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

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. [Display omitted] •The efficacy of Si as dopant on micromechanism of deformation of FCC ternary FeMnNi MEA is investigated.•The potency of solid solution hardening as a function of Si atoms has been investigated using the Varvenne's model.•Impact of lattice distortion and SFE has been modelled by DFT computations to explain deformation behaviour.•Si addition increases SFE and hence, deformation is predominantly slip–dominated.•Si addition leads to massive increase in the interlayer distortion, causing increased yield strength & strain hardening.