PNNL

Abstract

Although there have been numerous computer-simulation studies of the damage created by displacement cascades in metals, little attention has been paid to the influence of stress on defect generation in the primary cascade process. In the present work, molecular dynamics has been used to investigate defect production and clustering by displacement cascades in alpha-iron under uniform stress. Cascades of 10keV primary-recoil energy have been simulated in crystals with tensile strain of either 0, 0.1, 0.5 or 1% applied along a axis, with at least four events modelled for each condition. The results show that the number of interstitial and vacancy defects is smaller in the strained models, particularly for the strain of 0.1%. This decrease in the number of defects is possibly related to the effect of strain on self-interstitial motion, leading to enhanced recombination with vacancies. The number of interstitials in clusters is approximately independent of applied strain, however. The fraction of interstitials aligned parallel to the strain axis increases with increasing strain. The effect is small at 0.1% strain, but most single interstitials are created in this orientation at 0.5% and all single and clustered interstitials are aligned at 1%. These results are discussed in terms of the influence of strain on defect formation energy, and the mobility of interstitials.