The materials of mechanical parts are metal materials, non-metallic materials and composite materials.

Metal materials are divided into ferrous metal materials and non-ferrous metal materials. Ferrous metal materials, including all kinds of steel, cast steel and cast iron, have good mechanical properties (such as strength, plasticity, toughness, etc.). They are relatively cheap and easy to obtain, and can meet the requirements of a variety of properties and uses. Among all kinds of ferrous metals, alloy steel is often used to manufacture important parts because of its excellent properties. Non-ferrous metal materials, including copper alloy, aluminum alloy, bearing alloy and so on, have the advantages of low density, good thermal conductivity and electrical conductivity, and can also be used for friction reduction, wear resistance and corrosion resistance.

Non-metallic materials refer to plastics, rubber, synthetic fibers and other polymer materials and ceramics. Polymer materials have many advantages, such as rich raw materials, low density, good elasticity in the appropriate temperature range, good corrosion resistance and so on. Its main disadvantage is easy to aging, many of which have poor flame retardancy, generally speaking, heat resistance is not good. The main characteristics of ceramic materials are very high hardness, wear resistance, corrosion resistance, high melting point, high stiffness and less density than iron and steel. At present, ceramic materials have been used in seals, rolling bearings and cutting tools. Its main disadvantages are brittleness, low fracture toughness, high price and poor processing technology.

Composite material is a new type of material which uses two or more kinds of materials with obviously different physical and mechanical properties to obtain the required properties through the treatment of composite process. For example, non-metallic materials such as glass, graphite (carbon), boron and plastics can be composite into various fiber reinforced composites. The plastic composite steel plate with high strength and corrosion resistance can be obtained by attaching plastics to the surface of ordinary carbon steel plate. The main advantage is that it has high strength and elastic modulus, but the quality is especially small, it also has the disadvantages of poor heat resistance, poor thermal conductivity and poor electrical conductivity. In addition, the price of composite materials is more expensive. So at present composite materials are mainly used in aviation.