First-principles Calculations And High-throughput Modeling Of Atomic Diffu Sion In Metals Under Uniaxial Ten Sile Deformation

As the only way of mass transport in solid materials,diffusion is closely related to numerous phenomena and properties of materials.Also,for most materials that are in service,it is inevitable for them to have deformation occurred.Considering the fact that uniaxial tensile deformation is one of the commonest deformation modes in materials,it is of great significance to understand the effect of uniaxial tensile deformation on the diffusion.Within this context,we calculated and modeled the vacancy diffusion in fcc metals that under uniaxial tensile formation,also investigated the effect of uniaxial tensile deformation as well as rare earth elements(RE)on the carbon diffusion in ferrite.The main results are as follows,(1)By means of first-principles calculations combined with NEB method,we calculated the vacancy migration energies(Hvm)for vacancy migrates in 24 fcc metals(Ag,AI,Au,Ca,Co,Cu,Fe,Hf,Ho,Ir,Li,Mg,Na,Ni,Pb,Pd,Pt,Re,Ru,Sc,Tb,Th,Ti,Zr)with the presence of different degree(1%,2%,3%,4%,5%)of uniaxial tensile deformation.We discovered that the Hvm for vacancy migrates perpendicularly to the uniaxial tensile deformation is lower than Hvm of vacancy migrates along the deformation,indicating that the vacancy(self-diffusion atom)in fcc metals prefers to migrate perpendicularly to the uniaxial tensile deformation.(2)The vacancy migration model is built to effectively predict the vacancy migration energy(Hvm)in fcc metals without time-consuming NEB calculations by relating the atomic vacancy migration energy with the macroscopic mechanical properties(atomic volume V0,bulk modulus B0,Poisson's ratio v)of materials.This vacancy migration model applies not only to the ideal strain-free fcc lattices,also to the fcc lattices that under different degree of uniaxial tensile deformation and will be a powerful tool in the high-throughput calculations.(3)We studied the effect of uniaxial tensile deformation on the carbon diffusion in ferrite and discovered that the carbon in ferrite prefers to migrate at the direction that is perpendicular to the uniaxial tensile deformation.Besides that,we investigated the effect of RE(Sc,Y,La,Ce,Pr,Nd,Pm,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu)on carbon dififusion and discovered that with the addition of RE,carbon prefers to locate at the octahedral interstitial sites that are the second-and third-nearest-neighboring to the RE atom and is trapped in these two sites,indicating that the RE would inhibit the carbon diffusion in ferrite.