GA Study Notes On Alloy and their composition: SSC CGL Tier-1 2017

Alloys and their Composition

Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods.Pure metals have poor mechanical properties. Hence, they are not used in their pure form in industry. Their properties are modified by adding other elements.

Reasons for Alloying: To improve mechanical properties.Alloys are often made to alter the mechanical properties of the base metal.

Characteristics of alloys: Alloys are harder and tougher than the base metal and are resistant to corrosion. They are inert to commonly used chemicals.

An alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition.

Amalgams: Alloys of mercury with other metals like sodium, potassium, gold and zinc etc are called amalgams. Amalgams stored in iron bottles as iron cannot form an amalgam with mercury.
Rold Gold is a metal, such as brass, coated with a thin layer of gold, usually of above 9 carat purity.

Some commonly Used Alloys and their composition:

Brass

Composition- zinc 30%, copper 70%
uses- In the making of utensils, pipes and radiator statues etc.

Yellow Brass

Composition - Cu 67%, Zn 33%
uses - Hardware items

Bronze

Composition - Copper 90%, Tin 10%
uses - In the making of coins, ornaments, utensils and statues.

Stainless steel

Composition - Fe 82%,(Ni + Cr) 18
uses - In the making of surgical instruments, watches and utensils etc.

Magnalium

Composition- Al 95% ,Mg 5%
uses - In making light articles and physical balance etc.

Duralumin

Composition- Al 95%, Cu 4% ,Mn 0.5%
uses -In making parts of aeroplane and ship etc.

Alnico

Composition - Al 8-12% , Ni 15-26% , Co 5-24% ,Cu 6%, Remaining: Fe, Tl
uses - It is useful in making of magnets.

German silver

Composition - Cu 60% ,Zn 20%, Ni 20%
uses - It is useful in electroplating and making of utensils.

Sterling Silver

Composition - silver 92.5%, copper 7.5%
uses - jewellery, art object

Gunmetal

Composition - Cu 88%, Sn 10%,Zn 2%
uses - It is useful in making of guns, machine parts and canons..etc

Solder metal

Composition - Pb 50%, Sn 50%
uses - It is mainly useful to join electric wires.

Bell Metal

Composition - copper - 77%, tin - 23%
uses- In the casting of bells

Coin metal

Composition - copper 75%, nickel 25%
uses - U.S coins

Wood's metal

Composition - Bi 50%, Pb 25%, Sn 12.5%, Cd 12.5%
Uses - fuse plugs, automatic sprinklers.

Monel

Composition - Ni 67%, and copper, with small amounts of iron, manganese, carbon, and silicon.
Uses - It is resistant to corrosion and acids and thus used for making valves, pumps, shafts, fittings, fasteners, and heat exchangers.

Plumber's solder