Molecular Dynamics Simulation Of Solidification And Mechanical Properties Of Al_xCoCrFeNi High Entropy Alloy

As a new type of metal material,high entropy alloy has attracted more and more attention because of its unique properties such as high strength,high hardness,high temperature resistance and wear resistance.In this paper,the radial distribution function of Al_xCo Cr Fe Ni high entropy alloy at different cooling rates and the microstructure were compared and analyzed by molecular dynamics simulation.The effects of temperature,strain rate and Al content on the mechanical properties of the system were also studied.The main conclusions are as follows:Under the cooling rate of 1.0×10¹¹K/s,the radial distribution function of Al_xCo Cr Fe Ni high entropy alloy obtained by simulation showed obvious crystal characteristics.After solidifying at the cooling rate of 1.0×10¹¹K/s,the main crystal structure of Al_0.1Co Cr Fe Ni high entropy alloy was the face center cube and the hexagonal close-packed structure of grain boundary?FCC+HCP?,and the ratio is 96.8%.The main crystal structure of Al_0.3Co Cr Fe Ni high entropy alloy was still FCC+HCP,but the ratio decreased to 84.9%.With the increase of Al content,the main crystal structures of Al_0.5Co Cr Fe Ni and Al_0.7Co Cr Fe Ni high entropy alloys were face-centered cubic and body centered cubic?FCC+BCC?.For Al_0.5Co Cr Fe Ni high entropy alloy,FCC accounted for 32.1%and BCC accounted for 36%.The proportion of FCC and BCC in Al_0.7Co Cr Fe Ni high entropy alloy all of them accounted for 30%.When Al content continued to increase,the BCC of Al_0.9Co Cr Fe Ni high entropy alloy accounted for 77.3%.The BCC of Al_1.1Co Cr Fe Ni high entropy alloy increased to 81.8%.Therefore,the increase of Al content promoted the formation of BCC phase.According to the observation of its phase structure by Ovito,the Al_0.1Co Cr Fe Ni high entropy alloy is a single FCC phase structure,the Al_0.5Co Cr Fe Ni high entropy alloy is FCC+BCC dual phase structure,and the Al_1.1Co Cr Fe Ni high entropy alloy is a single BCC phase structure.When the tensile mechanical properties of A1_xCo Cr Fe Ni high entropy alloy are simulated at different temperatures,the stress-strain curve of A1_0.1Co Cr Fe Ni high entropy alloy under the action of tensile load goes through the elastic deformation stage with approximately linear change,and rapidly declines after the peak stress.With the further aggravation of deformation,the system enters a long plastic deformation process until fracture.At the same time,the Young's modulus calculated at 300K is 93.5717GPa,which is consistent with the data reported in the literature.From the perspective of the changes of atomic structure,when the strain is around 0.067 Yield stress peaked at 4.224 GPa,when the strain is 0.211 and 0.277,the corresponding part of the stress-strain curve is a decline in Yield stress and material of inhomogeneous plastic deformation stage.As tensile continues,model finally reached 0.539 in strain break.When the Al content is constant,the temperature is negatively correlated with the young's modulus and Yield strength of A1_xCo Cr Fe Ni high entropy alloy,and it decreases linearly.When the temperature is constant,the Young's modulus and Yield strength of the high entropy alloy in the system increase with the increase of Al content,and the higher the Al content is,the greater the Young's modulus increases.When the tensile mechanical properties of A1_xCo Cr Fe Ni high entropy alloy were simulated at different strain rates,the higher the strain rate was,the slower the model reached the peak in the tensile process,that is,the elastic deformation stage correspondingly became longer with the increase of the strain rate.When the Al content is constant,the strain rate is positively correlated with the Yield strength of A1_xCo Cr Fe Ni high entropy alloy.When the strain rate is constant,the Young's modulus of the high entropy alloy of the system increases with the increase of Al content.