Creep properties of a fully-lamellar Ti–48Al–2Cr–2Nb alloy

Minimum creep rates as a function of stress (100–300 MPa) and T=815 °C have been obtained for a Ti–48Al–2Cr–2Nb alloy with a fully lamellar microstructure. Transmission electron microscopy (TEM) investigation reveals that the deformation structures are dominated by jogged screw 1/2[110] dislocations in γ-laths. It is suggested that the creep in this alloy is controlled by the non-conservative motion of 1/2[110] unit dislocations, which are normally seen in varying proportions depending on the width of the γ-laths. The creep results are then compared with a binary Ti–48Al alloy. The difference in creep rates and stress exponents between these alloys (although differing in composition) have been explained in terms of the active volume fraction of γ-laths that are participating in deformation for a given applied stress. In this context, the effect of lamellar spacing on the creep rates are also been discussed.