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.

알루미늄合金 A5083 溶接金屬의 低溫 衝擊特性에 關한 硏究

李義吉 大田工業專門大學 1982 論文集 Vol.31 No.-

A Study has been performed on the characteristics of impact test at lower than foom temperature on weld metal of A 5083 Aluminum alloy. A 5083 aluminum alloy plate of 10㎜ thickness was welded by MIG pulse arc process. Then, impackt test was performed on base and weld metal at room temperature, -80 and -196℃ For the weld metal, Charpy impect test was also performed on the weld metal after homogenization at 500℃ for 20 hours. Charpy impact values were approximately the same at -196℃ as the room temperature for the base metal. For the weld metal, howerver, the values at -196℃ were lower than those at room temperature. This phenomenon was mainly due to the decrease of crack propagation energy. After the homogenization of the weld metal the Charpy impact values increased. Besides, crack initiation energy increased approximately linerly when the dissolved Mg content increased.

SNCM8 構造用合金鋼의 機械的性質 및 破壤特性에 관한 硏究

李義吉 大田開放大學 1986 論文集 Vol.5 No.-

Mechanical properties and fracture toughness of SNCM8 rolled alloy steel for structural purposes have been investigated under the condition of tempering temperature from 200℃ to 600℃ and tested direction. The tensile and yield strengths decreased with increasing tempering temperature and the properties did not vary much with roller direction. The elongaton, reduction ratio, charpy impact value and fracture toughness increased with increasing tempering temperature and these properties in the rolling direction have the higher value compared with that in transverse direction. Also impact value and fracture toughness in the rolling direction have the higher value compared with those in the transverse direction for the same yield strengths.

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.

SiCw / Al 복합재료의 열처리에 따른 계면현상에 관한 연구

李義吉 大田工業大學 1992 한밭대학교 논문집 Vol.9 No.2

In the present study, the effects of Al/sic interface reaction and the formation of Al_4C_3 compounds on the mechanical properties of the Al/siC composites prepared by squeeze casting were investigated. After squeeze casting, the size of dendrites in Al without whiskers were larger than those with whiskers. The hardness of composite materials(about 72 Hv) was found to be approximating 40% higher than that of matrix metal(29Hv), which gradually increases with heat treatment time showing maximum hardness at 12hr. The observation of increasing number of compounds in 12hrs heat treatment suggests that these compounds are responsible for the increase of hardness. E.P.M.A. analysis suggested that the formation of Al_4C_3 compounds near Al/SiC interface occurs through diffusion of Si in SiC into Al matrix. By X-ray diffraction studies, those compounds was identified to be Al_4C_3. The tensile strengh of composite materials was gradually decresed by heat treatment, which was in contrast to the behavior of hardness. With increasing heat tretment time, the fracture mode of composite materials was changed from large dimples and pull-out form of fiber to the fracture and rupture form of fiber.

이상강의 機械的 性質에 미치는 冷間加工의 效果

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.

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℃.

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.

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.

Versatic Acid-10에 依한 Zn(II)의 溶媒抽出 및 陰이온의 影響에 關한 硏究

李義吉 大田工業專門大學 1981 論文集 Vol.29 No.-