Alloy Definition, Examples, and Uses

What Is an Alloy in Chemistry?

An alloy is made by melting together a metal and another element.
An alloy is made by melting together a metal and another element. Hans-Peter Merten/ The Image Bank/ Getty Images

Alloy Definition

An alloy is a substance made by melting two or more elements together, at least one of them a metal. An alloy crystallizes upon cooling into a solid solution, mixture, or intermetallic compound. The components of alloys cannot be separated using a physical means. An alloy is homogeneous and retains the properties of a metal, even though it may include metalloids or nonmetals in its composition.

Alternate Spellings: alloys, alloyed

Alloy Examples

Examples of alloys include stainless steel, brass, bronze, white gold, 14k gold, and sterling silver. Although exceptions exist, most alloys are named for their primary or base metal, with an indication of other elements in order of mass percent.

Uses of Alloys

Over 90% of metal use is in the form of alloys. Alloys are used because their chemical and physical properties are superior for an application than that of the pure element components. Typical improvements include corrosion resistance, improved wear, special electrical or magnetic properties, and heat resistance. Other times, alloys are used because they retain the key properties of component metals, yet are less expensive.

For example:

Steel - Steel is the name given to an alloy of iron with carbon, usually with other elements, such as nickel and cobalt. The other elements add a desired quality to the steel, such as hardness or tensile strength.

Stainless Steel - Stainless steel is another iron alloy, which typically contains chromium, nickel, and other elements to resist rust or corrosion.

18k Gold - 18 karat gold is 75% gold. The other elements typically include copper, nickel, and/or zinc. This alloy retains the color and luster of pure gold, yet is harder and stronger, making it better suited for jewelry.

Pewter - Pewter is an alloy of tin, with other elements such as copper, lead, or antimony. The alloy is malleable, yet stronger than pure tin, plus it resists the phase change of tin that can make it crumble at low temperatures.

Brass - Brass is a mixture of copper with zinc and sometimes other elements. Brass is hard and durable, making it suitable for plumbing fixtures and machined parts.

Sterling Silver - Sterling silver is 92.5% silver with copper and other metals. Alloying silver makes it harder and more durable, although the copper tends to lead to a greenish-black oxidation (tarnish).

Electrum - Some alloys, like electrum, occur naturally. This alloy of silver and gold was highly prized by ancient man.

Meteoritic Iron - While meteorites may consist of any number of materials, some are natural alloys of iron and nickel, with extraterrestrial origins. These alloys were used by ancient cultures to make weapons and tools.

Amalgams - Amalgams are mercury alloys. The mercury makes the alloy much like a paste. Amalgams may be used ​in dental fillings, with the mercury intact, although another use is to spread the amalgam and then heat it to vaporize the mercury, leaving a coating of another metal.

Format
mla apa chicago
Your Citation
Helmenstine, Anne Marie, Ph.D. "Alloy Definition, Examples, and Uses." ThoughtCo, Feb. 21, 2017, thoughtco.com/alloy-definition-examples-and-uses-606371. Helmenstine, Anne Marie, Ph.D. (2017, February 21). Alloy Definition, Examples, and Uses. Retrieved from https://www.thoughtco.com/alloy-definition-examples-and-uses-606371 Helmenstine, Anne Marie, Ph.D. "Alloy Definition, Examples, and Uses." ThoughtCo. https://www.thoughtco.com/alloy-definition-examples-and-uses-606371 (accessed December 14, 2017).