서지주요정보
Nb-A286 초내열 합금에서 시효처리를 통한 $γ'$ 의 크기 및 $η$ 상의 양 조절이 고온 저주파 피로 특성에 미치는 영향 = Effects of the control of $γ'$ size and amount of $η$ phase by aging treatment on the high temperature low cycle fatigue properties in Nb-A286 superalloy
서명 / 저자 Nb-A286 초내열 합금에서 시효처리를 통한 $γ'$ 의 크기 및 $η$ 상의 양 조절이 고온 저주파 피로 특성에 미치는 영향 = Effects of the control of $γ'$ size and amount of $η$ phase by aging treatment on the high temperature low cycle fatigue properties in Nb-A286 superalloy / 김기재.
저자명 김기재 ; Kim, Ki-Jae
발행사항 [대전 : 한국과학기술원, 2001].
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소장정보

등록번호

8011783

소장위치/청구기호

학술문화관(문화관) 보존서고

MMS 01004

SMS전송

도서상태

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초록정보

A286 alloy is an iron-base superalloy and composition of this alloy was based on 51%Fe-29%Ni-14%Cr-2.1%Ti-0.2%Al(wt%) and contains other minor alloying additives. It is mainly strengthened by an aging treatment which precipitates the ordered FCC γ'. The specipic compositional modification of the Fe-base superalloy containing higher Ti and lower Al, investigated for this study was designed to increase the amount and stability of γ' by adding Nb element. Based on this new design, `Nb-modified A286 alloy` was developed to improve the strength, fatigue and creep-rupture resistances compared with the commercial A286 alloy. Recently, It has been examined the damage mechanism under the low cycle fatigue with temperature and strain in the Nb-A286 alloy. By the theory, the fracture mode is changed from transgranular fracture mode to intergranular fracture mode during the low cycle fatigue by the change of microstructure. It is known that this change is the main reason of decreasing of fatigue life. By the theory, the precipitation of the η phase at the grain boundary during the low cycle fatigue is provided for the site for the grain boundary cavitation which promotes the intergranular fracture at high temperature. The planar slip bands which appeared during low cycle fatigue impinge on the grain boundary so that stress concentration increases at this grain boundary. Further, this is contributed to the change of fracture mode from transgranular fracture to intergranular fracture mode. The control of η phase and planar slip is an important factor to improve the fatigue properties. In this study, the change of precipitates morphology, amount of η phase and control of γ' size are conducted by aging treatment. In the continuous low cycle fatigue, fatigue life is increased with increasing of aging time. In the investigation of fracture surface after low cycle fatigue, fracture mode is changed from intergranular fracture mode to transgranular fracture mode with increasing of aging time. It is changed from planar slip to bowing dislocation with increasing of γ' size. Slip induced cavitation by local stress concentration due to planar slip impinged on the grain boundary is retarded by larger γ'precipitation than none-aging treatment. Therefore, fatigue life is increased with increasing of aging time. The cellular η phase which grows in the grain prohibits crack propagation. Fatigue life is thought to be affected by cellular η phase. These results will be the basis of design new alloy for improvement of fatigue life.

서지기타정보

서지기타정보
청구기호 {MMS 01004
형태사항 iv, 65 p. : 삽도; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Ki-Jae Kim
지도교수의 한글표기 : 남수우
지도교수의 영문표기 : Soo-Woo Nam
학위논문 학위논문(석사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 62-65
주제 $γ'$
$η$ 상
입계파괴 및 입내파괴
고온 저주파 피로
전위거동 조절
$γ'$
$η$ 상
planar slip
Low Cycle Fatigue
intergranular fracture and transgranular fracture
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