Study On The Fabrication Of Al-Fe-Zr Heat-resistant Aluminum Alloy Wire By Backward Extrusion

Due to the development of electric power and the comprehensive promotion of smart grid construction,the higher requirement for overhead transmission lines was put forward.At present,the main conductors used in overhead transmission lines in our country are aluminium cable steel reinforced(ACSR).The heat resistance of ACSR is relatively poor,and it limits the transmission capacity of the lines.Compared with ACSR,the heat-resistant aluminium alloy conductors of the same specification have large transmission capacity,high strength,light weight and good conductivity,which have important application prospects in the context of long-distance,long-span and over-voltage transmission.In present paper,Al-0.35Fe-xZr(x is 0.1,0.2,0.3,0.4)alloy ingots with different Zr content were prepared by casting.Al-Fe-Zr alloy rods were prepared by backward extrusion,and then cold-drawn for several times to obtain excellent synthesis of different nominal diameters.The microstructural evolution and properties of the alloys during casting,extrusion and drawing were studied.The following results were obtained:(1)The effect of Zr content on the structure and properties of as-cast Al-0.35Fe alloy was obtained.With the increase of Zr content,the grain size of as-cast Al-0.35Fe alloy gradually refined from 73?m to 22.74?m,which is because the addition of Zr increases the nucleation rate of liquid metal during solidification,thus making the grain refined.And the addition of Zr element could refine the size of primary Al3Fe phase.With the increase of Zr content,the eutectic structure at grain boundaries decreased,and a large number of small short rod-shape Al3Fe phases formed clusters.The average diameter of clusters was 1.18?m,and the length of short rod-shape Al3Fe phases in clusters was 190nm.The tensile strength of Al-0.35Fe alloy increased with the increase of Zr content,from 54.93MPa to 71.23MPa,while the elongation decreased from 36.7%to 27.7%.(2)The micro structure and properties evolution of Al-Fe-Zr alloy during backward hot extrusion were obtained.Backward extrusion could obviously refine the grain of Al-Fe-Zr alloy and promote the precipitation of metastable Al3Zr particles.The Al3Zr particle was spherical and with an average size of 50nm.With the increase of Zr content,the volume fraction of Al3Zr particles increased,and its morphology and size had little change.Al3Fe phase broke up during deformation and distributes in streamline along the direction of metal flow.With the increase of Zr content from 0.1wt.%to 0.4wt.%,the tensile strength of Al-Fe-Zr alloy increased from 128MPa to 152MPa,and the elongation decreased from 33.32%to 25.69%.(3)The micro structure and properties evolution of Al-Fe-Zr alloy during cold drawing were obtained.During the cold drawing process,the grains were elongated along the drawing direction,forming a fibrous drawing structure.With the increase of the deformation,the dislocation density in the alloy conductor increased gradually.Under the influence of dislocation strengthening and second phase strengthening,the tensile strength increased gradually,the elongation decreased and conductivity increased.(4)Heat-resistant aluminium alloy conductors with nominal diameter of 4.3mm were obtained.The tensile strength,elongation and electrical conductivity of the alloy wire were 184.77MPa,16.16%and 60.13%IACS,respectively.So,the comprehensive properties of Al-0.35Fe-0.1Zr(wt.%)alloy are better than the requirement of AT1 and AT3 heat-resistant aluminium alloy conductors in the International Electrotechnical Commission Standards for Overhead Conductors.