Abstract: Transmutation elements produced by neutron irradiation significantly affect the irradiation response of materials, yet they are rarely considered in contemporary studies of ion irradiation to simulate neutron irradiation damage. Here, we present the first in-situ investigation of the effects of transmutation silicon on irradiation defect evolution and corresponding mechanisms in Al-Mg alloys in TEM, using Al⁺ and Si⁺ irradiation. The evolution of dislocation loops under Si⁺ irradiation was closely related to the implanted Si concentration, showing a distinct inhibition threshold at 0.05 at.%. The implanted Si increased the elemental complexity of the matrix and hindered the transition from faulted loop to perfect loop, which should be attributed to the simultaneous effect from both (1) interaction between Si interstitials and point defects and (2) competition between Si atoms and solute-Mg atoms for vacancies and the formation of atomic Mg-Si clusters. These findings revealed the key factors in irradiation-induced dislocation networks in aluminum alloys and the specific role of silicon, and indicated that the effects of transmutation elements needed to be fully considered when using ions to study the irradiation behavior of materials.

Key words: Irradiation, Al-Mg alloys, In-situ TEM, Silicon, Transmutation element