Microstructure and mechanical property correlation in Silicon-doped equiatomic FeMnNi MEA: Experiments and simulation

Abstract

The effect of minor addition of Si to the FCC equiatomic FeMnNi medium entropy alloy (MEA) has been systematically investigated using experiments and DFT calculations. We report here a detailed investigation on 0.5 – 2 at% Si addition in FeMnNi MEA by using SEM, EBSD and TEM with uniaxial tensile tests and strain rate jump tests, to establish structural-property correlation. The experimental investigation reveals that the MEA with 2 at% Si exhibits remarkably improved combination of strength (YS = 249 MPa, UTS = 528 MPa) and ductility (70%), with (111) dislocation glide being the predominant mode of plastic deformation. A correlation with regard to lattice distortion and microstrain, in the context of dislocation plasticity and microband formation is made with DFT modelling. The SFE is found to increase due to Si addition and local lattice distortion, therefore contributing significantly to the solid solution hardening.