composed of demographic characteristics, the practice of occupational health nursing and information regarding MSP was designed based on in-depth interviews with eight nurses. This study included 226 hospital nursing staff who worked at three university hospitals located in Seoul, South Korea. Statistical analysis was performed by using SPSS and AMOS 19.0. Results. Shoulder and neck pains occurred when subjects worked more than 46 h/week. Subjects who performed ‘work-time adjustment’ had lesser chance of having shoulder, leg/foot and wrist/finger pains. Overtime work hours showed an indirect effect on multiple sites of MSP by mediator variable, which was ‘work-time adjustment’. Organized night duty days eventually decreased multiple sites of MSP. Conclusion. Administration strategies for nurses to adjust work-time within 46 h/week should be considered.
10
Content available Study On The Electro-Refining Of Tin In Acid Solution From Electronic Waste
Son S. H., Park S. C., Kim J. H., Kim Y. H., Lee M. S., Ahn J.-W.
Archives of Metallurgy and Materials
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2015
|
Vol. 60, iss. 2B
1217--1220
EN
The tin metal could be retractable from wasted tin scrap, sludge, and wasted electroplated solution hydrometallurgical treatment, and purification process. In order to be used as resource of electronic devices, the retracted crude metal should be purified to the extent of higher than 99.9%. In this study, tin electro-refining process was performed to purify the casted tin crude metal at various experimental conditions: at the current density of 3, 5A/dm2, and in various electrolytes such as hydrochloric acid, sulfuric acid and methansulfonic acid. Additional experiment was conducted using Rotating Disk Electrode (RDE) in order to investigate the rate determining step of tin electro-refining process. The current efficiency, 65.6%, was achievable at the condition of current density, 5A/dm2, and in the electrolyte of Hydrochloric acid. During tin electro-refining process, impurity dissolved from tin crude metal into the electrolyte was analyzed using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), and the result showed the concentration of impurity metal gradually increased. Quantitative analysis on casted tin crude metal showed that it consists of tin with 93.9 wt.% and several impurity metals of Ag, Bi, Pb, Cu, and etc. After tin electro-refining process, the purity of tin increased up to 99.985 wt.%.
11
Content available Self-Consolidation Mechanism Of Porous Ti-6Al-4V Implant Prototypes Produced By Electro-Discharge-Sintering Of Spherical Ti-6Al-4V Powders
Lee W. H., Jo Y. J., Kim Y. H., Jo Y. H., Seong J. G., Van Tyne C. J., Chang S. Y.
Archives of Metallurgy and Materials
|
2015
|
Vol. 60, iss. 2B
1185--1189
EN
Electro-Discharge-Sintering (EDS) was employed to fabricate Ti-6Al-4V porous implant prototypes from atomized powders (100 – 150 μm), that were subjected to discharges of 0.75 to 2.0 kJ/0.7g-powder from 150, 300, and 450 μF capacitors. Both fully porous and porous-surfaced Ti-6Al-4V compacts with various solid core sizes were self-consolidated in less than 86 – 155 μsec. It is known that EDS can simultaneously produce the pinch pressure to squeeze and deform powder particles and the heat to weld them together. The formation of a solid core in these prototypes depends on the amounts of both the pinch pressure and heat generated during a discharge. The size of the solid core and the thickness of the porous layer can be successfully controlled by manipulating the discharge conditions such as input energy and capacitance.
12
Content available Recovery Of Valuable Metals In Tin-Based Anodic Slimes By Carbothermic Reaction
Han C., Kim Y.-M., Son S. H., Choi H., Kim T. B., Kim Y. H.
Archives of Metallurgy and Materials
|
2015
|
Vol. 60, iss. 2B
1213--1216
EN
This study investigated the recovery of anodic slimes by carbothermic reaction in the temperature range of 973~1,273K and amount of carbon as a function of time. Tin anodic slime samples were collected from the bottom of the electrolytic cells during the electro-refining of tin. The anodic slimes are consisted of high concentrated tin, silver, copper and lead oxides. The kinetics of reduction were determined by means of the weight-loss measurement technique. In order to understand in detail of carbothermic reaction, thermodynamic calculation was carried out and compared with experiments. From thermodynamic calculation and experiment, it was confirmed that Sn-based anodic slime could be reduced by controlling temperature and amount of carbon. However, any tendency between the reduction temperature and carbon content for the reduction reaction was not observed.
13
Content available Recovery Of Electrodic Powder From Spent Nickel-Metal Hydride Batteries (NiMH)
Shin S. M., Shin D. J., Jung G. J., Kim Y. H., Wang J. P.
