First-Principles Calculation Of Properties Of FeAlNiCrMn System High-Entropy Alloys

High-entropy alloys usually exist in a single solid solution structure of body-centered cubic,face-centered cubic or close-packed hexagonal phase,which makes high-entropy alloys have excellent mechanical,thermodynamic,physical and magnetic properties compared with other alloys.It can be widely used in many fields such as structural materials,functional materials and coating materials.There is a close relationship between these excellent properties of high-entropy alloys and their composition.Even for the same element system,slight differences in the content of each element can lead to completely different properties of high entropy alloys.In order to explore the relationship between the composition and the properties of FeAlNiCrMn-based high-entropy alloys,the effects of pressure,temperature,element Al and Ni content on the phase formation,structural stability,mechanical properties and thermodynamic properties of FeAlNiCrMn high entropy alloys were analyzed by first-principles analysis.The main research contents are as follows:(1)The crystal structure types of Fe Al_xNi CrMn were analyzed by the solid solution characteristic parameters and the first principles,and the influence of Al content on the crystal structure and related mechanical properties of Fe Al_xNi CrMn was investigated.From the aspects of calculation of solid solution characteristic parameters,energy analysis,and material mechanical stability criterion,it is found that Fe Al_xNi CrMn alloy mainly exists in a single face-centered cubic solid solution structure.It has shown that the elastic modulus of FeAlNi_xCrMn tend to increase first and then decrease with the addition of Ni content.The 0.5 mol Al is not only the critical value of the alloy from toughness to brittleness,but also the critical value of the alloy from anisotropy to isotropy.(2)The effects of pressure on the structure,elastic constants,ductile-brittleness and elastic anisotropy of FeAlNiCrMn high entropy alloy were studied by first principles.By calculating the lattice constant,binding energy and density of states of the alloy with the pressure-inducing,the influence of pressure on the structural stability of the alloy was investigated.The toughness and brittleness of the alloy in the pressure range of(0-100 GPa)are studied by B/G ratio,Poisson’sνand Cauchy pressure.As the pressure increases,the modulus,melting point and hardness of the alloy will increase gradually.Finally,the transition process of the alloy from anisotropy to isotropy with the increase of pressure had been analyzed in detailed.(3)The effects of Ni content on the structure,elastic modulus,ductility and brittleness and thermodynamic properties of FeAlNi_xCrMn high-entropy alloys(x=0,0.25,0.5 and 0.75)were systematically studied.The analysis of the total density of states and Debye temperature of FeAlNi_xCrMn shows that the structural stability of the alloy first increased and then decreased with the increasing of Ni content.According to the elastic constant,the influence of Ni content on the elastic modulus,toughness,brittleness,and elastic anisotropy of FeAlNi_xCrMn was analyzed.Finally,it is found that the thermal expansion coefficient and heat capacity show shows a strong temperature dependence only at low temperature.Furthermore,the dependence of temperature on the Grüneisen parameter is just the opposite of that of the Debye temperature.This study provides a reference and theoretical guidance for the design and performance prediction of HEAs components.