- An alloy is a mixture of two or more metals mixed in a certain percentage.
- Most pure metals are weak and soft. The properties of pure metals can be improved by making them into alloys.
- Alloys are made to
- increase the hardness of metals.
Magnalium is made from aluminium and magnesium to improve the hardness of the pure metals but at the same time, maintaining their lightness.
- prevent the corrosion of metals.
Stainless steel which can resist rusting is made by adding carbon, chromium and nickel to iron.
- improve the beauty and lustre of metals.
Copper and antimony added to tin produces pewter, used to make decorative items.
Q & A
Q: Explain why alloy of copper is harder than pure copper?
- In alloys of copper, foreign atoms are present.
- The impurities can prevent the layers of copper atoms slide over each others, thus making the metals harder, less malleable and ductile.
|(Pure metal – Atoms can slide over each other easily)|
|(Alloy – The presence of foreign atoms prevent the atoms of metal slide over each other)|
Copper Based Alloy
- Examples of copper base alloy are
- Most copper base alloy has shiny surface
Iron Based Alloy
- Examples of iron base alloy are
- stainless steel
- manganese steel
- The iron base alloys are usually very hard
Component: Fe 99%, C 1%
Applications: Vehicles, ships, bridges, buildings
Component: Fe73%, Cr 18%, Ni 8%, C 1%
Applications: Kitchen appliances, watches, machine parts, knives, forks, spoons
Component: Fe 85%, Mn 13.8%, C 1.2%
Applications: Helmet, spring
Aluminium Bases Alloy
- Examples of aluminium base alloy are
- Aluminium has low density, hence the density of aluminium base alloy is also low.
DuraluminComponent: Al 95%, Cu 4%, Mg 1%
Applications: Aeroplane parts, electric cables, racing bicycles
MagnaliumComponent: Al 70%, Mg 30%
Applications: Tyre rim of racing cars, skeletal body of aeroplanes