Composition Design And Optimization Of Al-si Cast Aluminum Alloy With High Thermal Conductivity And Corrosion Resistance

Al-Si casting alloys with excellent casting property and relatively good thermal conductivity,have been widely applied in the manufacture of heat sinks for communication infrastructure and electronic products.The development of 5G communication technology and diverse application outdoor environments demands better heat dissipation performance combining with anti-corrosion property of die-cast aluminum alloy radiators.It is urgent to develop die-cast aluminum alloy materials with high thermal conductivity combining with anti-corrosion resistance.In the present study,the effects of rare earth on the thermal conductivity and corrosion resistance of the hypo-eutectic Al-7Si alloy(JSDL-1)were firstly studied.Also,strengthening elements were selected to optimize the alloy system by orthogonal experiment.Moreover,the influences of Mg/Er recombination and low-temperature annealing on the thermal conductivity and corrosion behavior of the Al-Si alloy were studied in detail.The main results achieved in this thesis are as follows:After being modified by different RE elements(Ce,La,Y,Er,and Sm),the?-Al grains of JSDL-1(Al-7Si-0.8Fe-0.5Zn)alloy arranged more uniformly with fewer coarser phases.The elements of Sm,Ce,and Y could increase the thermal conductivity,and the value of the alloy modified by Sm is up to 157.7 W/(m·K).Y and Er reduce the corrosion rate by 26.1%and improve the corrosion resistance.The five RE elements do not significantly affect the hardness with hardness value of 51-53HB.Among the three strengthening elements of Zn,Mg,and Co,the Al-7Si-0.8Fe-0.5Mg alloy exhibits the best comprehensive properties,for relatively lower thermal conductivity but superior mechanical and corrosion resistance properties.Orthogonal experiments and element interaction experiments were used to determine the best synergetic action between Mg and Ce,Y and Er.The combination of Mg and Er,Y can reduce the detrimental effects of Mg on thermal conductivity.The heat dissipation capacity of different alloy systems is generally improved after being low-temperature annealed.The alloy system modified by Er has better corrosion resistance,and its corrosion resistance is further improved after annealing.The corrosion current density of the Al-7Si-0.8Fe-0.3Er alloy before and after annealing is 0.88?A·cm^-2 and 0.64?A·cm^-2.Alloys containing Mg exhibit remarkable softening resistance.The hardness of the Al-5Si-0.8Fe-0.9Mg-0.3Er alloy increases from80.0HB to 86.8HB after low-temperature annealing.The effects of Mg,Er,and Y elements on the corrosion behavior of Al-7Si-0.8Fe alloy were investigated.Corrosion kinetics demonstrates that the corrosion rates of the alloys fluctuate with the extension of corrosion time.The corrosion morphology shows typical pitting characteristics,and the main corrosion products are Al(OH)₃.The corrosion rate of the as-cast Al-7Si-0.8Fe-0.6Mg alloy is the lowest in the as-cast state,and that of the as-annealed Al-7Si-0.8Fe-0.6Mg-0.3Er alloy is the lowest.The EPMA results showed that the decrease of grain boundary segregation of Mg leads to lower weight loss rate and stronger corrosion resistance after low-temperature annealing,which is supposed to be related to the decrease of stress corrosion tendency induced by Mg-H compound.In this paper,an Al-7Si-0.8Fe-0.6Mg-0.3Er/Y alloy system with high thermal conductivity and corrosion resistance has been designed and developed.The thermal conductivity is as high as 188.6W/(m·K),and the corrosion rate is as low as 0.06 mg/cm^-2·d.The present study provides certain theoretical significance and reference value for their development and application in 5G communication field and other heat dissipation devices.