Transgranular transition metals

In zone 1, the metal is in a transition state from active to passive formation (Fig. 4.38). The conditions of film formation on crack wall and film dissolution at the crack tip exist in this zone. An active surface is necessary for the process of dissolution to occur, such as active surface provided by the anodic zones formed in the material. Similar conditions also exist in zone 2. The above conditions are ideal for transgranular cracking which takes place in the two zones, 1 and 2. 

---