Table 1
Chemical compositions of the HESA.
| Alloy | Chemical Composition (wt%) | |||||||
|---|---|---|---|---|---|---|---|---|
| Al | Co | Cr | Fe | Mn | Ni | Ti | ||
| (1) | Al15Co9Cr16Fe20Mn4Ni33Ti3 | 15 | 9 | 16 | 20 | 4 | 33 | 3 |
| (2) | Al15Co4Cr16Fe20Mn4Ni38Ti3 | 15 | 4 | 16 | 20 | 4 | 38 | 3 |
| (3) | Al20Co4Cr16Fe20Mn4Ni33Ti3 | 20 | 4 | 16 | 20 | 4 | 33 | 3 |
| (4) | Al20Co9Cr16Fe15Mn4Ni33Ti3 | 20 | 9 | 16 | 15 | 4 | 33 | 3 |
| (5) | Al20Co9Cr11Fe20Mn4Ni33Ti3 | 20 | 9 | 11 | 20 | 4 | 33 | 3 |
| (6) | Al24Co6Cr11Fe23Mn3Ni30Ti3 | 24 | 6 | 11 | 23 | 3 | 30 | 3 |
| (7) | Al25Co5Cr10Fe25Mn3Ni27Ti5 | 25 | 5 | 10 | 25 | 3 | 27 | 5 |
Table 3
| Al | Co | Cr | Fe | Mn | Ni | Ti | |
|---|---|---|---|---|---|---|---|
| Al | — | −19 | −10 | −11 | −20 | −22 | −60 |
| Co | −19 | — | −4 | −1 | −5 | 0 | −28 |
| Cr | −10 | −4 | — | −1 | 2 | −7 | −7 |
| Fe | −10 | −1 | −1 | — | 0 | −2 | −17 |
| Mn | −20 | −5 | 2 | 0 | — | −8 | −11 |
| Ni | −22 | 0 | −7 | 2 | −8 | — | −35 |
| Ti | −60 | −28 | −7 | −17 | −11 | −35 | — |
Table 4
Calculated parameters of the AlCoCrFeMnNiTi based HESAs.
| HESA | VEC (e/a) | δ (%) | ΔS mix (J/K mol) | ΔH mix (kJ/mol) | Ω |
|---|---|---|---|---|---|
| Al15Co9Cr16Fe20Mn4Ni33Ti3 | 7.985 | 6.79 | 13.78394 | −10.898 | 2.222 |
| Al15Co4Cr16Fe20Mn4Ni38Ti3 | 8.041 | 6.79 | 12.97311 | −11.183 | 2.035 |
| Al20Co4Cr16Fe20Mn4Ni33Ti3 | 7.791 | 6.77 | 13.47905 | −12.521 | 1.866 |
| Al20Co9Cr16Fe15Mn4Ni33Ti3 | 7.850 | 6.74 | 13.94583 | −12.765 | 1.892 |
| Al20Co9Cr11Fe20Mn4Ni33Ti3 | 7.954 | 6.74 | 13.80207 | −12.338 | 1.917 |
| Al24Co6Cr11Fe23Mn3Ni30Ti3 | 7.747 | 6.70 | 13.64152 | −13.223 | 1.753 |
| Al25Co5Cr10Fe25Mn3Ni27Ti5 | 7.575 | 6.67 | 13.86842 | −15.053 | 1.561 |

Figure 1
HESA production by PIM method.

Figure 2
Aging heat treatment by using sliding-flange tube furnace.

Figure 3
Photograph of injected specimens with varied metal contents (left), photograph of sintered specimen (right).

Figure 4
XRD patterns of the elemental powders and sintered HESA.

Figure 5
XRD patterns of the elemental powders and sintered HESA.

Figure 6
(a) SEM of as-sintered specimen, (b) SEM of solution treated specimen, (c) SEM of aged specimen, (d) EDS of aged specimen.

Figure 7
Optic microscope picture of the aged specimen.

Figure 8
Effect of heat treatment (left), and composition on the Tafel curves (right).

Figure 9
EIS test results of the HESA (left), electrical circuit model (right).

Figure 10
Effect of heat treatment (left), and composition on the Young’s modulus of the specimen (right).

Figure 11
Effect of heat treatment (left), and composition on the wear of the specimens (right).

Figure 12
Effect of heat treatment (left), and composition on the conductivity of the specimens (right).
Table 5
Strength values of the HESA.
| Alloy | Tensile strength (MPa) | |
|---|---|---|
| (1) | Al15Co9Cr16Fe20Mn4Ni33Ti3 | 765 |
| (2) | Al15Co4Cr16Fe20Mn4Ni38Ti3 | 742 |
| (3) | Al20Co4Cr16Fe20Mn4Ni33Ti3 | 680 |
| (4) | Al20Co9Cr16Fe15Mn4Ni33Ti3 | 685 |
| (5) | Al20Co9Cr11Fe20Mn4Ni33Ti3 | 690 |
| (6) | Al24Co6Cr11Fe23Mn3Ni30Ti3 | 690 |
| (7) | Al25Co5Cr10Fe25Mn3Ni27Ti5 | 699 |
| Reference | Inconel 718 (NiCr19Fe19Nb5Mo3) | 1,050 |

Figure 13
Unit cell (left), and superlattice (right).

Figure 14
Elastic constants of the high entropy alloys.

Figure 15
Young’s (E), shear (G) and bulk (B) modulus values of the alloys.

Figure 16
Poisson’s ratio and G/B ratio values of the alloys.

Figure 17
Energy values of the alloys at Fermi level.

Figure 18
Effect of heat treatment (left), and composition on the DSC curves of the specimens (right).

Figure 19
Oxidation results of the specimens at different durations.
Table 6
Mean cost and density values of the HESA.
| Alloy | Cost (US$/tonne) | Density (g/cm3) | |
|---|---|---|---|
| (1) | Al15Co9Cr16Fe20Mn4Ni33Ti3 | 12,003 | 7.29 |
| (2) | Al15Co4Cr16Fe20Mn4Ni38Ti3 | 10,729 | 7.29 |
| (3) | Al20Co4Cr16Fe20Mn4Ni33Ti3 | 9,957 | 6.98 |
| (4) | Al20Co9Cr16Fe15Mn4Ni33Ti3 | 12,110 | 7.04 |
| (5) | Al20Co9Cr11Fe20Mn4Ni33Ti3 | 11,773 | 7.07 |
| (6) | Al24Co6Cr11Fe23Mn3Ni30Ti3 | 10,027 | 6.80 |
| (7) | Al25Co5Cr10Fe25Mn3Ni27Ti5 | 9,170 | 6.65 |
| Reference | Inconel 718 (NiCr19Fe19Nb5Mo3) | 17,617 | 8.67 |