Effects of V on Microstructure and Properties of Al0.4Co0.5VxFeNi High- Entropy Alloys: First-Principles Study

The first density functional theory and virtual crystal approximation (VCA) method were used to establish the crystal structure model in order to calculate the structural properties, elastic properties and heat of energy of high entropy alloy Al0.4Co0.5VxFeNi. According to the minimum energy principle, the optimal K-point value of Al0.4Co0.5VxFeNi high entropy alloy is 12x12x12, and the cutoff energy is 1000 eV. The results show that fcc+bcc structure can be formed by Al0.4Co0.5VxFeNi alloy, and the mechanical stability of fcc is obviously better than that of bcc. When V content increases from 0.2 to 0.8, bcc lattice constant decreases by 4% and fcc lattice constant decreases by 6%. The bulk modulus and shear modulus of Al0.4Co0.5VxFeNi alloy decrease with the increase in V content. When the content of element V is 0.8, the Poisson's ratio of bcc structure increases abnormally, which further indicates that with the increase in element V content, the plastic deformation capacity of materials decreases and the brittleness of materials increases. The experimental results show that Al0.4Co0.5VxFeNi alloy is composed of fcc and bcc, and its microstructure is two-phase. When the content of element V increases from 0.2 to 0.8, the elongation decreases by similar to 85%. The experimental result is the same as that calculated by the first principles.