Search for: All records

In this research, we employ atomistic simulations to scrutinize the impact of hydrogen (H) on dislocation mobility in iron (Fe). Our study uncovers two critical aspects: Firstly, hydrogen atoms serve to stabilize the edge dislocation core, thereby elevating the shear stress threshold needed for dislocation mobilization. Secondly, hydrogen's influence on dislocation mobility is velocity-dependent; it enhances mobility at low velocities by diminishing lattice resistance but hampers it at high velocities due to increased viscous drag. These nuanced findings illuminate the multifaceted relationship between hydrogen atoms and dislocation mechanisms. They offer valuable insights for the development of materials with enhanced mechanical properties and contribute to strategies for mitigating hydrogen-induced material degradation. 

This study explores the impact of electric field and temperature on flash sintering of zirconia nanoparticles using molecular dynamics simulations. The findings suggest that the electric field effect is secondary to the temperature effect. A comparison of simulations varying temperature and electric field reveals a more significant difference in diffusion coefficient with temperature variations. Furthermore, the electric field effect does not exhibit a consistent monotonic trend, as seen in the changing order of curves when temperature increases. The induced electric field contributes to crystal orientation alignment and promotes surface mechanisms throughout sintering stages. While a higher electric field leads to greater atomic motion in the initial stage, the relationship is not strictly monotonic. However, it consistently enhances the diffusion coefficient of surface atoms, highlighting its role in surface mechanisms. Further research is warranted to fully understand the interplay between electric field, temperature, and sintering mechanisms. 

The Hydrogen Enhanced Localized Plasticity (HELP) mechanism is one of the most important theories explaining Hydrogen Embrittlement in metallic materials. While much research has focused on hydrogen's impact on dislocation core structure and dislocation mobility, its effect on local dislocation density and plasticity remains less explored. This study examines both aspects using two distinct atomistic simulations: one for a single edge dislocation under shear and another for a bulk model under cyclic loading, both across varying hydrogen concentrations. We find that hydrogen stabilizes the edge dislocation and exhibits a dual impact on dislocation mobility. Specifically, mobility increases below a shear load of 900 MPa but progressively decreases above this threshold. Furthermore, dislocation accumulation is notably suppressed at around 1 % hydrogen concentration. These findings offer key insights for future research on Hydrogen Embrittlement, particularly in fatigue scenarios.