Deformation and fracture behavior of a TiAl intermetallic compound in Compression tests at room temperature

In order to clarify the deformation and fracture behavior of a Ti-50 mol%Al alloy, discontinous compression tests have been performed at room temperature. Surfaces of specimens were observed by optical microscopy and scanning electron microscopy (SEM) to reveal the formation of deformation bands, initiation sites and propagating routes of cracks, and fracturing process at every a few per cent of plastic strain by interrupting the tests. The compressive plastic strain at crack initiation is 2-3% which is nearly twice as large as the tensile fracture strain reported in the other studies. From the observation of structural changes with cumulative strain the modes of initiation and propagation of cracks are classified. The interfaces of the α₂ phase which is present in equiaxed γ phase grains, in grains with a lamellar structure and on grain boundaries, give an initiation site for cracking at the early stage of deformation while the α₂ phase itself acts as an obstruction against crack propagation by necking and kinking on crack propagation routes.