Recycling of Al alloys

Reducing energy use is a major component of the UK’s policy for meeting its CO2 emission targets. Vehicle lightweighting, by replacing steel components with light alloy castings and wrought components, has been identified as one of the technologies with the greatest potential to contribute to this goal. Aluminium alloys are hence being used by the automotive and aerospace sectors. However, these industries are currently using primary grade aluminium, as recycled materials do not give adequate mechanical properties.  

A recent life cycle assessment for the Al industry showed that the production of 1kg of primary Al, when all the electricity generation and transmission losses were included, required 45kWh of energy and emitted 12kg CO2, whereas 1 kg of recycled Al required only 2.8kWh (5%) energy and emitted 0.6kg (5%) of CO2. Hence the use of recycled materials would considerably reduce the carbon footprint.

This project will investigate the ability of melt conditioning to improve the mechanical performance of recycled materials. Melt conditioning is defined as treatment of liquid metals by either chemical or physical means for the purpose of enhancing heterogeneous nucleation through manipulation of the chemical and physical nature of both intrinsic (naturally occurring) and extrinsic (externally added) nucleating particles prior to solidification processing. A prime aim of melt conditioning is to produce solidified metallic materials with fine and uniform microstructure, uniform composition and minimised cast defects and hence good mechanical properties.