ALLOY
Introduction
Many of the pure metals are not widely used because of their properties such as hardness, tensile strength, resistance to corrosion and lustre can be improved by combining them with other element. The mixtures are known as alloys.
An alloy is a mixture of two or more metals mixed in a certain percentage.
Alloys are made to:
- Increase the hardness of metals. Example: 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. Example: Stainless steel which can resist rusting is made by adding carbon, chromium and nickel to iron.
- Improve the beauty and lustre of metals. Example: Copper and antimony added to tin produces pewter, used to make decorative items
SOME ALLOYS, THEIR COMPOSITION AND APPLICATION
Copper Based Alloy: Most copper base alloy has shiny surface. Examples of copper base alloy are Cupro-nickel, Bronze and Brass
- Cupro-nickel
Component: Cu 75%, Ni 25%
Applications: Coins
- Bronze
Component: Cu 90%, Sn 10%
Applications: Decorative items, medals, artwork, pots and pans
- Brass
Component: Cu 70%, Zn 30%
Applications: Decorative items, electrical appliances, musical instruments, bell, nails, screw, pots
Iron Based Alloy: The iron base alloys are usually very hard. Examples of iron base alloy are steel, stainless steel and manganese steel
- Steel
Component: Fe 99%, C 1%
Applications: Vehicles, ships, bridges, buildings
- Stainless steel
Component: Fe73%, Cr 18%, Ni 8%, C 1%
Applications: Kitchen appliances, watches, machine parts, knives, forks, spoons
- Manganese steel
Component: Fe 85%, Mn 13.8%, C 1.2%
Applications: Helmet, spring
Aluminium Based Alloy: Aluminium has low density; hence the density of aluminium base alloy is also low. Examples of aluminium base alloy are Duralumin and Magnalium
Duralumin
Component: Al 95%, Cu 4%, Mg 1%
Applications: Aeroplane parts, electric cables, racing bicycles
Magnalium
Component: Al 70%, Mg 30%
Applications: Tyre rim of racing cars, skeletal body of aeroplanes
Tin Based Alloy: Most tin base alloy has shiny surface and low melting point. Examples of tin base alloy are pewter and solder
Pewter
Component: Sn 91%, Sb 7%, Cu 2%
Applications: Decorative items, souvenirs
Solder
Component: Sn 50%, Pb 50%
Applications: Welding and soldering work
