In-situ TEM investigation of unfaulting behavior of Frank loops in FCC Pd during H2+ & He+dual-beam irradiation

Abstract

A faulted Frank dislocation loop (FDL) can transform into an unfaulted perfect dislocation loop (PDL) under plastic deformation, quenching or particle irradiation. Here, we report our direct observation of the unfaulting processes of FDLs in palladium (Pd) by in-situ ion irradiation in transmission electron microscopy. Results indicate that the FDL unfaulting is a combination of three processes involving the interaction between adjacent FDLs, the interaction between FDL and PDL, and the nucleation and growth of Shockley partial dislocations within FDL. Meanwhile, bubbles tend to nucleate within dislocation loops, and the PDLs capture more He/H2 over FDLs, which confirms for the first time that the irradiation-induced loops play an important role in the aging of Pd and the unfaulting strengthens this process.