Deformation of multiphase materials: Experiments and numerical modelling

This exciting project aims to shed light on the long standing problem of how multiphase materials behave during deformation and how the deformation history influences material behaviour during subsequent deformation. This project is unique as it aims to capitalize on the knowledge base and experimental capabilities that are available in both materials science and geoscience research. In this innovative project you will use cutting-edge analytical and experimental techniques and combine results using novel numerical simulations. Outcomes promise to be of high impact in both materials science and geoscience.

Recently the search for new, high performance materials has expanded to multiphase materials, including metal matrix composites, superalloys and two-phase alloys. At the same time, in the earth sciences there is an urgent need to understand in depth the rheological behaviour of multiphase materials such two to three phase rocks as these constitute the majority of rock on Earth (Buergmann & Dresen 2008). In both disciplines, there is a need to develop an in-depth understanding of the processes ongoing during deformation, so that we can predict future material behaviour.

However, currently, there is still a lack of understanding how different phases that react differently to stress and strain will influence each other during deformation. In addition, the effect of the presence of different phase on the resistance of stress corrosion cracking is not well established. At the same time, in geoscience, we need to understand not only the flow properties of rocks at depth at high pressures and temperatures but also importantly the link of the high temperature ductile flow with that of lower temperature brittle failure. Hence, investigating the link between ductile-brittle deformation during and after deformation is pivotal to our understanding of both industrial materials and earth system science.

Processes that we need to understand include crystal plastic flow, twin generation and deformation, recrystallization processes including nucleation of new grains, recovery and grain boundary migration as well as fracture generation and propagation. For high strain deformation, generation of nanocrystalline materials and their evolving properties is important. Importantly, we need to understand the generation of local high stress and strain heterogeneities arising from a rheologically heterogeneous material. At the same time, since the materials investigated are not simple in their chemical composition, not only the physical rearrangement of grains needs to be understood but also the chemical changes that go hand in hand with such deformation processes.

Objectives
This project aims to achieve a new level of understanding and quantification of the underlying principles governing deformation of multiphase materials. Three main questions will¬ be addressed:
1) Processes: What physiochemical processes occur at different conditions of formation and deformation? How do the physical processes govern the chemical processes and vice versa?
2) Effect: How do these processes effect the rheological behaviour of the investigated material during deformation and after deformation?
3) Prediction: Based on the resolution of the two questions above, what are our possibilities to (a) predict material behaviour to allow development of new high performance multiphase materials and to (b) predict the behaviour of geological materials through time and pressure-temperature space.

Project plan and methods
In this project, the candidate will work with leading scientists in their fields at Leeds (Piazolo & Brydson), Manchester (Quinta da Fonseca), and Los Alamos, USA (Lebensohn) and Cambridge (Einsle). The team of supervisors and collaborators span across material science and geoscience allowing the postgraduate researcher to develop knowledge within both areas which will be the foundation for cross-disciplinary investigations of the deformation behaviour of multiphase materials. Within this exciting and challenging project, the researcher will be able to utilize the cutting-edge equipment and novel numerical approaches available through the research team and their institutions to answer the questions posed above.