Molecular dynamics study of microscopic deformation mechanism and tensile properties in Al_xCoCrFeNi amorphous high-entropy alloys

Molecular dynamic (MD) simulations have been performed to explore the microscopic deformation mechanism and tensile properties of Al_xCoCrFeNi amorphous high-entropy alloys (HEAs) during uniaxial tension. The effects of Al concentration, strain rate and temperature have been taken into account. Three amorphous HEAs with different aluminum concentrations were prepared by rapidly cooling from a high temperature of 3000 K at a cooling rate of 20 K/ps. The results of radial distribution function (RDF) and common neighbor analysis (CNA) show that the prepared amorphous HEAs do not contain crystalline structure. The uniaxial tensile results show that the increase in temperature impairs the tensile properties of all amorphous HEAs over the span of 300–1200 K, including Young's modulus, yield stress and yield strain. Especially at 1200 K, the intense thermal motion of the atoms makes them easier to migrate, which severely weakens the mechanical properties of amorphous HEAs. The atomic shear strain increases with increasing temperature and is uniformly distributed. In the range of the aluminum molar ratio of 1.0–3.0, the aluminum concentration has little influence on the Young's modulus and yield stress of the amorphous HEAs. Moreover, the increase in strain rate contributes to the increase in tensile properties of all amorphous HEAs with different aluminum concentrations, but it has no significant influence on the Young's modulus in the strain rate range of 10⁸-10¹⁰/s.