ABSTRACT
This chapter outlines the crystalline structure of metals, and explains how metals deform both elastically and plastically. The plastic behaviour is not fundamental, and the shape of the plastic flow curve can vary depending upon the state of stress in the metal. Metals are crystalline, that is to say their atoms are arranged in patterns with the highest degree of symmetry. Dislocation movements are studied by crystallographers, and have found that dislocations move by a process called slip on close-packed planes of atoms. The crystals will not be perfect, but will contain imperfections or defects of various kinds: point, line and area defects. From the point of view of construction materials, easily the most important type of defect is the edge dislocation. Plastic deformation is permanent deformation, as distinct from elastic deformation, which is temporary. Creep occurs in materials under stress, when they suffer a small amount of plastic deformation.
