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김승언 ( Seung Eon Kim ),정희원 ( Hi Won Jeong ),현용택 ( Yong Taek Hyun ),이동근 ( Dong Keun Lee ),이용태 ( Yong Tai Lee ),박중근 ( Joong Keun Park ),이준희 ( Jun Hee Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.6
Alloy design and in-vitro assessment of biocompatibilities of novel titanium alloys with low elastic modulus were studied. A contour map of elastic modulus which enables to predict low modulus alloy composition was established by using electron theory. Ti-30Ta-10Nb-10Zr, Ti-40Ta-10Nb-10Zr and Ti-40Ta10Nb-4Sn alloys were designed by using the contour map of elastic modulus, and Young`s moduli of those alloys were as low as around 60 GPa. Anodic polarization curves for the alloys represented that corrosion resistance of Ti-40Ta-10Nb-10Zr and Ti-40Ta-10Nb-10Zr was comparable to those of biomedically approved CP Ti and Ti-6Al-4V in simulated body fluid(Hank`s solution) at 37℃, while corrosion resistance of Ti-40Ta-10Nb-4Sn was inferior to those of CP Ti and Ti-6Al-4V. MTT assay with osteoblast-like cells(MG63) showed that the extent of initial cell attachment was similar in all alloys, while cell proliferation of Ti-40Ta-l0Nb10Zr and Ti-40Ta-10Nb-4Sn alloys was more sluggish than those in CP Ti and Ti-6Al-4V. It was therefore realized that the selection of alloying elements for designing low modulus alloys should be considered in the viewpoint of cell growth as well as cytotoxicity.
니켈계 초내열합금 CM247LC의 일방향응고 시 미세조직 형성거동 분석
서성문 ( Seong Moon Seo ),정희원 ( Hi Won Jeong ),윤대원 ( Dae Won Yun ),안영근 ( Young Keun Ahn ),이재현 ( Je Hyun Lee ),유영수 ( Young Soo Yoo ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.5
The Ni-base superalloy CM247LC was directionally solidified (DS) using the Bridgman-type furnace to understand the effect of the chill plate on the microstructural evolution, such as dendrite arm spacing, microporosity, and MC-type carbide. The DS process was also modeled by the PROCAST to predict the solidification rate, thermal gradient, and resultant cooling rate in the entire length of the DS specimen. Due to the quenching effects of chill plate, four distinct areas were found to form in the specimen, in which the solidification rate was changed, during DS at a given withdrawal rate of 0.083 mm/s. Among the microstructural features investigated, the dendrite arm spacings and average size of the MC-type carbide near the chill plate were found to be influenced by the quenching effect of the chill plate. However, no significant influence was found on the size and volume fraction of microporosity, and the volume fraction of the MC-type carbide. The relationship between the microstructural features and the solidification variables was also analyzed and discussed on the basis of a combination of experimental and modeling results
니켈계 초내열합금의 응고 및 용질원소의 편석 거동에 미치는 레늄 및 루테늄 첨가의 영향
서성문 ( Seong Moon Seo ),정희원 ( Hi Won Jeong ),이재현 ( Je Hyun Lee ),유영수 ( Young Soo Yoo ),조창용 ( Chang Yong Jo ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.11
The influence of rhenium (Re) and ruthenium (Ru) addition on the solidification and solute redistribution behaviors in advanced experimental Ni-base superalloys has been investigated. A series of model alloys with different levels of Re and Ru were designed based on the composition of Ni-6Al-8Ta and were prepared by vacuum arc melting of pure metallic elements. In order to identify the influence of Re and Ru addition on the thermo-physical properties, differential scanning calorimetry analyses were carried out. The results showed that Re addition marginally increases the liquidus temperature of the alloy. However, the γ` solvus was significantly increased at a rate of 8.2℃/wt.% by the addition of Re. Ru addition, on the other hand, displayed a much weaker effect on the thermo-physical properties or even no effect at all. The microsegregation behavior of solute elements was also quantitatively estimated by an electron probe microanalysis on a sample quenched during directional solidification of primary γ with the planar solid/liquid interface. It was found that increasing the Re content gradually increases the microsegregation tendency of Re into the dendritic core and γ` forming elements, such as Al and Ta, into the interdendritic area. The strongest effect of Ru addition was found to be Re segregation. Increasing the Ru content up to 6 wt.% significantly alleviated the microsegregation of Re, which resulted in a decrease of Re accumulation in the dendritic core. The influence of Ru on the microstructural stability toward the topologically close-packed phase formation was discussed based on Scheil type calculations with experimentally determined microsegregation results.
Ni 기지 초내열합금의 고온산화 저항성에 미치는 Ti의 영향
박시준 ( Si-jun Park ),서성문 ( Seong-moon Seo ),유영수 ( Young-soo Yoo ),정희원 ( Hi-won Jeong ),장희진 ( Hee Jin Jang ) 한국부식방식학회 2016 Corrosion Science and Technology Vol.15 No.3
The effects of Ti on the high temperature oxidation of Ni-based superalloys were investigated by cyclic oxidation at 850 °C and 1000 °C. The oxide scale formed at 850 °C consists of Cr2O3, Al2O3, and NiCr2O4 layers, while a continuous Al2O3 layer was formed at 1000 °C. The oxidation rate of the alloy with higher Ti content was higher than the alloy with less Ti content at 850 °C, possibly due to the increase in the metal vacancy concentration in the Cr2O3 layer involved by incorporation of Ti4+. However, Ti improved the oxidation resistance of the superalloy at 1000 °C by reducing oxygen vacancy concentration in Al2O3 layer.
