Structural materials: metals, ceramics, polymers and composites

Structural materials are improving at a rate not hitherto seen, and perceptions of the virtues of one material in relation to another may significantly affect the economies of nations. Improved purity and chemical control during refining have enhanced the properties of some steels, aluminium and magnesium. New processes have enabled parts to be cast of a complexity, thin section and cost that were previously impossible. High–strength low–alloy steels are increasingly used in automotive applications. Some aluminium alloys are approaching the strength of titanium alloys at high temperature. New surface coatings are being used to minimize corrosion. Ceramics are finding new applications as abrasives, as heat shields, as containers for molten metals and as high–strength structural materials. Zirconia alloyed with other materials can be made to be crack resistant, and there are signs that increasing use will be made of ceramics under tensile stress in high– temperature environments. Polymers are increasingly being used as structural materials (e.g. in airframe construction); often the material is a blend of one material in a matrix of another. High–performance composites including metal–matrix composites and ceramic– ceramic composites are showing considerable promise for the future.