Definition - What does Ductility mean?

Ductility is the ability of a material to deform under tensile stress. It is a measure of how much strain a material can take before rupturing. It can also refer to the property of malleability, which is the ability of a metal to be pounded into thin, flat sheets.

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 and drawing.

Corrosionpedia explains Ductility

Ductility is a solid material's likelihood to rupture under tensile stress, which is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized by the material's ability to form a thin sheet by hammering or rolling. The word ductility is sometimes used to encompass both types of plasticity.

Ductile materials show large deformation before fracture. The lack of ductility is often termed brittleness. Usually, if two materials have the same strength and hardness, the one that has the higher ductility is more desirable. The ductility of many metals can change if conditions are altered. An increase in temperature increases ductility. Similarly, a decrease in temperature causes a decrease in ductility and a change from ductile to brittle behavior.

High degrees of ductility occur due to metallic bonds, which are found predominantly in metals, and leads to the common perception that metals are ductile in general. The ductility of steel varies depending on the alloying constituents. Increasing 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.

Cold-working also tends to make metals less ductile. Minor additions of impurities to metals, either deliberate or unintentional, can have a marked effect on the change from ductile to brittle behavior. The heating of a cold-worked metal to or above the temperature at which metal atoms return to their equilibrium positions increases the ductility of that metal.

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