Effect of Interactions Among Elements on Diffusion Process Associated with γ′ Coarsening in a Ni-Based Single-Crystal Superalloy

• Published in: Acta metallurgica sinica : English letters 2020-07, Vol.33 (7), p.1013-1020
• Main Authors: Wang, Guang-Lei, Qi, Dong-Qing, Liu, Ji-De, Liu, Jin-Lai, Zhou, Yi-Zhou, Sun, Xu-Dong, Zhang, Hai-Feng, Sun, Xiao-Feng
• Format: Article
• Language: English
• Subjects: Alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Diffusion rate; Experiments; Influence; Materials Science; Metallic Materials; Nanotechnology; Nickel base alloys; Organometallic Chemistry; Parameter modification; Phase diagrams; Physical properties; Precipitates; Scanning electron microscopy; Single crystals; Spectroscopy/Spectrometry; Superalloys; Temperature; Temperature dependence; Tribology
• ISSN: 1006-7191; 2194-1289
• DOI: 10.1007/s40195-020-01009-z

Coarsening of cuboidal γ ′ precipitates and relevant diffusion process in Ni-based single-crystal superalloy CMSX-4 were investigated at 1000, 1020 and 1040 °C for specific times. The γ ′ coarsening kinetics followed a cubic rate law with time and was presumably controlled by bulk diffusion of elements in γ matrix. The associated diffusion activation energy was experimentally determined to be about 300 kJ/mol when it is considered the temperature-dependent thermo-physical parameters in modified Lifshitz–Slyozov–Wagner theory. The influence of temperature on γ / γ ′ microstructure is briefly discussed based on pseudo-binary [Ni]–[Al] phase diagram. Interactions among elements can effectively raise the local vacancy formation and vacancy–atom exchange barriers close to γ - and γ ′-partitioning elements, respectively. Thus, it can significantly reduce the inter-coupling migrations of atoms during the macroscopic cross-diffusion process associated with γ ′ coarsening of Ni-based superalloys.