STS 304 강의 저주기 및 고주기 피로에 있어 초기 마르텐사이트의 영향

The Effect of Initial α’ on Low and High Cycle Fatigue Behavior of STS 304 Stainless Steel

Zero to tension fatigue tests and strain controlled fatigue tests were carried out to find how initial strain induced martensite, α’ affects low and high cycle fatigue behavior and fatigue crack growth mechanisms. Microscopic study and phase analysis were carried out with TEM, SEM, EDAX, Optical Microscope, Ferriscope, and X-ray diffractometry. The amount of Initial α’ was controlled from 0% to 33% by controlling the temperatures for cold working and heat treatment. Lower contents of initial α’ showed higher fatigue resistance in low cycle fatigue but lower fatigue resistance in high cycle fatigue because it is ascribed to the more transformation of α’ martensite during low cycle fatigue and higher ductility. In high cycle fatigue, fatigue life is attributed to the strength and phase transformation of austenite into α’ during fatigue was negligible. γ boundary, γ/twin boundary, and γ/α’ boundary were found to be the preferred site of fatigue crack initiation.