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박원욱 ( Won Wook Park ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.2
N/A Rapidly Solidified (RS) Al-Zr base splats with various alloy contents were prepared by atomization-splat quenching method to understand the continuous and discontinuous precipitation in the aged alloys. And the RS alloys were consolidated by hot extrusion and swaging to analyze the effect of plastic deformation on the precipitation behavior. Discontinuous precipitation dominated at relatively low temperature in the Al-Zr alloy, whereas both V additions to Al-Zr alloys and hot metal working appeared to suppress the discontinuous precipitation. As continuous precipitation is favored in the grain interiors, the driving force for discontinuous precipitation become to disappear with a further process.
급랭응고한 Al-Fe-V-Si계 합금의 미세조직과 열안정성에 관한 연구
김선화,박원욱,Kim, Seon-Hwa,Park, Won-Wook 한국현미경학회 1991 Applied microscopy Vol.21 No.2
The main purpose of this paper was to investigate the change of rapidly solidified microstructures and dispersoid behavior according to heat-treatment in the Al-Fe-V-Si-(Mn) alloys. It was found that (111) preferred orientation identified by X-ray diffraction and fine subgrain/large grain were observed in the rapidly solidified Al-Fe-V-Si-(Mn) alloys. Cell boundary of the zone A was composed of the microcrystalline, whereas that of the zone B was amorphous. Decomposition of the Al-Fe-V-Si-(Mn) alloys occurred at about $300^{\circ}C$. These alloys exhibited excellent thermal stability at the elevated temperature. Microstructure of the zone B was more stable than that of the zone A. The spherical dispersoid and 5-fold symmetry phase was also more thermally stable than the amorphous structure of cell boundary.
BaTiO<sub>3</sub> 분말과 분산제 첨가에 따른 Fe계 나노결정 P/M시트의 전자파흡수 특성변화
김미래,조현정,박원욱,Kim, Mi-Rae,Cho, Hyeon-Jeong,Park, Won-Wook 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1
The amorphous $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was pulverized using a jet mill and an attrition mill to get flake-shaped powder. The flake powder was mixed with dielectric $BaTiO_3$ powder and its dispersant to increase the permittivity. The powders covered with dielectric powders and its dispersant were mixed with a binder and a solvent and then tape-cast to form sheets. The absorbing properties of the sheets were measured to investigate the roles of the dielectric powder and its dispersant. The results showed that the addition of $BaTiO_3$ powders and its dispersant improved the absorbing properties of the sheets noticeably. The powder sheet mixed with 5 wt% of $BaTiO_3$ powder and 1 wt% of dispersant showed the best electromagnetic wave absorption rate because of the increase of the permittivity and the electrical resistance.
수평연속주조에 의한 과공정 Al-Si 합금 제조에 관한 연구
류봉선,지무성,박원욱 ( Bong Sun You,Mu Sung Ji,Won Wook Park ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.2
N/A The equipment for the horizontal continuous casting was built to produce hyper-eutectic Al-Si bars with a small cross-section of 25㎜ in diameter. The manufacturing processes including withdrawal cycle and secondary cooling methods were modified to refine the primary and the eutectic Si. The longitudinal casting speeds varied over the ranges of 670-1100㎜/min for pure Al, and 200-350㎜/min for Al-17wt%Si alloy. Due to the difference of cooling rate in the mould, microstructural asymmetry between the lower and the upper part of bar was observed. Thus, manufacturing processes such as cooling and withdrawal method were optimally combinated to get the homogeneous cast structure. With the increase of casting speed, the primary Si size was refined down to 30㎛ near the surface, and 80㎛ in the center of the bar.
Fe계 나노결정립 분말 시트에 첨가된 CNT의 볼밀 공정에 따른 전자파 흡수 특성 변화
김선이,김미래,손근용,박원욱,Kim, Sun-I,Kim, Mi-Rae,Sohn, Keun-Yong,Park, Won-Wook 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.6
Electromagnetic wave energies are consumed in the form of thermal energy, which is mainly caused by magnetic loss, dielectric loss and conductive loss. In this study, CNT was added to the nanocrystalline soft magnetic materials inducing a high magnetic loss, in order to improve the dielectric loss of the EM wave absorption sheet. Generally, the aspect ratio and the dispersion state of CNT can be changed by the pre-ball milling process, which affects the absorbing properties. After the various ball-milling processes, 1wt% of CNTs were mixed with the nanocrystalline $Fe_{73}Si_{16}B_7Nb_{3}Cu_1$ base powder, and then further processed to make EM absorption sheets. As a result, the addition of CNT to Fe-based nanocrystalline materials improved the absorption properties. However, the increase of ball-milling time for more than 1h was not desirable for the powder mixture, because the ballmilling caused the shortening of CNT length and the agglomeration of the CNT flakes.
김선이,김미래,손근용,박원욱,Kim, Sun-I,Kim, Mi-Rae,Sohn, Keun-Yong,Park, Won-Wook 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4
The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.
과공정 Al-Si 합금의 초정 Si 미세화에 미치는 냉각속도와 P 첨가량의 영향
한상봉,김지훈,류봉선,박원욱,예병준 ( Sang Bong Hahn,Ji Hun Kim,Bong Sun You,Won Wook Park,Byung Joon Ye ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.4
N/A It is well known that the coarse primary Si in hypereutectic Al-Si alloys deteriorate castability, machinability, and mechanical properties. So, many treatment has been tried to refine the primary Si increasing cooling rate and adding refinement agent. Therefore, the purpose of our work was the observation of the effect on the refinement of primary Si and the analysis of the trend to apply to the casting process by changing the amount of P addition and the cooling rate while fixing the temperature at 750℃ of P addition and the type of AlCuP. In the condition of amount of P addition was fixed, primary Si was finer as cooling rate increased but in case of cooling rate was fixed, the effect of refinement was resisted as incersed the amount of P addition. At a relatively slow cooling rate of 22℃/sec, refinement was governed by the amount of P addition rather than cooling rate. At elevated cooling rate of 51℃/sec and 99℃/sec, the undercooling due to faster cooling rate promoted nucleation of primary Si rather than P addition more significantly.
수평연속주조한 과공정 Al-Si 합금 소경봉의 미세조직 및 기계적 성질
김완철,박지하,류봉선,박원욱 ( Wan Chul Kim,Ji Ha Park,Bong Sun You,Won Wook Park ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.6
N/A Hyper-eutectic Al-17.5wt%Si alloy bars of 25 ㎜ in diameter were produced by horizontal continuous casting process. Effect of both casting speed and primary Si refiner (AlCuP) on microstructure and mechanical properties of the alloy have been investigated. With increasing a weight fraction of AlCuP, the average primary Si size decreased down to 20 ㎛. On the contrary, there was no notable changes of microstructure and primary Si size according to the casting speed in the experimental range of this study, indicating that the cooling rate should be increased to optimize and refine microstructure and primary Si size. The experimental results including hardness, tensile strength and wear resistance tests of the processed alloy bars showed a good possibility to develop the high performance wear resistant Al-Si alloy. (Received October 21, 1997)