Deformation and damage micromechanisms in creep and tension in titanium alloy Ti-6.2.4.6 at 773 K

摘要

The behaviour, at 773 K, of the 6.2.4.6 titanium alloy in uniaxial tension and creep has been studied. The deformation mechanisms have been identified and the influence of different microstructural heterogeneities on plastic and viscoplastic flow is discussed in terms of back stress. For the creep behaviour, three stress domains are defined, which are characterized either by a saturation phenomenon, or by a more or less sharp transition towards a steady state regime. It is shown that a high back stress, associated with the two-phase structure, stabilizes the dislocation sub-grain structure, which means that the domain of saturation creep is favoured. Fracture in uniaxial tension or in creep under conditions of low stress triaxiality seems to be the result of a plastic instability.