Ph.D. topics
Ion Irradiation and Materials Characterization of Novel Additively Manufactured Materials for Fusion Applications
Ph. D. student
Oleksandr Bychkov
Supervisor
Dr. Cornelia Kaden (HZDR), Prof. Dr. Martina Zimmermann (TU Dresden)
Department
Structural Materials
Period
02/2026 - 01/2029
Desription
Source: Fraunhofer IWS
Future fusion reactors require structural materials capable of withstanding extreme neutron irradiation and high-temperatures conditions. Developing alloys with high irradiation tolerance and long-term microstructural stability is therefore a key challenge for fusion energy systems. This thesis focuses on the irradiation resistance of reduced-activation TiVCrMnFe high-entropy alloys (HEA) designed to form a stable single-phase body-centered cubic (BCC) structure. The work is part of the joint BMFTR-funded project AM-Shield, which combines computational alloy design, additive manufacturing, ion irradiation and advanced microstructural/mechanical characterization within a high-throughput development strategy to design low-activation high-entropy alloys with superior properties for fusion applications. The thesis results on defect evolution, swelling resistance, irradiation-induced hardening, and helium effects feed back into the alloy design process.
Fusion reactors require structural materials capable of resisting intense irradiation and high temperatures while maintaining long-term stability and low activation. HEAs, particularly body-centered cubic (BCC) systems, are promising candidates due to their enhanced irradiation resistance and reduced swelling.
This work focuses on the irradiation tolerance of reduced-activation TiVCrMnFe-based HEA designed to stabilize a single-phase BCC microstructure while suppressing the formation of brittle intermetallic phases. The alloy concept is guided by the requirements of fusion-relevant structural materials, including irradiation resistance and high-temperature microstructural stability. Particular attention is given to understanding the role of composition and phase stability in determining irradiation response and defect evolution.
The work employs compositionally graded HEA samples fabricated by Fraunhofer IWS to efficiently screen composition-dependent irradiation behavior. Ion irradiation serves as an accelerated surrogate for neutron exposure while enabling systematic control of irradiation parameters. To simulate fusion-relevant swelling effects, helium pre-implantation is combined with high-energy Fe-ion irradiation introducing both helium accumulation and displacement damage. The resulting microstructural and mechanical changes are analyzed using advanced characterization techniques, providing insights into the irradiation-induced microstructural evolution, including defect formation (loops, voids/bubbles), phase stability, hardening, and swelling. Special emphasis is placed on correlating irradiation response with alloy composition and microstructure. The study employs a tiered approach that combines fast proxy experiments for materials pre-screening and rapid feedback into the alloy design process and in-depth advanced characterization for the best performing alloy candidates.
The results contribute to the development of next-generation reduced-activation structural materials for fusion energy systems. By combining targeted alloy design with irradiation studies, this work supports the identification of BCC HEA compositions with improved resistance to irradiation-induced degradation and enhanced long-term stability under fusion-relevant conditions.
