Microstructural stability and high temperature isothermal oxidation behavior studies of high entropy alloy Al0.5CoCrFeNi
Akhmad Ardian Korda, Dimas Prayoga Trisna Muhammad, Fadhli Muhammad, Tria Laksana Achmad, Budi Prawara, Djoko Hadi Prajitno, Bagus Hayatul Jihad, Muhamad Hananuputra Setianto, Eddy Agus Basuki
Abstract
• The activation energy for the oxidation of Al 0.5 CoCrFeNi HEA is 195.7 kJ/mol. • The oxidation kinetics of the alloy follow a parabolic law. • The oxidation mechanism of the alloy is similar to the MCrAl alloy ( M =Fe/NiAl). • Shrinkage and spheroidization of the B2 phase reduce the hardness of the alloy. High entropy alloys of Al-Co-Cr-Fe-Ni have been developed for high-temperature applications due to their high melting points, superior microstructural stability, and the ability to form a protective oxide scale on the surface. This paper presents the results of research on the isothermal oxidation of the Al0.5CoCrFeNi alloy at temperatures of 900, 1000, and 1100 °C for 2, 16, and 40 h. A series of experiments were conducted to investigate the microstructural stability and oxidation behavior of the alloy. During oxidation, the alloy forms various oxides, including Fe 2 O 3 , Co 3 O 4 , spinel of Cr 2 NiO 4 , Cr 2 O 3 , and Al 2 O 3 , as well as AlN. It was found that the oxidation behavior of the alloy is closely related to that of the general medium entropy M -Cr-Al system ( M =Fe, Ni, Al). The oxidation kinetics of the alloy follow a parabolic rate law with an activation energy of 195.7 kJ/mol. The instability of the microstructure of the alloy is indicated by the spheroidization of the B2 phase due to thermal stress occurring at the A1/B2 phase interface, in addition to a decrease in its volume fraction. These microstructural changes result in a decrease in the alloy's hardness.