Research On Drawing Deformation And Properties Of Cu-Fe Alloy Wire

Cu-20%Fe alloys with higher strength,hardness,good electrical conductivity and excellent magnetic properties,are expected to be industrialized as electromagnetic shielding conductor material.The miscibility of Cu and Fe liquids during high-temperature melting leads to the non-uniform distribution of Fe elements in the Cu matrix,which is unfavorable for later processing and deformation.The inhomogeneous structure of Cu-Fe alloy can be improved by cold drawing deformation and intermediate annealing treatment,which is favorable for increasing both strength and electrical conductivity simultaneously.Since the Cu phase has the highest proportion in Cu-Fe alloy and plays a major role in electron transport,the relationship between the deformation structure and the mechanical properties and electrical conductivity of drawn pure Cu wires was firstly studied.On this basis,the two-phase coordinated deformation mechanism of drawn Cu-Fe alloy wires was investigated,and the main strengthening and electrical conductivity mechanisms were determined through quantitative microstructure characterization.The microstructure of Cu-Fe alloy wire was tailored by intermediate annealing treatment to obtain the optimal combination of strength and electrical conductivity.The main conclusions are as follows:（1）The grains of pure Cu wires are gradually elongated along the drawing direction after drawing deformation,and the fiber structure with staggered distribution of<111>and<100>textures is formed,and the dynamic recrystallization of Cu wire occurred and the dislocation density decreased when the drawing strain?>1.91.With the increase of drawing strain,the yield strength of Cu wire increases first and then decreases,reaching the maximum value at strain 1.91,which is 427 MPa.The fracture elongation decreased monotonously,and the decreasing tendance gradually became gentle.The change of electrical conductivity is opposite to that of strength,first decreasing and then increasing,and the lowest value is 92.1%IACS at strain 1.91.The strength of Cu wire is not only related to dislocation density and grain size,but also affected by texture components.The electrical conductivity is less affected by dislocation and vacancy,and most significantly affected by grain boundary perpendicular to the drawing direction,and is inversely proportional to the reciprocal of the longitudinal grain size d^-1.（2）Fe elements mainly form the dendritic second phase in the initial structure of the Cu-Fe alloy,and there are also a large number of nanoscale Fe precipitations diffusely distributed in the Cu matrix.There is a coherent relationship between Cu phase and nano Fe precipitation,and the crystal orientation conforms to K-S relationship.With the increase of drawing strain,the Cu phase forms<111>,<100>and<112>textures;the Fe phase forms a<110>fiber texture along the drawing direction.The nanoscale Fe phase in the Cu matrix hardly deforms and still maintains a spherical or ellipsoidal morphology;The Cu rich particles in the Fe phase undergo significant fiber refinement.（3）The drawing deformation resulted in a significant increase in the strength of the Cu-Fe alloy wire,but not a serious decrease in plasticity.The increase of strength is mainly affected by grain refinement and Fe fiber strengthening,and the good elongation is related to the dynamic recovery and dynamic recrystallization of Cu matrix.As the drawing strain increases,the electrical conductivity first decreases,then increases and remains unchanged,and finally decreases again.The electrical conductivity is affected by the comprehensive effects of Cu grain refinement,dynamic recovery,Fe fiber refinement,and Fe element solution.The electrical conductivity is mainly affected by the deformation structure of Cu matrix at strain?<2.06;and when strain increased to?>2.06,the electrical conductivity is more influenced by the strain-induced solid solution of Fe elements and Fe fiber fragmentation.（4）Cu-Fe alloy wires with drawing strain of 1.96 were annealed at 400～600℃.With the increase of annealing temperature,the tensile strength of the alloy wire decreased monotonously.But the electrical conductivity first increased and then decreased,and reached the highest value after annealed at 500℃for 1 hour with 50%IACS.The increase of electrical conductivity is related to the recovery of deformation defects,grain recrystallization and precipitation of solid solution Fe during annealing.When annealed at a higher temperature of 600℃,the solid solubility of Fe in Cu increases,resulting in serious impurity scattering and a decrease in electrical conductivity.Higher electrical conductivity can be obtained by selecting higher strain Cu-Fe alloy wires for intermediate annealing while keeping the total drawing strain constant.（5）A microstructure design strategy for the preparation of high-strength and high-electrical conductivity Cu-Fe alloys is proposed.Firstly,the Cu grains and Fe phase are refined and align along the drawing direction by initial drawing deformation;subsequently,the Cu-Fe alloy wire is annealed at medium temperatures to prevent the recrystallization of Cu phase and coarsening of Fe fibers,and to promote the precipitation of Fe elements from the Cu matrix;finally,the drawing deformation is performed again to produce higher dislocation strengthening and grain refinement strengthening effects.