Exploring the Ductile-to-Brittle Transition in Fusion Blanket Alloys – Materials Strand Project

Supervisors: Ed Pickering & João Fonseca (University of Manchester) and David Lunt (UKAEA). 

The majority of candidate alloys for in-vessel fusion power plant components have a body-centred cubic (BCC) crystal structure (e.g., reduced-activation ferritic steels, tungsten, vanadium, etc).  Although these BCC alloys show some impressive properties, one detrimental aspect of their use is that they exhibit a ductile-to-brittle transition (DBT) as they are cooled in temperature.  This means that they tend to be more ductile at high temperatures and more brittle at low temperatures.  Importantly, the transition temperature between the two regimes can be increased significantly by irradiation, as would be experienced in a fusion reactor. This may mean that the alloys become brittle at room temperature, or other intermediate temperatures, through which they are likely to be cycled during plant operation – this poses a serious challenge to the integrities of BCC alloy components.  

The changes in the behaviour of BCC alloys through their DBT originate from changes in their deformation behaviour at the micrometre scale and below.  These changes, which manifest in dislocation slip behaviour, can be examined using high-resolution digital image correlation (HRDIC).  Recent work by a completed Fusion Power CDT student examined the behaviour of pure iron using HRDIC following irradiation, and also at cryogenic temperatures. Significant changes were seen in both these cases, with the irradiation case shown in Fig. 1. 

This project will build on the previous work outlined above to generate more understanding of the changes in behaviour we observe in BCC alloys through the DBT.  This will likely include looking at samples with more complex composition, with different microstructural features, and also with the addition of stress-concentrating features like notches.  The project will involve extensive use of advanced electron microscopes in Manchester’s world-leading Electron Microscopy Centre, co-hosted with the Henry Royce Institute.  

The successful candidate will have a good undergraduate degree in a relevant subject, e.g., materials science, physics or engineering. Previous specialisation in metallurgy or fusion energy is not required as students will gain a broad understanding through the taught component of the CDT programme and through their preliminary research. This project will provide the opportunity to develop transferable skills and knowledge of industrial processes, metallurgy, electron microscopy, and other analysis techniques, which should ensure the candidate is prepared for a wide range of possible career paths after graduation.  Generic transferrable skills associated with programming, data manipulation and data interpretation will be gained. 

During the first six months of the PhD, materials strand students will typically travel to attend taught modules at all six of the Fusion CDT partner universities. This project will be based at University of Manchester, with occasional trips to UKAEA in Oxfordshire. 

This project is offered by University of Manchester. For further information please contact: Ed.pickering@manchester.ac.uk

This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.

For details on how to apply, please visit: Apply

Fig 1 (above): Deformation in iron at room temperature, measured using HRDIC.  Top: non-irradiated, bottom: irradiated.  Credit: Florence Goodrich.