EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

High Entropy Alloys (HEAs) and the strongly related Compositionally Complex Alloys (CCAs) constantly draw much attention from both fundamental and applied research prospective. For special high temperature applications, γ’-precipitation strengthened CCAs have a high potential to replace some types of classical Ni based superalloys. This is because they partially show similar or even better mechanical properties than the classical one-element based alloys. In connection with future material design concepts, it is important to get deeper insights into the mechanical properties and acting deformation mechanisms in CCAs at elevated temperatures. As a function of the stacking fault energy and temperature, deformation mechanisms in solid solutions can alter from formation of different types of twins to deformation by dislocation slipping. Coherent particles are usually sheared while incoherent are bypassed.
In this work, we investigate the deformation behaviour of a novel precipitation strengthened CCA in comparison to the well-established Ni-based superalloy IN718 at elevated temperatures. To this end, high temperature compression tests on the casted alloys in heat treated state are carried out. In order to compare the deformation mechanisms, SEM and EBSD investigations are performed on tested specimens, as these methods can provide indications to distinguish between dislocation slipping and twinning in the matrix and show changes in the precipitates’ appearance. Therefore, a quantification of localized slip deformation and twinning in the matrix, as well as shearing of the particles, caused by deformation, can be estimated. Moreover, additional DFT calculations along with alloy strengthening models are employed to provide physical insights into the mechanical properties of the CCA and the Ni-base superalloy and to analyse the differences between them.