Al-Co-Cr-Fe-Ni-Ti High Entropy Alloys: A Review of Microstructural and Mechanical Properties at Elevated Temperatures,Journal of Alloys and Compounds

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Al-Co-Cr-Fe-Ni-Ti High Entropy Alloys: A Review of Microstructural and Mechanical Properties at Elevated Temperatures
Journal of Alloys and Compounds ( IF 5.8 ) Pub Date : 2024-12-19 , DOI: 10.1016/j.jallcom.2024.178216
Arash Ghasemi, Ali Reza Eivani, Seyed Mahdi Abbasi, Hamid Reza Jafarian, Manojit Ghosh, Seyed Hashem Mousavi Anijdan

An overview of the microstructural and mechanical properties of Al-Co-Cr-Fe-Ni-Ti high entropy alloys (HEAs) at high temperatures is presented. With exceptional properties at high temperature and high dissolution temperature of the L1₂ phase (

γ'

), HEAs exhibit excellent wear resistance, thermal stability, high hardness and strength, superior corrosion resistance, and remarkable electrical and magnetic properties, which position them as ideal candidates to replace traditional superalloys. Refractory high entropy alloys (RHEAs) offer excellent mechanical properties at high temperatures. However, reducing price and weight without sacrificing mechanical properties is an essential requirement for broadening the applications of RHEAs. Among varieties of HEA systems, Al-Co-Cr-Fe-Ni-Ti has proven to be an optimum choice for high-temperature applications considering price and weight. The development of strength in this alloy system primarily depends on optimizing its chemical components regarding various phases and their phase fractions. An increase in Al+Ti content increases the formation of Ni₃(Ti, Al) or

γ'

and, consequently, the strength of the alloy. Conversely, Cr and Fe must be carefully balanced to prevent the formation of brittle phases. Exceeding the limiting values of Co, Cr, and Fe can lead to the formation of brittle phases like

Heusler, β, η,

and

σ

. In order to achieve better mechanical properties, the optimized [Al+Ti]-content should be around 15-16 at.%. At elevated temperatures, valence electron concentration (VEC) closely aligns with the corresponding microstructure, suggesting that VEC can be utilized to predict the microstructure. Superior oxidation resistance at elevated temperatures (higher than that of Ni-based superalloys) promotes Al-Co-Cr-Fe-Ni-Ti HEAs for high-temperature applications.

更新日期：2024-12-20

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