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Ni/Ni<sub>3</sub>Al 단결정의 냉간압연 거동에 미치는 결정방위 및 석출물의 영향
송성훈 ( S. H. Song ),위당문 ( D. M. Wee ),박노진 ( No-jin Park ),오명훈 ( Myung-hoon Oh ) 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.1
In this study, thin foil fabrication using Ni/Ni<sub>3</sub>Al single crystal was performed by cold-rolling. It was found that the cold-rolling behavior was strongly dependent on the initial crystallographic orientation rather than morphology of Ni<sub>3</sub>Al precipitates. The deformation banding was formed in the case of (100)[001]- and (210)[001]- oriented specimens at 83% reduction in thickness. However, the effects of Ni<sub>3</sub>Al precipitates morphology on the microstructure evolution of Ni/Ni<sub>3</sub>Al single crystals during cold-rolling were not so serious comparing with the effects of initial crystallographic orientation. Therefore, it could be concluded that the deformation behavior of Ni/ Ni<sub>3</sub>Al single crystals at serious strain level was strongly dependent on the initial crystallographic orientation rather than the morphology of Ni<sub>3</sub>Al precipitates, whereas the initial deformation behavior was related to both crystallographic orientation and the morphology of Ni<sub>3</sub>Al precipitates. (Received December 9, 2019; Revised December 17, 2019; Accepted December 27, 2019)
TiAl 합금의 내산화성 개선을 위한 Al-21Ti-23Cr 플라즈마 용사코팅
李在敬,吳明勳,李炯根,韋當文 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.10
To improve the oxidation resistance of γ-based TiAl alloy, Al-Ti-Cr coatings of approximately 150 ㎛ thickness were deposited on Ti-48Al alloy using an air plasma spraying(APS) process. We used Al-Ti-Cr powders with the composition of Al-2lTi-23Cr(at.%). Isothermal and cyclic oxidation tests at 1000℃ in air were utilized to investigate the oxidation resistance of both Al-Ti-Cr coatings and of TiAl alloys with Al-Ti-Cr coatings. Phase identification of Al-Ti-Cr coatings was performed by XRD. After exposure at 1000℃ in air, rutile TiO_2, which resulted from the oxidation of Ti during spraying, was always found in addition to protective α-Al_2O_3 in the oxide scale. However, isothermal and cyclic oxidation tests of a Ti-48Al alloy coated with an Al-Ti-Cr coating showed that this coating improved the oxidation resistance of TiAl alloy at 1000℃ despite partial spalling in the Al-Ti-Cr coating layer. Moreover, cyclic oxidation tests of Al-Ti-Cr coatings showed stable oxidation behavior at 1000℃ up to 100h because of good adhesion between the coating layer and the oxide scale although the growth rate of oxide was relatively high. Therefore, it could be suggested that the Al-Ti-Cr coating was effective in enhancing the oxidation resistance of the TiAl alloy at 1000℃, although the improvement of adhesion between the coating layer and the TiAl substrate was required.
윤의박,김기배,차정민,조순형,위당문,남태운 대한금속재료학회(대한금속학회) 1985 대한금속·재료학회지 Vol.23 No.7
In this paper decomposition and thermal stability of the supersaturated solid solution of Al-Cr alloys were investigated. Al-1.2 wt%Cr alloys were rapidly solidified by using a small droplet chill quenching method. The decomposition process of the supersaturated Al-Cr solid solution by annealing at 350℃ to 600℃ and up to 60 hours was examined by means of microhardness and X-ray diffraction analysis. Hardness measurements on supersaturated Al-Cr solid solution annealed isothermally showed no sign of age hardening. The activation energy for decomposition was estimated to be 52.6㎉ and the thermal stability to be 0.76. The microstructural change during isothermal aging was that the fine, globular particles, which were nucleated heterogeneously along the cell boundary, were grown into chunky particles. The decomposition process was considered by establishing a cylindrical cell model and by using Johnson-Mehl equation. At the initial stage of the decomposition process the decomposition was governed by the diffusion controlled growth of a fixed number of particles (that was, the time exponent of Johnson-Mehl equation n=3/2), and at the middle and final stage the decomposition was governed by the combination of the diffusion controlled growth of cylinders in axial direction only and growth on dislocation (that was, n=1∼2/3).
Si 및 C이 복합첨가된 TiAl-Nb 합금의 열적안정성 및 기계적 성질
김정환,김성웅,이호년,김민철,오명훈,위당문 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.8
Thermal stability of the lamellar microstructure in TiAI-Nb alloys containing Si and C was investigated by partial melting experiments. The proper compositions which have enough thermal stability to be used as a seed material were found for TiAl-Nb-Si-C alloy system. The lamellar microstructure of the Ti-44.5A1-3Nb-0.6Si-0.2C and Ti-45Al-2Nb-0.6Si-0.2C alloys was successfully aligned parallel to the growth direction by directional solidification using Ti-44.5A1-3Nb-0.6Si-0.2C alloy as a seed material. The DS ingots of these alloys exhibited a excellent combination of room-temperature ductility (8.5%) and high-temperature yield strength (700 MPa at 800℃). Nb was not an effective element to improve the lamellar stability. However, adding a small amount of Si and C to the TiAl-Nb system was very effective to improve the thermal stability of the lamellar microstructure.
급냉응고/분말야금법으로 제조한 Al-Fe-V-Si-Ti-W 합금의 고온크립거동
김인수,김낙준,남수우,위당문,오승철,최상우 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11
The elevated temperature creep properties and microstructural stability of RS/PM Al-10Fe-1.3V-2Si-1Ti-1W(wt.%) alloy have been investigated. The alloy showed high stress exponent of 12 to 18 and activation energy of 237 to 808 kJ/㏖, which was strongly dependent on the temperature and stress. The unusual creep behavior of the dispersion strengthened alloys cannot be described satisfactorily by current creep laws, Recently, Ro¨sler and Arzt proposed a new model assuming thermally activated dislocation detachment from dispersoids exerting an attractive force. In the present study, experimental evidence was achieved for the presence of attractive interaction between the dislocation and the dispersoids using TEM observations. The creep behavior of the alloy was analyzed using the model proposed by Ro¨sler and Arzt, and the experimental data were consistent with the prediction based on the model. It has been confirmed that the high temperature deformation of the alloy was dominated by the dislocation creep at the temperature range of 400 to 480℃, but the diffusional creep at the interface between powders also contributed to the deformation above 430℃.