Special tetrahedral twins in a cryogenically deformed CoCrFeNi high-entropy alloy

A special structure named tetrahedral twin was found in a cold-drawn CoCrFeNi high-entropy alloy. Crystallographic characterization using convergent beam electron diffraction indicated that the three-dimensional (3D) tetrahedral twins were achieved through the intersection of each couple of twin layers in four {111}FCC planes, which was caused by the low stacking fault energy and the special plane strain state during deformation. The calculation results revealed that the tetrahedron-morphological twins could result in significant stress concentration, thereby considerably deteriorating the plasticity of the high-entropy alloy.