High temperature strength of α TiAl alloys with a locally ordered structure

Tensile tests were performed in Ti—(7 ∼ 13)mol.%Al alloys at 1100 K. Stress—strain curves showed a large region of constant stress deformation. The results were analyzed by a Dorn type creep equation. The strain rate and the steady-state stress showed anomalous strength of the examined alloys in comparison with the previously reported Ti—(1 ∼ 5)mol.%Al alloys (H. Oikawa and T. Oomori, Mater. Sci. Eng., A104 (1988) 125). Both X-ray diffraction and transmission electron microscopy indicated the appearance of additional diffraction intensities that may owing to the formation of short range ordered (SRO) clusters. The anomalous creep strength observed in the present work seems to be caused by the retardation of dislocation glide by the SRO clusters.