ABSTRACT
The study of structure of metals is the first essential step towards the understanding of their behavior in service and during processing. Metals are crystalline solids, i.e., they exhibit a crystal structure. Atoms in a crystal structure occupy positions in an arrangement, which is characterized by periodicity. The atomic arrangement is systematically repeated in three-dimensional space. The discovery of X-ray diffraction by Laue and the observation, by Bragg, of X-ray scattering from evenly spaced planes within the crystal, set the foundations for the development of Physical Metallurgy. The scientific field concerned with the study of crystal structure is termed Crystallography. For the study of the structure of metals, it is important to describe crystallographic directions and crystal planes. The crystal structure can then be described by the lattice of positive metal ions. To continue the discussion of crystal structure, it is convenient to use the hard-sphere model, i.e., to describe the metal ions as hard and equally-sized billiard balls.
