Microstructural evolution mediated creep deformation mechanism for the AlCoCrFeNi2.1 eutectic high-entropy alloy under different testing conditions

Abstract

The AlCoCrFeNi2.1 high-entropy alloys (HEAs) with a unique eutectic microstructure of soft L12 and rigid B2 exhibit outstanding mechanical performance at both ambient and high temperatures. However, their high-temperature creep data are not available, which restricts their industrial application under extreme environments. For this, the current work investigated the effect of microstructural evolution on the creep behavior and deformation mechanism of the AlCoCrFeNi2.1. The creep tests were performed at 700–900 °C with a stress ranging from 0.2 to 0.6 times of the high-temperature yield strength. Detailed microstructural examination and theoretical analysis were conducted to explore the creep mechanism. The results showed that the precipitation behavior was responsible for the accelerated steady creep-strain rate and reduced creep life when performed at 800–900 °C, compared to 700 °C. The creep deformation mechanism and fracture behavior at 800–900 °C were also found to exhibit discrepancy with those at 700 °C, with the aid of calculating the stress exponents, activation energies, Larson-Miller and Orr-Sherby-Dorn parameters. Based on the creep data and microstructural examination conducted, the predominant creep deformation mechanism was uncovered for different testing conditions. The current work performed will be beneficial to understand the high-temperature deformation behavior of the AlCoCrFeNi2.1 EHEAs. The basic data acquired will also offer a guarantee for the application of EHEAs.