IB CHEMISTRY

2.4.3 Alloys

Enhancing strength by disrupting the lattice structure.

What is an Alloy?

An alloy is a homogeneous mixture of a metal with other metals or non-metals. They are created to enhance properties like strength, hardness, or corrosion resistance.

The "Disrupted Lattice" Mechanism

Pure Metal

Atoms are identical in size and arranged in regular layers. These layers can easily slide over each other when a force is applied (making it malleable/ductile).

Alloy

The introduction of an element with a different atomic radius disrupts the regular arrangement. The layers become "keyed" or locked together, making it much harder for them to slide.

Result: Increased Hardness, Reduced Malleability.

Common Examples

Steel

Iron + Carbon

Small Carbon atoms fit in interstitial spaces, locking the Fe lattice. High tensile strength.

Brass

Copper + Zinc

Substitutional alloy. Corrosion resistant. Used in instruments.

Bronze

Copper + Tin

Harder than pure copper (used in historic weaponry/tools).