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RISS 인기검색어
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- 저자 : 이기대(K. D. Lee) (검색결과 4 건)
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Ni-Cr-(Ti,Nb,Fe)계 초내열합금 제조 및 평가
이기영(K. Y. Lee),안장홍(J. H. Ahn),손희영(H. Y. Son),남희수(H.S. Nam),김동배(D. B. Kim),이락규(L. G Lee),이기대(K. D. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
Nickel based Ni-Cr-(Ti,Nb,Fe)Super-alloy has been used in gas turbine and valve spring because of its low thermal expansion ratio, corrosion resistance, and high creep strength properties. Likewise other super-alloys composed of Ni-Cr-(Ti,Nb,Fe) have been imported to advance domestic manufacturing technology in the field of ingot making and ingot’s break down. In this project, the overall manufacturing process has been successfully performed, and the appraisal on nickel based Ni-Cr-(Ti,Nb,Fe)Super-alloy forged bar has been also carried out in the analysis of microstructure and mechanical properties with heat treatment.
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Ag-20wt% Pd-20wt% Cu 3원합금(元合金) 및 Au첨가합금(添加合金)의 시효경화특성(時效硬化特性)
박명호,배봉진,이화식,이기대,Park, M.H.,Bae, B.J.,Lee, H.S.,Lee, K.D. 대한치과기공학회 1997 대한치과기공학회지 Vol.19 No.1
The Ag-Pd-Cu alloys containing a small amount of Au is commonly used for dental purposes, because this alloy is cheaper than Au-base alloys for clinical use. However, the most important characteristic of this alloy is age-hardenability, which is not exhibited by other Ag-base dental alloys. The specimens used were Ag-20Pd-20Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electic furace and centrifugal casting machine in Ar atmoshpere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at $350{\sim}550^{\circ}C$ Age-hardening characteristics of the small Au-containing Ag-pPd-Cu dental alloys were investigated by means of hardness testing, X-ray diffraction and electron microscope observations, electrical resistance, differential scanning calorimetric, emergy dispersed spectra and electron probe microanalysis. Principal results are as follows : Hardening occured in two stages, I. e., stage I in low temperature and stage II in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the Llo type face centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affedted by the Cu concentration. In stage II, decomposition of the $\alpha$ solid solution to a PdCu ordered phase(L1o type) and an Agrich ${\alpha}2$ phase occurred and a discontiunous precipitation occurred at the grain boundary. Form the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipitation procedure was ${\alpha}\to{\alpha}+{\alpha}2+PdCu\to{\alpha}1+{\alpha}2+PdCu$ at Pd/Cu = 1 Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at $450^{\circ}C$.
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Ag-20Pd-20Cu合金의 組織觀察 및 耐蝕性에 미치는 Au 添加의 影響
이화식,배봉진,김정숙,이기대 대구보건대학 1997 대구보건대학 論文集 Vol.17 No.-
The use of low-noble dental alloys in densitry has increased with the rising price of gold. A decrease in the noble metal content of such fairly complex alloys easily results in multi-phase structures. Dental Ag-Pd-Cu alloys exhibit the characteristics of age-hardenabifity. Palladium represses the sulphurization of silver, and the age-hardenability is caused by the addition of copper. In order to improve the corrosion resistance, a small amount of gold is added to the commercial alloys These alloys were melted and casted by induction electric furnace and centrifugal casting machine in AK atmosphere. They were rolled and drawn into plate and wire shape. These specimens were solution treated for 2hr at 800 C and were then quenched into iced water, and aged at 350-550℃ Microstructural characteristics of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of electron microscope observations, emergy dispersed spectra and electron probe microanalysis, and dental application was carried out by corrosion test. Principal results are as follows : It was very effective that addition of small amount of Au increased corrosion resistance in Ag base dental alloy and increasing the Pd content of Ag base alloys also increased corrosion resistance. The formation of the lamellar structure developed from grain boundaries by discontinuous precipitation. Lamella structure will contribute more to corrosion resistance and is prone to high corrosion rate.
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Ag-25Pd-15Cu合金의 組織觀察 및 熱分析에 미치는 Au 添加의 影響
배봉진,이화식,이기대 대구보건대학 1998 대구보건대학 論文集 Vol.18 No.-
Dental Ag-Pd-Cu alloys exhibit the characteristics of age-hardenability. Palladium represses the sulphurization of silver, and the age-hardenability is caused by the addition of copper. In order to improve the corrosion resistance, a small amount of gold is added to the commercial alloys. In dentistry, the gold content has increased year by year so that 20% is contained in the present commercial alloys. The specimens used were three Ag-Pd-Cu ternary alloy and three Ag-Pd-Cu-Au alloy. These alloys were melted and casted by induction electric furnace and centrifugal casting machine in Ar atmosphere. They were rolled and drawn into plate and wire shape. These specimens were solution treated for 2 hr at 800℃ and were then quenched into iced water, and aged at 350~550℃. Age-hardening characteristics of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of hardness testing, electrical resistance, differential scanning calorimetric, and electron microscope observations. Principal results are as follows : Hardening occured in two stages, i. e., stage Ⅰin low temperature and state Ⅱ in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the L10 type face-centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affected by the Cu concentration. In stage Ⅱ, decomposition of the α solid solution to a PdCu ordered phase (L10 type) and an Ag-rich α2 phase occurred and a discontinuous precipitation occurred at the grain boundary. From the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipetation procedure was α → α + α2 + PdCu → α1 + α2 + PdCu at Pd/Cu = 1.7. The formation of the lamellar structure developed from grain boundaries by discontinuous precipitation. Lamella structure will contribute more to hardenability. Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at 450℃.
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