The Study On High Thermal Conductivity And Low Expansion High Silicon Aluminum Alloy

High silicon contect aluminum alloy has been widely used in wear resistant piston materials because of its excellent wear resistance,good mechanical properties,low density and low cost.However,the high thermal conductivity of the aluminum matrix and the low thermal expansion coefficient of the silicon phase indicate that the application of the high silicon aluminum alloy in electronic packaging with a great development prospect.Our laboratory has developed a heat resistant high silicon contect aluminum alloy with low expansion,the composition is Al-20Si-2Cu-1Ni-04Mg-05Mn,which has good mechanical properties and low thermal expansion,But there is a lack of research on thermal conductivity.This paper is based on the previous research,commissioned by ZTE Corp to develop a new high silicon aluminum alloy for die casting of high thermal conductivity and low expansion coefficient,discusses the influence of alloying elements on the thermal physical properties,A suitable aging heat treatment process was developed for the alloy?By adjusting the content of Si and Mn elements,the thermal physical properties of alloy had been examined by laser thermal expansion tester and thermal analyzer,and study the variation of the thermal physical properties of high silicon Aluminum Alloy?The phase composition of the alloy was analyzed by XRD,and changes of the matrix lattice constant were calculated by Jade software,initially revealed the general the influence law offends,on the basis develop a new type of high silicon aluminum alloy with high thermal conductivity and low expansion which referred to as Al-20Si alloy,the main alloy elements are Si,Cu,RE and so on.its.The properties of the alloy prepared by the optimized P+RE composite modification process are as follows:the tensile strength is greater than 182.5MPa at Room temperature.In the range of 25¹59?,the thermal expansion coefficient is less than 17.676×10^-6?^-1,the thermal conductivity of not less than 116W/?m·K?.the effect of cooling rate on the thermal conductivity was investigated.In order to further improve the thermal properties of the alloy,we explore the possibility of the development of thermal conductivity by short-term T6 heat treatment and artificial aging heat treatment,It is found that aging 3H at 220?can increase the thermal conductivity of the alloy under gravity casting by 11.6¹2W/?m·K?,the promotion rate is about 9.2%,which is the best heat treatment process.The Al-20Si alloy casting by pressure casting,Results show the tensile strength is192.357MPa,elongation is 1.22%,the coefficient of thermal expansion is 17.05×10^-6?^-1 at room temperature,the thermal conductivity of 150.5W/?m·K?,meet the requirements of electronic packaging substrate,and after aging heat treatment,the tensile strength is as high as 219.516 MPa,the elongation increased to 1.65%pages,the thermal expansion coefficient is 17.09×10^-6?^-1 at room temperature,the thermal conductivity of 151.7W/?m·K?.The influence of Ni content on the thermal expansion coefficient of the alloy was discussed by using the theoretical model.It was found that the Kerner model fits the measured data.found that the Kerner model fits the measured data.With the addition of Ni element,the thermal expansion coefficient of the alloy decreased.At room temperature,the average thermal expansion coefficient decreased by 0.0015?^-1 per 0.1%Ni.At the same time,with the addition of Ni,the lattice constant of the Al matrix decreases,and the thermal conductivity decreases,with an average increase of 0.5%Ni,the thermal conductivity of the alloy decreases by about 2W/?m·K?.