Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture.
Examples of highly ductile metals are silver, gold, copper, and aluminium.
Ductility is the most important parameter to consider in metal forming operations such as rolling, extrusion, and drawing.
The ductility of steel varies depending on the alloying constituents. Increasing levels of carbon decreases ductility, i.e., the steel becomes more brittle.
Ductility can be quantified by the fracture strain, which is the engineering strain at which a test specimen fractures during a uniaxial tensile test.
Another commonly used measure is the reduction of area at fracture as shown in the adjacent sketch.