| The application of Cu-Cr alloy in vacuum electrical contact and high-speed iron contact line requires the material to have excellent mechanical and electrical properties at the same time,but the mechanical and electrical properties of metal materials often restrict each other and it is difficult to improve cooperatively.In this paper,Cu-Cr alloys with different Cr contents of Cu-30Cr(wt.%)and Cu-1Cr(wt.%)were firstly prepared,and then the effects of two large severe deformation on the microstructure and properties of the alloys were studied.It is an important method to achieve high strength and high conductivity by composition design and severe plastic deformation.Due to the high proportion of Cr element in Cu-30Cr(wt.%)alloy,and the Cu and Cr elements are almost insoluble and have large differences in melting point and density,it is easy to stratify in preparation process of traditional methods,resulting in uneven composition.It is difficult to prepare the high Cr content Cu-Cr alloy with uniform composition and fine structure.Therefore,Cu-Cr alloy was prepared by laser additive manufacturing(LAM).The content of Cr in Cu-1Cr is low,and it is prone to segregate and cause uneven distribution of the second phase.Therefore,Cu-1Cr-0.12 Zr alloy is formed by adding trace Zr to control the distribution and morphology of Cr phase.The experimental parameters and deformation characteristics of alloys were obtained by numerical simulation analysis.According to the deformation characteristics of the alloy,high strength and high conductivity were obtained by thermal and cryogenic shear deformation.Cu-30 Cr alloy with uniform distribution of second phase was prepared by LAM.Its tensile strength and electrical conductivity were 267.8 MPa and 43.9 %IACS,respectively.Through the hot compression test and the establishment of the constitutive equation,the CONFORM process was numerically simulated to obtain the CONFORM parameters.The density,tensile strength and electrical conductivity of Cu-30 Cr increased to 98.9%,415.8MPa and 46.8 %IACS,respectively,under the action of severe shear deformation during CONFORM.In continuous extrusion process,the uniform and fine original Cr phase in Cu-30 Cr prepared by LAM promoted the dynamic recrystallization and nucleation of Cu matrix,forming more than 90% of the ultra-fine Cu grain size less than 0.5 μm.In addition,<110> and <332> axial hard orientation texture and 10-20 nm nano-twin structure with thickness were formed in Cu and Cr,respectively.The addition of Zr element in small proportion of Cu-1Cr alloy forms a Cu-Cr-Zr alloy,which refines and spheroidizes the Cr phase which is prone to segregate.After obtaining the constitutive equation through hot compression test,combined with numerical simulation analysis,it is found that the cryogenic shear deformation process of Cu-1Cr-0.12 Zr is more conducive to its performance improvement.Therefore,the effectiveness of the friction angular extrusion process is verified by numerical simulation by using the inhibition effect of cryogenic environment on dislocations.The tensile strength and electrical conductivity of Cu-1Cr-0.12 Zr raw material after heat treatment are 461.33 MPa and 63.0 %IACS,respectively.The tensile strength and electrical conductivity were 485.10 MPa and56.9 %IACS,respectively,after being subjected to room temperature friction angular extrusion and heat treatment.After cryogenic deformation and heat treatment,the tensile strength and electrical conductivity were 576.21 MPa and 59.9 %IACS,respectively.The strength and electrical conductivity are 18.78% and 5.27% higher than those after room temperature frictional angular extrusion and heat treatment,respectively.After cryogenic deformation,due to the significant refinement of the grains and the uniform distribution of the second phase,the uniform and fine distribution is distributed in the matrix,and the strength of the material was greatly improved under the condition of a slight decrease in electrical conductivity. |
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