Temperature-dependent mechanical behavior of an Al_0.5Cr_0.9FeNi_2.5V_0.2 high-entropy alloy

High-entropy alloys (HEAs) with a ductile face-centered-cubic matrix and coherent nano-precipitates (L1₂) are promising candidate materials for heat-resistant applications. In the present work, we systematically investigated the mechanical behavior of a wrought L1₂-type-strengthened HEA, Al_0.5Cr_0.9FeNi_2.5V_0.2, at elevated temperatures ranging from 500 to 900 °C. We find that the Al_0.5Cr_0.9FeNi_2.5V_0.2 HEA shows a moderate strength (∼875 MPa) as well as ductility (∼15%) at 500 °C and then a distinct ductile-to-brittle transition at 600 °C due to the brittle body-centered-cubic phase and weak deformation accommodation at grain boundaries (GBs). The further increase in temperatures up to 850 °C caused a decrease in strength but an increase in ductility owing to the occurrence of dynamic restoration. Correspondingly, kernel average misorientation maps of specimens exhibited a strain concentration along GBs and different deformation accommodation abilities under various conditions.