Microstructure and mechanical properties of Al–Co–Cr–Fe–Ni–(Nb–Ti) high entropy alloys

ABSTRACT

The structure and mechanical properties of non-equiatomic Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₄, Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₂Ti₂ and Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Ti₄ high entropy alloys (HEAs) were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness and tensile testing. TEM and XRD analyses revealed the formation of γ''-Ni₃Nb/γ (FCC), double FCC and γ'-Ni₃Al/γ (FCC) structure for as-cast Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₄, Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₂Ti₂ and Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Ti₄ HEAs, respectively. The hardness and yield strength values were found to increase with the addition of Nb while the ductility of alloys increased with the increase in Ti concentration, significantly. The as-cast Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Ti₄ alloy exhibited an excellent combination of ultimate tensile strength of 844 MPa and an elongation of 29.8% due to the coherent phase relation between γ’ precipitates and γ matrix. The fractured surfaces of as-cast Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₄, Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Nb₂Ti₂ and Al₈Co₃₀Cr₁₈Fe₉Ni₃₁Ti₄ HEAs showed typical dimple type ductile fracture under tension test.

KEYWORDS:

• High entropy alloys
• microstructure
• XRD
• TEM
• mechanical properties

Acknowledgements

The authors would like to thank METU Central Laboratory for electron microscopy data collection.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.