Effect of Particles on the Mechanical Behaviour of CoCrFeNiAl0.3 High-Entropy Alloy Single Crystals

The effect of gamma'-phase particles on the mechanical behaviour was studied in single crystals of the fcc CoCrFeNiAl0.3 (at %) high-entropy alloy (HEA) under tensile strain. It was shown that ageing of the CoCrFeNiAl0.3 HEA single crystals at a temperature of 823 K for 150 hours and at 893 K for 50 hours, results in the precipitation of gamma'-phase particles of size d < 5 nm, with L1(2)-type ordering. In the [<(1)over bar>11]-oriented crystals, precipitation of gamma'-phase particles leads to an increase in critical shear stresses tau(cr) by 25-30 MPa in the temperature range T = 77-873 K, a decrease in the strain hardening coefficient Theta = d sigma/d epsilon and an increase in plasticity of 11-14% relative to the initial crystals without particles. The decrease in Theta = d sigma/d epsilon and the increase in plasticity are associated with the influence of the gamma'-phase particles on the localization of the deformation, predominantly in one system.