TY - GEN
T1 - Degradation of the strength of grains and grain boundaries of Ni-base superalloy under creep and creep-fatigue loadings
AU - Murakoshi, Takuya
AU - Sakamoto, Hayato
AU - Shinozaki, Taichi
AU - Suzuki, Ken
AU - Miura, Hideo
N1 - Funding Information:
This research has been supported partially by Japanese promoting science and technology, Japanese Grants-in-aid for KAKENHI Grant Number JP16H06357.
Publisher Copyright:
© 2017 Trans Tech Publications, Switzerland.
PY - 2017
Y1 - 2017
N2 - The degradation process of the micro texture of Ni-base superalloys was observed under fatigue and creep-fatigue loading conditions at elevated temperatures higher than 700°C by applying electron back-scatter diffraction (EBSD) analyses. The local distribution of the crystallinity of a grain and a grain boundary was defined quantitatively by analyzing the Kikuchi pattern obtained from each electron-beam-irradiated area with a diameter of 50 nm. The calculated image quality value was used for the analysis. It was found that the crystallinity of grain boundaries degraded seriously under creep-fatigue loading conditions due to the acceleration of anisotropic strain-induced diffusion of component elements. Since the initial finely-controlled strengthened micro texture disappeared due to the anisotropic diffusion of component elements, this degradation was found to cause the drastic decrease of the strength of grains and grain boundaries and thus, lifetime of the material. The decrease of the strength of both grains and grain boundaries was measured by micro tensile test system in a scanning electron microscope by making a small sample from bulk specimen using focused ion beam. The strength of a grain and a grain boundary varied drastically depending on their crystallinity, in other words, the image quality value.
AB - The degradation process of the micro texture of Ni-base superalloys was observed under fatigue and creep-fatigue loading conditions at elevated temperatures higher than 700°C by applying electron back-scatter diffraction (EBSD) analyses. The local distribution of the crystallinity of a grain and a grain boundary was defined quantitatively by analyzing the Kikuchi pattern obtained from each electron-beam-irradiated area with a diameter of 50 nm. The calculated image quality value was used for the analysis. It was found that the crystallinity of grain boundaries degraded seriously under creep-fatigue loading conditions due to the acceleration of anisotropic strain-induced diffusion of component elements. Since the initial finely-controlled strengthened micro texture disappeared due to the anisotropic diffusion of component elements, this degradation was found to cause the drastic decrease of the strength of grains and grain boundaries and thus, lifetime of the material. The decrease of the strength of both grains and grain boundaries was measured by micro tensile test system in a scanning electron microscope by making a small sample from bulk specimen using focused ion beam. The strength of a grain and a grain boundary varied drastically depending on their crystallinity, in other words, the image quality value.
KW - Creep-fatigue damage
KW - Micro texture
KW - Ni-base superalloy
KW - Order of atom arrangement
KW - Strength of grain boundary
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U2 - 10.4028/www.scientific.net/KEM.754.31
DO - 10.4028/www.scientific.net/KEM.754.31
M3 - Conference contribution
AN - SCOPUS:85029904171
SN - 9783035711684
T3 - Key Engineering Materials
SP - 31
EP - 34
BT - Advances in Fracture and Damage Mechanics XVI - 16th FDM
A2 - Mariano, Paolo Maria
A2 - Baragetti, Sergio
A2 - Casavola, Katia
A2 - Pappalettere, Carmine
A2 - Aliabadi, Ferri M.H.
PB - Trans Tech Publications Ltd
T2 - 16th International Conference on Fracture and Damage Mechanics, 2017
Y2 - 18 July 2017 through 20 July 2017
ER -