摘要
This study presents the design and microstructural investigation of a single-crystal (SX) Re-bearing high-entropy superalloy (HESA-X1) featuring a thermally stable gamma-gamma '-gamma hierarchical microstructure. The alloy exhibits FCC gamma nanoparticles embedded within L12-ordered gamma ' precipitates, themselves distributed in a gamma 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 gamma matrix, while Al and Ti were preferentially enriched in the gamma ' phase. Notably, Re demonstrated a unique partitioning behavior compared to conventional superalloys, facilitating the formation and stabilization of gamma nanoparticles during two-step aging (Ag-2). These gamma nanoparticles significantly contribute to improved mechanical properties. Long-term aging (up to 200 h) at 750-850 degrees C confirmed exceptional phase stability, with minimal coarsening of gamma ' and retention of gamma nanoparticles. The coarsening rate constant K of gamma ' at 750 degrees 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.