Effects Of Preparation Process On Mechanical Properties And Microstructure Of FeNiCrCoCu High-entropy Alloy

High-entropy alloys(HEAs)are newly emerged multi-principal alloys with excellent mechanical properties and good prospects for applications in aerospace,shipbuilding and other fields.Fe Ni Cr Co Cu HEA has a typical single-phase facecentered cubic(FCC)structure,and its excellent strength and plasticity is one of the important prerequisites for its engineering applications.In this thesis,a series of Fe Ni Cr Co Cu HEA with the same composition but different atomic structures were prepared by changing the preparation method and cooling rate using molecular dynamics simulations.The effects of preparation method and cooling rate on the tensile strength were investigated to reveal the strengthening mechanisms of FCC crystalline phases and atomic scale clusters on the strength of HEA.The work mainly includes:(1)The effect of the preparation method on the tensile deformation behavior of Fe Ni Cr Co Cu HEA was investigated.The best mechanical properties of the HEA samples prepared by the direct method were found,and the increase in the content of FCC crystalline phase increased the tensile strength and maximum tensile strain of the HEA.(2)The evolution of bond pairs and atomic clusters with FCC crystal phase content was investigated using common neighbor atomic analysis,bond pair analysis and Voronoi polyhedron analysis.The FCC crystalline phase transforms into hexagonal close-packed(HCP)phase and other phases during the tensile process.The change of the FCC crystalline phase structure is mainly caused by the change of 1421 bond pairs and <0,4,4,6> clusters,and the high content of 1421 bond pairs and <0,4,4,6>clusters can improve the mechanical properties of the HEA.(3)The effect of cooling rate on the content of FCC crystalline phase and tensile behavior of the alloy was investigated.The best tensile strength and maximum tensile strain of the HEA samples prepared at low cooling rates are mainly due to the fact that sufficient relaxation time at low cooling rates is conducive to the formation and growth of the FCC structure of the crystalline phase,which leads to an increase in the content of the FCC crystalline phase and facilitates the enhancement of mechanical properties.(4)To investigate the effect of cooling rate on the evolution of microscopic clusters.The low cooling rate effectively promotes the formation of 1421 bond pairs and<0,4,4,6> clusters,thus promoting the formation of more FCC crystalline phases;the high cooling rate promotes the growth of Other phases,with amorphous bond pairs such as 1551,1541,and 1431 dominating.