Abstract
Improving the properties of durable high-temperature alloys is based on the fundamental understanding of the link between microstructure and three-dimensional (3D) nanochemistry. Here we utilize a complementary approach of transmission electron microscopy and atom probe tomography to link microstructure and 3D nanochemistry of a ternary single crystal Ni83.9Si13Fe3.1 (at.%) model alloy. The formation of a γ/γ' microstructure is revealed, containing primary and secondary γ' precipitates analogous to Ni-based superalloys. Subsequently, microstructural hierarchy is created by the formation of γ particles inside primary γ' precipitates. The correlated supersaturation with γ forming elements (Ni, Fe) of primary γ' precipitates was identified as driving force for the formation of γ particles. The influence of aging on the mechanical properties is reported and peak hardness is achieved after 24 h of aging at 923 K. Thermo-Calc equilibrium phase concentrations based on the TTNi8 database where found to be closer to the APT data than the TCNi8 based values. Our results suggest that improved stability of γ particles can be achieved by tailoring the phase chemistry and the lattice misfit.
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