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극저온과 온간 압연을 적용한 6061 Al 합금의 강도 향상에 대한 연구
강의구(U. G. Kang),이호진(H. J. Lee),남원종(W. J. Nam) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Ultrafine-grained Al 6061 alloy which was fabricated by the combination of cryogenic rolling with warm rolling, exhibited high strength, ultimate tensile strength, 420㎫. The strengthening effect was compared with the results by other severe plastic deformation methods. This notable increase of tensile strength was achieved by the formation of fine precipitates during warm rolling. The presence fine precipitates of diameter below 100 ㎚, in ultrafine-grained matrix, were confirmed with TEM and STEM. Estimated precipitation-strengthening by the fine precipitates was approximately 100㎫. Based on the results, it was found that the cryogenic rolling combined with warm rolling would be effective in increasing strength and expanding application area in industries.
극저온 압연 및 온간 압연 기술을 이용한 고강도 및 고연성 5052 알루미늄 제조
정신웅(S. W. Jeong),강의구(U. G. Kang),남원종(W. J. Nam) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The effects of deformation temperatures and post-deformation annealing on mechanical properties, in conjunction with microstructural evolution in the 5052 AI alloy, were investigated. The combination of cryogenic rolling with warm rolling effectively increased tensile strength and yield strength without the decrease of ductility through the formation of ultra fine grains with dynamic recovery in the 5052 Al alloy. And static annealing, as a post heat treatment, enhanced the ductility. Therefore, ultra-fine grained 5052 Al alloy with high strength and a moderate level of ductility could be made by the combination of cryogenic rolling with warm rolling and the additional static annealing process.
탄소 함량에 따른 펄라이트의 변태거동 및 기계적 특성 분석
정신웅(S. W. Jeong),강의구(U. G. Kang),남원종(W. J. Nam) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
During the isothermal transformation, the volume fraction of pro-eutectoid ferrite does not follow the lever rule expressed in the equilibrium phase diagram. Thus, the carbon content in the pearlite varies with the heat treatment conditions. Since carbon content in pearlite is varied with chemical compositions and heat treated conditions, the variation of microstructural features such as volume fraction and the thickness of the cementite should be considered even at the same interlamellar spacing. Thus, the variations of microstructural features with carbon content and transformation temperatures were investigated, correlating with the variations of mechanical properties. In eutectoid steels, interlamellar spacing increases with the increase of transformation temperatures. But, interlamellar spacing does not seem to correlate with the increase of austenitizing temperature. The effect of increasing transformation temperatures resulted in the decrease of strength and the increase of ductility.