Microstructural evolution and tensile property of gradient microstructure CoCrFeMnNi high-entropy alloy induced by pre-torsion

Gradient-structure was obtained in CoCrFeMnNi high-entropy alloys utilizing both the forward pre-torsion and forward-reverse pre-torsion preparation technique. The slope between hardness and r/R is high cor-responding to increase in the pre-torsion angles attributable to the gradient structure after pre-torsion processing. Under 2% tensile strain, the change of dislocation and twin morphology takes place as pre-torsion angle increases, i.e., from discrete dislocations, to dislocation tangles and to dislocation cells, and from single twins to secondary twins. According to tensile test results, yield strength of samples increases but fracture strain linearly decreases with increasing pre-torsion angles as: Yield strength = 905.47 11.67elongation. Yield strength of FRPTed specimens is slightly higher than that of FPTed specimens under the same pre-torsion angles with the maximum increment of 56 MPa. Strength mechanism indicates that the improvement of yield strength of the HEAs is mainly attributed to gradient dislocation and twin strengthening. In addition, a strength predictive model, which takes gradient dis-location and twin strengthening into consideration, is proposed, and predictive yield strength match well with the experimental data of FPTed-and FRPTed-samples.(c) 2023 Elsevier B.V. All rights reserved.