The design of high entropy alloys (HEAs) employs a completely new paradigm to design alloys by mixing multiple principal elements in an equal or nearly-equal molar fraction. HEAs are different from the conventional alloy design, which is based on one and rarely two principal elements. Since their advent more than a decade ago, HEAs have been attracting tremendous research interest due to many of their superior properties, such as ultrahigh fracture toughness exceeding that of most pure metals and alloys, superb strength comparable to that of structural ceramics and metallic glasses, superconductivity and great corrosion resistance.
From an application viewpoint, the attractive properties of HEAs can bring about great opportunities for many new applications. To name a few, some HEAs can be as light as Aluminum alloys but stronger than some metallic glasses. By using these light-weight and high-strength HEAs in the transportation industry and energy sectors, we can reduce the total energy consumption and hence decrease harmful emissions for the protection of our natural environment. Furthermore, refractory HEAs containing Nb, Mo, W and Ta can maintain their high strength even above 1200 ºC, exceeding that of traditional superalloys like Inconel 718 and Haynes 230. This shows that these HEAs can offer great potentials to be used for extremely high temperature applications, such as gas turbines, rocket nozzles and nuclear plant construction. Meanwhile, the outstanding cryogenic properties, such as ductility and toughness, also make HEAs an excellent choice of material for cryogenic applications such as rocket casings, pipework, and liquid O2 or N2 storage equipment. Because of these fascinating properties of HEAs, the concept of high entropy design is just being extended to other materials systems, such as ceramics. Nevertheless, one key problem still remains: that is, how can one design a high entropy material (HEM) with the intended phases and desired properties out of many possible compositions? At the fundamental level, this is related to the very core concept of configurational entropy of mixing in a multicomponent system and the entropy-related mechanisms that govern phase stability in these new materials.
As motivated by the unresolved fundamental issues and promising properties of HEMs, this Research Topic is going to cover a wide range of sub-themes which are related to the fundamentals and applications of HEMs, as listed below:
1. Thermodynamics and statistic mechanics of HEAs
2. Atomistic simulations on HEAs
3. Stacking fault energy in HEA
4. Dislocation dynamics and deformation mechanisms in HEAs
5. Fracture of HEAs
6. In-situ micro- and nano-mechanics of HEAs
7. Development of HEA as nuclear materials, high temperature alloys and coatings
8. Refractory High-entropy alloys
9. High entropy metallic compound
10. High entropy shape memory alloys & TRIP HEA
11. High entropy ceramics
12. Eutectic high entropy alloys
13. Formation criterion of HEA
14. Dealloying in HEAs
15. Low dimensional HEAs (HEA nanowires)
16. HEAs as thermoelectric materials
17. Precious metal HEAs
18. HEAs as alternative binder for hard metals
19. HEAs as hydrogen storage materials
20. HEAs as superconducting materials
The design of high entropy alloys (HEAs) employs a completely new paradigm to design alloys by mixing multiple principal elements in an equal or nearly-equal molar fraction. HEAs are different from the conventional alloy design, which is based on one and rarely two principal elements. Since their advent more than a decade ago, HEAs have been attracting tremendous research interest due to many of their superior properties, such as ultrahigh fracture toughness exceeding that of most pure metals and alloys, superb strength comparable to that of structural ceramics and metallic glasses, superconductivity and great corrosion resistance.
From an application viewpoint, the attractive properties of HEAs can bring about great opportunities for many new applications. To name a few, some HEAs can be as light as Aluminum alloys but stronger than some metallic glasses. By using these light-weight and high-strength HEAs in the transportation industry and energy sectors, we can reduce the total energy consumption and hence decrease harmful emissions for the protection of our natural environment. Furthermore, refractory HEAs containing Nb, Mo, W and Ta can maintain their high strength even above 1200 ºC, exceeding that of traditional superalloys like Inconel 718 and Haynes 230. This shows that these HEAs can offer great potentials to be used for extremely high temperature applications, such as gas turbines, rocket nozzles and nuclear plant construction. Meanwhile, the outstanding cryogenic properties, such as ductility and toughness, also make HEAs an excellent choice of material for cryogenic applications such as rocket casings, pipework, and liquid O2 or N2 storage equipment. Because of these fascinating properties of HEAs, the concept of high entropy design is just being extended to other materials systems, such as ceramics. Nevertheless, one key problem still remains: that is, how can one design a high entropy material (HEM) with the intended phases and desired properties out of many possible compositions? At the fundamental level, this is related to the very core concept of configurational entropy of mixing in a multicomponent system and the entropy-related mechanisms that govern phase stability in these new materials.
As motivated by the unresolved fundamental issues and promising properties of HEMs, this Research Topic is going to cover a wide range of sub-themes which are related to the fundamentals and applications of HEMs, as listed below:
1. Thermodynamics and statistic mechanics of HEAs
2. Atomistic simulations on HEAs
3. Stacking fault energy in HEA
4. Dislocation dynamics and deformation mechanisms in HEAs
5. Fracture of HEAs
6. In-situ micro- and nano-mechanics of HEAs
7. Development of HEA as nuclear materials, high temperature alloys and coatings
8. Refractory High-entropy alloys
9. High entropy metallic compound
10. High entropy shape memory alloys & TRIP HEA
11. High entropy ceramics
12. Eutectic high entropy alloys
13. Formation criterion of HEA
14. Dealloying in HEAs
15. Low dimensional HEAs (HEA nanowires)
16. HEAs as thermoelectric materials
17. Precious metal HEAs
18. HEAs as alternative binder for hard metals
19. HEAs as hydrogen storage materials
20. HEAs as superconducting materials