Thermal and Elastic Properties of an A2/B2 Refractory High Entropy Superalloy and Its Constituent Phases

The microstructure and temperature dependence of linear thermal expansion and elastic properties of a two-phase, A2 + B2, Al 10 Nb 20 Ta 15 Ti 30 V 5 Zr 20 refractory superalloy (RSA) and its constituent phases are reported. After slow cooling from 1400 °C, this alloy has a nanometer-sized, two-phas...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-08, Vol.55 (8), p.2704-2717
Main Authors: Senkov, Oleg N., Kube, Sebastian A., Drazin, John W., Soni, Vishal, Miracle, Daniel B., Butler, Todd M., Pollock, Tresa M., Banerjee, Rajarshi
Format: Article
Language:English
Subjects:
Bulk modulus
Characterization and Evaluation of Materials
Chemistry and Materials Science
Constituents
Crystal structure
Decomposition
Elastic properties
High entropy alloys
High temperature
Intermetallic phases
Materials Science
Metallic Materials
Microstructure
Nanotechnology
Original Research Article
Precipitates
Shear modulus
Spinodal decomposition
Structural Materials
Superalloys
Surfaces and Interfaces
Temperature dependence
Thermal expansion
Thin Films
Zirconium
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Summary:The microstructure and temperature dependence of linear thermal expansion and elastic properties of a two-phase, A2 + B2, Al 10 Nb 20 Ta 15 Ti 30 V 5 Zr 20 refractory superalloy (RSA) and its constituent phases are reported. After slow cooling from 1400 °C, this alloy has a nanometer-sized, two-phase microstructure consisting of Nb-rich BCC (A2 crystal structure) cuboidal precipitates at the volume fraction of 0.63 and continuous channels of a Zr-rich ordered B2 matrix phase. This two-phase microstructure forms by spinodal decomposition of a high-temperature BCC phase. Differential scanning calorimetry shows that the order–disorder transformation in the Zr-rich phase occurs in the temperature range of 550 °C to 850 °C. The coefficient of thermal expansion (CTE) of the Nb-rich BCC phase increases slightly from 8.9 × 10 −6 to 9.1 × 10 −6  K −1 with increasing temperature from 20 °C to 1200 °C. The Zr-rich phase has CTE of 9.1 × 10 −6  K −1 in the ordered (B2) state, at 20 °C to 550 °C, and 12.2 × 10 −6  K −1 in the disordered (A2) state, at 900 °C to 1200 °C. The Nb-rich phase has higher Young’s and shear moduli, but lower bulk modulus and Poisson’s ratio, as compared to the Zr-rich phase, at 20 °C to 600 °C. The CTE and elastic properties of the two-phase RSA approximately follow the rule of mixtures of the constituent phases in the studied temperature ranges. Correlations between the morphology of the spinodally decomposed microstructure in the two-phase RSA and the thermal and elastic properties of the constituent A2 and B2 phases are established.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-024-07429-1