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