Hierarchical phase separation behavior in a Ni-Si-Fe alloy. (15th August 2020)

• Record Type: Journal Article
• Authors: Zaiser, E.; Zhou, X.Y.; Manzoni, A.M.; Haas, S.; Glatzel, U.; Zhang, X.P.; Thompson, G.B.; Li, W.; Vogel, F.
• Is Part Of: Acta materialia. Volume 195(2020)
• Page Start: 327
• Page End: 340
• Publication Date: 2020-08-15
• Subjects: High-temperature alloys -- Phase separation -- Microstructure -- Transmission electron microscopy -- Atom probe tomography; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.05.023
• Languages: English
• ISSNs: 1359-6454

Abstract

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 Ni83.9 Si13 Fe3.1 (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. Graphical abstract: Image, graphical abstract