PhD Studentship: Radiation Effects on Fatigue Performance of High Temperature Steels

The aim of this PhD project is to assess the impact of local microstructure and radiation damage on the fatigue performance of advanced high-temperature fusion steels, potential candidates for the first wall and tritium breeder components. Ferritic/Martensitic (F/M) steels are promising structural materials for nuclear fusion, due to their mechanical strength and resistance to radiation-induced void swelling. Reduced Activation F/M (RAFM) steels were developed to minimize nuclear waste, but their safe operation is limited to ~550 °C. Advanced RAFM steels are being designed aiming to operate at ~650 °C for better efficiency, using a fine F/M microstructure and optimized MX-type precipitates. Another approach is Oxide Dispersion Strengthening (ODS) steels, which include a nano-oxide dispersion in an F/M matrix to enhance high-temperature strength and creep behaviour.

Those new RAFM steels will face high radiation damage along with thermal and mechanical cyclic fatigue loads. An ongoing irradiation campaign aims to assess the stability of new steel grades under radiation and guide novel designs. However, the fatigue performance of these steels, especially under synergistic fatigue-irradiation effects, remains largely unexplored in the fusion community internationally. Fatigue cracks typically nucleate at (near-)surface stress concentrations and propagate through the material, influenced by local microstructure, plasticity, and residual stresses. Additionally, radiation can alter phase stability, distribution, and local plasticity near the surface or crack tip.

In this project, you will be assessing the fatigue behaviour and crack propagation rate of selected RAFM steels and ODS steels, both before and after having being irradiated at fusion-relevant temperatures. The emphasis will be on understanding the effect of temperature and radiation dose on the steel microstructure, crack propagation behaviour and fatigue life of the material. You will performing irradiation experiments using medium-energy ion beams, together with fatigue tests both before and after irradiation. Additionally, you will be able to monitor the crack propagation rate, local plasticity, and residual stresses in real time using hard X-ray imaging and diffraction at a synchrotron source. You will also be able to use the wide range of scanning and transmission electron microscopes available at the University of Birmingham to carry out ex-situ microstructure and fractography analysis of the tested specimens to correlate microstructure-fatigue performance. During the project, you will also have the opportunity to work with modellers at the UK Atomic Energy Authority to input your unique experimental data as key input and train advanced multi-scale models to predict the material performance over multi-year plant operations. Your project outcomes will provide essential information for fusion design engineers and regulatory bodies to ensure material readiness and operational assurance.

During this PhD project, the student will acquire a unique and valuable set of transferrable skills ranging from designing complex sample environments and experimental protocols, to programming and data mining, effective communication skills and project/time management. You will also gain in-depth knowledge about steel metallurgy, radiation effects and hands-on mechanical testing, focusing on materials critical for the deployment of fusion technology in the next years.

Additional Funding Information

A four-year PhD studentship is available within the fusion materials group of Prof. Enrique Jimenez-Melero (e.jimenez-melero@bham.ac.uk) within the School of Metallurgy and Materials at the University of Birmingham, with a stipend of at least £18,622 per year. This project is funded by the UK Atomic Energy Authority. You will be able to start this project in July 2025 or even earlier.

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