Temperature and Cr effect on dislocation loop formation in ion irradiated Fe and Fe-Cr model alloys

Author

Yao LiFollow

Date of Award

12-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

Steven John Zinkle

Committee Members

Arunodaya Bhattacharya, Brian Wirth, Maik Lang,Yury N. Osetskiy, Steven J. Zinkle

Abstract

The development of irradiation-resistant materials is paramount in the realization of advanced fission and fusion reactors. Among the numerous materials considered for this purpose, ferritic-martensitic (F/M) steels emerge as primary candidates due to their multifaceted advantageous properties. However, these F/M steels are not without challenges, particularly in the context of irradiation-induced effects such as hardening due to dislocation loops and irradiation-induced precipitates. Of particular interest in this domain is the persistent inquiry into the mechanisms governing the formation ofdislocation loops within the body-centered cubic (BCC) iron system following irradiation, a question that has remained unresolved for six decades.In this comprehensive research project, ultra-high purity BCC Fe and Fe-Cr model alloys were subjected to irradiation, followed by rigorous examination. The irradiation process involved the use of 6.7-8 MeV self-ions, spanning a wide temperature range from 250°C to 500°C, at two distinctdose levels (0.35 NRT-dpa and 3.5 NRT-dpa), and across three different dose rates ranging from 10-5to 10-3NRT-dpa/s. At lower irradiation temperatures (250°C and 350°C), the predominant effect observed was dislocation loop decoration. Conversely, at elevated irradiation temperatures (450°C and 500°C), self-organizing loops became evident. Notably, at lower damage levels, petal-shaped dislocation loops constituted the primary irradiation-induced defects, while dislocation loop walls predominated at higherdamage levels. Furthermore, a discernible Cr enrichment on the dislocation loops was noted at temperatures exceeding 450°C. This thesis delves into the elucidation of dislocation loop formation mechanisms, with a particular focus onloop formation, as well as the mechanisms underlying Cr segregation in these materials.

Recommended Citation

Li, Yao, "Temperature and Cr effect on dislocation loop formation in ion irradiated Fe and Fe-Cr model alloys. " PhD diss., University of Tennessee, 2023.
https://trace.tennessee.edu/utk_graddiss/11668