Microstructure stability and oxidation behaviour of (FeCoNiMo)90(Al/Cr)10 high-entropy alloys

In recent times, there has been a significant volume of work on Eutectic High Entropy Alloys (EHEAs) owing to their remarkable castability combined with excellent mechanical properties, which aids in clearing obstacles for their technological applications. One of the most common EHEAs, which has been of enormous interest at present, primarily owing to its solidification and tensile behavior, is AlCoCrFeNi2.1. However, to aim for high-temperature applications, oxidation behaviour of material is one of the major aspects that needs to be extensively investigated. To this end, the present work aims to study the phases evolved during oxidation at elevated temperatures as high as 950 and 1000°C in AlCoCrFeNi2.1 using XRD and also to determine the rate law followed for isothermal oxidation of this alloy at 950 and 1000°C, in order to understand the role of Al2O3 phase formed during isothermal oxidation at 950 and 1000°C.

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Synergistic effects of Al and Ti on the oxidation behaviour and mechanical properties of L12-strengthened FeCoCrNi high-entropy alloys

Corrosion Science ◽

10.1016/j.corsci.2021.109365 ◽

2021 ◽

Vol 184 ◽

pp. 109365

Author(s):

Z.Y. Ding ◽

B.X. Cao ◽

J.H. Luan ◽

Z.B. Jiao

Keyword(s):

Mechanical Properties ◽

Synergistic Effects ◽

Oxidation Behaviour ◽

High Entropy Alloys ◽

High Entropy

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The Effect of Ge Addition on the Oxidation of Nb-24Ti-18Si Silicide Based Alloys

Materials ◽

10.3390/ma12193120 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3120 ◽

Cited By ~ 5

Author(s):

Zifu Li ◽

Panos Tsakiropoulos

Keyword(s):

Oxidation Resistance ◽

Refractory Metal ◽

Isothermal Oxidation ◽

Oxidation Behaviour ◽

The Other ◽

High Entropy Alloys ◽

High Entropy ◽

Parabolic Kinetics ◽

Cast Alloys ◽

Oxidation In Air

In this paper, we report research about the isothermal oxidation in air at 800 and 1200 °C for 100 h of the as-cast alloys (at.%) Nb-18Si-5Ge (ZF1), Nb-18Si-10Ge (ZF2), Nb-24Ti-18Si-5Ge (ZF3), Nb-24Ti-18Si-5Cr (ZF4), Nb-24Ti-18Si-5Al (ZF5), Nb-24Ti-18Si-5Al-5Cr-5Ge (ZF6), and Nb-24Ti-18Si-5Al-5Cr-5Ge-5Hf (ZF9), the microstructures of which were reported in previous publications. Only the alloys ZF1, ZF2, and ZF3 suffered from pest oxidation at 800 °C. The Ge addition substantially improved the oxidation resistance of the other alloys both at 800 °C and 1200 °C, which followed parabolic kinetics at 800 °C and in the early stages at 1200 °C and linear kinetics at longer times, where there was spallation of the scales. The Nb2O5 and TiNb2O7 oxides were formed in the scales of the alloys ZF4, ZF5, ZF6, and ZF9 at 800 °C and 1200 °C, the GeO2 was observed in all scales and the SiO2 in the scales of the alloys ZF4 and ZF5, the CrNbO4 in the scales of the alloys ZF4, ZF6, and ZF9 and the AlNbO4 in the scales of the alloys ZF5, ZF6, and ZF9. Diffusion zones were formed below the scale/substrate interface only in the alloys ZF4 and ZF5 where the Nbss and Nb5Si3 were contaminated by oxygen. However, these phases were not contaminated by oxygen in the bulk of the alloys ZF4, ZF5, ZF6, and ZF9. The alloys ZF9 and ZF6 exhibited the best oxidation behaviour at 800 °C and 1200 °C, respectively. The alloys were compared with Nb-silicide based alloys of similar compositions without Ge and Hf additions and the alloy ZF9 with refractory metal High Entropy Alloys. Compared with the former alloys, the addition of Ge reduced the vol % of the Nbss. Compared with the latter alloys, the superior oxidation behaviour of the alloy ZF9 was attributed to its higher and lower values respectively of the parameters δ and VEC.

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