The Creep-Induced Micro- and Nanostructural Evolution of a Eutectic Mo-Si-Ti Alloy at 1200 °C

In the present study, the creep deformation mechanisms of a eutectic Mo-Si-Ti alloy (comprising a body-centered solid solution and a hexagonal silicide) are verified. The microstructural changes occurring at the various microstructural length scales are correlated to the nature of the creep curve. The creep curve exhibits a transient strain-hardening region followed by a distinct minimum and then creep rate accelerates after that. The formation of a high fraction of disperse (Ti,Mo)(5)Si-3 precipitates in the solid solution lead to significant strengthening in the transient creep regime. By the simultaneous decrease of the initially high dislocation density in the solid solution, diffusional creep contributes to effective creep behavior. At the minimum, the load and strain are also carried by the silicide phase which undergoes plastic deformation. Continuous coarsening of precipitates and loss of precipitation strengthening in the solid solution and dynamic recovery in the silicide phase lead to creep acceleration.