중간가공열처리를 거친 8090 Al-Li 합금의 Delamination과 저온기계적성질

맹선재,박기두 漢陽大學校 工學技術硏究所 1996 工學技術論文集 Vol.5 No.1

Low temperature tensile properties and charpy V-notch impact properties of 8090 Al-Li Alloy have been studied after thermomechanical treatment. The test samples were machined in the L-T direction. By decreasing the test temperature, both the strenghth and elongation, and the impact energy have been increased. The cracks have propagated along the grain boundaries in the longitudinal direction. Delaminations in the tested samples have been increased by decreasing the test temperature. The increase of total delamination length in a sample corresponded to the increased fracture toughness value, and the impact energies. Cold working after solution treatment contributed decreasing the delamination and impact energy, when compared with the non-cold worked case.

중간가공처리가 8090 Al-Li 합금의 파괴인성 및 응력부식균열성에 미치는 영향

맹선재,홍석주 漢陽大學校 工學技術硏究所 1997 工學技術論文集 Vol.6 No.1

Effect of cold working and aging treatment on the fracture toughness and stress corrosion cracking(SCC) sensitivity of 8090 Al-Li alloy has been studied. Fracture toughness was evaluated by Klc test using compact tension(CT) specimen. SCC sensitivity was evaluated by crack growth rate test in 3.5 wt% NaCl solution using single edge notched(SEN) specimen. Cold working prior to the aging treatment has resulted in decreased fracture toughness and increased SCC sensitivity. Peak aging decreased fracture toughness and increased SCC sensitivity compared to the underaged specimen. Aging treatment affected more largely on SCC sensitivity than cold working.

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

기념강연 : 금속강도 분야 학문 발전의 발자취

맹선재 ( Sun Chae Maeng ) 대한금속재료학회 ( 구 대한금속학회 ) 1997 재료강도 심포지엄 Vol.- No.-

한국 전통 금속 공업 : 일용품

맹선재 (Sun Chae Maeng) 대한금속학회 1999 大韓金屬學會會報 Vol.12 No.1

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.

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.

7075 Al 합금의 초소성 변형시 공동형성에 관한 연구

맹선재,신동혁,최능열,주연준 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.9

Cavitation during superplastic flow was investigated for 7075 Al alloy strained under uni-axial tension at 516℃. The 7075 Al alloy was thermomechanically processed to develop fine grain sizes of Bum and 12㎛, respectively. Cavitation and superplastic elongations between specimens with 8㎛ and 12㎛ were observed to be different. In the 8㎛ microstructure, the cavity stringers were formed along the tensile direction, whereas in the 12㎛ microstructure, the stringers were always oriented along the rolling direction, regardless of the tensile direction. The difference in the formation of cavity stringers seems to be mainly due to the distribution of the second phase particles in the matrix.

열작용과 변형을 받은 아연단결정의 전위구조

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.

냉간가공 및 열처리가 복합조직강의 기계적 성질과 Delamination 에 미치는 영향

맹선재,조항훈,김일영 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.11

Dual-phase steels with different phase ratios were produced by water quenching from different intercritical temperature of 740℃ and 780℃. The steels were then cold rolled and aged at 600℃. Tensile properties were not much different in spite of the different phase ratio. the aging treatment increased the strength and decreased the elongation of the steels studied. Cold working and aging treatment promoted delamination. Carbide precipitate on grain boundaries, which have been produced by the aging, affected the delamination most strongly.