Research Of The Influence And Regulation Of AlN_p/Al₃BC_p On The Electrical/thermal Conductivity And Mechanical Properties Of Cast Al-SI Alloys

In recent years,with the development of lightweight,miniaturization and integration of electronic devices and deployment of 5G strategies for many countries,the industry has proposed higher indicators and more urgent requirements for the heat dispersion and mechanical performance of high-power electronic systems and equipment.Aluminum and its alloys have always been favored in the field of electronic appliances due to their excellent electrical and thermal conductivity,comprehensive mechanical performance,and good processability,etc.,for example,heat dissipation materials for mobile electronic equipment,GIS for high voltage or ultra high voltage equipment,conductor materials inside chip in microelectronic device and so on.However,according to metal electronic theory and strengthening mechanism,it can be seen that increasement in electrical/thermal conductivity and inprovement in strength are usually contradictory.Therefore,for high-power electronic systems and equipments,it is of great significance to develop a convenient,efficient and economical methods to achieve the simultaneous improvement of electrical/thermal conductivity and mechanical performance of aluminum alloys.In this paper,by adding seed crystal alloys,nano AIN particles(AlNP)and micro-nano A13BC particles(A13BCp)were applied to A356 alloy and die-casting Al-Si-Fe alloy,and combined with boron treatment,and finally realized the improvement of electrical/thermal conductivity and mechanical properties of alloys synchronously.The main research contents of this article are as follows:(1)Effect of boron coupling nano-AlNP on electrical and mechanical performance of A356 alloyTaking A356 alloy as the research object,on the basic of boronizing,the morphology and size of the eutectic Si phase were further controlled by nano-AlNp,and finally obtained the synchronous improvement of conductivity and mechanical performance.Taking the heat-treated(500? solid solution for 3 h,180? aging for 8 h)alloy with 0.6%AlNp as an example,the electrical conductivity is 46.2%IACS,the ultimate tensile strength is 300 MPa,the yield strength is 240 MPa,and the elongation is 7.5%.Researches showed that the improvement of conductivity is due to boron treatment and nano-AlNp hinder the growth of eutectic Si which decrease the size and the mutual overlap of eutectic silicon and effectively reduces the scattering of electrons.The improvement of mechanical performance is mainly attribute to the modification of eutectic Si by nano-AlNp,the refinement of the SDAS(Secondary Dendrite Arm Spacing)of ?-Al grain and the dispersed or the small flocculent distribution of AlNp in matrix and at the Al/Si interface.(2)Regulation of AINp content and heat treatment on electrical conductivity and mechanical performance of A356 alloyBy adjusting the AlNp content and heat treatment to study the changes in conductivity and mechanical performance of alloy,which provides a reference for the matching between conductivity and strength of the equipment which used under different working conditions.The study found that if the conductivity needs to be above 45%,a lower solid solution temperature and a higher particle addition amount can be selected to ensure the strength at the same time.For example,the amount of AlNp is 1%and the heat treatment is solid solution at 500? for 3 h and aging at 180? for 8 h.If the yield strength needs to be above 270 MPa,a higher solid solution and a lower particle amount to ensure the conductivity at the same time.For example,AlNp content is 0.6%,and the heat treatment is solid solution at 545? for 3 h and aging at 180?for 8h.Or,the AlNp content is 0.8%and the aging time is shortened to 5 h.(3)Effect of micro-nano AbBCp on thermal conductivity and mechanical performance of die-cast Al-Si-Fe alloyTaking die-cast AlSiFe alloy as the research object,the micro-nano A13BCp were used to achieve the synchronous improvement of thermal conductivity and mechanical properties,and the reasons were revealed.Under the condition of gravity casting,the average tensile strength,yield strength,ductility,electrical conductivity and thermal conductivity were measured to be 201.8 MPa,106.1 MPa,11.5%,43.1%IACS and 195.2 W/(m·K).Compared with the case without micro-nano Al3BCp,the properties were improved by 8.4%,9.5%,10.6%,0.7%and 2.6%,respectively.Subsequently,the Al3BCp were successfully applied to high pressure die casting.