Wear and oxidation resistances of AlCrFeNiTi-based high entropy alloys

• Published in: Intermetallics 2018-10, Vol.101, p.144-151
• Main Authors: Nong, Zhi-Sheng, Lei, Yu-Nong, Zhu, Jing-Chuan
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum oxide; Cobalt base alloys; Dendritic structure; Electric arc melting; First principles; High entropy alloy; High entropy alloys; Microstructure; Oxidation; Oxidation behavior; Oxidation rate; Oxidation resistance; Reaction kinetics; Titanium dioxide; Wear behavior; Wear mechanisms; Wear resistance
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2018.07.017

Based on the AlCoCrFeNi high entropy alloy, by replacing Co with Ti, new cobalt-free high entropy alloys AlCrFeNiTi and its derivative AlCrFeNiTiMn0.5 were designed and prepared by arc melting, and as-cast microstructures, wear and oxidation behaviors were investigated. The results show that two alloys are all composed of an ordered body centered cubic (BCC) and a disordered BCC phases, and typical dendritic structures including dendritic (DR), interdentritic (ID) and ‘eutectic phase’ areas were observed, implying the feature of near-eutectic high entropy alloys for AlCrFeNiTi and AlCrFeNiTiMn0.5. Adhesive wear mechanisms for these two alloys are indentified mainly as delamination wear, while oxidative wear is gradually dominated in AlCrFeNiTi. The wear resistance declines with addition of a half mole of Mn into AlCrFeNiTi due to rising wear coefficients of alloys. The oxidation kinetics of AlCrFeNiTi and AlCrFeNiTiMn0.5 alloys oxidized at 900 °C meet the exponential rate law, and the oxidation rate of AlCrFeNiTi is lower than that of AlCrFeNiTiMn0.5, suggesting a better oxidation resistance. Comparing with AlCrFeNiTi, a new Mn2O3 subscale was formed between the outer TiO2 scale and the underlying Al2O3 subscale on surfaces of AlCrFeNiTiMn0.5, which is consistent with theoretical analysis from the view of forming ability level by the first principles calculations. [Display omitted] •Wear mechanism of AlCrFeNiTi presents pronounced feature of oxidative wear.•Oxidation kinetics of alloys oxidized at 900 °C meet the exponential rate law.•There is an outer TiO2 scale and an underlying Al2O3 subscale observed on surfaces.