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- 저자 : 맹선재 ( Sun Chae Maeng ) (검색결과 37 건)
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Al-Mg-Mn합금의 기계적(機械的) 성질(性質)에 미친 여비압재(予備?在)의 영향(影響)
예길촌,맹선재,Ye, Gil-Chon,Maeng, Sun-Chae 한국현미경학회 1974 Applied microscopy Vol.4 No.1
본 실험에서는 여비압연이 4. 6%Mg-0.5% Mn-0.18%Cr의 알루미늄합금의 균질화처리 및 그의 기계적 성질에 마치는 영향을 조사하였다. 여비압연후 균질화 열처리된 시편은 주조상태의 시편에 비하여 실온 인장강도 및 연신률이 증가되고 있음을 보여주었다. $400^{\circ}C$의 고온 인장시험의 결과는 여비압연후 균질화열처리한 시편이 주조상태 또는 그의 균질화처리만 시행한 것에 비하여 다소 낮은 인장강도와 현저히 향상된 연신률을 소지함을 보여주었다. 여비압연후 균질화열처리된 시편의 금속현미경조직은 다른 시편들에 비해 결정입계에 ${\beta}$ 상등의 제2상이 현저히 감소되고 있음을 나타내고 있다. 시편의 결정입내 및 입계에 있어서의 주된 합금첨가원소인 Mg 분포상태를 EPMA를 사용하여 조사하였다. 이 결과는 균질화처리를 시행하기 전에 여비압연을 도입함으로써 균질화처리의 효과가 증대되고 있음을 보여주고 있다. In this work the effect of pre-rolling on the homogenization and on the mechanical properties of 4.6% Mg-0.5% Mn-0.18% Cr-Al alloy has been studied. At room temperature tensile strength and elongation have been found to increase in the pre- rolled homogenized sample compared to those of the as cast sample. At $400^{\circ}C$ this pre-rolled homogenized sample has shown a little lower tensile strength and a remarkably higher elongation than the samples as casted or homogenized without pre-rolling. Metallurgical microstructure of the pre-rolled homogenized sample has shown conspicuously less secondary phase such as ${\beta}$-phase at the grain boundaries than the other samples. The difference of magnesium content between grain boundaries and within the grains has been also checked by EPMA. The test results show enhanced homogenizing effect by the pre-rolling before homogenizing heat treatment.
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탄소함량이 상이한 Fe-Al-Mn 이상조직강의 상분해에 관한 연구
맹선재,이동한 한양대학교 공학기술연구소 1992 공학기술논문집 Vol.1 No.1
The phase decomposition of dual phase(α + γ) Fe-Al-Mn alloys of different carbon contents has been studied by aging treatment at 600℃. The progress of the phase decomposition was different between the alloys containing more than 0.2wt%C and the alloy with 0.04wt%C. The phase decomposition of the alloys with more than 0.2 %C proceeded in the following process; α → αo + β-Mn → αo + β-Mn + κ γ → γ + α → αo + β-Mn + κ The α-phase decomposed at the early stage of the aging and the γ-phase decomposition proceeded at the later stage of the aging. It was hard to find some more progressive change in the decomposed microstructure, when the aging time has been increased from 250 hours to 500 hours. Phase decomposition of the alloy containing 0.04 %C proceeded very slowly and κ-phase was not produced with all the increased aging time of 500 hours. The phase decomposition of this alloy is as follows ; α → αo + β-Mn ; γ → γ + α → γ + αo + β-Mn
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저탄소 Ni-Cr-Mo-V 강의 Bainite 변태조직에 관한 연구
맹선재,강찬형,현도빈 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.4
低炭素鋼, 0.13C-1.8Ni-1.6Cr-0.5Mo-0.07V의 bainite變態組織을 電子顯徵鏡으로 調査하였다. Bainite變態組織은 試片을 austenite化溫度에서 부터 400℃, 450℃ 및 500℃로 유지되고 있는 鹽浴 속에 넣어 等溫處理시켜 줌으로서 얻었다. Bainite變態는, 試片이 austenite化溫度에서부터 等溫變態處理溫度로 冷却되는 過程에서 이미 일어났는데, 이와같이 初期 冷却過程中에 이미 生成된 變態組織과, 一定한 溫度에서 等溫變態시킬 때 形成되는 變態組織等을 調査하였다. 450℃및 500℃ 等溫變態의 경우에는 初期 冷却過程에서 粗大한 bainitic ferrite lath가 形成된다. 450℃및 500℃에서 等熊變態시킨 組織은 bainitic ferrite의 retained austenite의 混合組織으로 이루어지며, 變態處理時間의 經過에 따라 retained austenite는 점차 微細한 bainitic ferrite lath로 變態하고, 初期에 形成된 粗大한 bainitic ferrite內部에는 carbide가 析出한다. 400℃에서 變態處理시킨 경우에는 이들과는 다른 形態의 微細組織, 즉 이른바 granular bainite의 形態로 나타난다. Bainitic transformation structure in a low carbon alloy steel, 0.13C-1.8Ni-1.6Cr-0.5Mo-0.07V, has been studied by electron microscopy. Bainitic structure was obtained by isothermal transformation in the salt bath holding at 400℃, 450℃ and 500℃, Bainitic transformation has already begun at the initial cooling stage, from the austenitizing temperature to the respective transformation temperature. In the case of isothermal treatment at 450℃ and 500℃, mixed structure of coarse bainitic ferrite lath and retained austenite was observed in the specimens of short transformation time, for example, 200 sec. As the isothermal transformation time increased, the region of retained austenite was replaced gradually by finer bainitic ferrite lath, and carbide was precipitated in the revious coarse bainitic ferrite lath. Detailed microstructural features of the bainitic structure, produced at the initial cooling stage and at the later isothermal treatment stage, were studied, respectively. At the transformation temperature of 400℃, somewhat different microstructure, so-called granular type bainite, was developed.
