Journal of Powder Materials

Si-Young Chang

8 Articles

Microstructure and Hardness of TiC Particle-reinforced Fe Self-fluxing Alloy Powders Based Hybrid Composite Prepared by High Energy Ball Milling: Sung-Jin Park, Yo-Seung Song, Ki-Seok Nam, Si-Young Chang; J Korean Powder Metall Inst. 2012;19(2):122-126.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.122

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The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 µm and the irregular shape of less than 5 µm, respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 µm that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

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Compaction and Sintering Characteristics of High Energy Ball Milled Mn-Zn Ferrite Powders
Hyunseung Lee, Hoseong Rhee, Sangsoo Lee, Si Young Chang
Korean Journal of Materials Research.2021; 31(12): 677. CrossRef

Fabrication of Porous Cu by Freeze-Drying Method of CuO-Camphene Slurry: Min-Soo Kim, Sung-Tag Oh, Si-Young Chang, Myung-Jin Suk; J Korean Powder Metall Inst. 2011;18(4):327-331.; DOI: https://doi.org/10.4150/KPMI.2011.18.4.327

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In order to fabricate the porous metal with controlled pore characteristics, unique processing by using metal oxide powder as the source and camphene as the sublimable material is introduced. CuO powder was selected as the source for the formation of Cu metal via hydrogen reduction. Camphene-based CuO slurry, prepared by milling at 47°C with a small amount of dispersant, was frozen at -25°C. Pores were generated subsequently by sublimation of the camphene. The green body was hydrogen-reduced at 200°C for 30 min, and sintered at 500-700°C for 1 h. Microstructural analysis revealed that the sintered Cu showed aligned large pore channels parallel to the camphene growth direction, and fine pores are formed around the large pore. Also, it showed that the pore size was controllable by the slurry concentration.

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Freeze drying for porous Mo with different sublimable vehicle compositions in the camphor-naphthalene system
Sung-Tag Oh, Young Do Kim, Myung-Jin Suk
Materials Letters.2015; 139: 268. CrossRef
Effect of Solidification Condition of Sublimable Vehicles on the Pore Characteristics in Freeze Drying Process
Myung-Jin Suk, Ji Soon Kim, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2014; 21(5): 366. CrossRef
Synthesis and Microstructure of Porous Al2O3 with Nano-Sized Cu Dispersions
호석 유, 창용 현, 안기 김
Korean Journal of Materials Research.2013; 23(1): 67~71. CrossRef
Effect of Powder Characteristic and Freeze Condition on the Pore Characteristics of Porous W
Na-Yeon Kwon, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2012; 19(4): 259. CrossRef
Fabrication of Porous Mo by Freeze-Drying and Hydrogen Reduction of MoO3/Camphene Slurry
Wonsuk Lee, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2012; 19(6): 446. CrossRef
Fabrication and Properties of Porous Tungsten by Freeze-Drying Process
영숙 이, 승탁 오
Korean Journal of Materials Research.2011; 21(9): 520~524. CrossRef

Effect of Process Parameters on Microstructure and Magnetic Properties of Sm-Co Alloy Powder Prepared by High Energy Ball Milling: Bo-Sik Kim, Si-Young Chang; J Korean Powder Metall Inst. 2010;17(2):130-135.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.130

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Abstract PDF: Sm-16.7wt%Co alloy powders were prepared by high energy ball milling under the conditions of various milling time and the content of process control agent (PCA), and their microstructure and magnetic properties were investigated to establish optimum processing conditions. The initial powders employed showed irregular shape and had a size ranging from 5 to 110;µm. After milling for 5 h, the shape of powders changed to round shape and their mean powder size was approximately 5;µm, which consisted of the agglomerated nano-sized particles with 15 nm in diameter. The coercivity was reduced with increasing the milling time, whereas the saturation magnetization increased. As the content of PCA increased, the powder size minutely decreased to approximately 7;µm at the PCA content of 10 wt%. The XRD patterns showed that the main diffraction peaks disappeared apparently after milling, indicating the formation of amorphous structure. The measured values of coercivity were almost unchanged with increasing the content of PCA.

