Orientation relationships in engineering alloys analysed by TEM and simulations

The orientation relationship across boundaries between crystals in a microstructure can have a profound influence on the thermo-mechanical behaviour of that material. Solidification, precipitation, recovery and recrystallisation all depend on the atomic arrangement between phases and this in turn can explain the mechanical behaviour of materials after thermal treatments and forging – all of which are fundamental ideas in the study of materials science.

Transmission electron microscopy is ideally suited to studying the orientation relationships in materials. The resolving power of the TEM allows us to study individual atomic columns and atomic planes, allowing the interface to be characterised at the finest possible scale. More importantly the extremely high spatial resolution means that boundaries can be studied at the nanoscale allowing access to the smallest secondary phases and also to the local changes in crystallography and defects around the interfaces. TEM is also capable of providing significant 3D information through tomographic acquisition, which ca be applied to both imaging and crystallography.

The other side to this study is to take the orientation information provided by electron microscopy and use it to explain how and why particular orientation relationships exist. As part of the study the different crystal structures will be studied to find the geometrically favourable (i.e. low strain) ways in which they can fit together. Correlating this with the experimental data will help to explain how and why certain interfaces occur.

The initial application for this study will be on the precipitate structures in advanced magnesium alloys which are a key lightweight alloy for aerospace and automotive technologies. However there is the possibility to study a range of industrially important metal systems as well as technical ceramics within the project.

The project will involve developing techniques for sample preparation, characterisation of a range of interfaces in 2D and 3D and simulating a complete range of inter-phase orientation relationships to understand the possible low-strain orientation relationhips

This project is ideally suited to someone who is excited by explaining how technically significant materials systems exhibit the properties that can be exploited in industrial applcations. They will have access to state-of-the-art electron microscopy facilities and will be working with cutting edge characterisation techniques. The computer simulation software is established so direct coding skills aren’t necessary. However adapting code and improving the interactivity is always possible. All the necessary training will be undertaken during the project so experience is not required. The only requirements are enthusiasm for doing research in materials characterisation and metallurgy.