|Funding for:||UK Students, EU Students, International Students|
|Funding amount:||£15,609 per annum (plus £3,250 per year top-up)|
|Placed On:||17th December 2021|
|Closes:||31st January 2022|
Supervisors: Dr. Fabio Scenini & Professor Philip Prangnell
Collaborator: Airbus UK
Based at: The University of Manchester
Stipend: UKRI rate (currently £15,609 p.a.) plus £3,250 per year top-up
Open to: Candidate with a 2.1 or 1st class degree in a STEM discipline
This project is supported by Airbus UK and will contribute to their underpinning research in de-risking the application of new advanced ultra-high strength steel components in airframe applications. The research will be supervised through the Advanced Metallic Research Programme (AMRP) within Airbus Airframe R&T.
Ultra high-strength maraging stainless steels, are the strongest bulk metal alloys currently in existance. They can have yield strengths between 1500 - 2000 MPa and are widely used in landing gear components, because of their far higher performance in compressive loading compared to composite materials. Such materials are subject to a complex processing route to optimise their performance, which involves forging, and heat treatment to develop a quenched and tempered martensitic microstructure. This produces a ‘natural’ bulk nanomaterial which has a unique microstructure comprised of packets of very small submicron ferrite grains which are strengthened by nano-scale precipitates.
The steels are self-protected against corrosion by the formation of a thin passivating surface chromium oxide film. However, there is still a major concern regarding their susceptibility to Environmentally Assisted Cracking (EAC) in-service which is related to failure of the protective film in certain environments, when under stress. This can lead to local pitting attack and hydrogen charging which can cause cracks to develop through hydrogen embrittlement.
Therefore the aim of this project is to enhance the mechanistic understanding of EAC of high strength Maraging steels exposed to aqueous environments and to elucidate the role of microstructure on the materials performance that could be used for the optimization of future alloys (although the development of new alloys is not covered in this project). This will be realised by conducting a range of accelerated laboratory tests, combined with high resolution advanced microscopy, to develop a better understanding of the mechanisms involved in these complex materials.
The materials used for this project will be a selection of precipitation hardened, high-strength, steels which have different, performance properties, and microstructural and precipitation strengthening phases (e.g. Cu in 15-5 PH and NiAl PH13-8Mo). These materials will be microstructurally pre-characterized and tested in aqueous chloride containing environments to obtain electrochemical, corrosion, and stress corrosion cracking properties. Advanced electron microscopy analysis tools will be applied, in parallel with the testing programme, to understand the failure process and relationship to the materials microstructure, microchemistry, and hydrogen trapping behaviour. Given the possible very large number of variables, the philosophy of this project will be to investigate extreme conditions and identify the trends, as opposed to systematically investigating every possible combination.
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