Circular manufacturing of aluminium alloys

Aluminium alloys are in principle infinitely recyclable and recycling saves resources, energy and CO2, when compared to primary production. However, recycling aluminium is still a technologically challenging process due to the accumulation of tramp elements at each remelting cycle, which downgrades the material properties. These elements, particularly Fe and Si, have the tendency to segregate during solidification and precipitate into harmful intermetallic compounds (IMCs) which compromise materials performance even at small volume fractions. The current industry solution is to maintain tightly controlled alloy compositions and dilute recycled scrap with virgin, near-pure smelted alloy, with all the attendant logistical, cost and emission penalties.  An alternative solution is to learn how to control elemental segregation during solidification to manipulate impurities elements into forming benign and finely dispersed IMCs rather than the ’naturally’ occurring coarse and brittle compounds. To this end it is critical to advance our understanding of mass transport and multi-elemental diffusion in liquid aluminium. 

The project will use synchrotron X-ray imaging techniques, such as radiography and time resolved tomography, to capture in real-time the elemental segregation taking place at the solid-liquid interphase during solidification in aluminium alloys. X-ray radiography will be employed to study the segregation of element heavier than aluminium, such as Fe, Zn and Mn. The candidate will then work in a team to develop a novel experimental approach for the investigation of light alloying elements, such as Si and Mg, which cannot be studied using conventional X-ray imaging. This approach will involve the use of multiple techniques including X-ray fluorescence mapping, (high energy) X-ray diffraction and Pair Distribution Function (XPDF) and Compton scattering imaging. The work will comprise the use and adaptation of existing equipment for the study in-situ of solidification, the design and preparation of beamtime synchrotron experiments at national and international facilities (Diamond Light Source and ESRF in France), and the use of existing advanced machine learning code for the analysis of the large data collected. The candidate will join an exciting environment and be part of a team, which includes collaborators from UKRI and Diamond, working at the cutting edge of technology to develop new X-ray techniques to investigate the dynamic of metal manufacturing processes and improve metal recyclability.

This EPSRC-funded 3.5 year DPhil in Materials DTP studentship will provide full fees and maintenance for a student with Home/Republic of Ireland or Islands fee status.  The stipend will be at least £16,285 per year.  Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.  

Candidates will be considered in the November 2020 admissions field which has an application deadline of 13 November 2020 and, if the studentship is unfilled, in the January 2021 admissions field which has an application deadline of 22 January 2021.  

Any questions concerning the project can be addressed to Dr Enzo Liotti (enzo.liotti@materials.ox.ac.uk).  General enquiries on how to apply can be made by e mail to graduate.studies@materials.ox.ac.uk.  You must complete the standard Oxford University Application for Graduate Studies.  Further information and an electronic copy of the application form can be found at https://www.ox.ac.uk/admissions/graduate/applying-to-oxford.

Time series of solidification in Al

In-situ X-ray Imaging of Solidification in Al

 

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