Material properties
Strength
The ability of a material to withstand a force that is applied to it.
Tensile strength: the ability to resist a pulling force.
o Ultimate tensile strength: the amount of stress at which the material fails.
Compressive strength: the ability to resist a squeezing force.
Torsional strength: the ability to resist a twisting force.
Yield strength: the amount of stress needed to start permanently deforming a material
force
stress (N/mm−2 ) =
cross sectional area
Ductility
The amount that a material can be deformed, e.g. most thermoplastics are ductile, but ceramics are
not, as they would just fracture.
A measure of ductility is the length that a material extends when a load is applied:
∆ length
strain =
original length
Malleability
The ability of a material to be deformed without rupturing. This means the shape of the material can
be changed without the material breaking.
E.g. clay is malleable, but when it has dried it isn’t.
Hardness
The ability to resist wear and abrasion. The harder a material, the more difficult it is to mark its
surface.
Toughness/brittleness
Toughness is the ability to withstand an impact without breaking (but it might bend).
Brittleness is the opposite of toughness; the potential for a material to shatter when it experiences
an impact, e.g. glass.
Stiffness
The ability of a material to resist bending.
This is shown by the young’s modulus:
stress
youngs modulus (N/mm−2 ) =
strain
Metals and Alloys
Metals are made from metal ores; rocks or minerals dug from quarries or mines then
refined and processed, to turn the metal into a usable form.
Alloys are a mixture of metals (but can include non-metals, e.g. carbon in iron). They can
improve the properties of metals.
Types of metals:
Ferrous: contain iron, magnetic, can rust/oxidise (e.g. steel, iron)
Non-ferrous: No iron, not magnetic (e.g. aluminium, copper, lead)
, Ferrous
Ferrous Alloy elements Properties Typical uses
alloy include: include:
Cast iron 3-3.5% carbon Good compressive strength Anvils, vices,
Hard machine tool beds
Brittle
Poor corrosion resistance
Relatively low cost
Low-carbon Less than 0.3% Lower strength than other steels, Nail & screws, car
steel carbon but still stronger than non-ferrous bodies
Tough and relatively low cost
Cannot be hardened
High-carbon 0.8-1.4% Strong & hard, but not as tough Tools, such as saws,
steel carbon as low-carbon steel hammers, etc.
Difficult to form
Can be hardened
Stainless >11.5% carbon Strong & hard Knives, forks,
steel Difficult to machine medical equipment
Good corrosion resistance
Relatively expensive
Non-ferrous
Non-ferrous Properties Uses
metal
Aluminium Pure metal not as strong as steel, so alloyed to improve Cans for soft
it drinks,
More expensive than carbon steels, but better aircraft
resistance to corrosion wings and
Low density, makes it lightweight (perfect for planes) bodies
Copper, brass Good electrical conductor Electrical
and bronze Ductile wires, water
Commonly used in pure form, but copper oxide can be pipes
added to make it stronger
Used to make alloys brass and bronze, for aesthetics
and strength
Lead Soft, malleable and ductile Weights,
Very good resistance to corrosion radiation
High density, so very heavy shields
Can cause health problems in humans
Zinc Low melting point (approx. 420°c) Car door
Can be alloyed with aluminium to increase strength handles,
camera
bodies
Strength
The ability of a material to withstand a force that is applied to it.
Tensile strength: the ability to resist a pulling force.
o Ultimate tensile strength: the amount of stress at which the material fails.
Compressive strength: the ability to resist a squeezing force.
Torsional strength: the ability to resist a twisting force.
Yield strength: the amount of stress needed to start permanently deforming a material
force
stress (N/mm−2 ) =
cross sectional area
Ductility
The amount that a material can be deformed, e.g. most thermoplastics are ductile, but ceramics are
not, as they would just fracture.
A measure of ductility is the length that a material extends when a load is applied:
∆ length
strain =
original length
Malleability
The ability of a material to be deformed without rupturing. This means the shape of the material can
be changed without the material breaking.
E.g. clay is malleable, but when it has dried it isn’t.
Hardness
The ability to resist wear and abrasion. The harder a material, the more difficult it is to mark its
surface.
Toughness/brittleness
Toughness is the ability to withstand an impact without breaking (but it might bend).
Brittleness is the opposite of toughness; the potential for a material to shatter when it experiences
an impact, e.g. glass.
Stiffness
The ability of a material to resist bending.
This is shown by the young’s modulus:
stress
youngs modulus (N/mm−2 ) =
strain
Metals and Alloys
Metals are made from metal ores; rocks or minerals dug from quarries or mines then
refined and processed, to turn the metal into a usable form.
Alloys are a mixture of metals (but can include non-metals, e.g. carbon in iron). They can
improve the properties of metals.
Types of metals:
Ferrous: contain iron, magnetic, can rust/oxidise (e.g. steel, iron)
Non-ferrous: No iron, not magnetic (e.g. aluminium, copper, lead)
, Ferrous
Ferrous Alloy elements Properties Typical uses
alloy include: include:
Cast iron 3-3.5% carbon Good compressive strength Anvils, vices,
Hard machine tool beds
Brittle
Poor corrosion resistance
Relatively low cost
Low-carbon Less than 0.3% Lower strength than other steels, Nail & screws, car
steel carbon but still stronger than non-ferrous bodies
Tough and relatively low cost
Cannot be hardened
High-carbon 0.8-1.4% Strong & hard, but not as tough Tools, such as saws,
steel carbon as low-carbon steel hammers, etc.
Difficult to form
Can be hardened
Stainless >11.5% carbon Strong & hard Knives, forks,
steel Difficult to machine medical equipment
Good corrosion resistance
Relatively expensive
Non-ferrous
Non-ferrous Properties Uses
metal
Aluminium Pure metal not as strong as steel, so alloyed to improve Cans for soft
it drinks,
More expensive than carbon steels, but better aircraft
resistance to corrosion wings and
Low density, makes it lightweight (perfect for planes) bodies
Copper, brass Good electrical conductor Electrical
and bronze Ductile wires, water
Commonly used in pure form, but copper oxide can be pipes
added to make it stronger
Used to make alloys brass and bronze, for aesthetics
and strength
Lead Soft, malleable and ductile Weights,
Very good resistance to corrosion radiation
High density, so very heavy shields
Can cause health problems in humans
Zinc Low melting point (approx. 420°c) Car door
Can be alloyed with aluminium to increase strength handles,
camera
bodies
