Correlation between creep activation parameters and microscopic dislocation behaviour in γ TiAl alloys

The creep properties of an as-cast Ti48Al48Cr2Nb2 alloy have been studied at 750 °C and 150 MPa. The activation parameters have been measured by stress jumps during the creep test. TEM analyses have been performed to determine the rate-controlling deformation mechanism. Creep is controlled by the mixed climb of ordinary dislocations, which combines climb and glide components. It is shown that that the stress dependence of the creep rate is correlated to this mechanism.