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우기도,박영구,김석원,진영철,류재화,나종필 ( K . D . Woo,Y . K . Park,K . W . Kim,Y . C . Jin,J . H . Ryu,J . P . Ra ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.2
N/A The graphitization is affected by the addition of small amount of the elements, such as Si, Al, Ni, B, Cr and Mn etc. Boron is well known as the most effective element for the graphitization of cementite in high carbon steels. But a study on quantitative analysis of B effect on the graphitization is few reported. Therefore the effect of boron addition in Fe-0.65%C-1.0%Si-0.5%Mn steels on the graphitization is investigated quantitatively using hardness tester, optical microscope and scanning electron microscope, neutron induced microscopic radiography. The graphitization in high carbon steels is promoted with 0.003∼0.005%B addition. But the graphitization in steels which has no boron takes long holding time at 680∼720℃. The hardness of quenched steel containing 0.003%B is higher than that of 0.005%B added steel due to complete dissolution of fine graphites into the austenite. The 0.003%B added high carbon steel graphitized at 680℃ for 25hr is useful steel for the agricultural implements and automobile parts which needed a good formability and high hardness.
무가압 침투에 의하여 제조된 Al-5Mg-X(Si, Cu, Ti)/SiCp 복합재료의 시효 및 마멸특성에 관한 연구
우기도,김석원,나홍석,문호정 한국주조공학회 2000 한국주조공학회지 Vol.20 No.5
The objective of this work was to investigate the effects of SiC particle size(50, l00㎛) and additional elements such as Si, Cu and Ti on aging behavior in Al-5Mg-X(Si, Cu, Ti)/SiCp composites fabricated by pressureless infiltration method using hardness and wear test, scanning electron microscopy(SEM) and differential scanning calorimetry(DSC). The peak aging time in Al-5Mg-X(Si, Cu, Ti)/SiCp(50, 100㎛) composites is shorter than Al-5Mg-0.3Si alloy. The peak aging time of 50㎛ SiC particle reinforced Al-5Mg-X(Si, Cu, Ti) composites is shorter than those of 100㎛ SiC particle reinforced of Al-5Mg-X (Si, Cu, Ti) composites. The Al-5Mg-0.3Si-0.1Cu-0.1Ti/SiCp(50㎛) composites aged at 180℃ has higher hardness and better wear resistance than any other aged composite.The aging effect is promoted by the addition of Si and Cu in Al-5Mg/SiCp composites, so the wear resistance of Al-5Mg/SiCp composites with Si and Cu elements is enhanced by the aging treatment.
무가압 침투법에 의해 제조된 Al-5Mg-X(Si,Cu,Ti)SiCp 복합재료의 조직 및 마멸특성
우기도,김석원,안행근,정진호 한국주조공학회 2000 한국주조공학회지 Vol.20 No.4
Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partio sizes(50 and 100㎛) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of Al-5Mg-X(Si, Cu, Ti)/SiC_p composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound Al-5Mg-X(Si, Cu, Ti)/SiC_p(50 and 100㎛) composites were fabricated by pressureless infiltration method. The Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p composite with 50㎛ size of SiC particle has higher hardness and better wear property than any other composite with 100㎛ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of Al-5Mg/SiC_p(50 and 100㎛) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.
스파크플라즈마 소결에 의한 Ti-Nb-Zr-Mo-CPP 생체복합재의 기계적 성질 및 생체적합성
우기도,김상미,김동건,김대영,강동수,Woo, Kee Do,Kim, Sang Mi,Kim, Dong Gun,Kim, Dae Young,Kang, Dong Soo 한국재료학회 2013 한국재료학회지 Vol.23 No.2
The Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent mechanical properties and biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity of the Al and V elements. Therefore, non-toxic biomaterials with a low elastic modulus need to be developed. A high energy mechanical milling (HEMM) process is introduced to improve the effect of sintering. Rapid sintering of spark plasma sintering (SPS) under pressure was used to make an ultra fine grain of Ti-25 wt.%Nb-7 wt.%Zr-10 wt.%Mo-(10 wt.%CPP) composites with bio-attractive elements for increasing strength. These composites were fabricated by SPS at $1000^{\circ}C$ at 60 MPa using HEMM powders. During the sintering process, $CaTiO_3$, TixOy, and CaO were formed because of the reaction between Ti and CPP. The effects of CPP content on the physical and mechanical properties of the sintered Ti-Nb-Zr-Mo-CPP composites were investigated. The biocompatibility and corrosion resistance of the Ti-Nb-Zr-Mo alloys were improved by the addition of CPP.