Intergranular fracture is also a common fracture mode observed for both tempered martensite embrittlement in plain carbon steels and temper embrittlement in alloy steels in the presence of phosphorus.
Thus, the predominance of tensile ratcheting in the crack propagation phase highlighted two failure modes: time-dependent
intergranular fracture and stress-dependent ductile rupture.
Intergranular fracture was observed only in areas with relatively high amounts of ferrite (Figure 4(b)).
Fractographic studies were performed to determine the maximum portion of brittle
intergranular fracture ([eta]) in the fracture surfaces of Charpy specimens after impact tests, which correlates with the level of phosphorus concentration in grain boundaries of the material.
[5.] H N G Wadley, C B Scruby and G Shrimpton, Quantitative acoustic emission source characterisation during low temperature cleavage and
intergranular fracture, Acta Metallurgica, Vol.
Fatigue striations, broken crystals (caused due to granular and
intergranular fracture), failure facets, differently sized and shaped dimples are observed.
The micromorphology in RZ shown in Figure 11(c) illustrates a similar
intergranular fracture condition with Fe314.
"Quench Embrittlement:
Intergranular Fracture Due to Cementite and Phosphorus in Quenched Carbon and Alloy".