Ductile fracture is preceded by substantial plastic deformation. When a material contains relatively hard inclusions which do not deform at the same rate as the matrix, voids are nucleated to accommodate the incompatability. The nucleation event may involve, for example, the fracture of the inclusion, or decohesion at the inclusion-matrix interface.
Overall fracture of af a macroscopic sample does not occur until voids nucleated from different inclusions have grown sufficiently to link up. This is illustrated in the diagram below, which shows that a large number density of inclusions is associated with a smaller overall elongation. This is because the voids have to grow less before linking occurs.
When a ductile-fracture surface is examined, the appearance is of 'dimples', with each dimple corresponding to a void. It is frequently possible to observe the inclusion responsible for nucleating the void within the depth of the dimple.
The following fractographs showing ductile fracture of a tensile specimen are from a weld deposit of approximate chemical composition Fe-0.057C-0.36Si-1.3Mn-0.8Ni-0.08O wt%, deposited using the flux-cored arc process.
 2-15x2 |
 2-2000x3 |
 2-2000x4 |
 2-2000x5 |
 2-500x9 |
 2-3000x9 |
 2-2000x9 |
 2-2000x7 |
 2-500x4 |
 2-2000x0 |
 2-2000x2 |
 2-1500x9 |
 2-3000x8 |
 2-3000x7 |
The following fractographs showing ductile fracture of a tensile specimen are from a weld deposit of approximate chemical composition Fe-0.059C-0.4Si-1.42Mn-0.98Ni-0.07O wt%, deposited using the flux-cored arc process.
 1-250x |
 1-2000x4 |
 1-500x6 |
 1-2000x7 |
 1-1500x8 |
 1-2000x9 |
 2-15x |
 2-2500x3 |
 2-4000x4 |
 2-500x6 |
 2-2000x6 |
 2-500x7 |
 2-250x8 |
 2-1000x9 |
The following fractorgraphs are from broken Charpy impact samples. The one designated 'f' broke while absorbing an energy of 127 J, whereas that designated 'n' was associated with a fracture energy of 28 J.
The samples show a mixed mode of fracture, with some ductile dimples together with cleavage facets and quasi-cleavage.
 F-1 |
 f-10 |
 f-11 |
 f-12 |
 f-13 |
 f-14 |
 f-15 |
 f-16 |
 f-17 |
 f-18 |
 f-19 |
 f-2 |
 f-20 |
 f-21 |
 f-22 |
 f-3 |
 f-4 |
 f-5 |
 f-6 |
 f-7 |
 f-8 |
 f-9 |
 N1 |
 n10 |
 n11 |
 n2 |
 n3 |
 n4 |
 n5 |
 n6 |
 n7 |
 n8 |
 n9 |
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