Effect of δ-ferrite on the low cycle fatigue behavior of 12CrMoV steel = δ-페라이트가 12CrMoV 강의 저주파 피로 거동에 미치는 영향

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The 12CrMoV steel subjected to high temperature will inevitably contain some $\delta$-ferrite. The presence of $^\delta$-ferrite in this steel has been known to lead to discontinuites in the mechanical properties because of compositional differences and lack of cohesin between $\delta$-ferrite and tempered martensite matrix. The strain controlled fatigue test was carried out to nivestigate the effect of $\delta$-ferrite on the low cycle fatigue behavior of the 12CrMoV steel at room temperature. Two different microstructures, tempered martensite with and without $\delta$-ferrite, were developed by heat treatment schedules. The tensile properties for the two different specimen conditions were very similar. The cyclic behavior was characterized by softening and the plastic strain range vs. the number of reversals plots obeyed the Manson-Coffin relationship. The fatigue crack propagation mode was a transgranular. However, the specimen with $\delta$-ferrite had a longer fatigue life than that without $\delta$-ferrite. Introduction of $\delta$-ferrite resulted in the increase of cyclic strain hardening exponent and the more plastic work required to failure. The $\delta$-ferrite had influence on the crack path as a soft obstacle, which resulted that the crack passed around $\delta$-ferrite. An excess energy was required to propagate the crack and led locally to a decrease in crack growth rate. Therefore, the presence of $\delta$-ferrite in tempered martensite increased the resistance to crack propagation and resulted in the increase in fatigue life.
Advisors
Kim, In-Sup김인섭
Description
한국과학기술원 : 원자력공학과,
Publisher
한국과학기술원
Issue Date
1993
Identifier
68448/325007 / 000911530
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 원자력공학과, 1993.2, [ v, 53 p. ]

URI
http://hdl.handle.net/10203/49280
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=68448&flag=dissertation
Appears in Collection
NE-Theses_Master(석사논문)
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