METALLIC STRUCTURES

Materials differ from one another because of the differences in their pro­perties. Iron differs from a plastic material due to its higher density, stren­gth and electrical conductivity. Similarly gold differs from iron because of its colour, density and corrosion resistance.

Differences in properties of various materials are due to the differences in the structures of materials. Different materials possess different struc­tures. The structure of a material exhibits its internal and surface details. These details can be examined and expressed in different orders of magni­fication varying from a few times to several thousands. In order of decre­asing magnification, the structure of a solid material can be expressed as follows:

(i) Atomic structure (ii) Crystal structure (iii) Microstructure (iv) Macrostructure

All solid materials consist of a large number of particles called molecules which are bonded together to form the bulk material. Each molecule is fur­ther composed of tiny particles called atoms. Individual properties of atoms and their arrangement in the molecule determine the properties of the material. Therefore, to understand the properties and structure of materials, it is necessary to start with the structure and characteristics of individual atoms.