Twinning Engineering of High-Entropy Alloys: An Exercise in Process Optimization and Modeling

In a bid to improve the mechanical properties of high-entropy alloys, particularly their strain hardening capability, we adapted the time-proven concept of ‘twinning engineering’, developed in the context of TWIP steels, to this group of materials. The strategy chosen involved a two-step thermomechanical processing that consisted in low-temperature pre-straining and subsequent annealing. This approach was trialled on CoCrFeMnNi as an exemplary high-entropy alloy. The annealing conditions selected ensured that the deformation twins generated under low-temperature deformation were retained, whilst the dislocation density was recovered. The viability of this strategy was convincingly confirmed for room temperature deformation of the alloy. A constitutive model accounting for the effect of the pre-straining induced deformation twins was proposed. It was shown to provide a reliable description of the low-temperature and room-temperature deformation of CoCrFeMnNi.