Temperature-dependent compression behavior of an Al_0.5CoCrCuFeNi high-entropy alloy

Mechanical response of an Al_0.5CoCrCuFeNi high-entropy alloy (HEA) was investigated through uniaxial compression tests, the 0.2% offset yield strength decreases with increasing temperature up to 773 K. However, at temperatures above 773 K, two yield strength hardening regions peaked at 873 K and 1073 K were observed. Microstructure analyses reveal an enhanced L1₂ ordering with the increase of compression temperatures and the subsequent precipitation of B2 phase at 973 K. Meanwhile, transmission electron microscopy observations of the post-deformation microstructures show that plastic deformation is primarily carried by dislocation at room temperature, and changes to twinning at temperatures higher than 873 K. At deformation temperatures higher than 1073 K, a mixed microstructure of dislocations and deformation twins is observed. These results suggest that the emerging of the yield strength peaks at high temperatures is related to the precipitation of the L1₂ and B2 intermetallic phases and high-temperature deformation influences the phase separation and phase selection of the HEA.