Formation of a defect group in an FeCrNi alloy under irradiation investigated by molecular dynamics

Formation of a defect group containing a stacking fault tetrahedron (SFT) surrounded by several small black dots in an FCC FeCrNi alloy after irradiation has been generally observed experimentally. However, the related formation mechanism is not investigated clearly until now. In this work, based on molecular dynamics (MD) and transmission electron microscopy (TEM) image simulations, formation of such a defect group induce by displacement cascades in a perfect FCC-FeCrNi model or an FCC-FeCrNi model containing a pre-existing SFT, has been explored at atomic scale, presenting the same results to experimental reports. In the latter case, evolution of a SFT during its interaction with cascades through the absorption of cascade induced vacancies and formation of surrounding 3D nano-scale interstitial clusters or loops, have been observed. Furthermore, the elastic constants calculations imply the decrease of C₁₁, C₁₂ and C₄₄ with formation of a defect group while the stress–strain curves indicate the stronger pinning effects of a defect group than a perfect SFT to the gliding of edge dislocations. All these results indicate that formation of defect groups should be taken into the consideration for prediction of structure evolution and mechanical properties of an FCC FeCrNi alloy after irradiation.