| Fracture in a duplex gamma-TiAl alloy with equiaxed grains has been studied. The crack path in a notched Mode I crack growth specimen was analyzed using a combination of orientation imaging microscopy and selected angle channeling patterns as well as electron channeling contrast imaging techniques.; A fracture propagation parameter, incorporating the contributions from deformation twinning and ordinary dislocation systems, has been developed. This parameter, FA→B, is capable of identifying boundaries that are likely to nucleate microcracks. It was observed that microcracking is less likely when FA→B < 1.0 but is more likely when FA→B > 1.0.; The primary crack has a tendency to propagate towards clusters of weak boundaries (identified by the fracture propagation parameter). Where it is not possible to follow a boundary directly, the crack will cleave through a grain, via the shortest distance, towards the next cluster of weak boundaries. |
