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F. Iacoviello et alii, Frattura ed Integrità Strutturale, 34 (2015) 406-414; DOI: 10.3221/IGF-ESIS.34.45 411 disaggregation. This micromechanisms is more evident considering 3D images obtained according to the “3D reconstruction” procedure described in the Investigated material and experimental procedure paragraph. Figure 14 : Ferritized DCI. SEM fracture surface analysis (  K = 12 MPa  m). Figure 15 : Ferritized DCI. SEM fracture surface analysis (  K = 16 MPa  m). Figure 16 : Ferritized DCI. SEM fracture surface analysis: 3D reconstruction (  K = 14 MPa  m). Figure 17 : Ferritized DCI. SEM fracture surface analysis: 3D reconstruction (  K = 15 MPa  m). 3D reconstructed images confirm the micromechanisms formerly described: crack propagates in the matrix and in the shield obtained during the long annealing treatment, but avoids to propagate inside the graphite nodule: the result on the fracture surface can be a nodule embedded in the ferritic matrix or a void, depending on the crack propagation plane with respect to the nodule position. Overloads Overloads applied on DCIs have a different effect depending on the matrix microstructure. All the ferritic-pearlitic DCIs are characterised by the increase of a plastic-damaged zone at the crack tip that becomes more and more evident with the increase of the applied K I , but: - Pearlitic DCIs are characterized by a crack branching and a stable crack propagation; crack path after the overload is more tortuous than the path obtained during the fatigue crack propagation [11]; - Ferritic-pearlitic and ferritic DCIs are characterized by a negligible crack stable propagation, with an increase of the crack tip blunting with the increase of the applied K I [10]. Considering the ferritized DCI investigated in this work, the increase of the crack tip blunting with the increasing of the applied K I value is still evident, (Fig. 18), but there is also the stable crack propagation, although less important with respect to the same phenomenon in pearlitic DCIs.