Temperature dependence of γ-γ' lattice mismatch in Nickel-base superalloys

• Published in: Materials science and engineering 1985-11, Vol.75 (1-2), p.195-205
• Main Authors: Nathal, M.V., Mackay, R.A., Garlick, R.G.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals, semimetals and alloys; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Specific materials; Structure of solids and liquids; crystallography; Treatment of materials and its effects on microstructure and properties
• ISSN: 0025-5416
• DOI: 10.1016/0025-5416(85)90189-2

High temperature X-ray diffraction techniques were used to determine the γ-γ' lattice mismatch of three different nickel-base superalloys at temperatures between 18 and 1000°C. The measurements were performed on oriented single-crystal disks which had been aged to produce a semicoherent γ-γ' structure. The thermal expansion of the lattice parameters of the γ and γ' phases was described by a second-order polynomial expression. The expansion of the γ' phase was consistently smaller than that of the γ phase, which caused the lattice mismatch to become more negative at higher temperatures. It was also shown that high values of lattice mismatch resulted in increased rates of directional γ' coarsening during elevated temperature creep exposure.