Mechanical properties of the high-entropy alloy Al0.5CoCrCuFeNi in various structural states at temperatures of 0.5–300 K

The mechanical properties and fracture characteristics of the high-entropy alloy Al0.5CoCrCuFeNi are studied in different structural states (cast and after two heat treatments) at temperatures of 0.5–300 K with quasistatic deformation by uniaxial compression and distension. Mechanical resonance spectroscopy is used to measure the temperature variations of the Young modulus in the different structural states. It is found that heat treatment of the samples leads to an increase (by roughly 25%) in the Young modulus, the nominal yield point τ0.2, and the deforming stress. The form of the deformation curves is analyzed. The temperature interval for the transition from smooth to discontinuous plastic flow is determined. For the cast state the differences in τ0.2 under tension and compression are determined, an anomalous temperature dependence of τ0.2 (for temperatures in the 0.5–4.2 K range) is discovered, and thermal activation analysis of the experimental data yields empirical estimates for the parameters of the interactions of dislocations with local barriers. After heat treatment the samples break up into two parts under compression, as opposed to the cast state, where the samples acquire a “barrel” shape during compression. It is found that fracture of the heat treated samples at temperatures of 300–4.2 K has a viscous character.