Microstructural Evolution and Enhanced Thermal Stability of Al–Sc–Zr Alloys Modified with Sm and Si: A Multiscale Analysis
Year: 2025
Type: article
Abstract: This research investigates novel samarium (0.10 at.%) and/or silicon (0.10 at.%) additions to a cast base Al–0.02Sc–0.08Zr (at.%) alloy, focusing on their impact on L1 2 Al 3 (Sc, Zr) nanoprecipitates. Precipitation was studied via isochronal (25–575 °C), isothermal (400, 425 °C), and double-aging (400 °C + 425–475 °C) treatments, revealing superior thermal stability in Sm-containing alloys. Scanning electron microscopy (SEM) revealed significant grain refinement from Sm. Transmission electron microscopy (TEM) confirmed spherical L1 2 nanoprecipitates across all compositions, indicating that Sm does not alter the fundamental precipitate characteristics. Atom probe tomography (APT) revealed a core–shell structure with Sc in the core and Sm/Zr in the shell. Sm partitioned to nanoprecipitates (4.68–13.74 at.%) during aging, confirmed by HAADF-STEM and EDS mapping, without forming separate tri–aluminide intermetallics. The Sm/Si-modified alloy exhibited a cumulative effect between Sm and Si, the highest precipitate density (∼3.87 × 10 22 m −3 ), and enhanced coarsening resistance. Creep tests at 300 °C showed a substantial threshold stress increase, from 9.6 MPa (base alloy) to 15.1 MPa (Sm/Si-modified alloy). This correlated with increased Sc content in L1 2 Al 3 (Sc, Sm, Zr) nanoprecipitates, enhancing dislocation pinning. While Si slightly reduced coarsening resistance, it increased strength (∼80–150 MPa), contributing to improved creep resistance.
Source: Materials & Design
Authors: Hasan Vafaeenezhad, Hamid Reza Shahverdi
Institution: Tarbiat Modares University
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,650
OpenAlex ID: W4410459447