Dynamic tensile behavior of Al0.1CoCrFeNi high entropy alloy: Experiments, microstructure and modeling over a wide range of strain rates and temperatures

Abstract

High entropy alloys (HEAs) are considered as new metallic materials with great application prospects due to their excellent mechanical properties. Massive experimental studies have revealed simultaneous strength-ductility enhancements in face-centered-cubic (FCC) HEAs resulting from the plasticity mechanisms transition under much harsher conditions. However, it still lacks quantitative understanding of such extraordinary mechanical behaviors. Aiming at precisely comprehending and describing the mechanical behaviors of FCC HEAs, a physical mechanism-based constitutive model is quite desirable to be established. As such, we first systematically investigated the uniaxial tension behavior of Al0.1CoCrFeNi HEA over wide strain rate (10−3-7 × 103s−1) and temperature (77–298K) ranges. Subsequent microstructural analyses indicated that its plasticity was dominated by dislocation slip at 298K or during small strain, while deformation twins acted as an additional plasticity mechanism with an increase of flow stress at higher strain rates or cryogenic temperatures. Moreover, combining theoretical calculations and experimental verification we further determined the critical twinning stress for this HEA. On basis of these experimental analyses, some specific models were employed to quantify the evolution of dislocation density or twin volume fraction during the plastic deformation. Finally, a physical-based constitutive model was developed to accurately describe the strain rate and/or temperature-dependent behaviors of this typical FCC HEA. This work not only helps quantitatively understand effects of various micro-mechanisms on the mechanical behaviors, but also provides the numerical simulation foundation for their future applications.