Article Dans Une Revue Metals Année : 2025

On the Solidification and Phase Stability of Re-Bearing High-Entropy Superalloys with Hierarchical Microstructures

Wei-Che Hsu
  • Fonction : Auteur
Takuma Saito
  • Fonction : Auteur
Hideyuki Murakami
  • Fonction : Auteur
Taisuke Sasaki
  • Fonction : Auteur
an Chou Yeh
  • Fonction : Auteur

Résumé

This study presents the design and microstructural investigation of a single-crystal (SX) Re-bearing high-entropy superalloy (HESA-X1) featuring a thermally stable γ–γ′–γ hierarchical microstructure. The alloy exhibits FCC γ nanoparticles embedded within L12-ordered γ′ precipitates, themselves distributed in a γ matrix, with the suppression of detrimental topologically close-packed (TCP) phases. To elucidate solidification behavior and phase stability, Scheil–Gulliver and TC-PRISMA simulations were conducted alongside SEM and XRD analyses. Near-atomic scale analysis in 3D using Atom Probe Tomography (APT) revealed pronounced elemental partitioning, with Re strongly segregating to the γ matrix, while Al and Ti were preferentially enriched in the γ′ phase. Notably, Re demonstrated a unique partitioning behavior compared to conventional superalloys, facilitating the formation and stabilization of γ nanoparticles during two-step aging (Ag-2). These γ nanoparticles significantly contribute to improved mechanical properties. Long-term aging (up to 200 h) at 750–850 °C confirmed exceptional phase stability, with minimal coarsening of γ′ and retention of γ nanoparticles. The coarsening rate constant K of γ′ at 750 °C was significantly lower than that of Re-free HESA, confirming the diffusion-suppressing effect of Re. These findings highlight critical roles of Re in enhancing microstructural stability by reducing atomic mobility, enabling the development of next-generation HESAs with superior thermal and mechanical properties for high-temperature applications.

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hal-05188510 , version 1 (06-09-2025)

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Wei-Che Hsu, Takuma Saito, Mainak Saha, Hideyuki Murakami, Taisuke Sasaki, et al.. On the Solidification and Phase Stability of Re-Bearing High-Entropy Superalloys with Hierarchical Microstructures. Metals, 2025, 15 (8), pp.820. ⟨10.3390/met15080820⟩. ⟨hal-05188510⟩
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