The Effect Of Heat Treatment On The Microstructure And Mechanical Properties Of The Interfacial Layer Of The Cast-rolled Cu/Al Composite Sheet

Copper-aluminum composite material is a new type of composite material that uses two kinds of processing technology to achieve a solid combination of copper and aluminum with different mechanical,physical and chemical properties at the interface.Copper-aluminum composite materials can not only maintain the characteristics of the original metal base material,but also make up for the shortcomings of a single metal base material,enhance strengths and improve shortcomings,improve comprehensive performance,and also solve the problem of copper resource shortages to meet the requirements for materials in different environments Therefore,it has a wide range of applications in many fields.At present,there are many production methods of copper aluminum composite materials,cast rolling composite process is a new process developed in recent years in China.This process uses high pressure and high temperature of liquid metal materials during casting composite to realize the combination of solid metal and liquid metal,so as to achieve good performance of composite materials.In this paper,the Cu/Al clad sheets is made by casting rolling composite process.The casting rolling composite process can make the Cu/Al clad sheets achieve good mechanical combination,but the annealing treatment has an important influence on the formation and evolution of the interface layer of the Cu/Al clad sheets.In this paper,optical microscope,scanning electron microscope,X-ray diffractometer and energy spectrum analysis are used,The microstructure and thickness evolution of diffusion layer of Cu/Al clad sheets after annealing at different temperature and time were studied,The formation and evolution model of interface layer of Cu/Al clad sheets is analyzed,Through hardness test,tensile test,peel test and conductivity test,the mechanical behavior of intermetallic compounds in the interface layer was analyzed;The effect of different solution cooling methods on the microstructure of Cu/Al clad sheets interface was studied,and the formation mechanism of pores in the diffusion layer was explored.This paper provides a theoretical basis for improving the comprehensive properties of Cu/Al clad sheets and expanding the wide use of Cu/Al clad sheets.The main conclusions are as follows:?1?During the casting rolling process,a small amount of intermetallic compound was formed on the surface of Cu/Al clad sheets,and the interface diffusion layer was very small.With the increase of annealing temperature and time,the thickness of diffusion layer increases,and the growth rate of diffusion layer varies with the temperature and time.Three intermetallic compounds,Al₂Cu?AlCu?Cu₉Al₄ were formed in the interface diffusion layer at 250??300?and 400?,and four intermetallic compounds,Al₂Cu?AlCu?Al₂Cu₃?Cu₉Al₄ were formed at 450?/4h.Five intermetallic compounds,Al₂Cu?AlCu?Al₂Cu₃?Cu₉Al₄?AlCu₃ were formed at 500???2?The thickness of diffusion layer is small and the hardness is low;With the increase of annealing temperature and time,the hardness of Cu/Al clad sheets increases;With the increase of temperature,the tensile strength,conductivity and bonding strength first increased and then decreased;The elongation increases first and then decreases with the prolongation of annealing time.When the annealing time is 2h,the elongation increases with the increase of temperature,When the holding time is 4h,the elongation increases first and then decreases with the increase of temperature;This is related to the type and quantity of intermetallic compounds formed by the interface diffusion layer.The appropriate thickness of the interface layer can improve the comprehensive properties of Cu/Al clad sheets.Based on the experiments in this paper,the optimal heat treatment process is 350?holding time 2h.?3?Five intermetallic compounds,Al₂Cu?AlCu?Al₂Cu₃?Cu₉Al₄?AlCu₃ were formed after solution treatment at 500?for 2h.The thickness and hardness of the interface diffusion layer increased,the cooling rate decreased,and the thickness and hardness increased further.During the stripping process,the Cast-rolled composite plate broke near the Al matrix.After solution treatment at 500?×2h and different cooling methods,the clad sheets are all fractured in the interface diffusion layer;the reduction of cooling speed,the weakening of crack growth ability,the too thick brittle hard intermetallic compound is not conducive to the combination of clad sheets.?4?In a short period of time,the interface of the furnace cooling clad sheets will generate small holes.With the increase of the holding time,the holes will disappear.With the increase of cooling time,the number of holes increases,and with the decrease of cooling speed,the holes disappear.Due to the Kirkendall effect of the interface,when the interface is cooled rapidly,the vacancy can not be filled,which leads to the formation of holes in the interface.When the cooling rate is slow,the atoms with slow diffusion rate have enough time to fill the vacancy and the interface void disappears.