Production and Properties of Amorphous TiCuNi Powders by Mechanical Alloying and Spark Plasma Sintering: J.C. Kim, E.H. Kang, Y.S. Kwon, J.S. Kim, Si-Young Chang; J Korean Powder Metall Inst. 2010;17(1):36-43.; DOI: https://doi.org/10.4150/KPMI.2010.17.1.036

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In present work, amorphous TiCuNi powders were fabricated by mechanical alloying process. Amorphization and crystallization behaviors of the TiCuNi powders during high-energy ball milling and subsequent microstructure changes were studied by X-ray diffraction and transmission electron microscope. TEM samples were prepared by the focused ion beam technique. The morphology of powders prepared with different milling times was observed by field-emission scanning electron microscope and optical microscope. The powders developed a fine, layered, homogeneous structure with milling times. The crystallization behavior showed that glass transition, T_g, onset crystallization, T_x, and super cooled liquid range DeltaT=T_x-T_g were 628, 755 and 127K, respectively. The as-prepared amorphous TiCuNi powders were consolidated by spark plasma sintering process. Full densified TiCuNi samples were successfully produced by the spark plasma sintering process. Crystallization of the MA powders happened during sintering at 733K.

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Fabrication of Ultra Fine Grained Molybdenum and Mechanical Properties
Se-Hoon Kim, Young-Ik Seo, Dae-Gun Kim, Myung-Jin Suk, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(3): 235. CrossRef

The Aging Characteristics of Mg-6 wt.% Al-1 wt.% Zn Alloy Prepared by Gas Atomization: Du-Hyung Lee, Bo-Sik Kim, Si-Young Chang; J Korean Powder Metall Inst. 2009;16(4):275-279.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.275

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Abstract PDF: The aging characteristics of gas atomized Mg-6 wt.% Al-1 wt.% Zn alloy were investigated and compared to those of cast Mg-6 wt.% Al alloy. The gas atomized Mg-6 wt.% Al-1wt.% Zn alloy powders had spherical morphology between 1 and 100 mu m in diameter. After compaction under the pressure of 700 MPa at 320°C for 10 min, the Mg-6 wt.% Al-1 wt.% Zn alloy showed a grain size of approximately 40 mu m which is smaller than that of the cast Mg-6 wt.% Al alloy, and a relative compact density of approximately 93%. After ageing, the Mg-6 wt.% Al-1 wt.% Zn alloy showed much faster peak hardness than cast Mg-6 wt.% Al alloy. The Mg-6 wt.% Al-1 wt.% Zn alloy showed the new fine precipitations with ageing time, while the cast Mg-6 wt.% Al alloy was almost similar morphology.

Bi-materials of Al-Mg Alloy Reinforced with/without SiC and Al₂O₃ Particles; Processing and Mechanical Properties: Si-Young Chang, Han-Gyoung Cho, Yang-Do Kim; J Korean Powder Metall Inst. 2007;14(6):354-361.; DOI: https://doi.org/10.4150/KPMI.2007.14.6.354

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The bi-materials with Al-Mg alloy and its composites reinforced with SiC and Al_2O_3 particles were prepared by conventional powder metallurgy method. The A1-5 wt%Mg and composite mixtures were compacted under 150sim450;MPa, and then the mixtures compacted under 400 MPa were sintered at 773sim1173K for 5h. The obtained bi-materials with Al-Mg/SiCp composite showed the higher relative density than those with Al-Mg/Al_2O_3 composite after compaction and sintering. Based on the results, the bi-materials compacted under 400 MPa and sintered at 873K for 5h were used for mechanical tests. In the composite side of bi-materials, the SiC particles were densely distributed compared to the Al_2O_3 particles. The bi-materials with Al-Mg/SiC composite showed the higher micro-hardness than those with Al-Mg/Al_2O_3 composite. The mechanical properties were evaluated by the compressive test. The bi-materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. Their compressive strength was lower than that of Al-Mg alloy. Moreover, impact absorbed energy of bi-materials was smaller than that of composite. However, the bi-materials with Al-Mg/SiCp composite particularly showed almost similar impact absorbed energy to Al-Mg/Al_2O_3 composite. From the observation of microstructure, it was deduced that the bi-materials was preferentially fractured through micro-interface between matrix and composite in the vicinity of macro-interface.

