Alloying: definition in chemistry
Alloying: The process of combining a metal with one or more other elements, usually by melting them together, to make an alloy with improved properties.
In a substitutional alloy, atoms of similar size replace some of the metal atoms, as zinc does in brass. In an interstitial alloy, much smaller atoms such as carbon or nitrogen fit into the gaps between the metal atoms, as in steel. Either way, the different atoms distort the regular layers of metal atoms and make it harder for them to slide, so alloying usually makes a metal harder and stronger, and it can also improve corrosion resistance or lower the melting point.
Examples
- Adding a little carbon to iron makes steel
- Adding at least 10.5% chromium to steel makes it stainless
- Mixing gold with 25% other metals, often copper and silver, gives harder 18-karat gold
- Sterling silver — 92.5% silver alloyed mostly with copper
On the periodic table
Metals that mix in any proportion tend to sit close together on the table, with similar atom sizes and the same crystal structure, such as copper and nickel.