Alloys
An An alloy is a mixture of two or more elements, at least one of which is a metal. is a Two or more substances that are not joined together. The substances can be elements, compounds, or both. of two or more A substance made of one type of atom only., where at least one element is a Shiny element that is a good conductor of electricity and heat, and which forms basic oxides.. Many alloys are mixtures of two or more metals.
Alloy strength
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 | Relative tensile strength |
| Copper | 3 |
| Zinc | 2 |
| Brass | 5 |
| Metal | Copper |
|---|---|
| Relative tensile strength | 3 |
| Metal | Zinc |
|---|---|
| Relative tensile strength | 2 |
| Metal | Brass |
|---|---|
| Relative tensile strength | 5 |
Explaining alloy strength
Solid metals have a regular A regular grid-like arrangement of atoms in a material. structure. When a A push or a pull. The unit of force is the newton (N). is applied to a metal, layers of The smallest part of an element that can exist. 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 have 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 steels
Iron is alloyed with other metals to produce a range of Alloy produced by mixing iron with one or more other metals.. Different steels have different The characteristics of something. In chemistry, chemical properties include the reactions a substance can take part in. Physical properties include colour and boiling point., depending on their composition. The table shows three common examples.
| Alloy | Other elements | Properties |
| Mild steel | Carbon | Malleable, ductile |
| Tool steel | Tungsten | Hard, resistant to high temperatures |
| Stainless steel | Chromium | Hard, resistant to rusting |
| Alloy | Mild steel |
|---|---|
| Other elements | Carbon |
| Properties | Malleable, ductile |
| Alloy | Tool steel |
|---|---|
| Other elements | Tungsten |
| Properties | Hard, resistant to high temperatures |
| Alloy | Stainless steel |
|---|---|
| Other elements | Chromium |
| Properties | 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 Coating iron or steel with a layer of zinc to prevent rusting. and painting. Tool steel is useful for making drill bits. These do not easily become damaged by the heating caused by A force that opposes or prevents movement and converts kinetic energy into heat. during drilling.
Question
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.