Advantage Magnesium

The lightweight metal will replace several uses of aluminium in the car industry

Published: Tuesday 15 July 1997

Lighter wheels of fortune. maj (Credit: Amit Shanker /CSE)CAR manufacturers around the world are currently focusing on magnesium, which is increasingly being considered as the alternative to aluminium. The search for lighter cars with reduced fuel consumption and exhaust emissions is making car manufacturers around the world converge on magnesium.

Magnesium is a light, white metal occurring naturally as magnesite, dolomite, and carnallite. It is prepared by electrolysis of fused carnallite. The metal is widely used in light, high-tensile alloys for aircraft, and in pyrotechnic mixtures. Although small quantities of magnesium alloys have been used in cars, interest in this light, yet strong metal, is growing. It is increasingly being used in new vehicles to replace steel, aluminium, and in some cases, even plastic.

The advantage in using magnesium is its light weight. Despite the benefits, applications of magnesium as an engineering material have been slow to take off. The metal is highly inflammable and prone to corrosion - difficulties for which solutions have now been found. The highly pure magnesium alloys used now are made in a closely controlled processes. Their corrosion resistance is superior to that of the most common aluminium alloys.

While pure magnesium ignites easily when exposed to air, the machining of magnesium alloys does not pose a fire risk as long as the appropriate cutting conditions are maintained. Cutting fluids, for example, must be used to keep the alloy below its melting temperature. Another problem has been the cost. Magnesium is more than twice the price of aluminium, its main competitor for weight- reduction projects.

The main evidence that magnesium is high on the agenda of car manufacturers is the number of deals that companies, such as Volkswagen, Ford, General Motors and Toyota, are involved in with magnesium producers. According to a report in the Financial Times, London, the new Volkswagen Passat B5 features a magnesium gearbox casing, reducing weight by 4.5 kg. Volkswagen has gone into a partnership with Israel's Dead Sea Works, and owns 35 per cent of Dead Sea Magnesium Ltd, a production facility that the two companies have set up in a joint venture. Ford, meanwhile, has signed a multi-billion dollar con- tract with the Australian Magnesium Corporation.

Switching to magnesium does not necessarily mean higher costs. The diecasting process, which is used to produce the bulk of automotive components, favours magnesium. Parts which are complex, thin-walled, and require accuracy, can be die-cast from magnesium, but not from aluminium. This means automotive parts can be redesigned to ensure that, in spite of its higher price, magnesium does not incur additional costs when used to replace existing materials.

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