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입자 분산된 2024 Al기 복합재료의 기계적 성질에 관한 연구
李義吉 大田産業大學校 1993 한밭대학교 논문집 Vol.10 No.2
This study was performed in order to find mechanical properties variation according to heat treatment of Al composites strengthened by means of dispersing SiC, Al2O3 particulate and the extrusion temperature during extrusion. The composites were fabricated by vacuum-hot pressing for 1hr with each, pressure of 30MPa at 490℃ according to volume fraction variation(5v/o, 10v/o and 20v/o) of SiC, Al_2O_3 and then this composites were homogenized-aged, followed by microhardness test, tensile test and the observation of fracture plane, and was measured with microhardness tester after anealing for 90 minutes at intervals of 50℃ from 300℃ to 450℃. For microhardness test, hardness values increased with aging treatments, compared with homogenization treatments. This study concluded these increases of hardness valus are due to formation of precipitate phase (Θ'). Also, at tensile test, the relatively low values of tensile strength, elongation indicated that strength drops occure because of interface formation between matrix and strengthened material due to uniform mixture. The fracture type presented ductile fracture type as volume fraction of strengthened material decreases and presented brittle fracture type as the volume fraction increase. This study found that the optimum of extrusion temperature is 400-450℃.
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A5083 合金의 鎔接入熱變化에 따른 機械的性質에 관한 硏究
李義吉 大田開放大學 1984 論文集 Vol.1 No.-
A 5083 aluminum alloy was welded by high current MIG Process. The effects of solidified structures on their mechanical properties were investigated. Mechanical properties of Al- Mg alloy A 5083- F welds are influenced with the change of heat input. Tensile strength, elongation, and charpy impact value tend to be lowered with increase in heat input. DAS grows with increase in heat input. As DAS grows, Mg contents in matrix of dendrite cell structures decrease and mechanical properties tend to be lowered. Mechanical properties at the surface of the weld metal are lower than those at the center of the weld metal.
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李義吉 大田工業大學 1988 한밭대학교 논문집 Vol.5 No.1
Dual phase steels were prepared by cooling from intercritical temperature after each cold working at room temperature. And this research investigated the effect of cold working by the annealing time on the tensile strength and deformation behavior of the dual phase steels. High strength and food ductility was acquired by annealing highly cold worked steel for a short time. Formation of nuclear and grain growth of the austenite was continuous for dissolving cementite into austenite. The ductility was improved when the undissolved cementite was little. The mechanical properties were influenced by the volume fraction, the size and the shape of martensite and undissolved cementite.
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Versatic Acid - 10에 依한 Cd(II)의 溶昧抽出에 關한 硏究
李義吉 大田工業專門大學 1980 論文集 Vol.27 No.-
Cd(Ⅱ)의 Versatic Acid-10 에 의한 용매추출에 관한 연구결과를 종합하면 다음과 같다. 1)Cd(Ⅱ)이온의 농도가 10^-2M이고, Versatic Acid-10의 농도가 0.5~2.0M인 범위내에서 유기산은 이량체로 존재하며 추출종으로서 단일종만을 고사하면 그 평범추출종의 조성은 (CdR_2·2RH)_2이고, 이 때의 평범상수값은 2.35×10^-20이다. 2)황산이온에 의한 Cd(Ⅱ)의 생성착물의 안정도상수는 logβ_1 = 0.61 이고 log β_2 = 1.65 이다. 따라서 수용액중에 황산이온농도가 증가하면 Cd(Ⅱ)의의 추출률은 감소한다.
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입자 분산된 2024 Al기 복합재료의 열처리 거동에 관한 연구
李義吉 한밭대학교 산업과학기술연구소 1993 논문집 Vol.1 No.-
2024 Al composites were manufactured using SiC and Al_2I_3 reinforcements for the changes of volume percentage(5v/o, 10v/o and 20v/o). For the homogeneous distribution of powder particles for the volume percentage, jar mill was using for 20hrs and composite samples were obtained under the conditions of 490℃ 30MPA at hot press for 1hrs. After hest treatments for heating conditions, homogeneous, solid solution and aging seperately, physical and mechanical properties of composites were observed by SEM, optical microscope, XRD and micro hardness. In conditions, SiC reinforcement composites were observer better properties then Al reinforcement, and case of SiC, the hardness after aging treatments were 5.5-26.5% higher than the composites after manufactured.
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SiC 입자 강화 2024 AI 복합재료 압출재의 기계적 성질 연구
李義吉 大田産業大學校 1994 한밭대학교 논문집 Vol.11 No.0101
In this papers, SiC particles reinforced composites with 2024 aluminum alloy matrix have been experimentally fabricated fly hot extrusion. The microvickers hardness, fractographs and mechanical properties were examined on the extruded composites. Reinforcements were four volume fraction that increases with 5vf from 5vf to 20vf. The microhardness of the 2024 aluminum matrix composite increase with increasing volume fracrtion, the other way, tensile strength tends to decrease. The other hand, high temperature tensile strength was about 350-445MPa at room temperature, but 150MPa at 573k. According to increase the tensile temperature, fracture mode was increased dimple pattern of ductile fracture mode, and strain rate was shown maximum value at 573K.
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7075 A1기 복합재료의 제조및 기계적 특성(Ⅰ) 혼합 및 성형공정
이의길 大田産業大學校 1994 한밭대학교 논문집 Vol.11 No.0201
Fabrication processes of rapidly solidified 7075 Al alloy and commercial SiC_p powders has been studied by using a jar mill and attrition mill. The methanol as a milling agent has been added to maintain a balance between cold welding and fracturing. Mixing processes proceed by the continual cold welding and fracturing of the constituent powder particles when subjected to the large compressive forces between ceramic balls or stainless steel balls. The steady-state processing condition, i.e., an equiaxed particles, an uniform powder size distribution and a saturation hardness signifying the completion of mixing processes, has been reached at the attrition velocity 100rpm and mixing time more than 4 hours. The powders were produced by cold pressing, degassing and hot extrusion and their microstructures and hardness were investigated.
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이의길 한밭대학교 2006 한밭대학교 논문집 Vol.23 No.-
The cast cylinder cover for S60MC engine type was evaluated with respect to the soundness of the product, compared with the MAN B&W quality specification. The assessment results were summarized, in terms of non-destructive evaluation, chemical and mechanical properties and metallographic analysis.
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알루미늄合金 A5083 熔接金屬의 固溶Mg量과 機械的性質에 관한 硏究
李義吉 大田工業專門大學 1983 論文集 Vol.33 No.-
5083 aluminum alloy plate of 50 mm thickness was welded by high current MIG process. Then, static tensile test was performed on base and weld metal at both room temperature and -196℃. Tensile strength in the weld metal tended to decrease when a parameter increased. The values of y=0 and 100% represent the fusion boundary and the center of the weld metal, respectively. Mg content dissolved in the weld metal which had been obtained by X-ray diffraction technique decreased when the parameter y increased. At the center of the metal, the dissolved Mg content near the specimen surface was less then that near the root of the weld metal. The change of the dissolved Mg content affected the tensile strength. That is, the tensile strength increased approximately linearly when the dissolved Mg content increased.
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