Alloy design and high-temperature mechanics of plasma-facing materials (materials strand project)

Supervisors: Dr. Enrique Jimenez-Melero (University of Manchester) and Prof. Grace Burke (University of Manchester)

Tungsten stands as the main plasma-facing material for fusion reactors due to its melting point (3420°C), low sputtering yield, and good high-temperature strength and thermal conductivity. Unfortunately, tungsten is brittle by nature and its ductile-to-brittle transition temperature increases under neutron irradiation, due to the formation of lattice defects such as dislocations and voids. The limited data available on W-based binary alloys reveals that alloying elements such as Ti, V or Ta improves the material’s ductility. Unfortunately, alloy selection has to date been done by trial-and-error, and the existing data on high-temperature mechanics of irradiated tungsten alloys reduces mainly to nano-indentation studies in W-implanted specimens.

The aim of this project is to accelerate the development of the next generation of binary and ternary W alloys, by adopting upfront a systematic design approach using thermodynamic and ab initio calculations, coupled with density functional theory and Monte Carlo simulations of the phase stability under irradiation. The most promising alloys will be produced by powder metallurgy, and characterised in-depth using analytical electron microscopy in Manchester, including the Titan ChemiSTEM microscope with atomic resolution. The key to reliable predictions of in-reactor alloy performance is to monitor in situ the damage formation and the plastic deformation mechanisms at elevated temperatures (<1000°C). The former will be done by using ion irradiation in combination with a transmission electron microscope at MIAMI-2 (Huddersfield), in order to visualise in situ the atomic migration, local chemical segregations, and the lattice defect nucleation & evolution as a function of damage level and temperature. The plastic deformation mechanisms will be monitored in real time by performing in situ mechanical testing at high-brilliance synchrotron facilities such as Diamond (UK) or ESRF (France). Their experimental capabilities allow only in very recent days to reconstruct the bulk multi-grain structure in real time as plasticity evolves. These results are these days in very much need to validate and dictate multiscale modelling campaigns in the international fusion community, and are therefore expected to support safety cases and steer alloy design strategies for DEMO and future commercial fusion power plants.

The successful candidate should have an undergraduate degree in materials science, physics or mechanical engineering. Previous knowledge in metallurgy, nuclear energy or scientific computing would be an asset, but otherwise can be gained during the ‘materials strand’ CDT taught programme and also in the early stages of this research project in Manchester.

The project will be based in Manchester, but will involve short trips (max. 1 week each) to large-scale synchrotron facilities and to the ion irradiation facility in Huddersfield, and also to attend international fusion-related events.

The student will acquire a unique set of transferrable skills ranging from modelling and programming to design of complex sample environments, data mining, and effective communication skills. He/she will also gain in-depth knowledge about physical metallurgy, plastic deformation mechanisms in polycrystalline materials and grain reconstruction techniques. This will place the candidate in a privileged position to boost his/her future career in industry or academia beyond the PhD programme.

This project is offered by University of Manchester. For further information please contact: Dr. Enrique Jimenez-Melero (