The Microstructure Stability of Precipitation Strengthened Medium to High Entropy Superalloys

L12-strengthened high-entropy alloys for advanced structural applications

“…Tsao et al proposed a promising alloying design space in the FeCoNi-based system for studying the thermal phase stability of a series of L1 2 -strengthened HEAs. 71 By controlling the elemental partitioning between c/c9, a stable c-c9 structure with no topologically close-packed phases can be successfully maintained even after 300 h exposure at 1173 K (900°C). As shown in Fig.…”

Hierarchical microstructure strengthening in a single crystal high entropy superalloy

“…However, the high entropy composition scope 3,4 of 5.0 at.% ≤ x ≤ 35.0 at.% could jeopardize the thermal stability of ordered phase such as L1 2 phase [25][26][27][28] , and Ni-rich HEA with Ni content beyond 35 at.% has provided a window of opportunity to design thermally stable L1 2 precipitation in HEA while retaining the compositional configurational entropy |ΔS conf. |> 1.5 R, where R is the universal gas constant 3,4 ; this class of HEA has been named High Entropy Superalloys (HESA) [25][26][27][28][29] . Recently, the concept of HESA has been adopted by Zhang et al 29 , Ni 45 − x (Fe, Co, Cr) 40 (Al, Ti) 15 Hf x based alloys were studied in as-cast condition; the tensile strength of these HESAs could reach 960 MPa at 1,023 K.…”

“…Alloy design for higher L1 2 phase fraction and solvus temperature are required to further improve the high temperature tensile strength of HEAs. However, the high entropy composition scope 3 , 4 of 5.0 at.% ≤ x ≤ 35.0 at.% could jeopardize the thermal stability of ordered phase such as L1 2 phase 25 – 28 , and Ni-rich HEA with Ni content beyond 35 at.% has provided a window of opportunity to design thermally stable L1 2 precipitation in HEA while retaining the compositional configurational entropy |ΔS conf. |> 1.5 R, where R is the universal gas constant 3 , 4 ; this class of HEA has been named High Entropy Superalloys (HESA) 25 – 29 .…”

Structure and high temperature mechanical properties of novel non-equiatomic Fe-(Co, Mn)-Cr-Ni-Al-(Ti) high entropy alloys

“…In the Ni-based superalloys a face-centered cubic (fcc) matrix is strengthened by fine precipitates of a Ni 3 (Al, Ti) phase with an L1 2 structure [21]. Similar kind of microstructure (the fcc matrix with the L1 2 precipitates) can be produced in some HEAs [22][23][24][25][26][27][28]; in Refs. [25,27] such alloys have been referred to as high entropy superalloys (HESAs).…”