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Automotive Design


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. 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.)


oxygen-free conditions, this means using a barometric chamber to contain the parts under argon gas. The main challenge was building the chamber


itself: for a complete chassis, the chamber has to be 3.5 x 2 x 2m – which is larger than any chamber currently in existence, says Squance. “We were laughed out of the building by three


chamber manufacturers,” he says. “Nobody has ever made a chamber this large for titanium.” The challenge was to evacuate the chamber of


all traces of oxygen (and nitrogen). This is not easy when you consider that many materials – rubber, steel, ceramics – actually have oxygen embedded within them. “We were battling with items in the


chamber,” says Squance. “They outgas what you want to get rid of.” This meant that items like hosing had


to be redesigned. Out went rubber, in came high spec 216 stainless steel. The whole chamber was shrouded in special glass that contained no oxygen. Even after all this, the tolerance for


oxygen was very low. Anything over 100ppm was too much: it would lead to brittleness, and the likelihood of a catastrophic failure of the part. The aim was to weld in an atmosphere of 20-70ppm. To visualise this, Squance


Fig. 2. Niche vehicles could benefit from advances in titanium processing.


“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. The three companies are investigating the feasibility


of producing a titanium roll cage for lightweight niche vehicles. Because titanium must be welded under


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


12 www.engineerlive.com


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. To demonstrate the system, the team


produced Grade 5 Titanium (Ti-6Al-4V) – the most commonly used titanium alloy, with applications in the aerospace, biomedical and marine industries – at different cooling rates.


The most-rapidly cooled alloy was up to


12 per cent harder than the naturally-cooled alloy, with more than 30 per cent higher ductility. ●


likens it to a 3mm layer of water in an Olympic-sized swimming pool. “That’s how much oxygen we’re allowed in the


chamber,” he says. “Oxygen is our big enemy.” A titanium-based Atom car has now been built, and


is being tested. A limited edition will be launched in the near future. If successful, it will be added to the options list, says Squance. He says that the project was instigated because of the ongoing need to reduce the weight of cars in the


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