A Novel Precipitation-Hardened Medium-Entropy Alloy with Excellent Tensile Properties

In this work, we report a newly developed γ–γ′-strengthened Ni–Co–Cr–Al–Ti-based medium-entropy alloy (MEA) with a low density of 7.84 g cm⁻³, designed based on the CALPHAD approach for turbine disk applications. The alloy exhibits coarsened γ′ precipitates with an average diameter of 285 ± 70 nm and irregular eutectic (γ + γ′) phases in the interdendritic region in the as-cast condition. In contrast, fine γ′ precipitates with an average diameter of 154 ± 26 nm are uniformly distributed in the dendritic region. The alloy demonstrates outstanding tensile properties, including a yield strength of 833 ± 4 MPa, ultimate tensile strength of 1080 ± 14 MPa, and ductility of 22 ± 2 pct in the as-cast condition. Due to its low density and high specific yield strength (106 MPa g⁻¹ cm⁻³), this alloy has the potential to be a viable alternative to Waspaloy and other nickel-based superalloys.