Alloys

• Alloy


  A mixture of two or more elements, where at least one element is a metal
• Alloys


  • Have different properties from the pure metal
  • Can be more useful than the pure metal
• Pure metals


  Have a fixed, precise melting point
• Alloys


  Have a lower melting point and melt over a range of temperatures
• Melting points can be used to identify pure metals
• Alloys


  • Are usually harder than pure metals
  • The different sized atoms disrupt the regular structure making it harder for the layers of atoms to slip over each other
• Many pure metals are too soft for many uses
• Adding another element to a pure metal

  Forms an alloy that is often harder and has more uses than the pure metal
• Pure iron


  • Very soft
• Adding tungsten to iron

  • Makes tool steel, which is harder than pure iron
• Pure metal structure


  Giant metallic structure with atoms arranged in layers
• Force applied to pure metal

  Causes the layers to slide over each other
• The greater the force needed, the harder and stronger the metal
• The force needed to make the layers slide over each other is small in pure metals, explaining why they are soft
• Alloy structure


  • Atoms of different sizes distort the layers of atoms in the pure metal
  • A greater force is required for the layers to slide over each other
• The metal lattice structure is distorted in alloys