Irradiation Response in Equiatomic Multicomponent Alloys

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Title: Irradiation Response in Equiatomic Multicomponent Alloys
Author: Levo, Emil
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2018
Language: eng
Thesis level: master's thesis
Discipline: Fysiikka
Abstract: The development of future energy production concepts, such as Gen-IV fission reactors, has increased the demand on novel materials, suitable for the new concept's operational environments. High temperatures, strong magnetic fields, corrosive components and prolonged irradiation are some of the realities these novel materials will experience. In addition to this, the materials need to be chosen based on their sustainability and economic efficiency. One promising group of novel materials consists of alloys built up of at least five elements at near-equimolar concentrations resulting in a high configurational entropy. Due to this characteristic they are called high entropy alloys (HEA) and exhibit many promising properties when it comes to their utilization in energy production. A subgroup of the HEA-family consists of alloys built up of elements at equiatomic concentrations, so called equiatomic multicomponent alloys (EAMC-alloys). These EAMC-alloys can be built up of less than five elements, and they also exhibit very promising properties with energy production in mind. Research in the HEA-family with its subgroups has become an increasingly important field in the last couple decades. HEAs have been realised to be potential candidates as components for future nuclear reactors that involve extreme radiation exposure. The irradiation response in HEAs has been studied both experimentally and computationally, with results showing good radiation tolerance. A presentation of HEAs is given in this work, with an emphasis on their use as a part of future nuclear energy concepts. Radiation damage in HEAs is the main topic of conversation. Three molecular dynamics studies regarding irradiation response in HEAs are presented. In the first study, four different Ni-based single-phase EAMC-alloys and pure Ni are studied under prolonged irradiation. The second study investigates the dislocation loop mobility in pure Ni and two Ni-based EAMC-alloys. In the third study, several nanocrystalline Ni-based alloys and elemental Ni are investigated in three different potentials under prolonged irradiation for their structural stability. The general results of these studies are that more complex alloys have a better response to irradiation, and that a lesser dislocation mobility is one factor responsible for this.

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