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급속응고 Al-20 wt% Si 합금분말 압출재의 ECAP
윤승채,홍순직,서민홍,팜쾅,김형섭,Yoon, Seung-Chae,Hong, Soon-Jik,Seo, Min-Hong,Quang, Pham,Kim, Hyoung-Seop 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.2
In this paper processing and mechanical properties of Al-20 wt% Si alloy was studied. A bulk form of Al-20Si alloy was prepared by gas atomizing powders having the powder size of 106-145 ${\mu}m$ and powder extrusion. The powder extrudate was subsequently equal channel angular pressed up to 8 passes in order to refine grain and Si particle. The microstructure of the gas atomized powders, powder extrudates and equal channel angular pressed samples were investigated using a scanning electron microscope and X-ray diffraction. The mechanical properties of the bulk sample were measured by compressive tests and a micro Victors hardness test. Equal channel angular pressing was found to be effective in matrix grain and Si particle refinement, which enhanced the strength and hardness of the Al-2OSi alloy without deteriorating ductility in the range of experimental strain of 30%.
방전 플라즈마 소결법(SPS)으로 제조된 급속응고 p-type Bi<sub>2</sub>Te<sub>3</sub> 합금의 소결 특성
문철동,홍순직,김도향,김택수,Moon, Chul-Dong,Hong, Soon-Jik,Kim, Do-Hyang,Kim, Taek-Soo 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.6
The p-type thermoelectric compounds of $Bi_2Te_3$ based doped with 3wt% Te were fabricated by a combination of rapid solidification and spark plasma sintering (SPS) process. The effect of holding time during spark plasma sintering (SPS) on the microstructure and thermoelectric properties were investigated using scanning electron microscope (SEM), X-ray diffraction (XRD) and thermoelectric properties. The powders as solidified consisted of homogeneous thermoelectric phases. The thermoelectric figure of merit measured to be maximum ($3.41{\times}10^{-3}/K$) at the SPS temperature of $430^{\circ}C$.
자기펄스압축성형장치를 이용한 대면적 지르코니아 덴탈블록 제조 연구
박효영,김효섭,홍순직,Park, Hyo-Young,Kim, Hyo-Seob,Hong, Soon-Jik 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.5
Sintered bulks of $ZrO_2$ nanopowders were fabricated by magnetic pulsed compaction (MPC) and subsequent two-step sintering employed in this study and the formability effects of nanopowder on mixing condition, pressure and sintering temperature were investigated. The addition of PVA induced and increase in the formability of the sintered bulk. But cracked bulks were obtained on sintering with addition of over 10 wt% PVA due to generation of crack during sintering. The optimum compaction pressure during MPC was 1.0 GPa and mixing conditions included using 5.0 wt% PVA. The optimum processing condition included MPC process, followed by two-step sintering (first at 1000 and then at $1450^{\circ}C$). The sintered bulks with the diameter of 30 mm under these conditions were found to have non crack, ~99% density.
분말야금법으로 제조된 FeSi<sub>2</sub> 열전특성 화합물의 열처리 시간에 따른 미세조직과 상변화
박경태,신진교,홍순직,천병선,Park, Kyoung-Tae,Shin, Jin-Gyo,Hong, Soon-Jik,Chun, Byong-Sun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.6
In this study, $FeSi_2$ as high temperature performance capable thermoelectric materials was manufactured by powder metallurgy.The as-casted Fe-Si alloy was annealed for homogenization below $1200^{\circ}C$ for 3 h. Due to its high brittleness, the cast alloy transformed to fine powders by ball-milling, followed by subsequent compaction (hydraulic pressure; 2 GPa) and sintering ($1200^{\circ}C$, 12 h). In order to precipitate ${\beta}-FeSi_2$, heat treatment was performed at $850^{\circ}C$ with varying dwell time (7, 15 and 55 h). As a result of this experiment thermoelectric phase ${\beta}-FeSi_2$ was quickly transformed by powder metallurgical process. There was not much change in powder factor between 7h and 55h specimens.
기계적 합금화 공정에 의한 Fe가 코팅된 Mg 탈황 분말 제조 연구
송준우,천병선,홍순직,Song, Joon-Woo,Guillermo, Otaduy,Chun, Byong-Sun,Hong, Soon-Jik 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3
In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 ${\mu}m$ at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.
급속응고 6061Al/Graphite 복합재료의 볼밀링 시간에 따른 흑연 분산거동 및 기계적 특성
손현택,이재설,홍순직,천병선,Son, Hyeon-Taek,Lee, Jae-Seol,Hong, Soon-Jik,Chun, Byong-Sun 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.3
A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the gas atomized initially and spherical powders became elongated with a maximum aspect ratio after milling for 30 h. Then, refinement and spheroidization were achieved by further milling to 70 h with a homogeneous and fine dispersion of graphite particles forming between the matrix alloy layers. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.
자기펄스 성형법에 의한 TiO<sub>2</sub> 나노 분말의 치밀화
김효섭,이정구,이창규,구자명,홍순직,Kim, Hyo-Seob,Lee, Jeong-Goo,Rhee, Chang-Kyu,Koo, Jar-Myung,Hong, Soon-Jik 한국재료학회 2008 한국재료학회지 Vol.18 No.8
In this research, fine-structure TiO2 bulks were fabricated in a combined application of magnetic pulsed compaction (MPC) and subsequent sintering and their densification behavior was investigated. The obtained density of $TiO_2$ bulk prepared via the combined processes increased as the MPC pressure increased from 0.3 to 0.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7 GPa was attributed to the decrease of the inter-particle distance of the pre-compacted component. High pressure and rapid compaction using magnetic pulsed compaction reduced the shrinkage rate (about 10% in this case) of the sintered bulks compared to general processing (about 20%). The mixing conditions of PVA, water, and $TiO_2$ nano powder for the compaction of $TiO_2$ nano powder did not affect the density and shrinkage of the sintered bulks due to the high pressure of the MPC.
폐실리콘의 고에너지 밀링 과정에서 초기 입자 크기가 분말의 미세화에 미치는 효과
송준우,김효섭,김성신,구자명,홍순직,Song, Joon-Woo,Kim, Hyo-Seob,Kim, Sung-Shin,Koo, Jar-Myung,Hong, Soon-Jik 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.3
In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were investigated as a function of different initial powder size using the high-energy ball milling equipment, which produces the fine powder by means of an ultra high-energy within a short duration. The morphological change of the powders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasing milling time, the size of Si powder was decreased. In addition, more energy and stress for milling were required with the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball milling time. However, the refined powder started to agglomerate at 30 min milling time, while the powder size became uniform at 60 min milling time.