PSI - Issue 81

Jesús Toribio et al. / Procedia Structural Integrity 81 (2026) 135–139

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STEEL 0

STEEL 1

STEEL 2

STEEL 3

STEEL 4

STEEL 5

STEEL 6

Fig. 3. Fracture surfaces in all the steels used in the experimental programme.

To analyze the microscopic modes of fracture, a fractographic analysis by scanning electron microscopy (SEM) was performed on the fracture surfaces of all the broken samples, and results are given in Fig. 4 that shows the micro-fracture surfaces. In the first stages of cold drawing (steel 0 which is not cold drawn at all and steel 1) the microscopic fracture mode is cleavage-like. In steels 2 and 3 the fracture process initially develops by micro-void coalescence (MVC) and continues by cleavage. Thus a first MVC region is found before the cleavage-like (brittle) area, the depth of this MVC region being an increasing function of the degree of cold drawing. The most heavily drawn steels (4 to 6) exhibit anisotropic fracture behaviour with a 90º-step, as described above, although certain mode I crack growth appears before the step over a distance in which the MVC micro-fracture mode is predominant although the meso-roughness is higher, as explained above.