Grain boundary sliding is an important deformation mechanism in the creep and superplastic regimes. It is clear that sliding happens more readily on some boundaries than others but the links between grain boundary character and resistance to sliding have not been established. In polycrystals grain boundary sliding is generally thought to be accompanied by other accommodation processes such as diffusion, or dislocation mediated plasticity.
This project will use state of the art micro-mechanical testing methods to probe properties of individual grain boundaries isolated in FIB-machined micron scale test pieces. This uncouples grain boundary sliding from other accommodation processes and through testing many boundaries will link behaviour to structural characteristics of the boundaries. Similarly, diffusional creep processes may be studied on isolated boundaries under well-controlled stress gradients. The work on individual grain boundaries will be augmented by experiments on bulk polycrystalline samples. In particular, we would build on initial success in using diffraction contrast tomography to follow in 3-D and in the interior of polycrystals during superplastic flow the relative motion and neighbour grain switching events that must occur.
The description above outlines a possible new research project being offered to prospective new postgraduate students.