Alloys and Composites

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Alloys and Composites

• State that an alloy is a solid solution
• Describe the advantages of alloys over pure
  metals.
• Describe a composite material, explain how it is
  made.
• State two applications for composites.
• Describe two examples of composite materials.

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Which of these are alloys? Put your hand up if
you can name at least one.
Gold, Aluminium, Steel, Iron, Bronze, Mercury,
Brass, Amalgam.
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Steel ? Iron with a small amount of
carbon Bronze ? Copper Tin Brass ? Copper
Zinc Amalgam ? Mercury Silver
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Metals have a crystal structure their atoms
line up in regular patterns.
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But they are rarely perfect.
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Another elements atoms can join the lattice.
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Alloying atoms are of a different size.
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These Alien atoms

• Are dissolved in the main crystal structure.
• They change the physical properties
• They change the stiffness
• They change the strength.
• They change the melting point

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Why is an alloy a solid solution?
Because alien atoms are distributed amongst the
atoms in the parent crystal.
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Advantages
Alloys can be designed to have particular
properties. They can be stronger. They can be
stiffer. They can have a high melting point. They
can be used in applications where pure metals
would fail.
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Composites
A Composite material is one made from two
different materials, which have different
properties. Basically it is a polymer (plastic)
with reinforcing fibre inside.
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Carbon Fibre Matting
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A matrix of fibres is held in place by a resin.
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Whats the difference between an alloy and a
composite?
COMPOSITE mixes at a physical level. You can
see the different materials with your eye or a
simple microscope.
ALLOY mixes at an ATOMIC or MOLECULAR level.
Not even an electron microscope would show you
the structure.
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Making Alloys
Melt Mix Allow to cool
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Composites are more difficult to make
Fibreglass boat. Lay the matting in a mould.
Apply resin with a brush. Soak the matting. Let
it cure.
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High Tech Boat builder. Spray the resin into the
mould. The blades at the Wind turbine factory
(Vestas) are made of fibreglass and are made in a
similar way.
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When Production Engineers get their teeth into
something it looks more complicated. But
composites are still simple Two different
materials joined together.
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What would boy racers do without fibreglass?
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You will now follow instructions in a worksheet
to encourage you to take a few notes. To help
you the slide show will cycle through
continuously. For those who COOPERATE and do the
job, there is a practical demonstration to have a
go at.