Anomalous High-Temperature Strengthening of an Al <sub>0.5</sub>CoCrCuFeNi Dual-Phase High-Entropy Alloy

Abstract

Mechanical response of an Al0.5CoCrCuFeNi high-entropy alloy 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 anomalous 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 deformation structure reveal that reveal that plastic deformation is carried primarily by dislocation at room temperature, but changes to deformation twinning at temperatures higher than 873 K. At temperature higher than 1073 K, a mix of dislocations and deformation twins is observed. These findings suggest that the yield strength anomaly is strongly related to the phase stability of high-entropy alloys at high deformation temperatures.