Effect of solute elements (Ni, Mn) in Fe-based alloys on dislocation loop evolution under Fe2+ ion irradiation

Abstract

The dislocation loop is known as one of the irradiation defects that contributes to hardening and accompanying embrittlement in reactor pressure vessel steels. In this study, the effect of solute elements such as Ni and Mn in Fe-based alloys on dislocation loop evolution was investigated using ion irradiation. Pure Fe and Fe model alloys, Fe-0.6Ni and Fe-0.6Ni-1.4Mn, were irradiated by 2.8 MeV Fe ions to a peak dose of 3 displacements per atom (dpa) at 400 °C. Quantitative analysis of transmission electron microscopy (TEM) was conducted to analyze the evolution of dislocation loops. As a result, the presence of solute elements in Fe alloys increased the number density of dislocation loops significantly and decreased their mean size slightly. Both types of dislocation loops, ½<111> and 〈100〉 Burgers vectors, were observed in all specimens. Solute elements reduced the mobility of ½<111> dislocation loops, resulting in an increase in their number density and restricting the growth of <100> dislocation loops. Furthermore, an increase in the number density of <100> dislocation loops of small size was found with higher solute contents.