Formation of Small Prismatic Dislocation Loops via Double Cross-slip of Screw Dislocations in Iron: Dynamic Loop-type Identification Using in situ Transmission Electron Microscopy

To clarify the mechanisms of plastic deformation and ductile fracture, it is crucial to elucidate the defect-formation processes occurring during plastic deformation. In this study, we performed in situ transmission electron microscopy (TEM) observations of the formation of small prismatic dislocation loops via the double cross-slip of screw dislocations in high-purity iron during tensile deformation at elevated temperatures. Conventionally, the type of a dislocation loop (vacancy or interstitial) has been determined by exploiting the dependence of its image contrast on diffraction conditions, as well as the diffuse scattering patterns generated by the loop in electron diffraction. However, such “static” identification methods are inapplicable to small dislocation loops (approx.