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Ebihara, Kenichi; Kaburaki, Hideo; Takai, Kenichi*
Proceedings of 2012 International Hydrogen Conference; Hydrogen-Materials Interactions, p.553 - 561, 2014/02
The crack causing hydrogen embrittlement is observed in steels as the structural material. Accurate evaluation of hydrogen detrapping activation energy, which represents the binding strength between hydrogen atoms and the lattice defects, is crucial to the understanding of the mechanism of hydrogen embrittlement in steels. The Choo and Lee's method, which experimentally evaluates the detrapping energy from the hydrogen thermal desorption profile, should be scrutinized, because this method neglects the hydrogen diffusion in the specimen. By their method, we have evaluated detrapping activation energies from the experimental desorption profiles for pure iron, and also from that simulated by the 1D reaction-diffusion equation. We found that their method underestimates the detrapping energies as the specimen size is large. We also found that this dependence on the specimen size is caused by the degradation of the desorption peak of the detrapping process by the diffusion process.
Yamaguchi, Masatake; Kameda, Jun*
Proceedings of 2012 International Hydrogen Conference; Hydrogen-Materials Interactions, p.747 - 755, 2014/01
Atomistic mechanisms of grain boundary (GB) decohesion of iron by solute (P, Sn, Sb, H) segregation are investigated from first-principles calculations. The calculated GB cohesive energy, which is the energy difference between two fracture surfaces and GB, is shown to decrease with increasing the segregation coverage of P, Sn, Sb, H. Furthermore, Hydrogen-induced GB decohesion is shown to be enhanced by the mobility of hydrogen during crack propagation.