Multimaterial Joining Strategies for Fusion

Fusion reactors have to use materials with some of the most extreme properties yet developed. This frequently sees unusual and specific materials selected for certain components within the device. Inevitably therefore, these materials have to be bonded to each other, and their different nature can present severe joining challenges; for example, joining of tungsten to CuCrZr alloy must deal with a difference in melting temperature of almost 2500°C. We want to find new ways to make joints like these, and understand their effects on the materials, and this reactor operation.

Fortunately, there are some joining methods (such as brazing, where an additional filler metal is melted between the components to be joined, or diffusion bonding, where heat and pressure are applied across the joint interface to stimulate interaction between the materials) which can cope with very different materials, and still form successful, conductive joints of relatively high strength. Nevertheless, successful bonding is not guaranteed, and joining of many of these advanced materials, especially in multi-material combinations, has been little explored. With the proliferation of potential materials that could be used in a fusion device, the success or failure of different concepts may depend more on the capability and performance of the joint rather than the behavior of the materials in isolation. If we do not investigate joining therefore, we may miss an important aspect of deciding what will be effective.

In this project, we will explore the bonding of a variety of multimaterial joints between fusion-relevant materials. Candidates for exploration will include tungsten to fusion-grade steel, tungsten to vanadium alloys and tungsten to copper alloys, also considering the effect of using additively manufactured components. We will undertake experimental manufacture of such joints using a variety of available approaches, including both brazing and diffusion bonding. Samples will be produced at the laboratory scale and characterized for joint performance and the microstructure. Through doing this, as well as developing new understanding on the behaviour of these specific joints, valuable for fusion reactor design, we will seek to develop a more detailed view of the main challenges in such multimaterial joint fabrication, and develop protocols for making the best choices for joining strategy.

The project will be mainly based in Sheffield, with opportunities for frequent interaction and working with the project partner at their nearby site in the Fusion Technology Facility in Rotherham, as well as other UKAEA sites. National and international travel to conferences will be possible, as this is suitable for the needs and circumstances of the student.

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

This project is offered by University of Sheffield. For further information please contact Russell Goodall r.goodall@sheffield.ac.uk