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윤덕재,이상목,임성주,김응주 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
This paper presents the deformation behavior of commercial Mg-Al-Zn-Mn type alloys during hydrostatic extrusion process at elevated temperatures. In the current study commercial Mg-Al-Zn-Mn type alloys with different Al contents were subjected to hydrostatic extrusion process at a range of temperatures and at ram speeds of 4.5, 10 and 17 mm/sec. Under the hydrostatic condition at 518K, the alloy with Al contents of 2.9 wt% was successfully extruded at all applied speeds. The alloys with Al content of 5.89 and 7.86 wt% were successful up to 10mm/sec, and finally extrusion of alloy with Al content 8.46wt% was successful only at 4.5 mm/sec. These results show that the deformation limit in the Mg alloys in terms of extrusion speed greatly extended to higher value in the proximity of lower Al content. It is presumed that deformation becomes harder as Al content increases because of strengthening mechanism by solute drag to increase of supersaturated Mg17 Al12 precipitates. Also, microstructures of cast and extruded Mg alloys were compared. Defect-wide microstructure of cast alloy completely evolved into dense and homogeneous microstructure with equiaxed grains.
후벽 튜브의 스피닝 공정에서 롤러 단면 형상에 따른 성형성 분석
윤덕재(D. J. Yoon),신영철(Y. C. Shin),임성주(S. J. Lim),최호준(H. J. Choi) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
In this study, tube spinning process was tried to extend axial length of thick-walled tube. While the thick-walled tube is formed by spinning process, significant heat and excessive buildup can be generated. Therefore, it is very important to minimize the buildup and the heat generation by optimizing the roller geometry. For analysis of forming characteristics with various roller shapes, the three type of roller was fabricated. The experimental study was shown that the roller of concave type was superior for spinning of thick-walled tube to the others in this study.
ECAP된 마그네슘 합금(AZ31) 압출판재의 기계적 물성평가
윤덕재(D. J. Yoon),임성주(S. J. Lim),배성환(S. H. Bae),김응주(E. Z. Kim) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10
In this paper, a transversely isotropic behavior of AZ31 Mg alloy produced by equal-channel angular pressing (ECAP) process was investigated through tensile test and microstructure observation. As a result of the tensile test in three directions(0°, 45°, and 90° to the extrusion direction of the sheet) at room temperature, elongation of as-extruded AZ31 alloy showed an unusual anisotropic behavior depending on the extrusion direction although the yield strength and tensile strength are similar to the ECAPed AZ31 alloy. After 4 ECAP passes following route BC, microstructural observations showed a significant grain refinement, leading to an equiaxed grain structure with average size of 2.5μm. The microstructures of the extruded billet are observed by the use of an Electron Back-Scattering Diffraction (EBSD) technique to evaluate of the influence of extrusion process on the grain refinement and recrystallization mechanism of AZ31 Mg alloy.