Ductility

Ductility is a material’s ability to undergo substantial permanent deformation before fracturing. It is commonly measured by elongation or reduction in cross-sectional area during a tensile test.

Dislocation: A line defect in a crystal lattice around which atomic planes are misaligned. Dislocation motion enables crystalline metals to deform plastically before fracture.
Plastic deformation: Permanent change in a material’s shape after applied stress exceeds its elastic limit. Ductility describes how much plastic deformation occurs before fracture.
Metal forming: Manufacturing processes that shape metal by plastic deformation. Forming operations require materials to sustain large strains without cracking.
Toughness: A material’s ability to absorb energy before fracturing. Toughness combines strength and deformation, whereas ductility concerns deformation before fracture.
Slip system: A combination of crystallographic plane and direction along which dislocations move readily. Available slip systems determine how readily a crystal can accommodate plastic strain.
Stress–strain curve: A graph showing a material’s stress response as strain increases. Its post-yield region reveals the deformation used to assess ductility.
Wire drawing: A process that reduces a rod’s diameter by pulling it through a die. Wire drawing depends on sufficient ductility for repeated tensile deformation.
Malleability: A material’s ability to deform under compressive stress, such as hammering into sheets. Malleability emphasizes compression, while ductility is commonly assessed in tension.
Work hardening: An increase in a material’s strength and hardness caused by plastic deformation. As deformation accumulates, work hardening can delay localized thinning and fracture.
Tensile testing: A test that stretches a specimen under controlled load to measure mechanical properties. Standard ductility measures come from a specimen pulled to fracture.

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