Ti-Si 및 Ti-Fe-Si 주조합금의 열간정수압 성형에 의한 티타늄 실리사이드의 형성과 결정학적 특성
鄭喜元,金承彦,玄容宅,李龍泰 대한금속재료학회 2001 대한금속·재료학회지 Vol.39 No.12
The silicon addition in the titanium alloys yields the solid solution and titanium silicides. The morphology and distribution of the titanium silicides depend upon the alloy chemistry or the heat treatment condition, and play an important role in improving the mechanical properties of the alloys. In this study, the morphology, formation process, and crystallographic characteristics of the titanium silicides in the Ti-Fe-Si alloy system were studied. Three types of silicides were found in the alloys; (1) interconnected chain-like silicides at grain boundary, (2) coarse silicides over 1 ㎛, (3) fine silicides less than 0.2 ㎛. Ti_3Si was dominant in cast + HIP condition while Ti_5Si_3 was dominant in as-cast state. It is recognized that Ti_5Si_3 → Ti_3Si transition occurred by the peritectoid reaction and it may be promoted by pressure during HIP. However, in the case of the fine silicides, Ti_3Si and Ti_5Si_3 were found simultaneously even after HIP. Such a fine silicide was found to have crystallographic orientation relationship with β matrix.
Ti-6Al-4Fe-0.5Si 합금에서 Ti-Si 석출과 베타상의 방위관계
최병학,김진우,정희원,현용택,김승언,이용태 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1
This study examined the effect of Si addition in (α+β) Ti alloy on the phase stability about the Ti silicide precipitation from b matrix. The changes in the volume fraction and shape of precipitates with different Si contents were correlated with the tensile properties of the present alloys based on the detailed TEM micrographic observation. In Ti-6Al-4Fe-0.5Si alloy, the precipitates with rectangular or round shape were found at inter-grain of α/β interface and intra-grain of β phase. The precipitates were generally known as Ti5Si₃ with enough stabilizing thermo-mechanically. However, in this study, a new type silicide of Ti_(5)Si₄was mostly observed in the as-cast specimens, representing the metastable or unstable state phase thermo-mechanically compared to Ti_(5)Si₃. It was consistent with the phase transformation processes of TiSi₂TiSiTi_(5)Si₄Ti5Si₃ in the ternary alloy system of Ti-Al-Si. The improvement of mechanical properties including high temperature ones was to be induced by the fine precipitation of Ti silicides such as Ti5Si₄ and Ti5Si₃ in the ductile matrix of b phase. The precipitates of Ti_(5)Si₄ (P1) and Ti_(5)Si₃ (P2) have a coherent relationship with bcc β matrix of (200)_(β) //(220)_(P1) //(2111)_(P2) and (011)_(β) //(001)_(P1)//(0110)_(P2).
고상 Ti 기자에서의 반응생성에 의한 TiB 의 성장거동 및 계면특성
이용태,정희원 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.1
Formation behavior and characteristics of the interface which were in-situ formed between TiB₂ reactant powder and α-Ti matrix were investigated. Furthermore, the effect of a TiB growth on densification of Ti/TiB₂ mixture was also examined. Mixed powders of TiB₂ or B₄C powder with CP Ti powders were compacted and pre-sintered at 700℃ for 1 hr followed by sintering at 900, 1000. 1100, 1200. 1300℃ for 3hrs, respectively. In addition, another specimens were sintered at 1000℃ for various times in order to study the formation behavior of TiB reinforcement in-situ formed in the α-Ti matrix. TiB was formed through the different mechanisms - formation of fine TiB and formation of coarse TiB by Ostwald ripening or coalescence of fine TiB. There was no crystallographic relationship between TiB and matrix. There were voids at the interface between TiB reinforcement and α-Ti matrix because of the preferential growth of TiB without any crystallographic relationship with α-Ti matrix and the surface energy between Ti matrix and TiB reinforcements, and so densification of Ti/TiB₂ compacts was hindered by the coarse TiB growth.
원심주조법으로 제조된 Ti-(2 ~ 6) A1-4Fe-(0.5, 1) Si 합금의 미세조직과 기계적 특성
현용택,김승언,이용태,정희원 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.1
Ti-4Fe-(0.5, 1)Si had been investigated as a preliminary study for the development of a new titanium alloy having a low cost and high strength. The tensile strength of these alloys was comparable to that of a Ti-6Al-4V at room temperature, while lower at 400℃. For this reason, Ti-4Fe-(0.5, 1)Si-xAl (x = 2∼6 wt%) alloy system was redesigned to improve tensile strength even at 400℃ as well as at room temperature. In general, the new alloys exhibited the prior β grain size and the aspect ratio of a phase decreased with increasing Al content. The Ti_5Si₃ phase was precipitated mainly at β grain boundary in as-cast specimens. However, almost of the Ti_5Si₃ phase was transformed into Ti₃Si phase after HIP. The addition of Al to Ti-4Fe-(0.5, 1)Si alloy made the size of silicides finer, while in the case of Ti-4Fe-1Si-(2∼6)Al system coarse silicides were formed. The coarse silicides were formed mainly at grain boundary and decreased the ductility of the alloys at room temperature and at 400℃. After systematic investigation of these alloy system, suggested optimum composition is Ti-6Al-4Fe-0.5Si. Ultimate strength of this alloy was 1191 ㎫, and 930 ㎫ at room temperature, and at 400℃, respectively. These properties are superior to those of Timetal 62S as well as those of Ti-6Al-4V.