First-principles Study Of FeNi_1-xCr_x?0?x?1? Disordered Alloys From Special Quasirandom Structures

As the basis for synthesizing many types of austenitic,ferritic and martensitic steels,ternary Fe-Ni-Cr alloys have attracted the attention of many researchers due to their technical importance.Under some known compositions,this series of alloys can usually exhibit excellent magnetic properties,mechanical properties and corrosion resistance,which makes them often used as structural materials or alternative materials in the aerospace,nuclear and petroleum industries.However,since Fe-Ni-Cr alloy has composition disorder and complex magnetic structure,the research on it so far mainly relies on tedious experimental methods.This greatly limits the research and development of this series of alloys.Therefore,it is of great significance to use a convenient and accurate theoretical method to describe the physical properties of this series of alloys.In this work,the properties of ferromagnetic face-centered cubic and body-centered cubic FeNi_1-xCr_x?x=0,0.125,0.25,0.375,0.5,0.625,0.75,0.875,1?alloys were studied using first-principles calculations based on density functional theory,combined with special quasi-random structures and quasi-harmonic Debye model methods.The main contents are as follows:Firstly,the lattice constant,single atom volume and average magnetic moment of this series of alloys were calculated,and the close relationship between them and the complex magnetic structure was analyzed.Secondly,the electronic properties of this series of alloys were studied,and it was found that with the increase of Cr content,the density of states gradually moved towards a shallower energy level,indicating that the electron bonding ability of the alloy gradually weakened.Next,the formation enthalpy of this series of alloys was calculated,and it was found that only fcc alloys with x?0.25 were relatively easy to synthesize.In addition,the calculation results in this work were found to be in good agreement with the existing theoretical and experimental data,verifying that the special quasi-random structure model has high accuracy in simulating the crystal structure and material properties of FeNi_1-xCr_x alloy.Its first-principles calculation results can provide a theoretical reference for the application and development of this series of alloys.Finally,the elastic modulus,B/G value,Poisson's ratio,Cauchy pressure of fcc FeNi_1-xCr_x?x=0,0.125,0.25?alloy,as well as the relative volume,thermal expansion coefficient,Debye temperature and heat capacity at different temperatures and pressures were calculated.The effects of different Ni and Cr contents on the mechanical and thermodynamic properties of FeNi_1-xCr_x alloy were studied,which provided a theoretical reference for the optimal design of this series of alloys.