Fractography is the interpretation of features observed on fracture surfaces and, although it is simple in many cases, it can prove to be fairly difficult in practice. This is particularly the case on high strength quenched and tempered steels, or in alloys (such as cast irons and pearlitic steels) where the microstructure affects the crack path.

In general terms, there are three basic crack growth mechanisms possible in fast fracture - intergranular along grain boundaries (or interdendritic fracture), brittle fracture via cleavage along crystallographic planes (or through pearlite lamellae), and transgranular ductile fracture via microvoid coalescence. Fatigue, by definition, involves ductile fracture, which is usually transgranular (through the grains), although intergranular fatigue is possible under certain special circumstances. Although it may prove difficult to fractographically distinguish between fast fracture, fatigue or stress corrosion cracking under certain circumstances, overall consideration of the facts and circumstances of a particular case usually allow correct interpretations of the evidence.