Chemical aspects of brittle fracture: grain boundary segregation

The relationship between brittle fracture and chemical composition of grain boundaries is documented by the study of solute segregation in Fe-Si base alloys. Si, P and S segregation at the 013 symmetrical grain boundary in an Fe-6at.%Si alloy induce a small decrease of the cohesion energy. During brittle intergranular separation, segregants atoms are distributed between the two fracture surfaces. This distribution is homogeneous in the case of symmetrical boundaries but uneven for asymmetrical ones as shown in numerous examples and reflects asymmetry of sites in grain boundary core available for segregation.