Deformation mechanisms in a binary Ti-48 at.%Al alloy with lamellar microstructure

Abstract

The deformation mechanisms active in the eta- and alpha-lamellae of a Ti2 48 at.%Al alloy during room-temperature and 800 C tensile loading have been determined by transmission electron microscopy. A marked change in the plastic behaviour of the alpha-phase has been detected between room and elevated temperature, whereas the deformation mechanisms active in the eta-phase remained the same at both temperatures. At room temperature, plasticity in the alpha-phase occurred only locally by prism plane slip of dislocations with Burgers vectors parallel to 1120 where cross-lamellar twins in the eta-plane impinged on the eta alpha-interface. At 800 C more homogeneous plastic behaviour of the alpha/ phase resulted from slip and climb activity of dislocations with Burgers vector components parallel to 1120 and parallel to both 1120 and [0001]. The increased contribution to strain accommodation at 800 C by the alpha-lamellae coincided with a change in predominant fracture mode.