Composition Design And Properties Research Of Pipe Busbar Made From Aluminum Alloy

The electricity demand continuing to increase because of the rapid development of economy in our country bring new challenges to the high and ultra-high voltage transmission,therefore,more outstanding busbar at the low voltage side also demanded.6063 aluminum alloy with good electrical conductivity and mechanical properties and low cost advantages,is the most used material for manufacturing pipe busbar at present.In this paper,the effect of main elements and rare earth elements on the conductivity and tensile strength were mainly researched respectively and the relationship between the properties and microstructure were also analysised with the help of OM,SEM,EPMA and so on.The orthogonal experiment was performed with the Mg,Si,Cu as experiment factor and the content of Mg,Si,Cu as experiment level and electrical conductivity,tensile strength,hardness and elongation as the experimental index,respectively.The influence rule of different experiment factor on the different indicators was achieved through the analysis of the dates gained from the experiment by the method of K value and range analysis.Through comprehensive analysis,the optimal composition of the alloy is Al-0.6Mg-0.4Si-0.2Cu?wt%?.The mathematical expression between the levels of various factors and experiment indication was established through the linear regression analysis of the orthogonal experiment dates.In order to improve the comprehensive performance of the alloy furtherly,in this paper,the effect of Ce and La addition on the microstructure and properties of the alloy were studied respectively based on the results of the orthogonal optimization.The effect of different addition amount of Ce and La on the optical microstructure was studies with the aid of optical microscope,and the effect of different addition amount of Ce and La on the electrical conductivity and tensile strength was researched used the tensile strength tester and D60K conductivity.The composition,morphology,distribution about second phase and the distribution of alloy elements and rare earth elements were also analyzed using SEM and EPMA.The effect of the addition of rare earth elements on the microstructure and the second phase,and the relationship between properties change and the microstructure and the second phase change were also discussed.In consideration of the actual service products are heat treated alloy,in this paper the effect of rare earth elements on the conductivity and tensile strength in T6condition was further discussed.Besides,the evolution of microstructure and second phase before and after heat treatment were analysised,and the reason that the different influence law of the rare earth elements addition in different condition was also discussed.The adding of rare earth elements made the grains refined and the refining effect still exited after heat treatment.In cast condition,the adding of Ce and La made the electrical conductivity slightly decreased and the tensile strength enhanced at first and then weakened.After heat treatment,the electrical conductivity and the tensile strength both enhanced at first and then weakened.The mechanism of grain refinement is attributed to the increased constitution undercooling and decreased surface tension at solid-liquid interface frontier caused by the addition of rare earth elements.The change of alloy conductivity and tensile strength is mainly due to the purification and refinement effect on substrate by adding Ce and La,and complex second phases formed by the enrichment of Ce or La at solid-liquid interface frontier,like AlSiLa,AlSiCe,etc.Heat treatment made the segregation of elements eliminated and the compounds like Mg₂Si dissolution at first and then precipitation uniformly,so the properties of alloy in T6 state were superior to which in cast state.