Abstract: Due to the non-uniform nature of crack advance, when a cleavage front encounters a high-angle grain boundary, instead of simultaneous break-through along the whole boundary, the front transmission mode can be irregular, which results in a higher fracture resistance and a tortuous percolation behavior. In this paper, this phenomenon is studied quantitatively through the analysis on the work of separation and the change in strain energy for an Fe-3 wt pct Si alloy. The influences of the crystallographic misorientations, the break-through mode, the cleavage front profile, and the grain boundary properties are discussed in detail.

Key words: Fracture toughness, Transgranular, Iron-silicon alloy, Irregular mode