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맹선재 대한금속재료학회(대한금속학회) 1964 대한금속·재료학회지 Vol.2 No.1
Dislocation etch pits of zinc single crystals grown by modified Bridgman method were studied using etchants of Gilman. The effects of deformation and heat treatment on the substructure of etch pits were also investigated. Elongated cell structures, which were observed by Kratochvil and Sichovla were not found from the as grown crystals. But nonelongated cell structures were detected occasionally. The secondary substructures following homogenization of segregated impurities were not found. Annealed samples have shown grown subgrains and also secondary substructures. Some samples were deformed (bending) at 100℃ or 180℃ during the slow cooling following annealing, and proceeded further slow cooling until it reached room temperature. The substructures which were induced through deformation, were found but not the secondary substructures. With the samples, which were annealed at about 300℃ after deformation, deformation-induced substructures were not found mostly. But greatly grown secondary substructures were found. With the deformed crystals the growth of secondary substructures through heating were more enhanced than undeformed ones.
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상이한 초기조직에서 얻은 이상조직강의 열처리에 따른 인장변형 및 파괴거동
맹선재,신동혁,김일영 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6
The different starting structures of the present study were ferrite + coarse pearlite (F+ P₁), ferrit + fine pearlite(F+P₂) and martensite(M). True stress vs. true strain curves were analysed before and after tempering. When compared the work hardening rate before tempering, the DP steel with the M-starting structure has shown the highest value. Uniform true strain was decreased with increasing tempering temperatures up to 400℃, and then increased above 400℃. Void formation behavior beneath the fracture surfaces of the tensile specimens has been studied. Preferred sites of void formation are the ferrite-martensite interfaces, the elongated martensite ends and the precipitate particles. Voids are also formed by splitting of martensite phases in the case of tempering.
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상이한 초기조직을 갖는 저합금고강도강의 이상역가열에 의한 오스테나이트 형성과 기계적 성질
맹선재,신동혁,장동현,조현권 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.6
Austenite formation and mechanical properties of HSLA steel of different starting structures has been studied by intercritical annealing(IA). The different starting structures are: ferrite+pearlite (FP1), martensite(M1), cold worked ferrite+pearlite(FP2) and cold worked martensite(M2). Austenite was nucleated at ferrite grain boundaries in FP1 and FP2 and also at the interior of the grains in case of FP2. By increasing the IA time globular austenite structures were distributed uniformly all over the space enclosing the ferrite phase. Austenite in M1 and M2 was nucleated at the interface between prior martensite laths and the globular strutctures were formed from the former acicular structures. By increasing the IA time M2 has shown well developed globular austenite structure than M1 and the agglomerated continuous austenite networks surrounding ferrite phases were formed. Tensile strength in all the tested samples of different starting structures was increased by increasing the IA time. Any noticeable change in elongation was not found in FP1, FP2 and M2 by the increase of IA time. Exceptionally elongation of M1 was increased by increased IA time. Chapy V-notch impact values of all the different starting sturctures were decreased by increasing the IA time.
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