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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.