The role of the materials scientist is to establish the relationship between the composition, manufacturing route and behaviour of engineering materials in service. This provides confidence that a given manufacturing route will produce a material that is fit for application - clearly very important for structures that are safety critical. Historically, this has been achieved via experimental means and the gulf between empirically derived knowledge and understanding based on physics has been vast.
Metals used for engineering comprise very small crystals, such that a given component will contain millions of constituent crystals or 'grains'. The structural variables associated with a metal are superficially straight-forward and include grain size, properties of an individual grain as a function of orientation and crystal alignment from one grain to the next - referred to as preferred crystallographic texture or just 'texture'. Despite this apparent simplicity, predicting the mechanical behaviour, even when the variables above have been quantified, has, until recently, been impossible. It is truly remarkable that, at a macroscopic level, metals often appear homogenous and isotropic, yet at a microscopic level the opposite is true.
Zirconium and titanium, share a great deal more than their proximity in the periodic table. Both are used for safety critical structures; the former for reactor core components in nuclear power generation and the latter in aerospace for components in jet engines. Their metallurgical similarity is a result of a common crystal structure both at high temperature (cubic) and low temperature (hexagonal close packed). Texture is generated during the transformation from one structure to another and from deformation during manufacture. Texture is vital to the performance of the metal in service, therefore manufacturing routes are carefully controlled, yet the relationships between the two are not well understood.
The proposed project aims to develop the understanding of how the structure and texture of specific alloy types based on zirconium and titanium evolve. This will be achieved by hot rolling samples in orientations not possible during standard production. In addition, it will examine the mechanical behaviour of uniquely processed material to elucidate process property relationships. Two key aspects of this work make it particularly exciting; firstly, there have been very few researchers that have worked on both metal systems together, in order to exploit existing understanding and test hypotheses relating to one metal type on the other. In addition, a hitherto undreamt of range of experimental techniques are now available to the researcher. For example, use of neutron or synchrotron diffraction techniques for determination of the deformation mechanisms operative. Similarly, advanced electron microscopy allows detailed examination of where, and what type of, deformation has occurred both within individual grains and between them.
Significant benefits will arise from this programme, the aim of which is to clearly define the relative importance of mechanisms operative during manufacture and service. This is of vital importance to the next generation of physically based models. It is via such models that improved manufacturing routes will deliver more durable engineering alloys and improved predictive capability of their behaviour in service. This is of great importance in both the nuclear and aerospace sectors.