Ductile

Ductile refers to the ability of a material to undergo substantial plastic deformation before fracture. In engineering contexts, ductility is most commonly discussed for metals, though some polymers also display ductile behavior. Materials with high ductility can be stretched or formed significantly without breaking, which is advantageous for forming processes such as drawing, rolling, and bending.

Ductility is usually quantified in tensile testing as percent elongation and percent reduction in area at fracture. Percent elongation measures how long the specimen becomes compared with original length. Reduction in area measures the decrease in cross-section at the fracture. A ductile material typically shows pronounced necking before failure and a cup-and-cone fracture surface.

Factors influencing ductility include temperature, strain rate, composition, and microstructure. Temperature has a strong effect: most metals become more ductile with increasing temperature and more brittle at low temperatures (the ductile-to-brittle transition). Strain rate can also alter ductility, as can alloy composition and grain size. Purity and microstructure often determine how much a material can plastically deform before breaking.

Applications and implications: Ductility is desirable for forming and shaping components, as well as for energy absorption and impact resistance in applications such as automotive safety. Ductile failure generally provides warning before fracture and absorbs more energy than brittle failure.

Examples: Copper, aluminum, and mild steel are commonly cited as ductile metals. Titanium and nickel-based alloys can also exhibit high ductility. In contrast, cast iron and many ceramics tend to be brittle.