Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of elongation. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
Elongation is the standard measure of ductility. High elongation means the material deforms before it breaks; low elongation means it fails suddenly.
It is a strong indicator of machinability and of toughness, and it falls as strength rises — the two trade off directly. A hardened tool steel at 1,930 MPa tensile has 2% elongation; low-carbon steel at 440 MPa has 25%.
Common misuse
Reading elongation as a measure of toughness. A high-strength material with low elongation can still be tough, though usually at low strength levels.