Dynamic behavior of CrMnFeCoNi high-entropy alloy in impact tension.

• Both the tensile strength and plasticity of the CrMnFeCoNi high-entropy alloy were enhanced significantly at high strain rates. • High strain rate embrittlement effect of CrMnFeCoNi high-entropy alloy is suppressed. • Cooperation of twins and dislocations is the crucial mechanism for the synchronous enhancement of strength and plasticity in this alloy under dynamic tension. • A thermo-viscoplastic dynamic constitutive model based on dislocation and twin evolution was developed. High-entropy alloys (HEAs), recently emerging alloy materials with numerous excellent performances, may have a wide application prospect in impact engineering. However, previous research regarding the mechanical behavior of HEAs has primarily focused on quasi-static testing, whereas the dynamic mechanical behavior of HEAs at high strain rates remains elusive. In this paper, the unusual simultaneous strength-plasticity enhancement and the inhibition of the high strain rate embrittlement of CrMnFeCoNi HEA in impact tension were revealed via split Hopkinson tensile bar (SHTB) with high-speed photography. Quantitative microstructural analysis indicates that the cooperation of twins and dislocations is the crucial mechanism for the synchronous enhancement of strength-plasticity in this alloy under impact tension. A thermo-viscoplastic constitutive model based on dislocations and twins evolution was developed to describe dynamic mechanical behavior. The high plastic hardening under dynamic tension was revealed to be induced by high dislocation forest hardening and strong resistance of twins to dislocation motion. The excellent combination of dynamic strength-plasticity of CrMnFeCoNi HEA makes it becoming a promising candidate for impact engineering applications. [ABSTRACT FROM AUTHOR]