Effect of heterogeneous deformation on the creep behaviour of a near-fully lamellar TiAl-base alloy at 750 °C

The tensile creep behaviour of a near-fully lamellar Ti46A12W0.5Si alloy was studied at 750 °C in the stress range of 240–330 MPa. A long tertiary creep regime and a high stress exponent n = 7 were observed. On the basis of microstructural studies, the high stress exponent n was attributed to heterogeneous plastic deformation. The scatter of stress exponents reported in literature on TiAl-base alloys can be essentially interpreted by a proposed model considering the inhomogeneous deformation in terms of friction stress. The observed extensive necking and the successive localized microstructural degradation, resulting from the heterogeneous deformation, were considered to be the major causes of long tertiary creep stage.