13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- Figure 1 a) Schematic drawing shows the specimen section where was made cut perpendicular to the fracture surface b) fractured surface from the delamination region. The scan was performed with step size of 1μm and magnification of 1000 times. Pole figures were obtained from the (100), (110) and (111) centered planes. While orientation distribution functions (ODF) was performed from the Euler space and the Bunge notation. Whereas, Taylor factor maps and misorientation angles distribution were generated in software for further analysis. 3. Results and Discussion The chemical composition is according to the API standard [1], as shown the Table 1. The tensile properties obtained for the API X70 steel are shown in Table 2. The yield strength (YS), ultimate tensile strength (UTS) and elongation values are according to API standard [1]. Table 2. The tensile properties obtained from the tensile test for API X70 steel. YS (MPa) UTS (MPa) Elongation (%) Hardening exponent (%) Modulus Elastic (GPa) 515 586 23 15 207 Fig. 2.a shows the three dimensional view of the API X70 microstructure steel. It can be observed a microstructure consisting of alternated layer of ferrite and pearlite in the RD and TD directions as also random distribution of ferrite and pearlite in the DN direction. Fig. 2.b shows the delamination region which can be noticed the banded microstructure caused by delamination.
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