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오스테나이트계 고망간강에서 인장 특성과 피로거동에 미치는 변형유기상의 영향
최상민,권숙인 ( S . M . Choi,S . i . Kwun ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.4
The effect of grain size on the tensile properties and fatigue behavior of austenitic high Mn steel has been investigated. The recrystallized austenite grain size of the cold rolled high Mn steel was increased as the annealing temperature increased from 600℃ to 1000℃. Larger austenite grain size decreased the yield strength and the tensile strength, and increased the uniform elongation due to transformation of some austenite into twins or ε-martensite phase during deformation. Austenite grain refinement increased the tendency to form dislocation cells, instead. The specimen annealed at 1000℃ with large grain size showed lower fatigue crack propagation rate in low ΔK region due to rougher fracture surface caused by formation of deformation twins during fatigue at the crack tip region.
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.