Definition
A metallic substance made by combining two or more elements, at least one of which is a metal, to produce a material with properties different from those of its components. Alloys are used throughout aircraft construction to achieve combinations of strength, weight, corrosion resistance, and workability that pure metals cannot provide.
Plain English
A metal that has been mixed with one or more other elements to give it better qualities than the original metal alone — for example, stronger, lighter, or more resistant to rust.
Context Anchor
Seen in aircraft structure, engine, propeller, landing gear, and repair-material discussions.
Derivation
From the Old French aloi, meaning 'a mixture,' which itself comes from the Latin alligare, 'to bind together.' The idea of binding metals together to form a better material is exactly what the aviation meaning preserves.
Why Pilots Care
Almost every structural part of an aircraft — skin, spars, fasteners, engine components — is made of an alloy chosen for a specific reason. Knowing that 'aluminum alloy' is not pure aluminum helps when reading maintenance documents, weight-and-balance discussions, or damage assessments.
Analogy
An alloy is like a recipe for metal. The ingredients are chosen so the final material has the qualities needed for the job.
Intuition Check
Do not think of an alloy as a coating on metal. An alloy is the metal itself, made from a combination of elements.
Example Sentence 1
The wing skin is made from an aluminum alloy that is much stronger than pure aluminum but only slightly heavier.
Example Sentence 2
During preflight, the mechanic checked the landing gear for cracks in the alloy components.