| With the rapid development of modern industry and a large number of demands,the research and development of high strength and high conductivity copper alloy materials have attracted more and more attention.This kind of alloy can be widely used in welding joint materials,electronic switch contacts,wire rods and lead frame materials of high-speed electric locomotives,etc.Tellurium-copper alloy is a new type of copper alloy material.Because tellurium can not dissolve into the copper alloy matrix,but distributes in the form of the second phase（Cu2Te）in the intergranular or intragranular,the scattering effect of electrons is small,resulting in little influence on the conductivity of copper.However,because the second phase Cu2Te is very soft and has little hindrance to dislocation movement,the mechanical properties of Te on copper are limited.With the contradiction between high strength and high conductivity,it is of great significance to develop new high strength and high conductivity copper alloy materials on the basis of tellurium copper alloy.In this paper,Cu-Te alloy was used as the research object,and a small amount of alloying elements Zr and rare earth La were added to analyze the influence of microalloying elements on the microstructure and properties of Tellurium-copper alloy.The microalloyed alloy was further subjected to cold work deformation and heat treatment,and the influence of deformation and heat treatment on the microstructure and properties of the alloy was analyzed to obtain a Cu-Te alloy with higher strength and conductivity.Through the experimental analysis,the following conclusions are obtained:The grain refinement effect of different content of Zr on Tellurium-copper alloy is not obvious,and the grain size is not much different from that of Tellurium-copper alloy.With the increase of Zr element content,except for a small amount dissolved in the matrix,Zr element is unevenly distributed at the grain boundary,and mainly precipitates at the grain boundary with the second phase containing Cu,Te and Zr.The fracture mode of Cu-Te-Zr alloy is typical brittle fracture.Due to the brittle second phase on the grain boundary,the brittle phase is discontinuous at the grain interface,and the microalloying elements are segregated,resulting in microporous polymerization type intergranular fracture.The addition of the Zr element failed to improve the tensile strength and elongation of the alloy.However,the addition of Zr element can further improve the electrical conductivity and Brinell hardness of Cu-Te alloy.The conductivity of 0.06%Zr alloy reaches 95.0%IACS and the hardness peak is 41.6HBW,which are 6.4%and 20.2%higher than that of Cu-Te alloy,respectively.Rare earth microalloying elements can refine matrix structure,purify grain boundaries,remove impurities,and reduce or eliminate columnar crystals.The results show that the grain size of as-cast tellurium-copper alloy is refined by adding rare earth La,and the microstructures of as-cast tellurium-copper alloy change from large columnar grains to fine equiaxed grains.Rare earth La can improve the tensile strength and plasticity of the alloy.When 0.08%rare earth La is added,the tensile strength and elongation of the copper telluride alloy are 162.1MPa and 26.2%,respectively.Compared with the copper tellurium alloy without La,the tensile strength and elongation of the alloy are increased by 67%and 113%,respectively.With the addition of La element,the conductivity of the tellurium-copper alloy increases first and then decreases.When the content of La element is 0.01%,the conductivity reaches the peak value of 89.65%IACS.With the further increase of rare earth content,the conductivity and microhardness of the tellurium-copper alloy decrease slightly.The comprehensive properties of Cu-Te-La alloy were further improved by cold rolling deformation and heat treatment.After 70%cold rolling,the structure of Cu-Te-0.08La alloy is fibrous,and the tensile strength and microhardness of the alloy after cold rolling are greatly improved,which are 356.9MPa and 118.6HV,respectively,120%and 164%higher,and the elongation decreases to 8%.The conductivity increased slightly to 87.58%IACS.After 70%cold rolling,the Cu-Te-0.08La alloy annealed at different temperatures and times.With the increase of annealing temperature,the recrystallized grains gradually replaced the deformed structure of the fiber.Among them,the Cu-Te-0.08La alloy after 70%cold-rolling deformation can obtain good comprehensive properties after annealing at 400℃for 0.5h.Its microhardness is 108.6 HV and its conductivity is 88.79%IACS.After annealing at 400℃for1h,the conductivity is 88.57%IACS,the tensile strength is 264.8MPa,the elongation is29.1%,and the microhardness is 105.4 HV. |
