Journal of Powder Materials

Effect of Mold Dimensions on Temperature Distribution of Die during Plasma Activated Sintering: Gil-Geun Lee, IK-Min Park; J Korean Powder Metall Inst. 2004;11(5):363-368.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.363

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Abstract PDF: In the present study, the focus is on the analysis of the effect of the mold dimensions on the temperature distribution of a die during plasma activated sintering. The temperature distribution of a cylindrical mold with various dimensions was measured using K-type thermocouples. The temperature homogeneity of the die was studied based on the direction and dimensions of the die. A temperature gradient existed in the radial direction of the die during the plasma activated sintering. Also, the magnitude of the temperature gradient was increased with increasing sintering temperature. In the longitudinal direction, however, there was no temperature gradient. The temperature gradient of the die in the radial direction strongly depended on a ratio of die volume to punch area.

Manufacturing of Tungsten Heavy Alloy Composites for Kinetic Energy Penetrator: Heung Song, Eun Kim, Kyung Park, Joo You; J Korean Powder Metall Inst. 2004;11(5):369-375.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.369

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Abstract PDF: A new concept of tungsten heavy alloy composite was suggested and manufactured in this study for the kinetic energy penetrator. The composite heavy alloy was composed of two parts, the center was molybdenum added heavy alloy compositions which were designed to promote the self-sharpening effect and outside was conventional heavy alloy in order to sustain the severe stress condition in the muzzle during the firing. The center part showed an intergranular and brittle mode at tungsten/tungsten interfaces by which self-sharpening effect could be activated. On the other hand, that of outside showed conventional ductile fracture mode under high strain rate condition. From the sub-scale penetration test, the depth of penetration in heavy alloy composites showed greater values than those of conventional tungsten heavy alloys. It is suggested that the heavy alloy composite could be considered as one of the future penetrator materials.

Tribological Properties of Cu-Ni Alloy Nanopowders Synthesized by Pulsed Wire Evaporation (PWE) Method: J.S. Oh, J.H. Park, W.W. Kim, C.K. Rhee; J Korean Powder Metall Inst. 2004;11(5):376-382.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.376

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Nanoscale Cu-Ni alloy nanopowders have been produced by a pulsed wire evaporation method in an inert gas. The effect of Cu-Ni alloy nanopowders as additives to motor oil on the tribological properties was studied at room temperature. The worn surfaces were characterized by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Cu-Ni alloy nanopowders as additives lowered coefficient of friction and wear rate. It was found that a copper containing layer on the worn surface was formed, and deposited layers of the metal cladding acted as lubricant on the worn surface, reducing the friction coefficient. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives are able to restore the worn surface and to preserve the friction surfaces from wear.

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A Study on the Thermal Conductivity of Thermal Grease According to Cu-Ni Content
Haneul Kang, Hyunji Kim, Sunghoon Im, Jinho Yang, Sunchul Huh
Key Engineering Materials.2021; 880: 71. CrossRef

A Study on Abnormal Expansion of Fe-Cu Sintered Alloy: Young-Jun Song, Youn-Che Kim; J Korean Powder Metall Inst. 2004;11(5):383-390.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.383

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Abstract PDF: In order to investigate behavior of abnormal expansion of the iron-copper compacts, we compared the dilatometric curves of the compacts which mixed the copper powder to the iron powder with those of compacts which mixed the copper powder to the iron-copper alloy powder. The dilatometric curves were obtained below the sintering conditions, which heated up to 1150°C by a heating rate of 10°C/min, held for 60min at 1150°C and cooled down at a rate of 20°C/min to room temperature. The dilatometric curves of the compacts showed the different expansion behavior at temperatures above the copper melting point in spite of same chemical composition. All of the compacts of former case showed large expansion, but all of the compacts in latter case showed large contraction. The microstructures of sintered compacts also showed the different progress in alloying of the copper into the iron powder. Namely we could observe the segregation at alloy part of copper into iron powder in case of the sintered compacts, which mixed the copper powder to the iron powder, but could not observe the segregation in compacts which mixed the copper powder to the iron-copper alloy powder. But the penetration of liquid copper into the interstices between solid particles was occurred at both cases. Therefore, the showing of the different dimensional changes in the compacts in spite of same chemical composition is due to more the alloying of copper into iron powder than the penetration of liquid copper into the interstices between solid particles.

Phase Developments and Microstructure Changes of Calcium Phosphate Powders Synthesized by Recycling Eggshell: Sang-Jin Lee, Joo-Won Kim; J Korean Powder Metall Inst. 2004;11(5):391-398.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.391

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Abstract PDF: Calcium phosphate powders were successfully synthesized by using re-cycled eggshell and phosphoric acid. The crystallization behavior and powder morphologies of the synthesized powders were dependent on the starting condition of the eggshell, the mixing ratio and method of the eggshell and phosphoric acid, and calcination temperature. In general, beta-tricalcium phosphate was stably synthesized at about 900°C for 1h at each proper mixing ratio. And, the synthesized powders showed the similar microstructures to the morphology of original eggshell with uniform particle sizes. In this study, the calcium phosphate powders were synthesized with eggshell in various processing method. And their unique microstructures obtained from the eggshell were also. observed. The crystalline developments and microstructures of the synthesized powders were examined by X-ray diffractometer and scanning electron microscopy.

