Enhanced Oxidation Resistance of Ultrafine-Grain Microstructure AlCoCrFeNi High Entropy Alloy

Abstract

This work investigates the effect of ultrafine-grain microstructure on the oxidation behavior of AlCoCrFeNi high entropy alloy (HEA). The ultrafine-grain microstructure is obtained using stationary friction processing performed at two different rotational speeds, 400 and 1800 rpm, for 5 min duration. Processed samples demonstrate high depth of refinement (DOR) and ultrafine grain size (0.43–1 μm) at high rotational speeds along with significant phase transformations from BCC/B2 to FCC microstructure. Further, surface free energy of the ultrafine-grain microstructure is enhanced up to 35%. Oxidation kinetics of the ultrafine-grained sample is decelerated up to 12–48% in a temperature range of 850–1050 °C for a duration of 100 h. Chromia and alumina were the predominant oxides formed in almost all the samples oxidized at elevated temperature. In addition, spinel Co(Cr,Fe) 2 O 4 /Fe(Co,Cr) 2 O 4 formation is also detected in the unprocessed oxidized samples. Processed samples rich in grain boundaries (GBs) promote internal oxidation to form Al-rich inner oxides. The enhanced oxidation resistance of the processed samples is attributed to the microstructural refinement and homogenization resulting in the formation of protective chromia followed by Al-rich inner oxides.

Reaction with hot air of high entropy alloys strengthened by monocarbides formed from heavy metals: assessment of the oxidation kinetics from the analysis of the chemically changed subsurfaces

“…A series of investigations were already carried about the behavior of HEAs in high temperature oxidation. Among the studied alloys which are the closest to the Cantor composition but which are slightly different, there are Mn-free Al-containing ones (AlCoCrFeNi) [19,20], or some Ni-free ones [21,22], for instance. The oxidation behavior of the equimolar CoNiFeMnCr composition was specifically investigated in laboratory air at temperatures from 500°C to 900°C [23,24], and in synthetic air between 900 and 1100°C [25].…”

Modeling Oxidation of AlCoCrFeNi High-Entropy Alloy Using Stochastic Cellular Automata

“…The oxidation of Cr- and Al-based alloys is particularly interesting due to their good oxidation-resistance capabilities [ 16 ]. Recently, there have been more studies on the oxidation of the AlCoCrFeNi system [ 17 , 18 , 19 ]. As the composition space increases with the introduction of new HEAs, it becomes increasingly challenging to experimentally test them in variable oxidizing environments.…”

Microstructural Evolution and Magnetic and Corrosion Properties of FeCoNiAl0.2Yx High-Entropy Alloys

“…3 The special structure of HEAs with its excellent comprehensive properties, such as high hardness, excellent magnetic properties, outstanding oxidation resistance, superior corrosion resistance, and excellent wear resistance has a broad application prospect. [4][5][6][7][8] Although traditional soft magnetic alloys have excellent magnetic properties, there are some problems such as low strength and poor corrosion resistance. Studies have shown that HEAs are an ideal soft magnetic material with excellent soft magnetic properties and excellent mechanical properties.…”