Creep-Resistant Cr-Mn-Fe-Co-Ni High-Entropy Alloys Having a Single FCC Phase

High-entropy alloys (HEAs) have shown great potential as a structural material through various studies. Due to the core effects of HEA, it was expected that HEA would have excellent high-temperature properties, particularly good creep properties. However, the creep test result at temperatures of 650°C and 700°C for CrMnFeCoNi HEA was not as good as expected. This is because CrMnFeCoNi HEA forms a SIGMA phase at the temperature in the creep test, and therefore, the creep property degradation due to the SIGMA phase is more pronounced than the high entropy effect. In other words, it can be seen that phase stability at the test temperature is an important factor in creep properties.<br/>In this study, non-equiatomic CrMnFeCoNi HEAs with phase stability at 700 °C were selected through thermodynamic calculations, and the effect on creep strength was checked by using the alloy’s melting point and solid solution strengthening as variables. The melting point was predicted by the thermodynamic equilibrium phase diagram calculation, and the solid solution strengthening was predicted by the electronegativity difference. The effectiveness was evaluated on the melting point and solid solution strengthening of the selected alloys, and the degree of creep strength improvement due to phase stability and the degree of melting point and solid solution strengthening on creep strength were quantitatively evaluated through the creep test. Based on this result, an alloy with strong creep strength in Cr-Mn-Fe-Co-Ni HEA can be proposed.