2. Structural defects in metals and alloys

The first paragraph was devoted to the description of the perfect crystal. In reality, a crystal always contains defects, either because the presence of such defects is imposed by the laws of thermodynamic equilibrium, or because these defects have been introduced by quenching, work-hardening, irradiation, ... These defects are important to metallurgists, as they play a major role in determining most of the properties, particularly the mechanical properties, of metals and alloys. They can be classified as point, linear, surface or volume defects. We will examine these various types of defect in turn.