Investigation of the γ′ Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic s...

Full description

Saved in:
Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2021-11, Vol.52 (11), p.4767-4784
Main Authors: Rakoczy, Łukasz, Grudzień-Rakoczy, Małgorzata, Hanning, Fabian, Cempura, Grzegorz, Cygan, Rafał, Andersson, Joel, Zielińska-Lipiec, Anna
Format: Article
Language:English
Subjects:
Annealing
Characterization and Evaluation of Materials
Chemical composition
Chemical precipitation
Chemistry and Materials Science
Dissolution
Homology
Lattice parameters
Materials Science
Metallic Materials
Nanotechnology
Nickel base alloys
Original Research Article
Phase composition
Precipitates
Structural Materials
Superalloys
Surfaces and Interfaces
Thin Films
Transmission electron microscopy
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ  = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ / γ′ interface is strongly enriched in Co and Cr and depleted in Al.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-021-06420-4