Development and characterisation of a novel ultra-high strength steel for future aerospace applications (Advanced Metallic Systems CDT Project)

This project will help to develop and characterise a new ultra-high strength steel with a unique set of properties. The alloy has been designed to achieve a combination of high strength, high toughness and creep capability for use as a future shaft material within Rolls-Royce to be used in next generation jet engines.

The new material has a higher strength compared to the current shaft material, which will enable smaller shaft diameters to be achieved, offering opportunity for significant weight reduction for future aerospace engines.

The alloy development has been ongoing for several years and is now approaching deployment. The alloy was designed using thermodynamic modelling, looking at conventional high strength steels without the temperature capability and modifying the composition and heat treatment to stabilise the microstructure at high temperature.

Several chemistry and heat treatment variations of the alloy system have already been evaluated. The composition and heat treatment have now become fixed and several production scale melts have been produced. Extensive mechanical testing has been carried out. This includes tensile, fracture toughness, crack growth, creep and fatigue tests at a range of temperatures. Work has also been carried out to microstructurally characterise the material, using techniques such as optical microscopy, SEM, TEM, atom probe tomography and EBSD. As an ongoing project with several partners this position requires a collaborative outlook.

The alloy will also be used at elevated temperature for extended periods. Work will be required to demonstrate that the microstructure is stable at these operating temperatures and the mechanical properties are still acceptable.

This PhD will focus on improving the understanding between microstructure and properties of the alloy system. In particular, the link between the nanoscale precipitates and grain size on the strength, toughness and creep behaviour.

You will carry out mechanical testing of the samples, learning from previous work on this project, to create samples ready for detailed investigation. To do this you will use a correlative approach where regions of interest are tracked through multiple scales. This not only allows the finding of important regions but also means the high resolution analysis has a clear context within the larger component. You will use X-ray computed tomography (CT) for macro to micro scale characterization of damage. Scanning electron microscopy (SEM) for detailed microstructural analysis as well as focussed ion beam (FIB) and transmission electron microscopy (TEM) for local performance measurements and the nanoscale analysis of site specific regions.

Thus you will build up a detailed multiscale and multi-facetted picture of the microstructure and link this to the material performance of this critical component of the jet engine.

Advanced Metallic Systems Centre for Doctoral Training
The Advanced Metallic Systems CDT is a 4 year programme hosted jointly by the universities of Manchester and Sheffield building on their complimentary expertise and international reputations in materials science and engineering research. In year 1, students from a range of disciplinary backgrounds undertake taught courses in core materials topics. PhD research begins after 6 months. Our transferable skills and personal development programme leads to a Diploma in Professional Skills. Visit our website for more information www.metallicsCDT.co.uk.