Impact of Temperature on the Tensile Properties of Hypereutectic High-Entropy Alloys

Eutectic high-entropy alloys (EHEAs) can achieve a balance of high strength and ductility. It has been found that the mechanical properties of hypoeutectic high-entropy alloys are superior to those of EHEAs. In this work, hypereutectic Al1.1CoCrFeNi2.1 alloy was prepared, and the mechanical properties in a wide temperature range were studied. The presence of both soft ordered L12 and hard BCC (B2) phases results in a combination of ductile and brittle fracture modes. The Al1.1CoCrFeNi2.1 hypereutectic high-entropy alloy contains more primary soft L12 phases, which ensure excellent ductility. Moreover, the Orowan by-passing mechanism caused by the B2 precipitates increases in the strength of the alloy for low-temperature tensile tests (−100 °C and 23 ± 2 °C). The −100 °C test exhibits a dimple morphology and demonstrates the highest ultimate tensile strength of 1231 MPa, along with an excellent elongation of 44%. At high tensile temperatures (650 °C, 750 °C, and 850 °C), the dislocation cutting mechanism and dynamic recrystallization increase the plasticity. However, the presence of a large number of cracks near the spherical primary L12 phase significantly reduces the ductility and strength. The results show that the hypereutectic Al1.1CoCrFeNi2.1 exhibits superior plasticity and strength properties at low temperatures. The findings of the article provide a new approach to enhancing the comprehensive mechanical properties of hypereutectic alloys.