A study of the cleavage fracture behavior of PST TiAl alloys

Samples of two polysynthetically twinned (PST) TiAl alloys (Ti–49at.%Al and Ti–49at.%Al-0.6at.%Cr) were fractured in different environments at room temperature and the fracture surfaces were analyzed using scanning Auger and scanning electron microscopy. These techniques were employed to determine the fracture mode and the chemical composition of the fracture surfaces of the TiAl alloys. Our study clearly indicates that all of the fracture surfaces exposed by bend testing were α2, except when fracture occurred across the lamellae. No chromium enrichment was observed on any of the surfaces exposed during the fracture. From these observations, it was concluded that the fracture mode for these materials is cleavage through the α2-phase.