In situ tensile deformation and fracture behavior of Ti–24Al–14Nb–3V–0.5Mo alloy with various microstructures

The tensile deformation and fracture behavior of Ti–24Al–14Nb–3V–0.5Mo alloy (at.%) with various microstructures were studied at room temperature and 700 °C by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). O-phase precipitates in the aged alloy contributed to the improvement of the ductility by dispersing operative dislocations and suppressing the planar slip in the α2+O grains. The primary α2 grain was strengthened owing to interruption of the movement of dislocations by fine O plates, resulting in a blocking of the crack nucleation and propagation during the tensile loading. In this case, the slip bands were concentrated in the α2+O phases, and the cracks nucleated at the α2/B2 boundaries and/or at the cleavage of the secondary α2 grains followed by propagation across the secondary acicular α2-phases. In the alloy with low volume fraction of the α2-phase, the deformation was concentrated in the B2-phase showing coarse slip bands, and the cracks nucleated and propagated along the cleavage planes of the B2-phase. When the volume fraction of the α2-phase was moderate, the cracks nucleated within the primary α2-phases and/or along the α2/B2 boundaries, and propagated along the α2/B2 boundaries and/or sheared across the α2 grains.