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Effect of Heat Treatment on Microstructure and Mechanical Properties of Electromagnetic Duo-Cast Al Hybrid Material
Jun Young Suh, Sung Jin Park, Do-Kyun Kwon, Si Young Chang
Korean Journal of Materials Research.2018; 28(9): 499. CrossRef
Microstructure and Mechanical Behavior of Al-Mg-Si/Al Hybrid Alloy by Duo-casting
Ji-Min Han, Chong-Ho Kim, Jun-Pyo Park, Si Young Chang
Journal of the Korea Foundry Society.2012; 32(6): 269. CrossRef
Microstructure and Tensile Properties of Al-Mn/Al-Si Hybrid Aluminum Alloy Prepared by Electromagnetic Duo-Casting
Sung-Jin Park, Tingju Li, Chong-Ho Kim, Jun-Pyo Park, Si-Young Chang
Korean Journal of Materials Research.2012; 22(2): 97. CrossRef

Characteristics of Plasma Electrolytic Oxidation Coatings on Mg-Zn-Y Alloys Prepared by Gas Atomization: Si-Young Chang, Han-Gyoung Cho, Du-Hyung Lee, Taek-Soo Kim; J Korean Powder Metall Inst. 2007;14(6):372-379.; DOI: https://doi.org/10.4150/KPMI.2007.14.6.372

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The microstructure, mechanical and electrochemical properties of plasma electrolytic coatings (PEO) coatings on Mg-4.3 wt%Zn-1.0 wt%Y and Mg-1.0 wt%Zn-2.0 wt%Y alloys prepared by gas atomization, followed by compaction at 320 for 10 min under the pressure of 700 MPa and sintering at 380 and 420 respectively for 24 h, were investigated, which was compared with the cast Mg-1.0 wt%Zn alloy. All coatings consisting of MgO and Mg_2SiO_4 oxides showed porous and coarse surface features with some volcano top-like pores distributed disorderly and cracks between pores. In particular, the surface of coatings on Mg-1.0 wt%Zn-2.0 wt%Y alloy showed smaller area of pores and cracks compared to the Mg-4.3 wt%Zn-1.0 wt%Y and Mg-1.0 wt%Zn alloys. The cross section micro-hardness of coatings on the gas atomized Mg-Zn-Y alloys was higher than that on the cast Mg-1.0 wt%Zn alloy. Additionally, the coated Mg-1.0 wt%Zn-2.0 wt%Y alloy exhibited the best corrosion resistance in 3.5%NaCl solution. It could be concluded that the addition of Y has a beneficial effect on the formation of protective and hard coatings on Mg alloys by plasma electrolytic oxidation treatment.

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The Aging Characteristics of Mg-6 wt.% Al-1 wt.% Zn Alloy Prepared by Gas Atomization
Du-Hyung Lee, Bo-Sik Kim, Si-Young Chang
Journal of Korean Powder Metallurgy Institute.2009; 16(4): 275. CrossRef

Effect of ECAP on Microstructure of SiC_w/6061Al Composites Produced by Powder Metallurgy: Si-Young Chang; J Korean Powder Metall Inst. 2002;9(1):11-18.; DOI: https://doi.org/10.4150/KPMI.2002.9.1.011

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Abstract PDF: The 6061 Al alloy based composites reinforced with 10 vol% SiC whiskers were prepared by powder metallurgy with the powders having the different sizes, i.e. < 30µm and > 30µm The composites were subjected to equal channel angular pressing (ECAP) at various conditions and the microstructural changes during ECAP were examined In the composites SiC whiskers were clustered and randomly aligned. The clusters were relatively well distributed in the composite with the smaller initial powder size. After ECAP, the clusters were aligned parallel to flow direction and became smaller. In addition, the shape of clusters was changed from irregular to round. The microstructure of the ECAPed samples were compared with those of the conventionally hot-extruded composites. The uniform microstructure and enhanced microhardness could be obtained by using the powders having the smaller size, decreasing ECAP temperature and repeating ECAP.

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