The role of Cr, P, and N solutes on the irradiated microstructure of bcc Fe

The objective of this study is to understand irradiation-induced and assisted defect evolution in binary body center cubic (bcc) Fe-based alloys. The broader class of bcc ferritic alloys are leading candidates for advanced nuclear fission and fusion applications, in part due to their exceptional void swelling resistance. However, their irradiated microstructure evolution is sensitive to solute species present, since these solutes can act as traps for irradiation-induced defects due to the surrounding tensile or compressive stress fields. Here, three alloys (Fe9.5%Cr, Fe-4.5%P, and Fe-2.3%N) are selected for study because they systematically exhibit varying solute sizes and solute positions (i.e., substitutional or interstitial). Ex situ and in situ ion irradiations reveal that Fe-P has a considerably finer and denser population of irradiation-induced defects than Fe-Cr and Fe-N at the same irradiation conditions, which is attributed to strong defect trapping at undersized substitutional P, consequently hindering the development of extended defects. Meanwhile, oversized substitutional solutes (e.g., Cr) and interstitial solutes (e.g., N) may also suppress dislocation loop development due to weak solute-defect trapping.

Automated summary

The objective of this study is to understand the evolution of irradiation-induced and assisted defects in binary body center cubic (bcc) Fe-based alloys. Three alloys (Fe9.5%Cr, Fe-4.5%P, and Fe-2.3%N) with varying solute sizes and positions were selected for investigation. The results showed that the presence of different solute species affected the development of irradiation-induced defects in the alloys, with undersized substitutional solutes (e.g., P) hindering their formation and oversized substitutional or interstitial solutes (e.g., Cr and N) potentially suppressing dislocation loop development.