Strengthening mechanisms in polycrystalline nickel-based superalloys

Nickel-based superalloys are currently the material of choice for use in high-temperature applications due to their excellent high-temperature strength. It is understood that many mechanisms contribute to this property, but debate exists regarding how to model these mechanisms and predict the overall strength. This review covers the different strengthening mechanisms occurring in polycrystalline Ni-based superalloys and how these may be modelled, with the aim of revealing the gaps in the literature. It is found that models for precipitation and coherency strengthening are particularly controversial, and a unified model for the yield strength of superalloys is missing from the literature. This is of commercial importance for the design of new alloys with superior mechanical properties to those currently available. This review was submitted as part of the 2018 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.