Deformation mechanisms of TRIP–TWIP medium-entropy alloys via molecular dynamics simulations

Medium/high-entropy alloys (MEAs/HEAs) have become one of the primary research highlights in the material field due to their superior microstructure and mechanical properties. By means of molecular dynamic (MD) simulation, the tensile behavior of polycrystalline Fe_80-xMn_xCo₁₀Cr₁₀ (x=20, 30, 40, 50) MEAs was investigated under uniaxial stretching. The effects of various strain rates (1 × 10⁸ s⁻¹, 1 × 10⁹ s⁻¹, 1 × 10¹⁰ s⁻¹) and deformation temperatures (77 K, 300 K, 600 K, 800 K) on tensile properties and deformation mechanisms of Fe_80-xMn_xCo₁₀Cr₁₀ (x=30, 40) MEAs were explored, and the interaction of dislocation defects with stacking fault including intrinsic and extrinsic stacking fault (ISF/ESF) as well as the evolution of dislocation and cluster defects were further discussed. Moreover, the relationship between grain size and flow stress of polycrystalline Fe₅₀Mn₃₀Co₁₀Cr₁₀ MEAs was discussed. Results indicated that Fe₄₀Mn₄₀Co₁₀Cr₁₀ and Fe₅₀Mn₃₀Co₁₀Cr₁₀ alloys exhibited higher yield stresses and Young's moduli. The yield stresses, Young's moduli and average flow stresses of Fe₄₀Mn₄₀Co₁₀Cr₁₀ and Fe₅₀Mn₃₀Co₁₀Cr₁₀ MEAs increased with an increase in strain rates from 1 × 10⁸ to 1 × 10¹⁰ s⁻¹. Besides, the deformation temperature produced a considerable influence on its mechanical properties. The phase transformation, grain boundary glide, dislocation slip and twinning formation together accounted for the plastic deformation behavior of Fe_80-xMn_xCo₁₀Cr₁₀ MEAs under uniaxial stretching on an atomic scale.