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어트리션 볼밀링 조건 변화에 따른 마그네슘 분말의 미세화 거동
유효상,김용호,김정한,김태경,손현택,이성희,Yoo, Hyo-Sang,Kim, Yong-Ho,Kim, Jung-Han,Kim, Tae-Kyung,Son, Hyeon-Taek,Lee, Seong-Hee 한국재료학회 2014 한국재료학회지 Vol.24 No.11
In this research, magnesium powder was prepared by gas atomizing. Refinement behaviors of magnesium powder produced under different conditions were investigated using a mechanical milling (attrition milling) process. Analyses were performed to assess the characterization and comparison of milled powder with different steel ball sizes and milling times. The powders were analyzed by field emission scanning electron microscope, apparent density and powder fluidity. The particle morphology of the Mg powders changed from spherical particles of feed metals to irregular oval particles, then plate type particles, with an increasing milling time. Because of the HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, which results in producing plate-type powders. An increase in ball size and the impact energy of the magnesium powder maximizes the effect of refinement. Furthermore, it is possible to improve the apparent density and fluidity according to the smoothness of the surface of the initial powder.
Mg-Li계 합금의 Al 및 Sm첨가에 따른 미세조직 및 기계적 특성 변화
유효상 ( Hyo Sang Yoo ),김용호 ( Yong Ho Kim ),김정한 ( Jung Han Kim ),이성희 ( Seong Hee Lee ),손현택 ( Hyeon Taek Son ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.5
The effects of Al and Sm additions on microstructure and mechanical properties of as-cast and as-extruded Mg-8Li alloys were investigated. The microstructure of as-cast Mg-8Li alloy consists of α-Mg and β-Li phases. On the other hand, the addition of Sm led to significant grain refinement of Mg alloys due to the formation of Mg41Sm5 particles. Sm addition to Mg-Al resulted in the formation of the MgLi2Al, AlLi, and Al2Sm intermetallic compounds. The microstructure and precipitates of Al and Sm addition alloys were refined and elongated in the extrusion direction because of severe deformation during extrusion. The maximum values of the yield strength and ultimate tensile strength were 195.9MPa and 221.4MPa at Mg-8Li-5Al-2Sm alloy content. MgLi2Al, AlLi, and Al2Sm intermetallic compounds played significant roles in the increase of the mechanical properties. (Received June 29, 2015)
브레이징용 Al 합금 분말의 미세조직에 미치는 Sn 함량의 영향
김용호,유효상,나상수,손현택,Kim, Yong-Ho,Yoo, Hyo-Sang,Na, Sang-Su,Son, Hyeon-Taek 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.2
The powder manufacturing process using the gas atomizer process is easy for mass production, has a fine powder particle size, and has excellent mechanical properties compared to the existing casting process, so it can be applied to various industries such as automobiles, electronic devices, aviation, and 3D printers. In this study, a modified A4032-xSn (x = 0, 1, 3, 5, and 10 wt.%) alloy with low melting point properties is investigated. After maintaining an argon (Ar) gas atmosphere, the main crucible is tilted; containing molten metal at 1,000℃ by melting the master alloy at a high frequency, and Ar gas is sprayed at 10 bar gas pressure after the molten metal inflow to the tundish crucible, which is maintained at 800℃. The manufactured powder is measured using a particle size analyzer, and FESEM is used to observe the shape and surface of the alloy powder. DSC is performed to investigate the change in shape, according to the melting point and temperature change. The microstructure of added tin (Sn) was observed by heat treatment at 575℃ for 10 min. As the content of Sn increased, the volume fraction increased to 1.1, 3.1, 6.4, and 10.9%.
저항점용접된 Al5052/DP590 이종소재의 특성평가 및 공정의 최적화
조범지,김지선,유효상,김인주,이성희,김영곤,Jo, Beom-Ji,Kim, Ji-Sun,Yoo, Hyo-Sang,Kim, In-Ju,Lee, Seong-Hui,Kim, Young-Gon 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.2
IRW(Inverter Resistance Welding) process and DSW(Delta-spot welding) process for dissimilar materials of DP590 and Al5052 were performed to evaluate the welding quality and mechanical properties. IRW experiment was carried out with changing the welding current. The other welding parameters such as pressure force, weld time, squeezing time and holding time were fixed. On the anther hand, DSW experiment was performed using the process tape at welding current of 11.5kA. The other conditions were same as IRW conditions. The various testes such as shear tensile strength, nugget diameters, EDS, SEM and cross-sectional observation for weld zone was performed. As a result, IMC(Inter Metallic Compound) thickness at 11.5kA was thinner than those of 9.5kA and 10.5kA conditions. In addition, thined IMC layer was observed when high electric current apply to the materials(DP590 and Al5052) in a short time throught dissimilar resistance spot welding controling welding conditions. The relationship between the thickeness of IMC and current intensity was after discussed.
