20 Ductility

Ductility is a mechanical property commonly described as a material’s amenability to drawing (e.g. into wire). All metals are ductile. Metals can be melted and drawn into thin wires. Because of this property, metals are known as ductile. While being drawn into wires, metals are stretched. Because of the strong metallic bonds, the metal atoms do not separate easily.

Silver, copper, and aluminum are very ductile, and very thin wires can be made out them. But not all malleable metals are ductile. Lead is malleable, but it is not strong enough to be stretched very far without breaking. It is not very ductile.

In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure. Ductility is an important consideration in engineering and manufacturing. It defines a material’s suitability for certain manufacturing operations (such as cold working) and its capacity to absorb mechanical overload.

Some metals that are generally described as ductile include gold and copper, while platinum is the most ductile of all metals in pure form. However, not all metals experience ductile failure as some can be characterized with brittle failure like cast iron. Polymers generally can be viewed as ductile materials as they typically allow for plastic deformation.

Ductility is especially important in metalworking, as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering, rolling, drawing or extruding.

The ductility of steel varies depending on the alloying constituents. Increasing the levels of carbon decreases ductility. Many plastics and amorphous solids, such as Play-Doh, are also malleable. The most ductile metal is platinum, and the most malleable metal is gold. When highly stretched, such metals distort via formation, reorientation and migration of dislocations and crystal twins without noticeable hardening.

Ductility is especially important in metalworking, as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering, rolling, drawing or extruding. Malleable materials can be formed cold using stamping or pressing, whereas brittle materials may be cast or thermoformed.

Derived from Ductility – Wikipedia accessed and available 5 March 2024 and The Virtual Machine Shop (http://jjjtrain.com/3engineering/5eng_metallurgy/eng_metallurgy_03.html) accessed and available via the WayBack Machine internet Archive 16 January 2024.