Temperature and dose rate effects on dislocation loop formation and decoration in self-ion irradiated high-purity Fe-Cr model alloys

Abstract

Body-centered cubic (BCC) Fe-based alloys are promising candidate materials for advanced nuclear reactors. A widespread perception is that the addition of Cr favors the formation of ½ dislocation loops. However, the Cr effects on dislocation loop formation/evolution remain unclear due to the limited experimental studies. In this study, we irradiate ultra-high purity bulk BCC Fe-xCr (x = 3, 5, and 8 wt%) with 6.7-8 MeV Fe ions over a wide range of temperatures (Tirr = 250-500 °C) and dose rates (10⁻⁵ to 10⁻³ dpa/s) to two midrange doses (0.35 and 3.5 dpa). The major irradiation-induced microstructures are loop decoration along non-screw dislocation lines at low temperatures and high dose rates as well as self-assembled loops at elevated temperatures. Post-irradiation Burgers vector analysis via g•b method on loops and electron tomography reveals that preponderance is observable in all irradiated Fe-Cr samples at elevated temperature, resulting from stronger elastic energy originating from edge.