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MA법으로 제조된 Ni기 합금에서 Y<sub>2</sub>O<sub>3</sub> 첨가에 따른 인장강도변화와 시효처리 효과
김일호,이원식,고세현,장진만,권숙인,Kim, Il-Ho,Lee, Won-Sik,Ko, Se-Hyun,Jang, Jin-Man,Kwun, Sook-In 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1
Ni-20Cr-20Fe-5Nb alloy with or without $Y_2O_3$ was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with $Y_2O_3$ was smaller than that of alloy without $Y_2O_3$ which results from the effect of $Y_2O_3$ suppressing grain growth. The tensile strength at room temperature was increased by the addition of $Y_2O_3$ but decreased abruptly at temperature above $600^{\circ}C$. It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above $600^{\circ}C$ while internal dislocation movement is predominant at below $600^{\circ}C$. After conventional heat treatment process of solution treatment and aging, a small amount of ${\delta}(Ni_3Nb)$ phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of ${\gamma}"(Ni_3Nb)$ was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.
분말야금 및 주조형 니켈기 초내열합금 크리프 신뢰성의 초음파 모니터링
최찬양,송진헌,오세웅,김정석,권숙인,오승탁,현창용,변재원,Choi, Chan-Yang,Song, Jin-Hun,Oh, Se-Ung,Kim, Chung-Seok,Kwun, Sook-In,Oh, Sung-Tag,Hyun, Chang-Yong,Byeon, Jai-Won 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3
An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of ${\gamma}^{\prime}$ precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of ${\gamma}^{\prime}$ precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.
오석균,현승철,윤상현,김화택,김형곤,최성휴,윤창선,권숙일,Oh, Seok-Kyun,Hyun, Seung-Cheol,Yun, Sang-Hyun,Kim, Wha-Tek,Kim, Hyung-Gon,Choe, Sung-Hyu,Yoon, Chang-Sun,Kwun, Sook-Il 한국진공학회 1993 Applied Science and Convergence Technology Vol.2 No.2
SbSI : V, SbSeI : V, BiSI : V, BiSeI : V, SbSI : Cr, SbSeI : Cr, BiSI : Cr, BiSeI : Cr, SbSI : Ni, SbSeI : Ni, BiSI : Ni, 및 BiSeI : Ni 단결정을 고순도(99.9999%)의 성분원소에 혼합물을 투명석 영관내에 넣고, $1{\times}10^{-6}mmHg$의 진공에서 봉입하여 합성한 ingot를 사용하여, 수직 Bridgman 방법으로 성장시켰다. 성장된 단결정의 구조는 orthorhombic 구조이며, 광학적 energy band gap 구조는 간접전이형 이었고, energy gap의 온도의존성은 상전이에 관계되는 2개의 변곡점이 나타났으며, 연속된 영역에서는 Varshni 방정식을 만족하였다. 첨가한 3d 불순문(V, Cr, Ni)은 모결정의 $T_d$ 대칭을 갖는 주격자점에 +2가 ion으로 위치하며, 이들 ion의 energy 준위간의 전자전이에 의하여 불순물 광흡수 peak가 나타난다. Single crystals, SbSI : V, SbSeI : V, BiSI : V, BiSeI : V, SbSI : Cr, SbSeI : Cr, BiSI : Cr, BiSeI : Cr, SbSI : Ni, SbSeI : Ni, BiSI : Ni, and BiSeI : Ni were grown by the vertical Bridgman method. It is found that the grown single crystals have an orthorhombic structure and the indirect optical transitions. The temperature dependence of energy gap shows the two reflection point related with the phase transitions and is well fitted with Varshni equation in the continuous region. The optical absorption peaks due to the doped impurities (V, Cr and Ni) are respectively attributed to the electron transitions between the split energy levels of $V^{+2}$, $Cr^{+2}$ and $Ni^{+2}$ ions sited at $T_d$ symmetry of the host lattice.
이축하중을 받는 SM45C강의 피로균열의 발생과 성장거동
김상태(SANG-TAE KIM),박선홍(SUN-HONG PARK),권숙인(SOOK-IN KWUN) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.6
Fatigue tests were conducted on SM45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading systems, were employed fully-reserved cyclic torsion without a superimposed static tension or compression fully-reserved cyclic torsion with a superimposed static tension and fully-reserved cyclic torsion with a superimposed static compression. The test results showed that a superimposed static tensile mean stress reduced fatigue life however a superimposed static compressive mean stress increased fatigue life. Experimental results indicated that cracks were initiated on planes of maximum shear strain whether or not the mean stresses were superimposed. A biaxial mean stress had an effect on the direction that the cracks nucleated and propagated at stage 1 (mode Ⅱ).
초음파현미경을 이용한 Co 기 초내열 합금 열화재의 비파괴평가
김정석(Chung Seok Kim),송진헌(Jin Hun Song),권숙인(Sook In Kwun),임재생(Jea Seang Lim),박익근(Ik Keun Park) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
This research investigates the feasibility of ultrasonic microscope for nondestructive assessment of thermal degradation in artificially aged commercial Co-base superalloy, FSX414. This alloy has been used for high temperature structure applications such as stationary gas turbine blade and nozzle chamber in fossil plant. Microstructural change was found that the fine carbides became coarser and spheroidized in matrix as aging time increased. The leaky surface acoustic wave velocity gradually decreases by a maximum of 4.7% with increasing aging time up to 4,000hours. However, the longitudinal wave velocity has a little change. Also, it has a good correlation between leaky surface acoustic wave velocity and Vickers hardness. Consequently, LSAW can be used to examine the degree of degradation in thermally aged Co-base superalloy.
노일주(Ill-Joo Noh),권기환(Gi-Hwan Kwon),채수원(Soo -Won Chae),권숙인(Sook In Kwun),김명호(Myung-Ho Kim),황선근(Sun Keun Hwang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Equal channel angular pressing (ECAP) has been employed to produce materials with ultra-fine grains that have<br/> high strength and high corrosion resistance properties. In order to obtain super plastic deformation during ECAP, multipass<br/> angular pressing is frequently employed. In this paper, three-dimensional finite element analyses have been<br/> performed to investigate the deformation behavior of pure-Zr specimen and the effects of process parameters for equal<br/> channel multi-angular pressing (ECMAP) process. The results have been compared with some experimental results