Homework 4
Problem 2
The material properties of many materials are determined by the atoms at the microstructure level. As most materials are the build up of several crystal structures, the material properties are determined based on the amount of exposed material from each crystal and the individual crystal structure. The most common crystal structures are body centric cubic (bcc), face centric cubic (fcc), and hexagonal close packed (hcp). The hcp and fcc structures are similarly arranged in that the next layer of atoms sits within the hollow of the below layer as shown below.
The hcp crystal structures follows an ABAB pattern, in that the structure starts to repeat itself after the second layer. The fcc crystal structure follows an ABCABC pack, repeating itself after three layers. The bcc structure does not follow a similar close packed structure as the the other two systems. These structure is centered around a single atom and is more loosely packed.
The microstructure plays a key role in the material properties as they each have different energy densities that will result in differences such as the energy required to dislocate atoms leading to different failure properties on the macro level for the materials.