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Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Takaya, Shigeru; Koyama, Toshiyuki*; Morinaga, Masahiko*
Journal of Nuclear Materials, 401(1-3), p.13 - 16, 2010/06
Times Cited Count:3 Percentile:24.16(Materials Science, Multidisciplinary)The correlation of defect energies with precipitation of the ferromagnetic phase near MC carbide during creep tests at high temperature in Type 304 austenitic steel was examined by estimating the defect energies near the carbide, based on micromechanics. As one of the defect energies, the precipitation energy was calculated by assuming MC carbide to be a spherical inclusion. The other defect energy, creep dislocation energy, was calculated based on dislocation density data obtained from transmission electron microscopy observations of the creep samples. The dislocation energy density was much higher than the precipitation energy density in the initial stage of the creep process, when the ferromagnetic phase started to increase. Creep dislocation energy could be the main driving force for precipitation of the ferromagnetic phase.
Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Takaya, Shigeru; Koyama, Toshiyuki*; Morinaga, Masahiko*
Journal of Nuclear Materials, 401(1-3), p.154 - 158, 2010/06
Times Cited Count:6 Percentile:40.42(Materials Science, Multidisciplinary)A phase-field method was applied to the simulation of simultaneous nucleation and growth of both MC carbide and ferromagnetic phases during the creep process in Type 304 steel. The defect energy of the creep dislocations near the carbides, which increases during creep, was integrated into the nucleation driving force for the phase. The simulation used in this study accurately reproduced changes in the amounts of the precipitated phases as a function of creep time. Furthermore, we examine the effect of the dislocation density on precipitation of the phase, and show that the phase-field method is useful for examining the stochastic and kinetic phenomenon of phase transformation.
Shiraki, Atsuhiro*; Wada, Takumi*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
no abstracts in English
Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
no abstracts in English
Shiraki, Atsuhiro*; Tsukada, Yuki*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
This study demonstrates the mechanism of transformation in creep test on the basis of the energy of the system. The experimental result shows that the strain energy around MC carbide becomes very high due to dislocations stored during creep. As a result, the system free energy in the local region near the carbide increases with increasing creep time but it decreases by the formation of ferromagnetic phase.
Shiraki, Atsuhiro*; Tsukada, Yuki*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
We evaluated the system free energy of SUS304 for understanding the phenomenon that ferromagnetic phase is formed in austenitic stainless steel during creep test. As result, it was thought that there are regions with high system free energy due to increase in strain energy locally, where ferromagnetic phase may be formed.
Murata, Yoshinori*; Shiraki, Atsuhiro*; Takeda, Kotaro*; Tsukada, Yuki*; Saito, Yoshihiro*; Morinaga, Masahiko*; Koyama, Toshiyuki*; Takaya, Shigeru
no journal, ,
no abstracts in English
Shiraki, Atsuhiro*; Tsukada, Yuki*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
Authors have shown that ferromagnetic phases are induced in SUS304 by strain concentration during creep test. In this paper, we simulate the formation of carbide which is important as trapping site of dislocation by using the phase-field method.
Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
The formation of the ferromagnetic phase during creep deformation in SUS304 steel was simulated by aphase-field method. In order to consider the precipitation and growth of the phase simultaneously, we haveconstructed a model based on experimental results. In this model, strain energy stored near carbideduring creep deformation increases the driving force for precipitation of the phase. This strain energy isestimated on the basis of distribution function of dislocation density in space near the carbide and is used inthe calculation of the activation energy for nucleation of the phase. Changes in mole fraction of both carbide and the phase are reproduced well in this simulation. Furthermore, it is found that theincrease rate of dislocation density during creep process affects the manner of the change in mole fraction ofthe phase.
Shintani, Tsuyoshi*; Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Morinaga, Masahiko*; Takaya, Shigeru; Koyama, Toshiyuki*
no journal, ,
The magnetic flux density of SUS316 changes lesser than that of SUS304 during creep deformation. In this study, the reason of this difference was investigated based on system free energy. As result, it was revealed that the strain energies of both steels, which contribute to the formation of ferromagnetic bcc phase, were almost the same. Therefore, the dependency of magnetic flux density change on steel grades will be related to that activation energy for the formation of ferromagnetic phase of SUS316 is larger than that of SUS304.
Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Koyama, Toshiyuki*; Takaya, Shigeru; Morinaga, Masahiko*
no journal, ,
Phase-field simulation was conducted based on thermodynamic data base and experimental data on dislocation density near carbides to reveal the relationship between carbide and the formation of ferromagnetic phase in SUS304. The results showed that it is important to consider change in dislocation density near carbides and threshold stress for the formation of ferromagnetic phase to show quantitative relationship between damage at elevated temperature and the content of ferromagnetic phase.
Tsukada, Yuki*; Shiraki, Atsuhiro*; Murata, Yoshinori*; Takaya, Shigeru; Koyama, Toshiyuki*; Morinaga, Masahiko*
no journal, ,
Phase-field simulation of phase transformation during creep in Type 304 austenitic steel is performed and simultaneous nucleation and growth of both carbide and ferromagnetic phases are reproduced. Nucleation events of these product phases are explicitly introduced through a probabilistic Poisson seeding process based on the classical nucleation theory. Creep dislocation energy near the carbide is integrated into the nucleation driving force for the phase. We examine the effect of the dislocation density on precipitation of the phase, and it is found that a small difference in the dislocation density leads to a significant change in precipitation behavior of the phase.