In-situ TEM observation and MD simulation of the reaction and transformation of <100> loops in tungsten during H 2+ & He+ dual-beam irradiation

Low mobility < 100 > loops significantly affect the mechanical properties of body-centered cubic materials and their generation and evolution have been a hot research topic recently. However, there is still a lack of direct observation on the reaction of the formed < 100 > loops during subsequent irradiation, which hinders a better understanding of the degradation of mechanical properties induced by irradiation. Here, we reported for the first time that the reaction between < 100 > loops produced 1/2 < 111 > loop through in-situ TEM observation during 30 keV H 2 + & He + dual-beam irradiation in tungsten. Molecular dynamics simulation showed that this reaction required appropriate relative position of the initial < 100 > loops and high temperature that could induce < 100 > loop split into 1/2 < 111 > segments and then transformed into 1/2 < 111 > loop. Meanwhile, the evolution of < 100 > loops was in-situ observed. The average size and areal number density of < 100 > loops were quantified as a function of irradiation fluence. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.