Collaborative research aims to boost aluminium recycling
1 Sep 2020
An innovative method for aluminium recycling has been boosted by research demonstratiing the microscopic changes that take place when molten alloys cool.
Dr Biao Cai from the School of Metallurgy and Materials at Birmingham University employed high-speed X-ray imaging to record the formation of micro-crystals as alloys cool and solidify, under a magnetic field.
His Greenwich University collaborator Dr Andrew Kao’s mathematical model predicted whether micro-crystals would form, and what shape they would have. It inferred helical ‘screw-like’ crystals would form under the influence of strong magnetic stirring, and the high-speed X-ray confirmed that this occurred.
The micro-meters wide crystals are ten times smaller than a human hair but have implications for industrial-scale processes, explains Biao:
“These microscopic crystals ultimately determine the physical properties of the alloy. To be able to adjust their shape, structure and direction of growth will enable us to perfect processes for both manufacturing and recycling of metals and alloys”.
Biao previously invented a technique to improve aluminium recycling by removing iron. The presence of iron can make aluminium brittle.
Existing methods used or removing iron during recycling are either expensive or inefficient, but Biao’s technique uses magnets and a temperature gradient to remove the contaminants.
Birmingham University has patented the invention, supported by the Midlands Innovation Commercialisation of Research Accelerator which awarded Biao a grant to build a scaled-up prototype.
University College London and the Diamond Light Source and European Synchrotron Radiation Facility also partnered the work on the high-speed X-ray tomography