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페라이트기 9Cr 내열강의 크리프-피로손상에 따른 미세조직 및 초음파 비파괴평가
김정석,권숙인,박익근,Kim, Chung-Seok,Kwun, S.I.,Park, Ik-Keun 한국재료학회 2007 한국재료학회지 Vol.17 No.8
The microstructural evolution of ferritic 9Cr-1Mo-V-Nb steel, subjected to creep-fatigue at $550^{\circ}C$, was evaluated nondestructively by measuring the ultrasonic velocity. The variation of the ultrasonic velocity with the fatigue life fraction exhibited three regions. In the first region ($N/N_f$<0.2), a significant increase in the velocity was observed, followed by a slight increase between the fatigue life fractions of $0.2N_f$ and $0.8N_f$, and then a decrease in the final region. The change of the ultrasonic velocity during creep-fatigue was interpreted in relation to the microstructural properties. This study proposes an ultrasonic nondestructive evaluation method of quantifying the level of damage and microstructural change during the creep-fatigue of ferritic 9Cr-1Mo-V-Nb steel.
질소 이온 주입시킨 7050Al 합금의 표면 미세구조 변화와 저주기 피로거동
이창우,권숙인 ( C . W . Lee,S . I . kwun ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.4
The surface microstructure modification by N^+ ion implantation into 7050Al alloy and its low cycle fatigue behavior were investigated. Ion implantation method is to physically implant accelerated ions to the surface of a substrate. High dose of nitrogen(5×10^(17)ions/㎠) were implanted into 7050Al alloy using current density of accellerating voltage of 100KeV. The implanted layers were characterized by Electron Probe-Micro Analysis(EPMA), Auger Elecron Spectroscopy(AES), X-Ray Diffraction(XRD), X-Ray Photoelectron Spectroscopy(XPS), and Transmission Electron Microscopy(TEM). The experimental results were compared with computer simulation data. It was shown that AlN was formed to 4500Å deep. The low cycle fatigue life of the N^+ ion modified material was prolonged by about three times the unimplanted one. The improved low cycle fatigue life was attributed to the formation of AIN and the damaged region on the surface by N^+ ion implantation.