Effect Of Rare Earth Elements On Electrical Conductivity Of Pure Aluminum

Traditional cables use copper as conductor,but the copper resources in China are relatively scarce,and the manufacturing cost is relatively expensive.If pure aluminum conductor material is used,the long-term service aluminum alloy conductor material will have a greater degree of creep,which will lead to greater resistance and easy to cause accidents.In this paper,the effect mechanism of rare earth elements on the electrical conductivity of 1070 pure aluminum was analyzed by adding proper amount of rare earth Ce,La and mixed rare earth to 1070 pure aluminum,and by means of microstructure analysis and resistivity test.In addition,according to the actual production requirements of enterprises,the microstructures and resistivity changes of three kinds of aluminum alloy conductors at different annealing temperatures were studied.Experiments show that rare earth elements La,Ce and mixed rare earth can refine the as-cast structure of pure aluminum.The intermetallic compounds formed at grain boundaries become the core of heterogeneous nucleation,which makes other alloying elements easy to segregate and adsorb between grains,thus having the effect of grain refinement.Moreover,Fe and Si elements which are harmful to the conductivity of the material can be precipitated from the aluminum matrix in the form of Al_3.21Si_0.47.47 and FeAl₃,which greatly improves the conductivity of the material.After the three types of rare earth aluminum alloys are subjected to the same conditions of hot extrusion process,it was found that when the mass fraction of rare earth La was 0.2%,the resistivity of rare earth lanthanum alloys could be reduced to 2.811×10^-8?/m.When the mass fraction of rare earth Ce is 0.3%,the resistivity can be reduced to 2.813×10^-8?/m.When the mass fraction of mixed rare earth is 0.3%,the resistivity of mixed rare earth aluminum alloy can be reduced to2.820×10^-8?/m.In addition,all three kinds of aluminum alloys produce hard phase FeAl₃.During extrusion,not only the crack source is produced,but also the formation of Al₃Fe reduces the metal bonds between metal ions in the material structure,which decreases the number of free electrons moving inside the material and increases the resistivity of the material.After annealing,the resistivity of three kinds of rare earth aluminum alloy rods decreases with the increase of annealing temperature.The resistivity of La aluminum alloy annealed at 340?decreases to2.804×10^-8?/m,that of Ce aluminum alloy annealed at 340?decreases to2.808×10^-8?/m,and that of mixed rare earth aluminum alloy annealed at 340?decreases to 2.820×10^-8?/m.The annealing treatment can dissolve the rare earth compounds in the rare earth aluminum alloy rod,reduce the segregation of the internal components of the structure,and stabilize the structure compounds.In the process of annealing and heat treatment,in all rare earth structures with Ce element,Si element not only does not dissolve back into the matrix,but precipitates from the matrix with the increase of annealing temperature.In the structure of mixed rare earth aluminum alloy,rare earth La element can restrain Ce element from dissolving back into the matrix without affecting the precipitation effect of Si element.