Materials Science
• Introduction to Materials
• Properties of Materials
• Metals
• Plastics
• Woods
• Composites
• Heat Treatment
Introduction to Materials
• Materials are used to make or build objects.
• During the past 200 years there has been an
enormous increase in the range of materials
available to us. It is therefore important that the
correct materials be used for a particular use.
• In Selecting the best material you need to look
at 4 things: Physical properties, Cost and Time,
Shaping and Forming and Availability.
Selecting the best material – A checklist
1 PHYSICAL PROPERTIES
Hardness
Tensile Strength
Compressive Strength
Shear Strength
Stiffness
Toughness
Malleable
Corrosive
Appearance
Weight
Conductivity
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2 WHAT COST?
The materials
The extras (fittings etc)
3 SHAPING & FORMING
Cutting out
Moulding
Casting
Joining
4 AVAILABILITY
Are they easy to obtain
including fittings.
Properties of Materials
• Each material has many properties. It is
incorrect, for example to describe a material
as just ‘strong’ or ‘weak’ as for example
concrete is strong in compression but weak
in tension.
Hardness
Toughness
Strength
Brittleness
Malleability
Ductility
Elasticity
Plasticity
Conductivity
Density
Fatigue
Stiffness
Hardness
• The ability of a material to resist wear
indentation and scratching.
An example of a
hardness test that
can be carried
out in the lab.
Different materials
are used and the
depth of indentation
measured
Toughness
• The ability of a material to withstand
blows or sudden impact.
Different materials are
used, the hammer is
swung from the same
height each time about
a fixed fulcrum. The
distance travelled
after impact or
fracture is used to find
toughness
Strength
• The ability of a material to withstand
forces of tension, compression and torsion
Tensile Strength – the ability to withstand
pulling forces or Tension forces
Compressive Strength – the ability to withstand
‘squeezing’ forces or Compression forces
Torsional Strength – the ability to withstand
‘twisting’ forces or Torsion forces
Brittleness
• A material that is easily fractured by
impact is said to be brittle e.g. Glass
The same as the
toughness test
however those
materials that
fracture easily
are said to be
brittle.
Malleability
• A material that can be rolled or hammered
into shape without rupture.
As ring rises
the side of
Coke can is
thinned out
Ductility
• A material that can be pulled or stretched
into a thin wire or thread.
Get picture of wire
drawing
Elasticity
• The ability of a material to return to its
original shape after deformation.
Get picture of someone
stretching elastic band
Plasticity
• The ability of a material to be permanently
deformed without fracture..
Conductivity
• The ability of a material to allow Heat or
electricity to flow through it.
Ball Bearing
drops from most
conductive 1st.
Density
• Is the mass of 1 cubic centimetre (cm3) of a
substance. (Mass per unit Volume)
Q. Which is heavier a tonne of feathers or
a tonne of lead?
Q. Which has the greatest density?
Density =
Mass
Volume
Fatigue
• Occurs when materials have become
overworked and fracture or fail.
Find picture
Stiffness
• The ability of a material to resist bending
deformation.
Metals
• There are two types of metals
• Ferrous
• Non- Ferrous
Ferrous Metals
All the metals in this group contain Iron.
They include wrought iron, mild steel and
cast steel. Ferrous metals rust easily when
exposed to the atmosphere and are
magnetic.
Plain Carbon Steels
Alloy Steels
Plain Carbon Steels
These steels are a series of iron and
carbon alloys with carbon content
varying between 0.05% and 1.4%
Dead mild Steel
•Low carbon content 0.05-0.15%.
•Ductile and easily formed
•Uses: chains, rivets, nails, thin wire
Mild Steel
•carbon content 0.15-0.30%.
• Bright mild and Black mild, Bright mild
used in benchwork Black mild used for
forging
•Ductile, easily cut, machined and welded,
cannot be hardened or tempered
•Uses: General engineering work, girders,
plates for ship building, gates.
Medium Carbon Steel
•carbon content 0.30-0.60%.
•Greater strength than mid steel but not as
ductile or malleable.
•Uses: Axles, rail tracks,spades wire ropes..
High Carbon Steel (Cast Steel)
•carbon content 0.6-1.4%.
•Hard and wear resistant can be hardened
and tempered.
•Uses: Cutting tools (chisels, saws, files)
dies punches springs hammers..
Silver Steel
•carbon content @ 1.0%, contains chromium
•Does not contain silver gets its name from
appearance
•Uses: Scribers and screwdriver heads.
Tool Steel
• Used for making engineering tools.
Tinplate
•Tinplate is produced by coating thin
sheets of steel containing 0.1% carbon
with Tin.
•The process of coating the steel is called
Electro-plating.
• Uses: for food containers. It is also used
as containers for many other products such
as paint, lubricants etc.
Galvanised Iron
• This is mild steel coated with Zinc.
•The coating is usually achieved by
dipping the steel article in a bath of molten
zinc.
•Uses: for roof sheeting, gates, water
tanks, dust bins and other outdoor articles.
Alloy Steels
These steels are produced from adding
elements such as chromium, tungsten,
nickel and manganese to steel.