A fundamental study of deformation mechanisms in advanced polycrystalline nickel-base superalloys

As one of the most important classes of high-temperature structural materials, nickel-base superalloys exhibit unique high temperature properties, which make them the first choice in demanding applications such as the hot sections of turbine engines for both aircraft and power-generation applications. Nickel-base superalloys rely upon a combination of matrix strengthening and precipitation hardening to give outstanding high-temperature mechanical properties. This research project will study the effect of gamma prim precipitate distribution on the deformation mechanisms in advanced gamma (matrix)/gamma prime (precipitates) nickel-base superalloys for high temperature applications. It takes an interdisciplinary approach, combining detailed metallurgical studies, in-situ mechanical testing on neutron and high-energy x-ray synchrotron diffraction beam lines and mathematical modelling. Instead of studying macroscopic mechanical properties as a function of microstructure, our approach will allow us to study directly strengthening mechanisms as a function of microstructure. In advanced superalloys, fundamental studies have often been limited by the complexity of the microstructure. We will overcome this by first studying simplified model microstructures and using these to validate and tune advanced models, before moving on to commercially more relevant but also more complex microstructures.This project will provide an improved fundamental understanding of the interplay of gamma prim-distribution and deformation mechanisms, which is key to harnessing the full potential of these new high temperature alloys. Although a number of new gamma prim strengthened polycrystalline nickel-base alloys have recently emerged from worldwide development programs, the optimisation of the mechanical properties of these alloys through thermomechanical processing has been, to date, strongly empirical. This new understanding will make it possible to identify optimum microstructures, which will not only help definite the ideal thermomechanical processing routes for newly developed alloys, but also illuminate future alloy development.