Automotive Design
forming process that is not economically viable for large-volume production.
The forming tool, which measures around 1.4 x 1.2m, is made from materials such as nickel-base alloys which remain stable above 800°C without oxidising. A special coating, just a few microns thick, prevents titanium from adhering to the tool, which can lead to component cracking and severe damage to the surface.
Above 500°C, titanium reacts readily with oxygen and nitrogen in the atmosphere. For this reason, shielding gases such as
extensive testing with various materials, we developed the ideal coating for the special conditions encountered within the various temperature ranges.”
Oxygen is the enemy At the same time, a collaborative team in the UK has devised a way to make a welded titanium car chassis. Sports car manufacturer Ariel is planning to incorporate titanium tubing into the chassis of its Atom series of sports cars, with help from Caged Laser Engineering and Reynolds Technology.
Reynolds makes high strength metal tubing (usually in steel, but also in titanium) for applications ranging from cycles to the Bloodhound SSC.
Fig. 2. Niche vehicles could benefit from advances in titanium processing.
argon are used at very high temperatures to prevent oxidisation.
Martin Weber, an expert in tribological coatings at Fraunhofer IST, says: “After
Make it quick R
esearchers at the University of Rostock in Germany have
developed a technique to boost the strength of metallic alloys, which claims to be more energy efficient – and less costly – than existing methods. It relies on a modified Spark Plasma Sintering (SPS) system, which has an integrated gas quenching
mechanism that can alternate the phase compositions and retain the smallest grain features inside a structured metallic alloy. SPS is used to fuse fine powders into a solid material, by applying electric current and mechanical pressure. By varying SPS cooling rates, it is possible to tune its mechanical properties by controlling phase and grain sizes.
The team showed that rapidly cooling a material directly after SPS fabrication can enhance hardness, strength and ductility. After sintering, most SPS systems are left to cool naturally, or are flooded with argon gas. The new system pumps nitrogen gas into the chamber at high speed, which rapidly cools the material. ●
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Caged Laser specialises in steel roll cages for cars. It says that making the Ariel Atom 3’s roll cage from titanium tubing could make it 40 per cent lighter – shaving up to 10 per cent off the weight of the car. (With the wind in the right direction, this could allow Ariel to bring the Atom in at 500kg or less.)
“Titanium is lightweight and strong – a perfect material – but it’s hard to machine, hard to cut and weld, and hard to do anything with,” says Phil Squance, technical director at Caged Laser.
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