Converting pure metals into alloys often increases the strength of the product. For example, brass is an alloy of copper and zinc. It is stronger than copper or zinc alone.
|Metal||Tensile strength (MPa)|
Solid metals have a regular lattice structure. When a force is applied to a metal, layers of atoms can move past each other. The more difficult it is for the layers to move, the more force is needed and the stronger the metal.
Copper and zinc atoms are different sizes. This distorts the regular lattice structure in brass, so layers of atoms cannot slide over each other so easily. This makes brass stronger than copper or zinc alone.
|Alloy steel||Additional elements||Properties|
|Mild steel||Carbon||Malleable, ductile|
|Tool steel||Tungsten||Hard, resistant to high temperatures|
|Stainless steel||Chromium||Hard, resistant to rusting|
Mild steel is useful for making car body parts because it is easily pressed into shape. Although mild steel rusts, it can be protected by galvanising and painting. Tool steel is useful for making drill bits. These do not easily become damaged by the heating caused by friction during drilling.
Explain why stainless steel is used to make washing machines and dishwashers.
Washing machines and dishwashers contain water. This would cause other steels to rust, but stainless steel does not rust.