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.

석출분산형 마그네슘 합금 제어기술

손현택 ( Hyeon Taek Son ),김대근 ( Dae Guen Kim ),이재설 ( Jae Seol Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2009 재료마당 Vol.22 No.3

Mg-Al-Ca-RE 합금의 주조재 및 압출재의 미세조직과 기계적 특성과의 상관관계 규명을 통하여 RE 첨가는 결정립 미세화, 금속간화합물의 미세 균일 분포 및 집합조직 제어에 의해 강도 및 연성의 향상된 특성을 얻을 수 있었다. 또한 라멜라 형상을 가지는 C14 공정상은 압출시 미세하게 분쇄되므로 강도 및 연성향상에 기여하는 것으로 분석되었으며, RE 금속 중 Sm이 다른 RE 금속보다 Al2RE 금속간화합물의 미세균일 분포하게 되고 소량의 Sm 첨가에 의해 결정립미세화 및 Random texture를 형성한다는 것을 알 수 있었다. 따라서, 연구되어진 Mg-Al-Ca-RE 합금에서 강도 및 연성을 동시에 향상시키기 위하여 RE 금속으로는 Sm을 선택하고 C14 공정상의 분율을 증가시키기 위하여 Al 함량을 감소시키는 합금설계 방안을 마련하였다. Mg-Zn-Sn계 합금의 경우 Zn 함량이 증가함에 따라 시효 경도 값이 증가하였고, 최대 Peak ageing 시간 또한 감소하였다. 이는 Zn 함량의 증가에 따른 용체화처리시 고용되어 있던 Zn이 시효처리에 의해 기지에 미세하게 석출함으로써 시효경도 및 Peak ageing 시간도 감소하는 것으로 사료된다. Mg-Al-Sn계 합금에서 Al 첨가함량이 증가함에 따라 최대 시효 경도는 증가하였다. 두 합금에서 나타나는 석출상의 조성 분석 결과 다른 조성을 갖는 석출상임을 확인 하였다. Zn이 3wt% 첨가된 함금의 경우, Mg2Sn 상이었으며 다른 상은 관찰 되지 않았다. Zn이 5wt% 첨가된 합금의 경우, 수 백 나노 크기의 석출상은 Mg51Zn20 상이었으며 수 나노크기의 석출상은 Mg97Zn2 상이었음을 알 수가 있었다. 또한 Mg-Zn-Sn계 합금에 나타난 석출상은 모상과 평행하는 면을 갖는 면이 존재하였으며 정합성을 가짐을 알 수가 있었다. 따라서, 구조용 금속재료의 경우 서로 반비례 관계를 갖는 강도와 성형성을 동시에 향상시키기 위해 위에 나열한 다양한 방법들이 시도되어 왔으며, 이러한 노력의 일환으로 석출상 또는 분산상 등 제 2상을 제어하는 기술을 개발하기 위한 연구가 활발하게 진행되고 있다. 특히 마그네슘 합금의 경우 다른 경쟁 재료에 비하여 절대강도 및 성형성이 낮으므로 구조용 소재로서 그 적용범위를 확대하기 위해서는 강도 및 성형성의 동시 향상 기술 개발이 절실하게 요구된다.

방전플라즈마 소결공법을 이용한 Mg₉₇Y₂Zn₁ 합금 소결체의 특성평가

홍지민,손현택,장세훈,이재설,차용훈,오익현,Hong, Ji-Min,Son, Hyeon-Taek,Chang, Se-Hun,Lee, Jae-Seoul,Cha, Yong-Hun,Oh, Ik-Hyun 한국재료학회 2007 한국재료학회지 Vol.17 No.6

[ $Mg_{97}Zn_1Y_2$ ] alloy powders were prepared from gas atomization process, followed by consolidation using spark plasma sintering (SPS) process. The atomized $Mg_{97}Zn_1Y_2$ alloy particles were entirely spherical in shape and dendritic microstructure. The compacts sintered by SPS process had theoretical density more than 99%. The compressive yield strength was decreased as sintering temperature increased. It was found that the compressive strength showed the maximum value of 303MPa at the $Mg_{97}Y_2Zn_1$ specimen sintered under load of 255 MPa at $350^{\circ}C$.

방전플라즈마 소결법으로 제작된 순 마그네슘 분말 소결체의 특성평가

홍지민,손현택,장세훈,이재설,차용훈,오익현,Hong, Ji-Min,Son, Hyeon-Taek,Chang, Se-Hun,Lee, Jae-Seoul,Cha, Yong-Hun,Oh, Ik-Hyun 한국재료학회 2007 한국재료학회지 Vol.17 No.6

The pure Mg powder compacts were successfully fabricated using SPS process. The machined chip powder showed flake shaped morphology with coarse surfaces, while gas atomized powders were spherical in morphology with smooth surfaces. In this study, SPS process was used to consolidate the pure Mg powder because this process allows high density consolidation in a short time. The results showed that increased sintering temperature from $350^{\circ}C$ to $500^{\circ}C$ with pressure of 30MPa, the maximum values of the density was increased from 98.1% to 99.8% of theoretical density, respectively. However, density of the sintered chip powders was higher than that of gas-atomized powder due to larger contact areas between particles.

