An alloy is a metallic material consisting of at least two elements, produced by alloying in the liquid state, meaning the components are melted together. Alloying describes the deliberate combination of two or more elements in the melt so that the resulting material has properties that differ from those of the individual pure metals used to create it.
Why Metals Are Alloyed
Pure metals rarely meet the requirements of technical applications on their own. By alloying two or more elements together, foundries and material producers can improve properties such as strength, hardness, corrosion resistance, and castability compared with the pure base metal. Well-known alloy groups used in foundry practice include iron-carbon alloys such as steel and cast iron, aluminum alloys, and copper alloys such as bronze and brass. In practice, alloying elements are sometimes introduced into the melt in a controlled way, for example through a preliminary alloy, to ensure an even distribution throughout the material.
Examples of Common Alloys
| Alloy | Main Elements |
|---|---|
| Steel | Iron (Fe) + Carbon (C) |
| Cast Iron | Iron (Fe) + Carbon (C, higher content) |
| Bronze | Copper (Cu) + Tin (Sn) |
| Brass | Copper (Cu) + Zinc (Zn) |
| Aluminum Alloy (e.g. AlSi) | Aluminum (Al) + Silicon (Si) |
Frequently Asked Questions
What is the minimum number of elements in an alloy?
An alloy must consist of at least two elements, at least one of which is a metal. These elements are combined by melting them together in the liquid state.
Why are metals alloyed instead of used pure?
Metals are alloyed because pure metals often do not have the combination of properties required for a given application. Alloying is used to specifically improve strength, corrosion resistance, and castability, results that cannot be achieved with a single pure metal alone.
What is the difference between an alloy and a compound alloy?
The general term alloy covers any metallic material made of at least two elements. A compound alloy refers to a more specific alloy composition; see the linked entry for details on this particular term.
Designation of Alloys
In Europe, the naming of alloys is often governed by standards. DIN EN 10027, for example, defines the designation and numbering system used for steels, allowing a steel’s composition and properties to be identified from its standardized name or material number.