Phase transformations during creep of a multiphase TiAl-based alloy with a modulated microstructure

The creep behavior of a novel type of TiAl alloy with a composite-like microstructure has been investigated. The constitution and microstructure of the alloy result from decomposition reactions of the high-temperature β/B2 phase. The characteristic constituents are structurally modulated laths that are comprised of several stable and metastable phases. Tensile creep tests have been correlated with characterization by high-resolution transmission electron microscopy. The creep behavior of the material is mainly limited by the early onset of tertiary creep at higher stresses and temperatures. The processes associated with this behavior are several phase transformations towards thermodynamic equilibrium, dynamic recrystallization and the relaxation of constraint stresses that exist between misfitting phases.