13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- obtained from ODF are (221) [1-10] (223) [1-10] (112) [1-3 -2] and (332) [023] orientations. Pole figures shown in Fig. 5c) confirm the presence of the α fiber components identified by the ODF. Figure 6. Misorientation angles between adjacent grains near to edges of delamination Furthermore, materials with crystallographic plane with (100) orientation aligned in the rolling direction show a strong tendency to occur cleavage fracture during impact [1,2,6,7,8,9,10]. To identify whether in this case occurred the separation of the (100) planes were measured microtexture on the edge of the fractured surface where was generated the delamination. This sample was the same used in the analysis of Fig. 6b), but using step size of 1 micron and 1000X magnification, and the results obtained are displayed in Fig. 7. It can be observed in Fig. 7a) the difference of depth between the ferrite and pearlite. While in Fig. 7b) shows the distribution orientations map, there is a heterogeneous distribution of grain sizes and a few areas where there were not indexing of the plans, there is also the presence of (100) plans. The ODF to Bunge angle Φ2 = 45° is shown in Fig 7c) and its indexing shows the main texture components was (223) [0-32] and (332) [1-10]. The pole figures are shown in Fig. 7d) where it is possible to notice that higher centering occurred in the (111) plane, however, it also notice that occurred to the (100) plane and indexing of some components reveals the presence of {100} planes families and the <011> families directions. As seen in Fig.5c) the crack nucleated by delamination separated grains with (111)||ND and (101)||ND texture components. It is evident that in this case should be noticed, the presence of the (111)||ND components close to the delamination, confirming the separation of ferrite plans. However the presence of the (100) planes was also confirmed. Whereas when if analyzes the microtexture, it cannot confirm whether this is a general rule for the nucleation of delamination in the material under study. Experimentally, it is known that the stored energy during deformation changes with the crystallographic orientation of the grains. The Taylor factor is a parameter that correlates to macroscopic deformation behavior with microstructural characteristics of the material [11]. According to the theory of plasticity, the stored energy increases with the Taylor factor which in turn, depends on the crystallographic orientation of the grain in relation to the direction of applied stress [12]. The Taylor factor is defined as: ∑= δε δγ i M (1)
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