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일방향 응고한 Al-CuAl2 공정복합재료에 관한 연구 - 층상간격과 결함밀도에 미치는 응고조건과 진동의 영향 -
이길홍,이현규 ( Kil Hong Lee,Hyun Kyu Lee ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.2
N/A The effects of solidification condition and vibration on structure refinement were investigated for unidirectionally solidified Al-CuAl₂eutectic composites. Eutectic composites were unidirectionally solidified under vibration with different growth rates (R) and thermal gradient(G). The lamellar structure was varied according to growth condition (G/R ratio). For the structure refinement the effect of G/R was found out to be greater than that of vibration. The interlamellar spacing(λ) in this materials was varied with the growth rates(R) with λ²R=constant relationship.
진동하에서 일방향응고 시킨 Al-CuAl2 공정복합재료의 응고에 관한 연구
이현규,이길홍 ( Hyun Kyu Lee,Kil Hong Lee ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3
N/A Unidirectional solidification of Al-CuAl₂ eutectic composites was studied under the condition of forced convection by vibration. It has been shown that thermal gradient for solid is different from that for liquid during solidification under force convection by vibration. With increase of vibration, mobility of liquid increases, but decreases with decreasing vibration. The rate of solidification is very high initially, and decreases suddenly. For further solidification, the rate of solidification decrceases slowly, and shows a L-type behavior. The mechanical vibration during solidification effects efficiently on nucleation, and induces a forced convection in liquid. By the forced convection, great thermal gradient of liquid interface between solid and liquid can be obtained. The amount of solute near the interface also decreases as solute distribution is improved by the forced convection. (Received November 14, 1997)
박수정 ( Su Jung Park ),이길홍 ( Kil Hong Lee ),이현규 ( Hyun Kyu Lee ) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.5
N/A The structure and properties of HSLA steel obtained by Osprey forming process were investigated. The porosities were generated at the bottom of specimen due to the quenching effect of cold substrate during forming. The steel had a bainitic structure. The grain size were different among positions due to the cooling rates. The elements such as Mn, S, Si. Cr, Mo and etc. were contained in inclusions. They were formed at grain boundries. The size of them was 1∼2㎛ and has nothing to do with the chemical composition. MnS and NbC were precipitated during rolling and aging.
오스템퍼드 구상흑연주철의 질량효과가 마모 및 절삭성에 미치는 영향
이현규,이길홍 한국주조공학회 1999 한국주조공학회지 Vol.19 No.4
Austempered ductile iron(ADI) has recently attracting attention due to its property of superior strength with considerable elongation .However, its actual production has not increased as much as was expected. This is due to its poor machinability which is attributed to the deformation induced martensite transformation of unstable austenite. In this study, the influence of chemical composition, casting thickness, volume fraction of unstable retained austenite and graphite nodule count on the abrasion and machinability of ADI have been investigated. The machinability of ADI is improved by reduction in volume fraction amount of unstable austenite. Therefore, the ADI with high graphite nodule count shows a higher machinability than the other specimen with low nodule count. The amounts of abrasion were increased as the retained austenite content increased but the hardness were decreased.(Received July 1,1999)