Developing New Type of High Temperature Alloys–High Entropy Superalloys

Abstract

Novel high temperature alloys -high entropy superalloys (HESA) have been developed by elevating the mixing entropies of Ni-Al-Co-Cr-Fe-Ti systems, these alloys contain stable FCC γ matrix and L1 2 γ' precipitates; compositions spaces are outside the scopes of traditional Ni-base superalloys and equimolar high entropy alloys. The thermal stability of high entropy γ' precipitates can be enhanced through alloy design by thermodynamic calculation based on Thermo-Calc. HESAs have potentials to high temperature structural application; alloy densities are below 8.0 g/cm 3 with lower cost of raw materials than those of conventional Ni-base superalloys.

L12-strengthened high-entropy alloys for advanced structural applications

“…To date, there have been limited studies on oxidation behaviors of the L1 2 -strengthened HEAs. [64][65][66]…”

“…Tsao et al conducted isothermal oxidation of L1 2 -strengthened Ni 44 Co 22.3 Fe 11.8 Cr 11.7 Al 3.9 Ti 6.3 HEA (wt%) at 1100°C for 5-200 h and no obvious oxide spallation was observed 64,65. High content of various solutes in L1 2 -strengthened HEAs lead to the formation of complex oxides.…”

Effects of Mo, Nb, Ta, Ti, and Zr on Mechanical Properties of Equiatomic Hf-Mo-Nb-Ta-Ti-Zr Alloys

“…Some HEAs have been found to have attractive properties on diffusion [13], oxidation [14], corrosion [15], fatigue [16], creep [17], fracture toughness [18], and elevated-temperature strength [19]. High-entropy superalloys (HESAs) [20], eutectic HEAs (EHEAs) [21], light-weight HEAs (LWHEAs) [22], refractory high-entropy alloys (RHEAs) [23], etc. have been proposed and attract increased attention.…”

A new single crystal high entropy alloy with excellent high-temperature tensile property

“…Zhao et al [8] designed a (NiCoCr) 94 Al 3 Ti 3 alloy containing γ′ precipitate with an outstanding RT tensile strength. Zhang et al [16] prepared Ni 47 [17]. The tensile yield strength of the directionally solidified Tsao alloy is 476 MPa at 950°C, which is close to that of single crystal (SC) superalloy CMSX-2 [18].…”

“…There are some transition metal HEAs which are designed to obtain coherent L1 2 precipitates (γ′ phase) via the addition of Al and Ti elements into the FCC matrix (γ phase), which always have good mechanical properties [8,[13][14][15][16][17][18]. Liu et al [13] studied the effect of Al addition on microstructure and mechanical properties of Ni 70−x Co 15 Cr 15 Al x .…”