Micro-Mechanical Properties of Dissimilar Metals Diffusion Bonds

Diffusion bonding is an attractive method of making high quality joints between materials (similar or dissimilar) based on the solid state diffusion of atomic species between the two parts being joined. As no filler material is required the quality of the joint can be very high and little residual stress is generated compared to traditional welding methods. However in the case of dissimilar metal joints interdiffusion will result in a compositional gradient. Depending on the phase diagrams and reaction kinetics this can result in the generation of a range of second phases, often intermetallic compounds which are usually brittle and deleterious to bulk mechanical behaviour.

This project will use a combination of high resolution SEM based EDX and EBSD and TEM based diffraction and EDX microscopy to study the production of such phases in a range of diffusion couples based on the copper-titanium, copper-iron and iron-titanium systems. These systems have been chosen as they represent the three common metallic crystal structures, and are all of interested in the nuclear community. The mechanical properties of the phases produced will be studied using ultra high resolution nanoindentation using newly installed equipment, funded through the Royce Institute.

There are three major outputs envisaged for this project. One is the development of the testing methodologies and protocols for studying chemo-mechanical relationships in diffusion bonds. This is of interest to diffusion bonds in the nuclear industry which are not easily studied, due to cost and safety, and as such not suitable for development work. Secondly the systems chosen are of technological interest to the wider nuclear industry and understanding the evolution of joints in these will allow better design of complex structures such as the divertor in fusion rectors. Thirdly diffusion bonds can be used to generate a wide compositional gradient which can be used for combinatorial alloy design and gaining a better understanding of

The project will be in collaboration with industrial contacts in the nuclear industry. It would suit a student with strong background in materials science or engineering with an interest in developing high resolution micromechanical testing methods and applying these.

The image below shows a cantilever in a tungsten iorn interface