Al-2Zn-1Cu-0.3Mg합금의 Sc첨가에 따른 미세조직, 전기전도도, 열전도도 및 기계적 특성 변화

나상수,김용호,손현택,이성희,Na, Sang-Su,Kim, Yong-Ho,Son, Hyeon-Taek,Lee, Seong-Hee 한국재료학회 2020 한국재료학회지 Vol.30 No.10

Effects of Sc addition on microstructure, electrical conductivity, thermal conductivity and mechanical properties of the as-cast and as-extruded Al-2Zn-1Cu-0.3Mg-xSc (x = 0, 0.25, 0.5 wt%) alloys are investigated. The average grain size of the as-cast Al-2Zn-1Cu-0.3Mg alloy is 2,334 ㎛; however, this value drops to 914 and 529 ㎛ with addition of Sc element at 0.25 wt% and 0.5 wt%, respectively. This grain refinement is due to primary Al₃Sc phase forming during solidification. The as-extruded Al-2Zn-1Cu-0.3Mg alloy has a recrystallization structure consisting of almost equiaxed grains. However, the as-extruded Sc-containing alloys consist of grains that are extremely elongated in the extrusion direction. In addition, it is found that the proportion of low-angle grain boundaries below 15 degree is dominant. This is because the addition of Sc results in the formation of coherent and nano-scale Al₃Sc phases during hot extrusion, inhibiting the process of recrystallization and improving the strength by pinning of dislocations and the formation of subgrain boundaries. The maximum values of the yield and tensile strength are 126 MPa and 215 MPa for the as-extruded Al-2Zn-1Cu-0.3Mg-0.25Sc alloy, respectively. The increase in strength is probably due to the existence of nano-scale Al₃Sc precipitates and dense Al₂Cu phases. Thermal conductivity of the as-cast Al-2Zn-1Cu-0.3Mg-xSc alloy is reduced to 204, 187 and 183 W/MK by additions of elemental Sc of 0, 0.25 and 0.5 wt%, respectively. On the other hand, the thermal conductivity of the as-extruded Al-2Zn-1Cu-0.3Mg-xSc alloy is about 200 W/Mk regardless of the content of Sc. This is because of the formation of coherent Al₃Sc phase, which decreases Sc content and causes extremely high electrical resistivity.

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.

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%.

인발가공에 의해 제조된 전선용 Al-Fe-Mg-Cu-B계 합금의 기계적 및 전기적 특성

정창기,우츠노미야 히로시,손현택,이성희,Jung, Chang-Gi,Hiroshi, Utsunomiya,Son, Hyeon-Taek,Lee, Seong-Hee 한국재료학회 2017 한국재료학회지 Vol.27 No.11

In this study, an Al-0.7wt%Fe-0.2wt%Mg-0.2wt%Cu-0.02wt%B alloy was designed to fabricate an aluminum alloy for electrical wire having both high strength and high conductivity. The designed Al alloy was processed by casting, extrusion and drawing processes. Especially, the drawing process was done by severe deformation of a rod with an initial diameter of 12 mm into a wire of 2 mm diameter; process was equivalent to an effective strain of 3.58, and the total reduction in area was 97 %. The drawn Al alloy wire was then annealed at various temperatures of 200 to $400^{\circ}C$ for 30 minutes. The mechanical properties, microstructural changes and electrical properties of the annealed specimens were investigated. As the annealing temperature increased, the tensile strength decreased and the elongation increased. Recovery or/and recrystallization occurred as annealing temperature increased, and complete recrystallization occurred at annealing temperatures over $300^{\circ}C$. Electric conductivity increased with increasing temperature up to $250^{\circ}C$, but no significant change was observed above $300^{\circ}C$. It is concluded that, from the viewpoint of the mechanical and electrical properties, the specimen annealed at $350^{\circ}C$ is the most suitable for the wire drawn Al alloy electrical wire.

방전플라즈마 소결법에 의해 제조된 다공질 타이타늄 임플란트의 평가

오익현 ( Ik Hyun Oh ),손현택 ( Hyeon Taek Son ),장세훈 ( Se Hun Chang ),김형모 ( Hyung Mo Kim ),이기용 ( Ki Yong Lee ),박순섭 ( Sun Sub Park ),송호연 ( Ho Yeon Song ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.6

Porous Ti compacts were fabricated by spark plasma sintering (SPS) method and their Young`s modulus and biocompatibility were investigated in this study. Ti powders were made from commercially available pure Ti electrode (grade 2) using the plasma rotating electrode process (PREP) in an Ar atmosphere. Porous Ti compacts for biomedical applications were successfully fabricated in the porosity range from 5 to 36 vol%. Young`s modulus of porous Ti compacts having porosity from 31 to 36 vol % is almost the same as that of human cortical bone. To investigate the biocompatibility of pure Ti, fibroblast-like L-929 and osteoblast-like MG-63 cells were cultured with the presence of the extract solution from pure Ti powder and porous body. The viabilities of cells cultured with the diluted extract solutions were almost the same compared to that of the control. Also, porous Ti compacts did not induce any morphologic damage of cell.

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.