PhD Studentship: Micro-mechanics and Irradiation Creep of Vanadium-base Fusion Alloys

Vanadium alloys have resurged as key materials solutions for structural components in the first wall and tritium breeder module of fusion power plants. This is due to their compatibility with liquid lithium, their low activation under fusion neutron irradiation and their relatively high strength at elevated temperatures. Additionally, the body-centred cubic nature of the vanadium matrix provides these materials with good resistance to radiation-induced void swelling. Despite these advantages, vanadium alloys are still a low 'readiness level' material, though structural materials with the potential to meet all these key criteria are lacking. Therefore, vanadium development & fusion-relevant testing is quickly needed to enable improved and viable reactor designs (e.g. early manufacture of STEP components is targeted within the next 5-6 years).

This project aims at exploring the radiation damage effects and mechanical loading on the micro-mechanics and creep behaviour of vanadium-base alloys. The focus will be on the synergistic radiation-mechanical load effects at relevant fusion temperatures, in the vicinity of the upper temperature limit for the alloy of approx. 650 °C, and investigate the characteristics of the precipitate distributions and interface characteristics that can lead to enhanced stability and tolerance against radiation damage and creep phenomena. This will be assessed on the current vanadium-base frontrunner (V-4Cr-4Ti alloy). Cr is added to the material as an effective solid-solution strengthener that increases the thermal creep and oxidation resistance, while Ti enhances the void swelling resistance of the alloy. However, we will also develop novel alternative alloys through chemistry and thermo-processing variations. This can lead to improvements in mechanical and irradiation performance through e.g. the variation of Ti-rich nano-precipitates population, the density of interfaces or substitutional atom effects on (radiation-induced/enhanced) lattice defect diffusivity. Alloy design and production will be led through collaboration with the University of Sheffield, who will produce together with the student alloys with systematically varied parameters for characterisation and analysis, together with the baseline V-4Cr-4Ti alloy. You will have the opportunity of using the Sheffield processing capabilities within the national Royce Institute of Materials.

During this PhD project, you will acquire a unique set of transferrable skills ranging from designing complex sample environments and experimental protocols, to programming and data mining, and effective communication skills. You will also gain in-depth knowledge about physical metallurgy, plastic deformation mechanisms in polycrystalline materials and liquid lithium corrosion testing. 

References:
[1] Zinkle and Ghoniem, Operating temperature windows for fusion reactor structural materials, Fusion Eng. Des. 51–52 (2000) 55-71

[2] Muroga et al, Present status of vanadium alloys for fusion applications, J. Nucl. Mater. 455 (2014) 263-268.

[3] Ghosh et al, Alloy design and microstructural evolution in V–Ti–Cr alloys, Mater. Charact. 106 (2015) 292-301.

[4] Impagnatiello et al, Atomically resolved chemical ordering at the nm-thick TiO precipitate/matrix interface in V-4Ti-4Cr alloy. Scripta Mater. 126 (2017) 50-54.

[5] Muroga et al, Microstructural Control for Improving Properties of V-4Cr-4Ti Alloys, Adv. Sci. Tech. 73 (2010) 22-26.

[6] Impagnatiello et al, Monolayer-thick TiO precipitation in V-4Cr-4Ti alloy induced by proton irradiation. Scripta Materialia, 130 (2017) 174-177.

Additional Funding Information 

A 3.5-year PhD studentship is available in the group of Prof. Enrique Jimenez-Melero with a stipend of at least £18,622 per year. This project is funded by the UK Fusion Skills Programme run by the UK Atomic Energy Authority, with additional funding, project support and supervision by Frazer-Nash Consultancy.