Structures and phase transformations in the Mn-Ni system near equiatomic concentration

Abstract

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 Fe80-xMnxCo10Cr10 (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 Fe80-xMnxCo10Cr10 (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 Fe80-xMnxCo10Cr10 MEAs under uniaxial stretching on an atomic scale.