Planar fault energies to order

Stronger and more resistant alloys are required in order to increase the performace and efficiency of jet engines and gas turbines. As our ability to control alloy properties and microstructure increases, greater attention is drawn to designing new alloys that outperform the current state-of-the-art. In order to design the alloys of the future, the research community will have to undergo a step change, and think of advanced alloys as composite materials that include individual phases with remarkably different properties. The morphology, size and distribution of phases, together with their individual properties, work in unison to provide superior performance. For example, the superalloys of the future will need to display specific desirable dislocation behaviours that lead to higher strength and better high-temperature properties. This can be achieved by planar faults engineering: a finer control of planar fault energies and deformation mechanisms by fine tuning the chemistry of individual phases. This project has two aims. The first aim is to understand how wider compositional changes and temperature affect all planar fault energies in ordered intermetallic compounds, using the L12 phase as a case study. The second aim is to develop a framework for designing the composition of new alloys considering also desired planar fault energies as an input parameter.

This research programme aims to link the composition of alloyed intermetallic compounds to their planar fault energy, in order to predict deformation behaviours and understand how these are affected by temperature. Indeed, the mechanical properties of advanced alloys under a variety of conditions are often dependent on planar fault energies. This research programme will allow the scientific and industrial community to tighten the link between the composition of an advanced alloy and its performance in a variety of applications, and to decouple the effects of microstructure and composition. This will have a profound academic, industrial and societal impact.

Academic beneficiaries (see Academic Beneficiaries section) will be able use the output from this research programme to understand the deformation behaviour of advanced commercial alloys, and to predict mechanical properties of new ones. In the very short term this will happen thanks to knowledge transfer with collaborators at the University of Birmingham and project partners. Collaborators will be able to include planar faults engineering in the early stages of the alloy design process, and to understand how certain elements may promote or hinder different deformation mechanisms in individual phases. This will be the first opportunity for the community to design the composition of individual phases for desired beneficial deformation mechanisms. It is expected that the knowledge and academic impact will extend beyond the field of superalloys, to any advanced alloy system that relies on ordered intermetallic compounds for its strength and performance.

The knowledge and academic impact will translate into industrial, economic and strategic impact. This project will lead to the design of future grades of advanced alloys, which will give a significant competitive edge to UK industry, such as Rolls-Royce plc. The ability to design low-cost variants of common commercial superalloys, without the need to sacrifice performance, is also a route to significant industrial and economic impact. Moreover, a more quantitative understanding of the role of certain solute elements on the deformation mechanisms will allow the possibility of removing or reducing the use of rare or strategic elements. In turn, this will limit the UK's reliance on unstable regimes or geographical areas for the acquisition of these elements.

Finally, the industrial and economic impact will result in a considerable societal impact. In the case of superalloys, for example, new compositions may allow the industry to raise the running temperature of jet engines and gas turbines, significantly increasing their efficiency. This will have substantial beneficial knock-on effects on the environment and the population. In the case of all advanced alloy systems, the ability to design new alloys at relatively low costs will unlock the possibility to tailor alloy compositions for specific components. This will boost both the efficiency of the component and the efficiency of raw-materials use in making the component.