Atomistic simulations of Ni segregation to irradiation induced dislocation loops in Zr-Ni alloys

The role of Ni segregation on the stability of dislocation loops in the Zr-Ni binary system is elucidated by employing molecular dynamics/Monte Carlo simulations. The effect of the concentration of the alloying element on the strain energy around both interstitial and vacancy loops was investigated. Ni atoms are found to accumulate around the dislocation loops. Our results suggest that the driving force of Ni segregation to the loop is a combination effect of the release of the strain energy of the dislocation core and the reduction of energy arising due to annihilation of point defects associated with those Ni atoms previously substitutionally solute far from the loop. The anisotropic stress field of the dislocation loop is presented in cylindrical coordinates, and is used to explain the influence of the alloying element on the stability of the dislocation loop. Furthermore, cascade simulations in the vicinity of dislocation loops were employed in the irradiated Zr-Ni binary system, and a significant enhancement of the stability of the dislocation loops was related to the change of the stress field as well as the core energy of the loop due to the alloying segregation.

644