Mg-11Li-3Zn-1Sn-0.4Mn 마그네슘 합금의 Ca 첨가에 따른 미세조직 및 기계적 특성평가
김정한,김용호,유효상,손현택,이성희,Kim, Jung-Han,Kim, Yong-Ho,Yoo, Hyo-Sang,Son, Hyeon-Taek,Lee, Seong-Hee 한국재료학회 2015 한국재료학회지 Vol.25 No.6
The effect of adding Ca on the microstructural and mechanical properties of as-cast Mg-11Li-3Zn-1Sn(wt%) alloys were investigated. Mg-11Li-3Zn-1Sn-0.4Mn with different Ca additions (0.4, 0.8, 1.2 wt%) were cast under an $SF_6$ and $Co_2$ atmosphere at $720^{\circ}C$. The cast billets were homogenized at $400^{\circ}C$ for 12h and extruded at $200^{\circ}C$. The microstructural and mechanical properties were analyzed by OM, XRD, SEM, and tensile tests. The addition of Ca to the Mg-11Li-3Zn-1Sn-0.4Mn alloy resulted in the formation of $Ca_2Mg_6Zn_3$, MgSnCa intermetallic compound. By increasing Ca addition, the volume fraction and size of $Ca_2Mg_6Zn_3$ with needle shape were increased. This $Ca_2Mg_6Zn_3$ intermetallic compound was elongated to the extrusion direction and refined to fine particles due to severe deformation during hot extrusion. The elongation of the 0.8 wt% Ca containing alloy improved remarkably without reduction strength due to the formation of fine grain and $Ca_2Mg_6Zn_3$ intermetallic compounds by Ca addition. It is probable that fine and homogeneous $Ca_2Mg_6Zn_3$ intermetallic compounds played a significant role in the increase of mechanical properties.
AZ31 마그네슘 합금의 리튬 첨가량 변화에 따른 미세조직 및 기계적 특성 변화
김용호 ( Yong Ho Kim ),김정한 ( Jung Han Kim ),유효상 ( Hyo Sang Yoo ),최정원 ( Jeong Won Choi ),손현택 ( Hyeon Taek Son ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.5
Effects of Li addition on the microstructure and mechanical properties of as-cast and as-extruded AZ31-xLi alloys were investigated. AZ31 alloys with different Li addition(0, 2, 5, 8 and 11 wt%) were cast under atmosphere at 720 ℃ and extruded at 200 ℃. Li addition to AZ31 resulted in the formation of AlLi and MgLi2Al intermetallic compounds and random texture. With increasing Li addition from 5 to 8 and 11 wt%, ultimate tensile strength was decreased from 264 to 232 and 193 MPa. On the other hand, the elongation was improved remarkably from 15.6% to 14.2% and 38.6% at room temperature due to the transformation from HCP to BCC crystal structure and a weaker basal texture. With increasing Li addition from 5 to 8 and 11 wt%, compression yield strength was increased from 156 to 193 and 178 MPa. MgLi2Al intermetallic compounds played a significant role for the increase of the mechanical properties.
알루미늄 주조용 SKD61 금형강의 표면처리 방법에 따른 특성 평가
최세원 ( Se-weon Choi ),김철우 ( Cheol-woo Kim ),김용호 ( Yong-ho Kim ),유효상 ( Hyo-sang Yoo ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.6
Arc ion plating (AIP), laser cladding, and nitriding are methods that can prevent mold damage or repair and create cracks and breakages on the die surface. The dissolution and soldering behavior of coated SKD61 by using arc ion plating, laser cladding, and nitriding was investigated. The structure of the coating was investigated as a function of deposition conditions by X-ray diffraction and the crystallographic orientation was determined using the texture factor. The TiAlN film deposited with AIP showed excellent corrosion resistance in the molten aluminum alloy at 680℃. In this paper, we have detailed the corrosion and mass loss phenomena associated with these steel-cast metal interactions. (Received Septemer 23, 2021; Revised Septemer 30, 2021; Accepted October 12, 2021)