Slip and Twinning in the [\( \overline{\mathbf{1}} \)49]-Oriented Single Crystals of a High-Entropy Alloy

Abstract

Using [\( \overline{1} \)49] - oriented single crystals of an FCC Fe₂₀Ni₂₀Mn₂₀Cr₂₀Co₂₀ (at.%) high-entropy alloy subjected to tensile deformation, the temperature dependence of critical resolved shear stresses τ_cr(T) and the deformation mechanism of slip and twinning are investigated in the early stages of deformation at ε ≤ 5% within the temperature interval T = 77–573 K. It is shown that τ_cr increases with decreasing the testing temperature and the τ_cr(T) temperature dependence is controlled by the slip of perfect dislocations a/2<110>. The early deformation stages ε ≤ 5% are associated with the development of planar slip by pileups of perfect dislocations a/2<110>, stacking faults and mechanical twins, which is observed in the temperature interval from 77 to 423 K. A comparison of the temperature dependence τ_cr(T) and the development of mechanical twinning is performed between the [\( \overline{1} \)49] -oriented single crystals of the Fe₂₀Ni₂₀Mn₂₀Cr₂₀Co₂₀ high-entropy alloy, the single crystals of the austenitic stainless steel, Fe – 18% Cr – 12% Ni – 2Mo (wt.%) without nitrogen atoms (Steel 316) and Hadfield steel, Fe – 13% Mn – (1–1.3)% C (wt.%).