C1.3.2 Alloys

• Alloys are mixtures of metals to change the properties for a specific purpose
• The different sized atoms distort layers in the lattice
  • More difficult for the layers to slide over each other
  • Hence alloys are harder than pure metals
    • e.g pure copper, gold, iron and aluminium are too soft
• Most metals in everyday use are alloys

Cast iron

• Iron oxide reduced to iron in a blast furnace
• Iron from the blast furnace is about 96% pure
• The impurities make it brittle and limits its uses
• Used as cast iron

Steels

• Steel is an alloy- mixtures of iron and carbon, and often other metals
• Low carbon steel - easily shaped
• High carbon steel - hard
• Stainless steel - resistant to corrosion