title: Evolution of nanoscale clusters in γ' precipitates of a Ni-Al-Ti model alloy.
abstract: The evolution of phase separation and ordering processes determines the structure and properties of Ni-based superalloys. Here we use atom probe tomography to clarify the origin of γ particles occurring in ordered (L12) γ' precipitates in a Ni86.1Al8.5Ti5.4 alloy. Particularly, we elucidate the evolution from nanoscaled Ni-rich heterogeneities (Ni-rich clusters) to γ spheres and then γ plates inside γ' precipitates from the compositional and the thermodynamic point of view. We find that Ni supersaturation of γ' precipitates is relieved by formation of Ni-rich clusters, which results in an energetically more favorable state. Subsequently, coalescence introduces necking between the Ni-rich clusters and leads to the formation of γ particles. Our results demonstrate that phase separation of γ' precipitates is characterized by different stages with various governing driving forces.
authors.affiliation: Helmholtz-Zentrum Berlin, Institute of Applied Materials, Hahn-Meitner-Platz 1, 14109 Berlin, Germany. Electronic address: florian.vogel@helmholtz-berlin.de.
authors.forename: F
authors.initials: F
authors.lastname: Vogel
authors.affiliation: Helmholtz-Zentrum Berlin, Institute of Applied Materials, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Wanderka
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institute of Materials Physics, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
authors.forename: Z
authors.initials: Z
authors.lastname: Balogh
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institute of Materials Physics, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ibrahim
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institute of Materials Physics, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Stender
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institute of Materials Physics, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schmitz
authors.affiliation: Technische Universität Braunschweig, Institut für Werkstoffe, Langer Kamp 8, 38106 Braunschweig, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Fedorova
authors.affiliation: Helmholtz-Zentrum Berlin, Institute of Applied Materials, Hahn-Meitner-Platz 1, 14109 Berlin, Germany; Technische Universität Berlin, Department of Materials Science and Technology, Hardenbergstr. 36, 10623 Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Banhart
keywords: Atom probe tomography; Cluster; Phase separation; Superalloy; Transmission electron microscopy