Behaviors of bubble-loop complexes in He-irradiated CLAM steels at elevated temperatures

摘要

The behavior of bubble-loop complexes formed in reduced activation ferritic/martensitic (RAFM) steels under He+ irradiation at elevated temperatures was investigated by transmission electron microscope (TEM), and corresponding simulations on the interaction between He bubbles and dislocation loops were also carried out by molecular dynamics (MD). China Low Activation Martensitic (CLAM) steels were irradiated under 18 keV He+ with the fluence of 1 x 10(20) ion/m(2) at room temperature, 250 degrees C, 350 degrees C, 400 degrees C, 450 degrees C and 550 degrees C, respectively. Bubble-loop complexes were observed in all specimens when irradiated at 250 degrees C and above. Almost all of He bubbles were located inside the dislocation loops when the irradiation temperature reached up to 550 degrees C. Moreover, the formation of the complexes was independent of the type of dislocation loops since both a 0 < 100 > and a(0)/2 < 111 > loops could form bubble-loop complexes. He bubbles were situated to be more stable inside the dislocation loops than that in the matrix according to the experimental results. The MD simulations showed that the dislocation loop can be locked by the He bubble, which could elucidate the mechanism of the observed bubble-loop complexes formed in He irradiated RAFM steels. The mean size of dislocation loops decreased when irradiation temperature increased to 550 degrees C, which can be ascribed to the high emission rate of point defects from dislocation loops at high temperature. (C) 2019 Elsevier B.V. All rights reserved.