Research enhances aluminum recycling technology

Through new research into the effects of crystallisation, aluminium recycling has received a boost.

Researcher Dr Biao Cai from the School of Metallurgy and Materials of the University of Birmingham used advanced high-speed X-ray imaging to record microcrystal formation as alloys cool and solidify under a magnetic field.

His collaborator, Dr Andrew Kao from the University of Greenwich, developed a mathematical model to predict whether microcrystals would form and what shape they would have.

The model predicted that, under the influence of intense magnetic stirring, helical 'screw-like' crystals would form, and the high-speed X-ray verified that this occurred.

Although these elegant crystals are only micrometers wide (10 times smaller than a human hair), they have repercussions for processes on an industrial scale.

"The physical properties of the alloy are essentially determined by these microscopic crystals. In order to be able to change their form, structure and growth path, we will be able to manufacture and recycle metals and alloys in perfect processes,' said Dr Cai.

A technique to boost aluminium recycling by extracting iron has already been patented by Dr Cai. Iron is a detrimental factor that can make aluminium fragile in premium applications such as aircraft and restrict its use.

During recycling, existing methods for extracting iron are either costly or ineffective, but to remove iron contamination, this simple , inexpensive technique uses magnets and a temperature gradient.

The technology was patented by the University of Birmingham Enterprise and funded by the Research Accelerator's Midlands Innovation Commercialisation, which granted Dr Cai a grant to build a large-scale prototype.