We have now arrived at the core of the book, the purpose of which is to introduce the designer to the main areas of materials technology. We first consider aspects of the design process which should point up the differences between the performance of classes of materials in practice; and then in later chapters we make a brief review of the main materials properties available. This done, we then consider the ‘envelope of properties’ of individual materials, which must be defined in order to demonstrate suitability for exploitation in particular designs.

The design process must take into consideration the many aspects of materials behaviour, so that there is never too great a mismatch between the materials actually selected and the realistic performance demanded of the final product. Table 3.1 (Judd 1983) identifies mechanical, thermal, electrical and other performance aspects of materials which have to be considered as a whole or in part during the initial design and materials selection processes. Many of these properties and responses to outside influences are functions of all materials used for engineering designs, although some specifically refer only to metals or only to non-metals.

The properties of materials selected control to a considerable degree, the fabrication methods that can be employed on the ultimate product. Aspects of production, apart from consideration of manufacturing volumes, include the weight of material needed, shapes and sizes of preformed components such as sheet metal and rod, part-size tolerances, and the surface finishes to be adopted.