Local composition and nanoindentation response of <i>δ</i>-phase and adjacent <i>γ</i>′′-free zone in a Ni-based superalloy
Vitor V. Rielli, Felix Theska, Yin Yao, James P. Best, Sophie Primig
Abstract
Experimental differentiation of individual strengthening effects from the nanoscale precipitates in Alloy 718 remains challenging due to co-precipitation of γ′ and γ′′. Here, we examine a region adjacent to the δ-phase consisting of γ-matrix containing γ′-precipitates only. The width and compositional profile of this γ′′-free zone is uncovered via high-resolution characterization. Nanomechanical analyses reveal that the lack of γ′′-precipitates lower the hardness of the γ′′-free zone by 10–20%, while the δ-phase is found to be ∼80% harder than the γ-matrix. These findings may guide mechanical modelling and microstructural engineering of stronger superalloys critical to aerospace industry.