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다공질 Ni 및 Ni-Cr으로 강화한 AC4C 복합재료의 제조 및 특성연구
김용현 ( Young Hyun Kim ),김억수 ( Eok Soo Kim ),여인동 ( In Dong Yeo ),이광학 ( Kwang Hak Lee ) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.1
Ni and Ni-Cr porous metals which are estimated to be easy to fabricate by squeeze casting are used as strengtheners for composite materials. As a matrix material, Al-7%wtSi-0.3 wt%Mg(AC4C) has been used. In case of Ni/AC4C and Ni-Cr/AC4C composite, 750℃ melt temperature and minimum 25 MPa squeezing pressure are needed to produce sound composite materials. The observation of interfacial reaction zone at various heat treatment condition showed that solutionizing temperature of above 520℃, the interfacial reaction zone increased proportionally with increasing heat treatment time and reaction products formed by interfacial reaction are mainly composed of Al3Ni and Al3Ni2 phases. The tensile strength of Ni/AC4C and Ni-Cr/AC4C composite is lower than the matrix metal and this can be explained by the brittle intermetallic compounds formed at the interface of Ni and Ni-Cr reinforcements. But the properties of hardness, wear resistance and thermal expansion are better than the matrix due to the strengthening effect of Ni-Cr porous metals.
과공정 Al-Si 합금의 초정 Si 미세조직변화에 미치는 P 첨가와 fading 시간의 영향
박주열 ( Joo Yul Park ),김억수 ( Eok Soo Kim ),이광학 ( Kwang Hak Lee ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.2
N/A Mechanical property of hypereutectic Al-Si alloy is changed according to size and distribution of primary Si. Consequently, the study on the refinement for primary Si is progressed for a long time. But such effect of refinement comes out fading phenomena with the lapse of time. Therefore, this study investigated the optimum condition of primary Si refinement for hypereutectic Al-Si alloy. And we observed various primary Si size with P`s fading phenomena. The experiment results were as follows. For experiment of primary Si refinement, we made hypereutectic Al-Si alloy with various amounts of P addition. As a result of experiment, we obtained the fine microstructure at 0.01wt.%P. And the optimum condition of P addition, for reventing from growth of primary Si by P fading, is estimated 0.1wt.%P.
아공정 Al-Si 합금의 개량처리와 주단조에 의한 조직변화에 관한 연구
윤지현(Ji Hyun Yoon),설은철(Eun Cheol Seol),이광학(Kwang Hak Lee),김억수(Eok Soo Kim) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.1
N/A For application of cast-forging process with Al-Si alloys, casting experiments are carried out by adding Sr and TiB to Al-Si alloys for grain refinement treatment. We experimented on the mechanical properties according to microstructural changes, forging ability test and also investigated the mechanical properties after forging. The finest microstructure could be observed respectively when 0.05 wt.%Sr and 0.1 wt.%TiB were added. In this case, tensile strength and elongation increased much more than as casting. After high temperature deformation simulation test with grain refinement specimens was carried out, about 60N per unit area(㎟) of specimen was confirmed. After hot forging, tensile strength and elongation were increased. It was considered that casting defect was removed by compressive working.
진공다이캐스트법에 의한 Al 합금과 Fe-17wt%Cr 강의 주조접합 특성연구
김흥식,김용현,이광학,김억수 한국주조공학회 1999 한국주조공학회지 Vol.19 No.5
To overcome the undesirable deformation, peeling off and geometrical restrictions which were mainly caused by differences in thermal expansion coefficients during the cladding of aluminum strip and stainless strip, new processing method based on vacuum die casting is designed and implemented in fabricating Fe-17wt%Cr steel (stainless steel). To increase cast-bonding ability, the surface of Fe- 17wt%Cr steel is electrochemical etched to have optimum pit size (above 0.2 mm) and pit density (above 30%). The implementation of vacuum die casting by using surface treated stainless steel (Fe-17wt%Cr Steel) produces good trial products having acceptable cast-bonding ability. The enabling conditions for cast-bonding are pouring temperature 690˚C, filling speed 30 m/sec and casting pressure 800 ㎏/㎠. The microscopic observation of cast-bonded Al/Fe-17wt%Cr steel does not show any evidence of intermetallic compounds. The bonding strength of trial products is 150-400 ㎏/㎠ and this is stronger than conventionally cladded metal having 30-70 ㎏/㎠. (Received September 3, 1999)