Effect of Twinning on Shear Localization of Al0.1CoCrFeNi High Entropy Alloy at High Strain Rates: Experiment and Crystal Plasticity Modeling

Abstract

As one of the most important plastic deformation mechanisms of high-entropy alloys, deformation twinning can increase the strength without losing plasticity. Nevertheless, recent studies have shown that high-density twins can form "soft spots" and promote the occurrence of shear localization failure at high strain rates. The extent to which deformation twins contribute to the formation of shear localization remains unclear. In this study, a series of dynamic uniaxial compression experiments have been performed with Al_0.1CoCrFeNi HEAs under different conditions to disclose the dynamic recrystallization mechanism. Corresponding to the dynamic recrystallization and plastic dissipation mechanisms at high strain rates, a dislocation entanglement model has been established in conjunction with deformation twinning and physically based heat dissipation to capture the process of shear localization formation. The dislocation entanglement model has been integrated into the theoretical framework of crystal plasticity to perform finite element simulations of high-strain rate deformations. The results predicted by the crystal plasticity simulations are in good agreement with the experimental data, confirming the rationality of the new constitutive model. Deformation twinning can significantly improve strain hardening ability and resistance to shear localization. Interestingly, when the volume fraction of twins reaches a certain level, the mechanism of twin-assisted continuous dynamic recrystallization is triggered due to the interaction between dislocations and twins, resulting in the formation of many “soft spots” (corresponding to the twin region with high density). Upon further deformation, these “soft spots” continue to evolve and aggregate to eventually form the bands of shear localization. Our results can be used for the microstructure design of dynamic high-performance metals with high strength and plasticity to artificially control shear localization.