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SiCp 입자강화 Al 복합재료에 대한 합금원소의 영향과 시효특성에 관한 연구
김석원(Sug Won Kim),이의종(Ui Jong Lee),우기도(Kee Do Woo),김동건(Dong Keun Kim) 한국주조공학회 2001 한국주조공학회지 Vol.21 No.1
The research on new DRA(discontinuous reinforced alloy) and CRA(continuos reinforced alloy) composites has been carried out to improve the properties of ceramic fiber and particle reinforced metal matrix composites(MMCs). Effects of alloying elements and aging conditions on the microstructures and aging behavior of Al-Si-Cu-Mg-(Ni)-SiCp composite have been examined. The specimens used in this study were manufactured by duplex process. The first squeeze casting is the process to make precomposite and the second squeeze casting is the process to make final composite. The hardening behavior was accelerated with decreasing the size of SiCp particle in the composites. It is considered that the dislocation density increased with increasing SiCp size, due to the different thermal deformation between Al matrix and SiCp during quenching after the solution treatment. Peak aging time to obtain the maximum hardness in 3㎛ SiCp reinforced Al composite was reduced than that in large size(5, 10㎛) of SiCp because of difference in dislocation density. Aging hardening responce(ΔH = H_(max)-H_(S.T)) of composites was greater than that of unreinforced Al alloy because of higher density of second phases in matrix.
ADI 의 미세조직과 기계적 특성에 미치는 특수열처리 및 합금원소의 영향
한상원(Sang Won Han),김석원(Sug Won Kim),이의종(Ui Jong Lee),박진성(Jin Sung Park),우기도(Kee Do Woo),김동건(Dong Keun Kim) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.2
N/A The effects of heat treatments and alloying elements on the microstructure and mechanical charaterisitics of specially austempered ADIs containing alloying elements such as Cu, Mo and Ni were investigated. To compare with the effect of conventional and normal(CN) austempering treatment, two kinds of special austempering treatments which are those with pre-quenching and pre-heating were conducted. The hardness and uniaxial fatigue tests were carried out to evaluate the mechanical charateristics. The hardness of ADI treated by CN heat cycles was higher than those of other ADIs. Cu added ADI (Cu-ADI) tempered at 400 after austenitizing exhibited the highest fatigue life cycles. While austempering after prequenching makes the austenite with high carbon stable, which resulted in transformation to highly strengthened bainites from the carbon enriched austenite phases during tempering. The high carbon enriched banites is considered to improve the fatigue strength.
고속도강의 미세조직 및 기계적 특성에 미치는 합금원소 및 수직원심주조 조건의 영향
김동건,우기도,김석원,이의종 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.2
This study was carried out to investigate the effects of alloying elements and vertical centrifugal casting(V.C.C.) conditions on microstructural behavior and mechanical properties, including hardness and wear characteristics in high speed steel. The hardness and wear test were used to evaluate the mechanical property of high speed steel manufactured by both gravity casting and V.C.C. With the increase in V element addition, the hardness increased. It was found that the amount of MC carbide was increased and M_7C₃ carbide were decreased with the increase in V and Nb content, The cell and carbides became finer and the amount of M_7C₃ carbide was decreased, according to the increase in revolution speed due to increase cooling rate.
고속도강의 미세조직에 미치는 합금원소 및 주직원심주조 조건의 영향
김동건,우기도,김석원,이의종 한국주조공학회 2000 한국주조공학회지 Vol.20 No.5
The HSS consists of hard carbide and matrix of martensite, and so its characteristics of wear resistance, fracture resistance, and surface roughness are good. This study was undertaken to investigate the influence of Nb and V and manufacturing conditions on microstructural behaviors and characteristics in the HSS cylindrical specimens(90 ㎜^(O.D.)×60㎜^(I.D.)×50㎜^H) manufactured using VCC(Vertical Centrifugal Casting). In the specimen of Fe-2C-6Cr-1.5W-3Mo-4V alloy, the amount of MC carbide was increased and M_7C₃ carbide was decreased with the increase of V and Nb contents. The primary VC carbide was formed and followed by the rod-type eutectic MC carbide was formed in the cell boundary in 9%V added specimen. MC carbide was increased, and M_7C₃ carbide was decreased with the addition of Nb content. In the specimen containing more than 3%Nb, primary NbC carbide was formed within the cell of matrix. With increase in rpm, cell and carbides became fine, and amount of carbide M_7C₃ was decreased due to increase in cooling rate.