Archives of Metallurgy and Materials
|
2015
|
Vol. 60, iss. 2B
1139--1143
EN
This study was focused on recycling process newly proposed to recover electrodic powder enriched in nickel (Ni) and rare earth elements (La and Ce) from spent nickel-metal hydride batteries (NiMH). In addition, this new process was designed to prevent explosion of batteries during thermal treatment under inert atmosphere. Spent nickel metal hydride batteries were heated over range of 300°C to 600°C for 2 hours and each component was completely separated inside reactor after experiment. Electrodic powder was successfully recovered from bulk components containing several pieces of metals through sieving operation. The electrodic powder obtained was examined by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and image of the powder was taken by scanning electron microscopy (SEM). It was finally found that nickel and rare earth elements were mainly recovered to about 45 wt.% and 12 wt.% in electrodic powder, respectively.
14
Content available Characterization Of The Graded Microstructure In Powder Sintered Porous Titanium
Oak J.-J., Bang J. I., Bae K.-C., Kim Y. H., Lee Y. C., Chun H. H., Park Y. H.
Archives of Metallurgy and Materials
|
2015
|
Vol. 60, iss. 2B
1265--1269
EN
The proposed sintering process produce porosity and functional graded microstructure in the sinterd titanium powders. Titanium powders with different micro sizes were sintered at the proposed temperature region at 1200 and 1300°C for 2h. The apatite-forming on the graded microstructure is observed by immersion test in Hanks balanced salt soluion at 37°C. Sintering condition of titanium powders is estimated by thermogravitmetry-differential thermal analysis (TG-DTA). The synthersied surface structures and apatite-forming ability were characterized by a field emission scanning electron microscopy (FE-SEM) observation and energy dispersive X-ray spectroscopy (EDS) analysis. As results, these graded microstructure of sintered porous titanium powders reveals apatite-forming ability as osseointegration by calcification in Hanks balanced salt soluion(HBSS) at 37°C.
15
Content available remote Kinematic and kinetic analyses of novice running in dress shoes and running shoes
Lee Y., Kim Y. K., Kim Y. H., Kong S., Lee K. K.
Acta of Bioengineering and Biomechanics
|
2011
|
Vol. 13, no. 3
55-61
EN
The purpose of the study was to investigate how novice runners adjust their lower extremities in heel-toe running while they wear dress shoes and running shoes. Ten novice male runners repeatedly ran across a force plate at 4 m/s in each type of shoes. Joint kinematics and kinetics, vertical ground reaction force, and utilized coefficient of friction during the stance phase were quantified. The results obtained showed no differences in impact peaks, stance time, stride length and joint kinematics. However, dorsiflexion moment was significantly greater with dress shoes (407 Nm) compared to that with running shoes (304 Nm; p < 0.05). Compared to the runners in running shoes (0.23), the runners in dress shoes (0.20) achieved a significantly lower utilized coefficient of friction ( p < 0.05). When running in dress shoes, novice runners tended to use better a dorsiflexion moment than when running in running shoes. This adaptation appears to minimize the chances of slipping at the moment of heel strike.
16
Content available remote Shear force allowance in lumbar spine under follower load in neutral standing posture
Kim K., Kim Y. H., Lee S.
Acta of Bioengineering and Biomechanics
|
2010
|
Vol. 12, no. 4
49-53
EN
It has been shown experimentally that the load carrying capacity of the spine significantly increases when compressive loads are carried along the follower load (FL) direction. However, it is necessary to modify the current FL concept because a certain amount of shear force is produced during activities in daily life. In this study, a clinically allowable range of shear force was investigated using the modified FL concept. The shear force allowance was defined as the maximum ratio of the shear force to the follower force at each vertebral body center. Then, it was shown that the appropriate shear force allowance was within approximately 0.2 ~ 0.5 from the investigation of the follower forces, the shear forces, and the muscle force coordination. The predicted shear force allowance indicated that the resultant joint force is directed to a certain inside region between a half vertebral body and whole vertebral body.
17
Content available remote Development and application of environmentally degradable plastics in Eastern Asian countries
Kim Y. H., Kim S. H.
Polimery
|
2002
|
T. 47, nr 7-8
556-559
EN
General demographic and economical situation in Eastern Asian countries has been characterized. For several of those countries (Japan, South Korea, Taiwan, Singapore, China) the present state of plastic wastes utilization and environmentally degradable plastics (EDP) production has been described.
PL
Scharakteryzowano ogólną sytuację demograficzną i ekonomiczną w krajach wschodnio-azjatyckich (tabela 1). W odniesieniu do kilku spośród tych krajów (Japonii, Korei Płd., Tajwanu, Singapuru i Chin) omówiono obecny stan zagospodarowywania odpadów tworzywowych oraz produkcji tworzyw sztucznych ulegających degradacji pod wpływem środowiska naturalnego (EPD, tabele 2-4).
18
Content available remote Quotient structure of BCI-algebras via fuzzy ideals
Kim Y. H., Kim H. S.
Demonstratio Mathematica
|
2002
|
Vol. 35, nr 3
461-467
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