Effects of processing route on phase evolution and mechanical properties of CoCrCuFeNiSix high entropy alloys

Oxidation study of CoCrCuFeNiSix high entropy alloys

“…Therefore, F2 is preferentially oxidizing as CuO was the only oxide peak in figure 2. Additionally, with increasing Si content, the amount of F2 phase fraction decreases, as discussed in our previous work [21]. Hence, the decrease in the phase fraction of oxidation prone phase (F2) leads to lesser oxidation.…”

“…As, Cu has high positive mixing enthalpy with other constituent elements in the alloy, thus, Cu tends to segregate at the grain boundaries which led the formation of F2 phase. Whereas, the F1 phase could be the Ni-Fe-Co FCC phase with some amount of Cr and Cu as Ni is an FCC austenite stabilizer in Ni-containing steels [21]. After oxidation, the formation of CuO along with existing FCC solid solutions and σ phase was observed in all the HEA samples.…”

“…In the heat treatment cycle, the initial heating rate was maintained at 100°C min −1 from 570°C to 800°C. Later it was decreased to 50°C min −1 until the temperature reached 1000°C [21]. Isothermal oxidation temperatures were chosen in the range of 06-08 T m of the lowest melting element (Cu) of the alloys.…”

“…The decrease in oxidation after the addition of Si (up to 6%) can be explained by the following: 1) During spark plasma sintering process F1, F2 and σ phases were formed, out of which F2 phase contains maximum Cu [21]. Therefore, F2 is preferentially oxidizing as CuO was the only oxide peak in figure 2.…”

“…Among all the HEAs, Co-Cr-Cu-Fe-Ni-Si x based alloy is one of the vital alloys which exhibits the most superior properties such as wear resistance, microhardness, oxidation resistance, etc. Recently, in our previous work, [21] Co-Cr-Cu-Fe-Ni-Si x HEAs were synthesized via vacuum arc melting and spark plasma sintering, and the study reported that increase in Si content leads to better microhardness and wear resistance for both the cases those are processed differently. Also, Co-Cr-Cu-Fe-Ni-Si x HEA prepared by spark plasma sintering process provided superior physical properties compared to the vacuum arc melting process due to the existence of sigma phases.…”