Molecular dynamics simulation of size dependent plastic deformation mechanism of CoCrFeNiMn crystalline/amorphous dual-phase high-entropy alloys*

Recently proposed crystalline/amorphous dual-phase high-entropy alloy is an effective strategy to obtain high-entropy, high-strength and high-toughness alloys. And the relative plastic deformation mechanism is dependent on the size of component phases. The effect of component phase size on the plastic deformation mechanism of CoCrFeNiMn crystalline/amorphous dual-phase high-entropy alloy is investigated by molecular dynamics simulation. The results indicate that the size of amorphous phase has a significant effect on the mechanical behavior and plastic deformation mechanism of high entropy alloy. For the sample with small thickness of amorphous phase, the plastic deformation is dominated by dislocation slip and phase transformation of face-centered-cubic structure to hexagonal-close-packed structure. Especially, the deformation twins and Lomer-Cottrell locks are observed in the sample with amorphous layer spacing of 1 nm. When the thickness of the amorphous layer is moderate, the plastic deformation of the dual-phase high-entropy alloy is realized mainly through the dislocation slip, phase transformation of face-centered-cubic structure to hexagonalclose-packed structure in crystalline part and shear band multiplication in amorphous part. If the amorphous layer spacing is larger, the plastic deformation of the high-entropy alloy is dominated by the formation of uniform shear bands in the amorphous phase. In addition, the amorphous phase in the dual-phase high-entropy alloy structure can stabilize the crystalline grains. The results of this study can provide a guidance for designing and preparing high entropy alloy with high performance.