Difference between intermetallic compounds and alloys
Answers
Both inter metallic and alloys are solid + solid mixtures. In formation of both the types of substances a primary metal acts as solvent while other metal(s) act as solute. A binary solid-solid solution would contain two metals while forming a solid –solid solution when the solute is more than the limit of solubility of solvent, then a second arrangement appears distinct apart from the primary solid solution. This secondary arrangement with the primary arrangement is termed as Inter metallic compounds. In inter metallic compounds the binding is metallic between the primary arrangement and ionic in the secondary arrangement leading to different property of inter metallic compounds. The ionic bonding is due to greater difference in elector-negativities between the solute metal and solvent metal.
Due to partial ionic bonding the inter metallic compounds are always very hard, brittle and have similar properties to that of ceramic material in terms of their mechanical properties.
Inter metallic compounds are of two types
Stoichiometric inter metallic compounds: The compounds which have composition similar to that represented by the molecular formula e.g Au2Pb in Au- Pb system, MoSi2 in Mo-Si system
Non-Stoichiometric inter metallic compounds:: The compounds systems have range of composition
gama brass Cu5An8 Solid
e.g. beta phase in brass. Gama phase in Mo-Rh system
The properties of inter metallic solids are
High strength
Good creep at high temp
High toughness at cryogenic temp
Good machinibility
The uses of inter metallic solids are in
Making of pistons (Copper Aluminide)
Rivets for aircraft construction (Copper Aluminide)
Car bodies (magnesium silicates)
But in alloys there is no secondary arrangement possible and ionic bonding is also not possible
So alloys slightly differ from inter metallic compounds