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Substitutional Alloys vs. Interstitial Alloys: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 18, 2023
Substitutional alloys have one metal replaced by another, while interstitial alloys have smaller atoms fitting into the spaces between larger metal atoms.

Key Differences

Substitutional alloys are formed when atoms of the primary metal are replaced by atoms of similar size from another metal. Interstitial alloys, conversely, are created when smaller atoms of a metal or non-metal fill the interstices or spaces between atoms of a larger metal.
In substitutional alloys, the solute atoms take the place of the solvent atoms in the metal lattice, leading to a change in the overall structure. In the case of interstitial alloys, the solute atoms don't replace but instead fit into the gaps of the solvent metal's atomic lattice.
The properties of substitutional alloys depend on the nature and proportion of the substituting metal. Interstitial alloys, on the other hand, often display significant changes in properties due to the presence of small atoms in the interstitial spaces, leading to a distortion of the lattice.
Brass is a classic example of a substitutional alloy, where some copper atoms are replaced by zinc. Steel, in contrast, is an example of an interstitial alloy where carbon atoms fit into the interstices of the iron lattice.
Both types of alloys are essential in various industries for their unique properties. Substitutional alloys tend to be more malleable, while interstitial alloys are often harder and stronger due to the distortion caused by interstitial atoms.

Comparison Chart


Atoms of primary metal replaced by another metal
Smaller atoms fit into spaces of a larger metal lattice

Lattice Structure

Atoms replaced in the lattice
Atoms added in interstitial spaces of the lattice

Typical Atoms Involved

Similar sized atoms
Combination of larger and smaller atoms


Brass, Bronze
Steel, Cast iron

Key Property Changes

Based on substituting metal
Often harder and stronger due to lattice distortion

Substitutional Alloys and Interstitial Alloys Definitions

Substitutional Alloys

Alloys formed by replacing metal atoms with other metal atoms of similar size.
Brass is a substitutional alloy of copper and zinc.

Interstitial Alloys

Alloys formed by inserting small atoms into the gaps of a larger metal's atomic network.
The interstitial nature of carbon in steel gives it unique properties.

Substitutional Alloys

Mixtures of metals where one metal is substituted for another in the crystal lattice.
In bronze, tin atoms substitute some copper atoms.

Interstitial Alloys

Compounds where smaller elements fit within the interstices of a metal lattice.
Steel derives its strength from carbon atoms in iron's interstitial spaces.

Substitutional Alloys

Compounds where certain atoms in the base metal's lattice are replaced by atoms of another metal.
The formation of brass involves the substitution of zinc in a copper lattice.

Interstitial Alloys

Metal mixtures with small atoms residing in the gaps of the primary metal's atomic structure.
Carbon's presence in the interstitial spaces of iron makes cast iron.

Substitutional Alloys

Metallic solutions where primary metal atoms are replaced in their lattice.
Sterling silver substitutes some copper for silver atoms.

Interstitial Alloys

Alloys where smaller atoms occupy the spaces between larger metal atoms.
Carbon fills the spaces in the iron lattice to form steel.

Substitutional Alloys

Alloys characterized by the replacement of host metal atoms.
Nickel silver has nickel substituting for some of the copper atoms.

Interstitial Alloys

Metallic solutions characterized by smaller atoms fitting into the spaces of a primary metal.
The hardness of certain steels is due to carbon's interstitial placement.


Which alloy has atoms of a similar size?

Substitutional alloys.

Which alloy type is brass?

Substitutional alloy.

Why are interstitial alloys often harder?

Due to lattice distortion by the interstitial atoms.

What's the main formation difference between the two?

Substitutional alloys replace metal atoms; interstitial alloys have atoms in spaces of the metal lattice.

Which alloy would you find carbon fitting in iron?

Interstitial alloy.

Are all substitutional alloys malleable?

They tend to be more malleable, but properties vary based on composition.

Does the solute atom replace or fit in gaps in substitutional alloys?

It replaces in substitutional alloys.

What's a common example of an alloy with tin and copper?

Bronze, a substitutional alloy.

Which alloy might involve nickel and copper?

Nickel silver, a substitutional alloy.

Do both alloy types play crucial roles in industries?

Yes, both are essential for their unique properties.

Which alloy type is bronze?

Substitutional alloy.

Why do interstitial alloys have unique properties?

Due to the presence of smaller atoms in the lattice spaces.

In which alloy type would zinc replace copper?

Substitutional alloy, as in brass.

Which alloy might be preferred for its strength?

Interstitial alloys, due to lattice distortion.

Are the atoms in interstitial alloys always metal atoms?

No, they can be non-metals like carbon.

Is steel a substitutional or interstitial alloy?

Interstitial alloy.

What causes the distortion in the metal lattice of interstitial alloys?

The presence of smaller atoms in the interstices.

Can interstitial alloys involve non-metals?

Yes, like carbon in steel.

How do substitutional alloys affect a metal's crystal lattice?

By replacing certain atoms with those of another metal.

Is the formation of substitutional alloys dependent on atom size?

Yes, substituting atoms are usually of similar size to the host metal atoms.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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