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

The influence of solutes and stacking fault energy on sazuration grain size after severe plastic deformation was studied recently for binary alloys, whereby the saturation grain size (ds) correlates with the solid solution strengthening contribution and not with the stacking fault energy. In this context we investigate the microstructural evolution of a series of Nickel diluted compositions from pure Nickel to the chemically complex equiatomic CrMnFeCoNi Cantor alloy ((CrMnFeCo)xNi1-x) with x=0.8, 0.4 and 0.08 after high pressure torsion. The solid solution strengthening was determined using the conventional Labusch model and the more recent Varvenne model, which was specially developed for chemically complex alloys. A correlation between the solid solution strengthening contribution and the saturation grain size can be found, whereby higher Δτ cause smaller ds. Isochronal heat treatments were performed in order to reveal the microstructural instability i.e. the decomposition tendencies and grain growth. Significant changes in hardness as well as Young´s modulus were observed for Ni20 and Ni60 for different annealing temperatures between 450 and 600 °C, which indicate the formation of second phases. Nanoindentation strain rate jump tests on the deformed samples show similar low strain rate sensitivities of the deformed states without any pronounced transient regimes. Additionally, all compositions exhibit a history dependent softening, which indicates an unstable microstructure.