Tracing the three-dimensional nanochemistry of phase separation in an inverse Ni-based superalloy

• Published in: Acta materialia Vol. 157; pp. 326 - 338
• Main Authors: Vogel, F., Ngai, S., Fricke, K., McKechnie, M., Wanderka, N., Hentrich, T., Banhart, J., Thompson, G.B.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-09-2018
• Subjects: Atom probe tomography; Inverse microstructure; Phase separation; Superalloy; Transmission electron microscopy; Superalloy; Transmission electron microscopy; Phase separation; Atom probe tomography; Inverse microstructure
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2018.07.038

Tailoring the properties of intermetallic alloys and phases, which resemble the foundation of a vast variety of high-temperature materials like nickel-based superalloys, is a challenge for improving this class of materials that requires comprehensive understanding of their three-dimensional (3D) nanochemistry. Here we use high-resolution microscopy techniques to reveal the microstructural and 3D nanochemical evolution of disordered γ particles from nanoscale nickel-rich heterogeneities (clusters) to γ spheres and then γ plates in an inverse Ni78Al13Ti9 alloy having an ordered (L12) γ′ matrix. The γ particles require aging to achieve a thermodynamically stable morphology and composition, determined by reducing the Gibbs free energy. The fundamental analogy between γ particles in a γ′ matrix of an inverse alloy and γ particles in γ′ precipitates of a hierarchical Ni86.1Al8.5Ti5.4 alloy is established. Our results demonstrate that this analogy can be harnessed as a novel approach for improving the properties of nickel-based superalloys.
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