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MOTORINDIA
l
May 2012
the automotive industry, and 78
per cent lighter than steel. Its me-
chanical properties cover much the
same spectrum as aluminium. Ex-
perts believe that a modern car may
well take 50 to 80 kg of the metal
to be used in motor blocks, gearbox
housings, door panels, door locking
devices, mirrors, tailgates, steering
wheels, consoles and else.
The German Fraunhofer Institute
for Machine Tools and Forming
Technology IWU, Chemnitz, has
designed a car door weighing 4.7 kg
(steel: 10.7 kg). Advanced applica-
tions are magnesium foam parts or
composite materials using magne-
sium and e.g., aluminium together.
Other usages in laptops, cameras,
mobile phones and medical instru-
ments should be
mentioned for the
sake of complete-
ness. Here, the
excellent dampen-
ing properties re-
garding sound and
electromagnet ic
waves are highly
welcomed advan-
tages of the metal.
In some ap-
plications
the
inferior thermal
stability
and
conductivity of
magnesium com-
pared to alu-
minium may be a
drawback. Also,
aluminium tends
to be more resist-
ant to corrosion.
When used for
exterior
parts
magnesium usually requires spe-
cial coating. Forging is weak spot:
only few magnesium alloys can be
forged. So, just as for every other
material, there is a generic frame
of properties within which the great
advantages of magnesium can be
exploited.
For a given structure and a realistic
production volume probably a mix
of advanced materials will yield best
results. A European project jointly
run by Daimler, Fiat, Opel, Porsche,
Renault, Volvo and Volkswagen has
made proposals for a Super Light
Car (SLC). Its body uses a blend of
materials and consists of aluminium
(53 per cent), steel (36 per cent),
magnesium (7 per cent), and plastics
(4 per cent). Compared to the con-
ventional reference body the weight
reduction has been 35 per cent.
In automotive applications today
pressure die-casting (PDC) is the
widest spread technology for magne-
sium-made components. Due to its
superior flow-characteristics mag-
nesium will allow very fine struc-
tures with a wall thickness of below
one millimetre. This gives greater
freedom to tool design and permits
further weight reduction when thick
walls are not really required for e.g.,
stability or heat transfer. Lower risk
of porosity is another advantage of
magnesium PDC parts. The better
flow properties of magnesium allow
to push the lifetime of a PDC-tool
from, say, one lakh shots to three
lakh shots which can be a significant
cost saving in mass production. Fur-
ther savings may arise out of shorter
cycle times in the casting process.
But is it not very expensive? No,
not when one compares apples to
apples. On a per volume basis, mag-
nesium tends to be even cheaper
than aluminium. As a component
will not normally change its basic
geometry when made of magnesium
rather than aluminium, the more ap-
propriate basis for comparison is a
Handbrake.lever, Audi A 3, magnesium PDC components
Prices of magnesium and aluminium
technology