1.Introduction. All engineers are involved with materials on daily basis. We manufacture and process materials, design and construct components or structures using materials, select materials, analyze failures of materials. As responsible engineers we are interested in improving the performance of the product we are designing or manufacturing. Civil and architectural engineers wish to construct strong, reliable, structures that are aesthetic and resistant to corrosion. Aerospace engineers demand lightweight materials that perform well both at high and low temperatures. Metallurgical, ceramic, and polymer engineers wish to produce and shape materials that are more economical and possess improved properties.
2.Types of materials. Materials are classified into several groups: metals, ceramics, polymers, semiconductors, composite materials. Materials in each of these groups often possess different structures and properties. Metals-are alloys which include steel, aluminium, magnesium, zinc, cast iron, titanium, cooper, nickel, and others. Metals are good electrical and thermal conductors, are high strength, stiffness, shock resistance. Combinations of pure metals are called alloys they are designed to improve properties or permit better combination of properties. Ceramics-brick, glass, refractory, abrasives, have low electrical and thermal conductivities are often used as isolators. Ceramics are strong and hard but very brittle. Are used in load bearing applications (impellers in turbine). Polymers include rubber, plastics and others adhesives. Produced by creating large molecular structures from organic molecules in a process known as polymerization. Have low electrical and thermal conductivities, low strength, not suitable for use at high temperatures. Thermoplastic polymers (long molecular chains aren’t rigidly connected) have good ductility and formability. Thermosetting polymers are stronger but more brittle, because molecular chains are tightly linked. Semiconductors silicon, germanium and a number of compounds such as GaAs are very brittle, they used at computer, electronic, communication applications. The electrical conductivity of these materials can be controlled. Used in transistors, diodes, processors,...

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