Explain Hume- Rothery Rule for the formation of a solid solution

Hume- Rothery Rule for the formation of a solid solution:



There are some rules to form the substitutional solid solution and control the solubility in alloy system.

If the size of solute and solvent along with the electron chemical nature are same then the substitutional solid solution is obtained.

These rules govern the solid solution formation.

About the factors:

1. Depends on the size of the factor.

2. Chemical combination factor.

3. Relative valency factor.

4. Lattice Formation.


1. Depends on Size of the Factor:

For the formation of a solid solution, the metal is said to be a required size factor. The formation of a solid solution is less when the size is larger than 15%. there must be lower than 8% for the complete solid solubility.

2. Chemical combination factor:

The solid solubility doesn’t form when two metals chemical affinity is high. the solubility of solid is increased when the metals are very small.

3. Lactice formation: 

If the Lattice formation is the same in the metal then the solid solubility is formed.

4. Relative Valency  factor:

In this Relative factor the metal with high valency can dissolve a small amount of  metal with lower valency but in the lower metal valency can dissolve a huge quantity of  metal with higher valency. If there is a difference in valence in base metal the electron ratio is not equal.

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