A new process for die-casting copper car components is just like pouring ketchup, says Dr. Helen Atkinson of the University of Sheffield, UK, speaking at the British Association Festival of Science. Called thixotropy, this common property shared by ketchup and copper means that they can become soft and runny before hardening back into a more solid form. Despite the fact that the thixotropic behaviour of metallic alloys such as aluminium was discovered in the 1970s, the potential has only recently been realised for commercial use of the process. Car companies in Italy, the US and Japan now manufacture car parts by thixoforming, or by stirring alloy material while it is cooling so that it solidifies as round particles which can then flow smoothly, like ketchup, when reheated.
Atkinson, from the university's Department of Engineering Materials, one of the world leading groups in thixoforming research, says, "Thixoforming has advantages relative to processes like die-casting because the metal flows into the die in a smooth way rather than the turbulent flow that occurs when fully liquid metal is injected into a die." Accordingly, the thixoforming process avoids the defects that can occur during turbulent flow, such as when oxide particles get folded into solidifying metal and react with the atmosphere; and because the metal does not have to be fully melted before forming to shape, energy is saved during manufacturing as well.
Examples of components being made from a range of alloys by thixoforming at Sheffield University include a rotor for car motors made from copper alloy, a challenging system to process, which cannot usually be made by die-casting. Rotors such as the one shown by Atkinson have a much higher electrical conductivity than aluminium rotors and therefore make motors for cars more efficient and also offer more energy savings. The next step for the university is the development of alloys specifically for thixoforming that are more economic than die-casting or forging and could even open up applications for thixoforming in the aerospace industry. In addition, Atkinson says, despite having one of the world's leading thixoforming research groups, the UK has yet to commercialise the process in the same way as other major motor manufacturing countries.
For further information please contact:
Dr Helen Atkinson
Tel: +44 (0)114 222 5512
Email: h.v.atkinson@sheffield.ac.uk
Andrew McLaughlin
The Institute of Materials
Tel: +44 (0)20 7451 7395
Email: Andrew_Mclaughlin@materials.org.uk
Notes for Editors
1. Dr. Helen Atkinson will present her lecture, "Soft Solids from Mascara to
Parts for Cars" at 15.00hrs (BST) on 15 September at the British Association's
Festival of Science 1999 at the University of Sheffield. The festival runs from
Monday 13 September to Friday 17 September. www.britassoc.org.uk
2. This lecture has been organised by The Institute of Materials, the
professional organisation for materials scientists, engineers and technicians.
www.materials.org.uk