These caracteristics, along with the great availability of iron alloys, lend them to be used in many applications including the automotive, building and bridge construction, and aerospace industries. Most iron alloys are contain a certain amount of carbon, and are classified as steels. Pure iron is much weeker then its alloyed counterpart, and can be found in with two crystal structures. Ferrite is has a BCC crystal structure, and austenite has an FCC crystal structure. In this exercise we are examining two types of defects common to this material, vacancies and planar defects.
Vacancies are defects arising when a lattice site is mising an atom.
They are caused by atomic vibrations present during the solidification of a material. The shell of atoms surrounding a vacancy will move in toward the vacancy, and the next shell of atoms will move out slightly. This relocation of atoms is termed relaxation. The planar defect examined here is a free surface. At the free surface of a material the atoms are not permitted to attach to the maximum number of atoms, resulting in an increased energy then found within the material.