Examples of alloys and what they are made of
An alloy is a mixture of a metal with one or more other elements, usually other metals but sometimes nonmetals such as carbon. Alloys are usually made by melting the ingredients together, and they tend to be harder, stronger or more resistant to corrosion than the pure metals they contain. Here are common alloys and what they are made of.
- Bronze — copper and tin (often about 12% tin); used for statues, bells and cymbals.
- Brass — copper and zinc; used for musical instruments, door handles and plumbing fittings.
- Steel — iron with a small amount of carbon (up to about 2%); used in buildings, bridges and cars.
- Stainless steel — iron with at least 10.5% chromium, often plus nickel; resists rust and is used for cutlery and sinks.
- Cast iron — iron with about 2–4% carbon plus some silicon; hard but brittle, used for pans and engine blocks.
- Sterling silver — 92.5% silver and 7.5% other metals, usually copper; used for jewelry and silverware.
- Solder — tin with small amounts of silver and copper (older solder was tin and lead); melts easily to join electronic parts.
- Pewter — mostly tin with small amounts of copper and antimony; used for tableware and ornaments.
- White gold — gold mixed with palladium, nickel or silver, often plated with rhodium; used in jewelry.
- Duralumin — aluminum with about 4% copper plus magnesium and manganese; light and strong, used in aircraft.
- Nichrome — about 80% nickel and 20% chromium; used for the heating wires in toasters and hair dryers.
- Dental amalgam — mercury mixed with silver, tin and copper; used for silver-colored tooth fillings.
Why alloys are stronger than pure metals
In a pure metal, the atoms are arranged in neat layers that can slide over each other, which makes the metal fairly soft and easy to bend. Adding atoms of a different size, such as tin in copper or carbon in iron, disrupts these layers so they cannot slide as easily. That is why bronze is harder than copper and steel is stronger than pure iron.
Are alloys mixtures or compounds?
Most alloys are mixtures, because their composition can vary: brass, for example, can contain anywhere from about 5% to over 40% zinc. Many are homogeneous mixtures called solid solutions, although some alloys also contain tiny crystals of compounds, such as iron carbide in steel.