Twinning and critical resolved shear stresses for twinning in single crystals of high-entropy alloys

Effect of the crystal orientation, test temperature and value of stacking fault energy γ0 on the twinning and tw critical resolved shear stresses for twinning τcrtw was studied in single crystals of CoCrFeNiMn, Fe40Mn40Co10Cr10 and CoCrFeNiAl0.3 (at. %) high-entropy alloys (HEAs). It was shown that in the [1̅11] -oriented single crystals of CoCrFeNiMn, Fe40Mn40Co10Cr10 HEAs with low γ0 = 0.02–0.025 J/m2 twinning with the formation of intrinsic stacking fault (SF) develops after strain of 5–10% at 296 K. At 77 K in these alloys twinning develops not only with the formation of an intrinsic SF, but also with the formation of an extrinsic SF in the [001]-oriented single crystals after strain of 5%. With an increase in γ0 = 0.05 J/m2 in the CoCrFeNiAl0.3 HEA twinning takes place only in the [1̅11]-oriented single tw crystals after strain of 15% at 77 K. The critical resolved shear stresses for twinning τcrtw are dependent on the crystal orientation, the test temperature and the value of γ0. The minimum values of τcr [1̅11] -oriented single crystals of CoCrFeNiMn, Fe40Mn40Co10Cr10 HEAs at 296 K.