13th International Conference on Fracture June 16–21, 2013, Beijing, China Fig. 7 Surface of cracked specimen Surface microstructure observation after fracture shows as in Fig.7. Red arrow indicates a grain which has PSBs in it. In this PSB grain, crack opens along the PSBs which formed long time before crack occurs in this grain. Yellow arrow indicates the crack along a grain boundary. Intergranular crack takes place at grain boundary between two grains whose PSB are perpendicular to each other. Blue arrows denoted a transgranular crack. Crack stairs in the surface of this grain correspond to the appearance of slip bands below the fracture surface. a) b) c) d) 10 μm 10 μm 1~3 μm
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