Zaiser, E.; Zhou, X.Y.; Manzoni, A.M.; Haas, S.; Glatzel, U.; Zhang, X.P.; Thompson, G.B.; Li, W.; Vogel, F.: Hierarchical phase separation behavior in a Ni-Si-Fe alloy. Acta Materialia 195 (2020), p. 327-340
10.1016/j.actamat.2020.05.023
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 complemen-tary 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 g/g' micro-structure is revealed, containing primary and secondary g' precipitates analogous to Ni-based superalloys. Subsequently, microstructural hierarchy is created by the formation of g particles inside primary g' precipi-tates. The correlated supersaturation with g forming elements (Ni, Fe) of primary g' precipitates was identi-fied as driving force for the formation of g 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 concen-trations 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 g particles can be achieved by tailoring the phase chemistry and the lattice misfit.