Deformation and mechanical characteristic of FeCoNiCr alloy using in-situ compression and atomic simulation

In this study, the FeCoNiCr high-entropy alloy (HEA) with (2 0 0) lattice orientations is manufactured via vacuum arc melting (VAM). The mechanical response of FeCoNiCr HEA is measured using dynamic compression, nanoindentation, and scratching tests, both experimentally and through simulation methods. The effect of microstructure on the mechanical properties of compressed FeCoNiCr HEA pillars was further investigated using Molecular dynamics (MD) simulations. The experimental results showed that the FeCoNiCr HEA micropillars under a 50 μN loading exhibit more considerable strain energies and compressive displacements than those under a 10 μN loading. The FeCoNiCr HEA micropillar can withstand a 10 μN cyclic loading without significant damage but develops a clear concave fold at 250 μN loading. The hardness measured by nanoindentation was 5.74 GPa. Moreover, the elastic modulus of FeCoNiCr HEA, measured by nanoindentation and in-situ TEM, was 44.36 and 2.85 GPa, respectively, exhibiting a lower elastic modulus than the (1 1 1) lattice orientations. The H/E values for the experimental and MD simulations are calculated to be 0.13 and 0.14, respectively, demonstrating their similarity. The simulation results show that the elastic modulus, ultimate compressive strength, and dislocation density decrease with increasing the aspect ratio. The dislocation distribution with an aspect ratio of 1.5 increases after overcoming the ultimate compression strength. The stacking faults and shear bands are concentrated at the top side grain of the nanopillar, leading the atoms to slip along the grain boundaries.