Ductility: The capacity of a material to undergo large inelastic deformation prior to fracture. It is highly dependent on the operating temperature of the material. At very low temperatures materials tend to lose their ductility and become brittle.
Elongation:
A measure of material ductility, it is defined as the percent change in the specimen length at the point of fracture. Usually denoted by e, it can be obtained by multiplying the fracture strain by 100.
e= (L'-Lo/Lo)100
Where L' = specimen gage length after fracture, Lo= original gage length. Note that since percent elongation is determined as a function of gage length, it is important to specify the gage length when mentioning percent elongation.