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A5052-H112 합금의 겹치기 마찰교반접합 조직 특성
고영봉,이중헌,박경채,Ko, Young-Bong,Lee, Joong-Hun,Park, Kyeung-Chae 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
The Friction Stir Welding(FSW) has mainly been used for making butt joints in Al alloys. Development of Friction Stir Lap Welding(FSLW) would expand the number of applications. Microstructure of FSLW in A5052-H112 alloy was investigated under varying rotation and welding speed. As the rotation speed was increased and the welding speed was decreased, a amount of heat was increased. As a result, bead interval was narrower, bead width are larger, and experimental bead interval was almost similar to theoretical bead interval. Typical microstructures of FSLW A5052-H112 alloy consist of three zones, including Stir Zone(SZ), Thermo-Mechanically Affected Zone(TMAZ) and Heat Affected Zone(HAZ). As a amount of heat was increased, average grain size was larger in three zones. Nevertheless, the aspect ratio was almost fixed for FSLW conditions. The misorientation of SZ, HAZ and TMAZ was examined. A large number of low angle grain boundaries, which were formed by severe plastic deformation, were showed in TMAZ as comparison with SZ and HAZ. Microhardness distribution was high in order of BM, SZ, TMAZ, and HAZ. The Micro-hardness distribution in HAZ, TMAZ of upper plate were lager than lower plate. Relationship between average grain size and microhardness was almost corresponded to Hall-Petch equation.
폴리머 기판 위의 나노 스케일 금속 박막의 탄성계수 평가에 대한 연구
최현주(Hyun-ju Choi),김재현(Jae-Hyun Kim),이희정(Hee-jung Lee),이중헌(Joong-Hun Lee),김경식(Kyung-Sik Kim),이학주(Hak-Joo Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Nano-scale metal thin films have been extensively utilized in many fields including semiconductor, MEMS, display, and bio-medical applications. Elastic modulus of a metal thin film is a basic parameter for designing a device utilizing it, but it is difficult to measure the elastic modulus of the film when it’s characteristic size is nano-scale. When a stiff thin film is compressively stressed on a soft polymer substrate, it usually forms a wrinkled pattern with a characteristic wavelength due to buckling. The wavelength is closely related to the elastic moduli of the thin film and the substrate. In this study, residually-compressed Au and Ti thin films are deposited on thick PDMS(polydimethylsiloxane) substrates and the resulting wrinkled patterns are analyzed using white light interferometer. The elastic moduli of the thin films are esi mated based on the analysis of the wrinkled patterns and the estimated elastic moduli are compared with those measured by micro tensile test.