Constitutive Modeling with Critical Twinning Stress in CoCrFeMnNi High Entropy Alloy at Cryogenic Temperature and Room Temperature

Abstract

Constitutive modeling of CoCrFeMnNi high-entropy alloy (HEA) at cryogenic temperature (77 K) and room temperature (293 K) has been investigated. The effect of temperature on deformation behavior such as twinning, forest hardening, and back stress hardening has been established. The enhanced ductility and strength of CoCrFeMnNi HEA at 77 K are due the combination of sub-grain structure, twinning, and dislocations. This phenomenon is explained in terms of quantitative values of twin volume fraction, inter-twin spacing, and dislocation density. The isotropic kinematic constitutive model is constructed with a critical twinning stress parameter to obtain the criteria for twinning initiation. The developed finite element model simulation results at 77 K and 293 K are in good agreement with the experimental data. The model displays a smooth increase in the twin volume fraction until fracture point (maximum twin fraction region). Also, different modeling parameters are obtained for each temperature to account for the changing deformation behavior.