Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

2.2.1.1 - Crystal Structures

 

· Understanding crystal structures can help understanding of crystalline materials such as metals.

 

· Think of dropping balls into a box. it can fall randomly, but often it will fall into patterns. This is like atoms in a solid.

 

· If all of the balls fall into a single organized pattern then we can say there is a single crystal.

 

· Three of the basic structure types to consider are,

  1. bcc - body centered cubic
  2. fcc - face centered cubic
  3. hcp - hexagonal close packed

 

 

· In a common solid there will be many regions in the crystal, but there will also be boundaries where the crystal properties change. These are known as boundaries.

 

· A common effect that can occur is slippage along one of the planes of the crystal. An example is pictured below,

 

 

· Different crystal structures will result in different possible slip planes.

  1. bcc has 48 possible slip planes
  2. fcc has 12 possible
  3. hcp has 3 possible

 

· Other slip structures are also possible