Research On Composition,Microstructure And Properties Of High-Strength And High-Conductivity Al-Si-Mg Casting Alloy

Compared with 4G technology,5G has the characteristics of high speed,low delay and Dalian connection.With the development of 5G commercial application,the requirements for high performance of conducting and heat conducting materials are more and more strict.The electrical conductivity and thermal conductivity of Al-Si-Mg cast aluminum alloy,such as A356 and ZLD101A,are relatively low.For example,the use requirement specified in the enterprise production standard is that its electrical conductivity should be greater than 23.20MS/m,but in actual production of enterprises,they are often only 20.88?22.62MS/m,which translates into a thermal conductivity of 153?165W·m-1·k-1,after T6 heat treatment,the tensile strength can reach 280MPa,obviously it can not meet the comprehensive performance requirements of this kind of alloy in 5G communication era.Therefore,to carry out relevant experiments to study the factors affecting the strength,conductivity and thermal conductivity of Al-Si-Mg alloy and try to improve its mechanical properties conductivity and thermal conductivity become an urgent problem.In this paper,a new type of high strength and high conductivity Al-Si-Mg casting alloy was successfully designed and prepared by adjusting the contents of Alloying Elements Si and Mg in turn.The main results of the study are as follows:(1)The melt of aluminum is very easy to getter and oxidize,introducing a small amount of alloying element Si,the pore defects of the corresponding parts of the casting disappear,and as the content of added Si increases,the average length of the alloy flow sample is significantly longer,significantly the casting fluidity is improved;the appearance of a small amout of alloying element Si in A1 causes thermal cracking in the casting,but with the increasing amount of Si added,the thermal cracking sensitivity coefficient HTS of the alloy casting decreases to zero,which significantly reduces the casting heat cracking thedency.In addition,the tensile strength of the alloy increases first and then decreases with increasing Si content,and the elongation and thermal conductivity have been decreasing.(2)Al-4Si alloy has high electrical conductivity and elongation,its electrical conductivity is above 25MS/m,and its elongation can reach 15%;but its tensile strength is very low,only 145MPa.After the introduction of trace alloy element Mg in Al-4Si alloy,its tensile strength did not increase significantly,the electrical conductivity decreases slightly,and the elongation is severely reduced.After T6 heat treatment,the tensile strength is greatly improved and the electrical conductivity also increased,but the elongation has become lower.(3)The best chemical composition of high-strength and high-conductivity Al-Si-Mg casting alloy is obtained through experiments.That is,the mass fraction of Si is 4%and the mass fraction of Mg is 0.5%.During the trial production of pressure casting,the die-casting parts obtained are of complete filling shape and good appearance,and there are no casting defects such as pores,shrinkage and cold insulation inside.After T6 heat treatment,the tensile strength is 31 0MPa,the conductivity is greater than 25MS/m,and the thermal conductivity is as high 184 W·m-1·k-1,and performance indicators are better than the squeeze casting rack products of A356 alloy.