Effects of heat treatment on the properties of arc melted AlCuFeNiSi_0.4 and AlCuFeNiTi_0.2 high entropy alloys for engineering applications

¹ * Tshwane University of Technology, Department of Chemical, Metallurgical and Materials Engineering, 0001, South Africa
² Tshwane University of Technology, Department of Chemical, Metallurgical and Materials Engineering, 0001, South Africa
³ Tshwane University of Technology, Department of Chemical, Metallurgical and Materials Engineering, 0001, South Africa
⁴ National Laser Centre, Council for Scientific and Industrial Research, Meiring Naudé Road, Brummeria, Pretoria 0185, South Africa
⁵ Center for Energy and Electric power, Electrical Engineering, Faculty of Engineering and Built Environment, Tshwane University of Technology, Pretoria, South Africa
⁶ Tshwane University of Technology, Department of Chemical, Metallurgical and Materials Engineering, 0001, South Africa
⁷ Tshwane University of Technology, Department of Chemical, Metallurgical and Materials Engineering, 0001, South Africa

Abstract

In this study, AlCuFeNiSi_0.4 and AlCuFeNiTi_0.2 high entropy alloys (HEAs) were synthesized using arc melting. The as-cast alloys were heat treated at 750 °C for 4hrs then quenched in water and oil and aged for 6hrs to examine the influence of the quenching media (water and oil) on the microstructural, nanomechanical, corrosion and wear characteristics of the alloys. The XRD results revealed that both alloys had BCC phase and FCC phase structures, where Ti and Al were the BCC stabilizers and Cu and Ni acted as FCC stabilizers. The excellent combination of hardness and elastic modulus of both alloys quenched in water shows that ageing can improve the properties of the alloys. The alloys quenched in water after ageing offered improved properties compared to those quenched in oil for both alloys. The wear resistance was higher in AlCuFeNiSi_0.4 than inAlCuFeNiTi_0.2 attributed to the strengthening mechanism of the alloy. Electrochemical tests also showed that the AlCuFeNiSi_0.4 alloy composition was more corrosion resistant and easier to passivate in 3.5% NaCl. The combined action of the elements in the HEA composition produced surface oxide layers that were more stable and resistant to corrosion. Hence, the heated treated Si_0.4 HEA derivative has the potential to be used as materials in wider corrosive environments in the energy industry.