Alloy - Definition, Examples, Types of Alloys with FAQs,

Alloys are materials made by combining two or more metals—or sometimes a metal and a non‑metal—while melted. The result usually has different traits than the individual ingredients. Compared to pure metals, alloys often become stronger and harder . For example, red gold is made by mixing copper with gold, giving it a warm reddish color. White gold is formed by blending silver—or metals like nickel or palladium—with gold, creating a silvery-white alloy. These mixed metals are very useful in jewelry and everyday tools because they combine improved strength with pleasant colors and finishes.

Alloys are metals (or metal-based mixtures) held together by metallic bonds. For everyday use, we measure their composition by weight percent; in scientific studies, it’s often by atomic fraction. Alloys fall into two structural types:

1. Substitutional alloys – atoms of similar size swap places within the metal’s crystal lattice (like copper with zinc in brass).

2. Interstitial alloys – very small atoms fill the tiny spaces between larger metal atoms, as carbon does in iron to form steel.

They’re also classified by phase count: homogeneous alloys have a single uniform phase, while heterogeneous alloys consist of two or more distinct phases within the material.

Examples of alloys

Babbitt metal, also known as bearing metal, is a soft alloy first created in 1839 by American inventor Isaac Babbitt.

It typically contains around 90 % tin, 7 % antimony, and 3 % copper. This combination yields a metal matrix with tiny hard crystals in a softer base, letting it support heavy loads while embedding debris and preventing shafts from seizing if lubrication fails.

Its smooth, low‑friction surface makes it ideal for lining simple bearings, especially when matched with steel, reducing wear and improving performance

The chemistry of Alloys

A strong electron microscope can reveal the atoms inside a metal. Then the atoms are grouped in a regular arrangement called a crystalline lattice.

Types of Alloys

Substitution Alloy

A substitutional alloy is made when atoms of one metal swap places with atoms of another in the metal’s crystal structure. This only works when the atoms are about the same size and chemically similar—often because they're close together on the periodic table.

A common example is brass, which is mostly copper with about 10–35% of the copper atoms replaced by zinc. Copper and zinc are a good match because their atoms are similar in size and structure, so zinc fits neatly into the copper lattice without disrupting it.

Substitutional alloys like brass keep the original metal’s crystal pattern but gain improved traits—such as more strength, better resistance to wear, and sometimes enhanced electrical or thermal characteristics.

Interstitial Alloy

Alloys with interstitial atoms

Certain alloys form when the added element has much smaller atoms than the main metal. These tiny atoms slip into the empty spaces, or "interstices," within the metal’s crystal structure, creating an interstitial alloy. A common example is steel, where a few carbon atoms fit between the iron atoms in its crystal lattice.

Bell Metal

Bell metal is a special kind of bronze used mainly to cast bells and cymbals. It contains about 78–80% copper and 20–22% tin, giving it a stiff and resonant quality that produces clear, long-lasting sounds. Aside from bells, it's also used for decorative items, cookware, and even mechanical parts like bearings and valve components . Its higher tin content strengthens the alloy, makes it more elastic, and helps it resist wear and corrosion. Over time, a natural greenish patina forms on its surface, which protects it from further oxidation.

Bronze

Bronze is primarily a mix of copper and tin—usually about 88% copper and 12% tin—sometimes with tiny amounts of metals like manganese, aluminum, nickel, silicon, phosphorus, or arsenic to improve its properties.

It's much harder and stronger than pure copper and also more resistant to corrosion. These qualities make it easier to machine and shape. As a result, bronze is commonly used to make items like medals, coins, trophies, heavy gears, tools, and electrical parts . Its durability and toughness suit various industrial and decorative applications.

Nichrome

Nichrome is an alloy made mainly of nickel and chromium, usually around 80% nickel and 20% chromium, with small amounts of iron or other metals. It’s best known as resistance wire, where it converts electricity into heat, making it ideal for devices like toasters, space heaters, hair dryers, and industrial furnaces.

Nichrome is also used in dental fillings, igniters for fireworks and model rockets, and in foam-cutting tools. Thanks to its high melting point (around 1,400 °C), resistance to oxidation, and stable electrical resistance, it withstands repeated heating and cooling cycles without degrading.

Steel

Steel is mainly an alloy of iron and carbon, but many types also include other metals like chromium, manganese, nickel, sulfur, phosphorus, copper, or molybdenum. Iron makes up most of its weight—at least around 75%. The amount of carbon and added elements varies by steel type.

For instance, stainless steel typically contains about 85–88% iron, at least 10.5% chromium, and less than 1.2% carbon. These added elements give steel extra strength, resistance to rust, and toughness, making it more durable and versatile than pure iron.

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