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Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*
Modelling and Simulation in Materials Science and Engineering, 27(6), p.064001_1 - 064001_15, 2019/08
Times Cited Count：16 Percentile：65.43(Materials Science, Multidisciplinary)Plasticity of body-centered-cubic (BCC) metals at low temperatures is determined by screw dislocation kinetics. Because the core of screw dislocation in these metals has non-planar structure, its motion is complex and unpredictable. For example, although density functional theory (DFT) predicts slip on a { 110 } plane, the actual slip plane at elevated temperatures departs from the prediction, its mechanism having been a mystery for decades. Here we conduct a series of molecular dynamics simulations to track the screw dislocation motion and successfully reproduced the transition of the slip plane. We then devised an algorithm to scrutinize the activation of dislocation jump over the Peierls barrier and discovered the possible origin of this unexpected phenomenon, i.e., a large fluctuation leads to the kink-pair nucleation for the cross-slip jump without transition of dislocation core structure.
Onitsuka, Takashi*; Okubo, Manabu*; Fukumoto, Kenichi*; Suzudo, Tomoaki
no journal, ,
Many of BCC metals are used as structural materials in nuclear devices. A possible cause of embrittlement of such metals under neutron radiation is accumulation of lattice defects that hamper the dislocation motions. Molecular dynamics have been used for the analyses of such dislocation motions, but interaction mechanism between the lattice defects and screw dislocation are still unclear. In this talk, we utilize molecular dynamics and analyze the interaction between void and screw dislocation in BCC Fe.
Onitsuka, Takashi*; Okubo, Manabu*; Suzudo, Tomoaki; Fukumoto, Kenichi*
no journal, ,
Reactor structural materials such as pressure vessels become brittle under neutron irradiation. It is widely known that a cause of such phenomenon could be formation of extended lattice defects under irradiation such as voids that become obstacles for dislocation motion, but we do not know the strength of these obstacles accurately enough for establishing a quantitative model. In the present study, we choose pure iron as a substitute of steel and numerically simulate the interaction between screw dislocation and a void using molecular dynamics method. Especially, we analyze the critical shear stress.
Taniguchi, Keisuke*; Onitsuka, Takashi*; Fukumoto, Kenichi*; Suzudo, Tomoaki
no journal, ,
It is known that a cause of irradiation hardening of nuclear materials by neutron irradiation can be ascribed to voids as an obstacle against dislocation motion. In this research, molecular dynamics (MD) simulations were exploited in order to analyze the dynamical reaction mechanism at the atomic level of the screw dislocation and void in BCC pure Fe. In particular, the relationship between the dislocation-void contact position and the strength of interaction was analyzed. As a result, it turned out that there is a rule between the contact position and the shear stress.
Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*
no journal, ,
The irradiation produces various defects such as dislocation loops, voids, and solute clusters. Since they become obstacles for dislocations, research on the interaction between dislocations and obstacles has been pursued. Regarding the slip plane of BCC iron, the slip plane is {110} at low temperature but changes to {112} when the temperature increases to about room temperature; however, this phenomena has not been reproduced by molecular dynamics. We reconsidered the interatomic potential to reproduce the above temperature transition of the slip plane by molecular dynamics. In addition, the mechanism of the transition was discussed from the Peierls potential of the screw dislocation. As a result, it was found that the temperature transition of the slip plane can be reproduced by selecting an appropriate interatomic potential. It was also found that the temperature transition was likely to have been caused by temperature fluctuations of the lattice.
Suzudo, Tomoaki; Fukumoto, Kenichi*
no journal, ,
Body-centered cubic (BCC) metals are applied as structural materials to many components of nuclear reactors, and their thermal and mechanical integrity are of great importance. Much of the deformation of BCC metals at low temperatures is due to the movement of screw dislocations. The motion of screw dislocations in BCC metals is known to be complex. In this research, we succeeded in reproducing the transition of the slip plane as the temperature rise observed in the experiment for the first time using the latest molecular dynamics modeling method. Next, we devised an algorithm to analyze dislocation jumps over the Peierls barrier with high resolution, and showed that the cause of this slip-plane transition phenomenon is likely thermal fluctuation of lattice.