Development of a CAE Tool for P/M Compaction Process and Its Application: Suk-Hwan Chung, Young-Sam Kwon; J Korean Powder Metall Inst. 2004;11(5):399-411.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.399

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Crack generation during die compaction and distortion during sintering have been critical problems for the conventional pressing and sintering process. Until now, trial and error approach with engineers' industrial experiences has been only solution to protect the crack generation and distortion. However, with complexity in shape and process it is very difficult to design process conditions without CAE analysis. We developed the exclusive CAE software (PMsolver/Compaction) for die compaction process. The accuracy of PMsolver is verified by comparing the finite element simulation results with experimental results. The simplified procedures to find material properties are proposed and verified with iron based powder and tungsten carbide powder. Based on the accurate simulation result by PMsolver, the optimal process conditions are designed to get uniform density distribution in a powder compact after die compaction process by using a derivative based optimization scheme. In addition, the effect of non-uniform density distribution in a powder compact on distortion during sintering is shown in case of the fabrication of tungsten carbide insert.

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Analysis of cold compaction for Fe-C, Fe-C-Cu powder design based on constitutive relation and artificial neural networks
Da Seul Shin, Chi Hun Lee, Suk Hyun Kim, Dong Yong Park, Joo Won Oh, Chang Woo Gal, Jin Mo Koo, Seong Jin Park, Seung Chul Lee
Powder Technology.2019; 353: 330. CrossRef
A Study on the Structural Analysis for Plastic Door Handle of Automobile
S.R. Park, D.C. Shim, D. Kim, M.Y. Lyu
Transactions of Materials Processing.2010; 19(3): 185. CrossRef

The fabrication and characterization of hard rock cutting diamond saw: Hyun-Woo Lee, Woo-yong Jeon, Oh-yeon Lee, Kyeong-won Seol; J Korean Powder Metall Inst. 2004;11(5):412-420.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.412

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Abstract PDF: The purpose of the present study is to determine an optimum composition using cheaper powders keeping with high performance of hard rock cutting diamond saw blade. With 50Fe-20(Cu . Sn)-30Co specimen, a part of Co was replaced by Ni(5%, 10%, and 15%, respectively). These specimens were hot pressed and sintered for predetermined time at various temperature. Sintering is performed by two different methods of temperature controlled method and specimen dimension controlled method. In order to determine the property of the sintered diamond saw blade, 3 point bending tester, X-ray diffractometer, and SEM were used. As the Co in the bond alloy was replaced by Ni, the hardness of the specimen increased. Thus the 50Fe-20(CuㆍSn)-15Co-15Ni specimen showed the maximum hardness of 104(HRB). The results of 3 point bending test showed that flexure strength decreased along with increase in Ni content. This is attributed to the formation of intermetallic compound(Ni_xSn) determined by X-ray diffraction. The fracture surface after 3 point bending test showed that diamond was fractured in the specimen containing 0%, 5%, and 10%Ni, and the fracture occurred at the interface between diamond and matrix in the specimen containing 15%Ni. The cutting ability test showed that the abrasive property was not changed in the specimen containing 0%, 5%, and 10%Ni. The optimum composition determined in this study is 50Fe-20(CuㆍSn)-20Co-10Ni.

Effect of Sintering Atmosphere Changing Temperature on Microstructure and Mechanical Property of Al₂O₃/Cu Nanocomposites: Sung-Tag Oh, Se-Joong Yoon; J Korean Powder Metall Inst. 2004;11(5):421-426.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.421

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Abstract PDF: The microstructure and mechanical property of hot-pressed Al_2O_3/Cu composites with a different temperature for atmosphere changing from H_2 to Ar have been studied. When atmosphere-changed from H_2 to Ar gas at 1450°C, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when atmosphere-changed at low temperature of 1100°C the composite showed more homogeneous microstructure, higher fracture strength and smaller deviation in strength. Based on the thermodynamic consideration and microstructural analysis, it was interpreted that the Cu wetting behavior relating to the formation of CuAlO_2 is probably responsible for strong dependence of microstructure on atmosphere changing temperature. The reason for a strong sensitivity of fracture strength and especially of its deviation to atmosphere changing temperature was explained by the microstructural inhomogeneity and by the role of CuAlO_2 phase on the interfacial bonding strength.

다공성 TiNi 생체재료의 생체적합성 및 의료적 활용: J Korean Powder Metall Inst. 2004;11(5):427-432.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.427

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