Dynamic compression behavior of CoCrFeMnNi high-entropy alloy fabricated by direct energy deposition additive manufacturing

Abstract

High-entropy alloys (HEAs) have attracted significant interest in recent years because of their unique physical properties, which make them suitable for usage in extreme environments. The fabrication of HEAs using metal additive manufacturing (MAM) has shown potential for improving their performance. This study investigates the mechanical properties of CoCrFeMnNi HEA manufactured through direct energy deposition using compression tests conducted at various strain rates ranging from quasi-static to dynamic (10−4 - 4200 s−1). The effect of the strain rate on the mechanical properties was analyzed, and a Johnson-Cook constitutive model was employed to simulate the dynamic compression test using the finite element method. The temperature and strain distributions during high-strain-rate compression were analyzed, reflecting the local temperature rise in the finite element analysis. The comparison of the strain distribution results of the simulation and microstructure after deformation showed that the microstructural behavior was influenced by strain localization, which occurred more prominently at the edge of the material. Because the CoCrFeMnNi HEA had a low stacking fault energy, twin formation was accelerated at high strain rate deformation by easily overcoming the critical twinning stress. The edge region, where strain localization was activated, exhibited a higher twin fraction than the central region (uniform deformation). The partitioned strain in the edge region was absorbed by twin formation, effectively suppressing the formation of the adiabatic shear band. These findings present significant implications for the design and development of MAM-processed HEAs with improved mechanical properties under extreme environments.