Iron Interstitial Defects Stability: Under the Uniaxial Stress Effect

Abstract

Understanding of defect kinetics under stress fields is important for multiscale modeling of nuclear materials degradation. By means of molecular dynamics (MD) simulation, the formation and migration energies were evaluated for self-interstitial atom (SIA) and SIA clusters (1~3 interstitials) in alpha Fe. Effects of 0~3% uniaxial tensile [100] strains were tested for SIAs of <110> and <111> dumbbell configurations. Regarding the stability, the <111> dumbbell configurations becomes more stabilized at larger strains and larger clusters. For the mobility, the diffusion of single SIA defects under tensile stresses were traced. Under the free-strain condition, the diffusivity of the SIA clusters has a gradual transition from three dimensional (3D) to one dimensional (1D) at saturated strain. The 1D transition was observed for large clusters and large strain while the 3D transition was for small clusters and lower strains and presented mainly for the <110> SIA alignment configuration. Under the tensile stress and for small clusters, diffusivity enhancement is bigger at a higher temperature. However, the temperature effect was small for larger clusters. These effects of strain fields can be explained by elastic interaction between defects and applied stress fields.