Fractal characteristics of fracture surfaces were investigated with different methods for the CK45 steel subjected to different heat treatments and mechanical tests. And the obtained fractal dimensions were compared with their corresponding mechanical properties. The results have shown that the fractal dimension which comes from the vertical section, secondary electron line scanning and slit island analyses of f"island within lake" has different values for a fracture surface but varies in the similar manner with the mechanical properties. However, this variation trend is contradicted with that obtained from the slit island analysis of "lake within island" and the cause resulting in this phenomenon has been discussed in detail. Moreover, the roughness parameter of fracture surface can be directly measured from secondary electron scanning lines. The secondary electron line scanning method more reflects the tilt angle distribution of facets on fracture surface than the vertical section method and, as used, is more convenient than others so that it is a feasible way to characterize fracture surface. The further analyses have shown whether the quantitative relationship of fractal dimensions with their corresponding properties exists or not is still a question to be studied.
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