Alloys

Alloys:

An alloy is the mixture of two or more metals in a fixed proportion. An alloy is made to enhance the mechanical properties of its base metal. For example Steel in an alloy of iron which has improved mechanical properties than iron.

Alloys of Copper:

Brass (Copper-Zinc alloy): The percentage of zinc varies from 5 to 45% and percentage of copper varies from 57 to 70%. Metals like tin, lead, iron, aluminium and manganese are also added to improve the properties.

Bronze (Copper-Tin alloys): The percentage of Tin varies from 2 to 12%.

When phosphorous is added (maximum 4%) to the bronze, it is known as phosphor bronzes.

The gun metal consists of 80% copper, 10% tin and 2% zinc.

Engineer’s bronze contains 880% copper, 10% tin and 2% zinc.

Bell metal: It contains 20 to 25% tin.

Aluminium bronze (Copper-Aluminium alloys): These contains 5 to 11% of aluminium. Small quantities of other metals like manganese, iron and nickel are also added to improve the properties.

 

Alloys of Aluminium:

They are light weighted as compared to other alloys. They have good corrosion resistance and have good thermal and electrical properties.

Duralumin: It is used to fabricate the parts of automobiles and aircrafts.

The alloy consists of Copper (3.5 to 4.5%), Magnesium (0.4 to 0.7%), Manganese (0.4 to 0.7%), Iron or silicon (less than 0.7%) and rest of the aluminium.

 

Alloys of Nickel:

Monel metal: It consists of 60% nickel, 33% copper and a small amount of iron and manganese and a very small amount of silicon and carbon.

German silver: It consists of 25% nickel, 60% copper and rest of the zinc.

Constantant: It contains 45% Nickel and 55% Copper.

 

Alloys of Tin:

Solder: It contains lead and tin. Commonly used composition of solder is as follows.

a. 67% Tin and 33% Lead

b. 50% Tin and 50% Lead

c. 33% Tin and 67% Lead

Babbit metal: It contains 70 to 90% Tin, 7 to 24% Antimony and 2 to 24% Copper.

 

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Multiple Choice Questions on Alloys