Effect of Crystal Orientation on Dislocation Loop Evolution Under Electron Radiation in Pure Aluminum

Aluminum, the primary structural material used in spacecraft, operates in low Earth orbit (LEO). It is subjected to high-energy electron irradiation with energies ranging from 0.1 to 10 MeV, which produces significant irradiation damage. Understanding the characteristics of irradiation defects with crystallographic orientations is crucial for analyzing the failure of spacecraft components and for developing aerospace materials with improved irradiation resistance. In this study, pure aluminum was irradiated in situ at room temperature using 200 kV transmission electron microscopy. The irradiation defects were comparatively analyzed for four crystallographic orientations, focusing on the size, density, and interstitial content of <111> and <110> dislocation loops. For all four irradiation directions, the interstitial atom density (IAD) within <111> loops is significantly higher than that in <110> loops. Notably, under [110]-direction irradiation, IAD in <111> loops is approximately 55 times that in <110> loops. This phenomenon is attributed to the one-dimensional migration of <110> loops. Among the four irradiation directions, the total IAD in the two types of loops decreases in the order: [110] > [111] > [310] > [100]. The threshold displacement energy (E_d) of aluminum at room temperature is inferred to follow the relationship: [110] < [111] < [310] < [100].