About this Abstract |
| Meeting |
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Symposium
|
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Presentation Title |
Effect of Helium Bubbles on Screw Dislocation Mobility in Iron: An Atomistic Simulation Study |
| Author(s) |
Silas John, Li Yang, Brian David Wirth |
| On-Site Speaker (Planned) |
Silas John |
| Abstract Scope |
Molecular dynamics (MD) simulations are used to investigate the mobility of a/2<111> screw
dislocation without and with helium (He) bubbles in alpha-iron submitted to shear strain at
temperatures between 100K and 1000K. The simulation results confirm that the mobility of screw
dislocations in pure iron is significantly affected by both stress and temperature [1]. Specifically, at
low temperature and applied stresses the screw dislocation moves by thermally activated kink pair
nucleation and propagation, while it moves through phonon drag mechanisms for stresses above a
critical value. At the temperature of 500K and above, the phonon drag is the only mobility
mechanism for pure iron regardless of the value of applied stress. In the presence of helium, dislocation mobility is impacted by helium segregation. Based on the bubble
distribution predicted by an object kinetic Monte Carlo methodology [2], we found that the
dislocation bypasses the nano-size He bubbles via a shear mechanism at all temperatures
considered. Using the MD simulation results, we developed a fitted mobility law to predict the
velocity of a screw dislocation as a function of stress and temperature as well as a fitted law to
estimate the yield strength of a screw dislocation interacting with small He bubbles at a given
temperature and strain rate. Our results can be used as input for larger scale simulations
like the dislocation dynamics and crystal plasticity models.
References:
[1]. M.R. Gilbert et al. Physical Review B 84, 174103 (2011)
[2]. E. Martinez et al. Acta Materialia 84 (2015) 208-214 |
| Proceedings Inclusion? |
Undecided |