Date of Award
8-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Committee Chair/Advisor
Enrique Martinez Saez
Committee Member
Garrett Pataky
Committee Member
Zhaoxu Meng
Abstract
Radiation-induced segregation (RIS) is a significant phenomenon that occurs in alloys subjected to irradiation, particularly in environments such as nuclear reactors. This thesis investigates RIS in ferritic Fe- Cr alloys through the use of Atomic Kinetic Monte Carlo (AKMC) simulations, focusing on the interaction between solute atoms and migrating grain boundaries. The study explores the influence of temperature, solute concentration, and grain boundary velocity on solute drag, a critical process driving RIS. The results show that solute migration is strongly influenced by the presence of vacancies and interstitials generated under irradiation, which are absorbed by grain boundaries and other defect sinks. Simulations were conducted for different Cr concentrations (6% and 9%) at temperatures ranging from 500K to 700K, under different applied stresses. The work investigates how grain boundary migration rate and the segregation energy profile impact solute accumulation and redistribution at defect sinks. Notably, the thesis analyzes both thermal and radiation-induced segregation, highlighting the complex interactions between thermal vacancy diffusion and radiation-induced solute transport. The solute drag effect, governed by the velocity of grain boundary migration, exhibits distinct behaviors at different temperatures, with higher temperatures generally decreasing the effectiveness of solute drag. Additionally, the thesis explores the counterintuitive case of negative solute drag, where local compositional asymmetries result in apparent acceleration of grain boundary (GB) motion due to energetically favorable rearrangements of solute atoms. This phenomenon challenges traditional models and suggests that RIS can sometimes promote grain boundary migration instead of impeding it. Cluster analysis across varying conditions reveals the size, density, and spatial distribution of Cr-rich clusters, which are closely tied to segregation amplitude and GB kinetics. These clusters are formed as a result of local solute enrichment near the grain boundary, and their properties are influenced by the migration rate and the competition between different solute diffusion mechanisms. The migration of chromium precipitates near grain boundaries under radiation-induced conditions is also explored. Precipitate dissolution and reprecipitation processes were observed as the grain boundary migrates through the microstructure, with precipitation occurring under low-temperature and high-radiation conditions. The simulation results offer valuable insights into the roles of both vacancy-mediated and interstitial-mediated diffusion processes in governing the microstructural evolution of Fe-Cr alloys under irradiation, ultimately influencing their stability and performance in nuclear applications.
Recommended Citation
Dhoriya, Mohit, "Grain Boundary Migration and Radiation Induced Segregation in Fe-Cr Alloys" (2025). All Theses. 4577.
https://open.clemson.edu/all_theses/4577
Author ORCID Identifier
https://orcid.org/0009-0009-3515-6519