Investigation of the effects of point defects on the tensile strength of BCC-Fe using molecular dynamics

The formation and impacts of point defects can provide insights into the structural failure and mechanical properties of reactor pressure vessel steel to improve its manufacturing and lifetime. In this study, the effects of point defects, such as vacancies, interstitials, and Frenkel pairs, on the tensile strength of body-centered cubic Fe were investigated using molecular dynamics at 300 K with a tensile load applied along the [001] direction of the samples. The results suggest that peak stress decreases with increasing defect concentration. From the perspective of microstructure and dislocation evolution, interstitial clusters were formed and eventually evolved into dislocation loops during the stretching of the interstitial sample. In the vacancy sample, the vacancies gradually aggregated and formed vacancy clusters, which are regarded as precursors of dislocation loops. Furthermore, the existence of point defects prevented the formation of twin bands. The interstitial atoms had the strongest effect among the three types of defects.