The effect of alloying on the mechanical properties of single crystals of high-entropy alloys

The mechanical properties of the (CoCrFeNi)93Al7 and (CoCrFeNi)94Al4Ti2 (at %) high-entropy alloys were studied in the single-phase state along [001]- and [111]-orientation under tensile strain. It was established that initial yield behavior along these orientations is governed by a dislocation slip mechanism and the critical resolved shear stresses for slip are independent of crystal orientation within a wide temperature range of 77–973 K. The strain hardening coefficient Θ = dσ/dε and plasticity depend on the crystal orientation. It has been found that in the (CoCrFeNi)94Al4Ti2 high-entropy alloy single crystals, the dependence of Θ = dσ/dε and plasticity on the crystal orientation are due to the influence of alloying with Ti atoms on the strain localization and the value of the stacking fault energy. The maximum Θ = dσ/dε of 1730–2320 MPa and the maximum plasticity of 40–48% were found in [111] - and [001]-oriented crystals of the (CoCrFeNi)94Al4Ti2 high-entropy alloy, respectively, within the temperature range of 77–296 K.