The automotive industry is constantly looking for improvements in materials and processes in order to try and reduce the weight of their vehicles to improve fuel efficiency. While improvements in aluminium alloys and ultra high strength steels can assist in light-weighting improvements have been relatively incremental in recent years. Titanium on the other hand has a superior strength-to-weight and corrosion resistance to both steels and aluminium alloys. There have been small scale demonstrations of titanium in road vehicles but major barrier for titanium's introduction into the mass production automotive market is its cost. The introduction of cost effective solid state extraction routes for titanium from its ores or oxides (Metalysis FFC, Cristal Metals, CSIRO TiRO™ and others) has renewed research interest in the cost reduction of titanium. These processes in particular produce powders directly from the extraction cells, which requires a low cost powder consolidation method for a true step change in the economics of the resultant titanium products. Standard solid state consolidation methods tend to rely on batch processes and require multiple steps to produce a fully dense product. The severe plastic deformation that occurs within the Conform process has the potential to solve these problems and provide a truly cost effective thermomechanical processing for titanium particulates. Even though Conform has been around since the 1970s and primarily used to extrude aluminium and copper based alloys significant development has been slowed by a lack of understanding of the thermomechanical behaviour material within the process. Work presented in this thesis demonstrates the successful extrusion of grade 2 hydride-dehydride (HDH) titanium powder through the Conform process to obtain a fully dense rod product with a fine grain size. A finite element model has also been produced in order to demonstrate the evolution of certain microstructural features in the extruded titanium wire. The models are extended to help predict a general titanium powder processing window for continuous extrusion machines.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:684607 |
| Date | January 2016 |
| Creators | Thomas, Ben |
| Contributors | Jackson, Martin |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/12486/ |
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