| Carbon fiber reinforced aluminum alloy laminates have a wide application prospect in aerospace for its low density,high specific strength,excellent corrosion resistance and size stability.However,the poor wettability and interfacial reaction result in troubles in making well-combined interface,which limits its further application.It is an effective mean to solve the problem of interface bonding by using solder alloy between 5052 Al matrix and carbon fiber.Zn-8Al alloy has good plastic toughness and strength,which contributes to its good infiltration into carbon fiber and the formation of an effective interface with the Al sheet at low temperature.The focus of this research is to improve the mechanical properties of solder itself and laminate by adding alloy elements into Zn-8Al solder.In this paper,the solder was modified by addition of Cu and Si elements and application of the homogenization annealing process.Effects of Cu contents,Si contents and homogenization annealing times on mechanical properties of laminates in research were investigated.In this paper,solder alloy smelting was carried out in magnetic levitation smelting furnace and laminates were fabricated by hot-pressing method to realize the high quality interface between solder and 5052 Al sheet.The box type resistance furnace is used for annealing.The microstructure morphology was observed by OM and SEM.The phase analysis was conducted by EDS and XRD.Tensile properties and micro-nano mechanical properties were analyzed by universal material testing machine and nano indenter.The results indicate that:（1）The microstructure of Zn-8Al-XCu solder alloy is composed of η（Zn）,α（Al）and ε（Cu Al2）,the dendritic ε（CuAl2）phase precipitated from η（Zn）and α（Al）are closely related to the mechanical properties of laminates.When Cu content increased from 1% to 5%,ε（CuAl2）gradually increased and wound into a network,the tensile strength of the laminate gradually increased,elongation increased at first and then reduced.A small amount of ε（CuAl2）phase improves the plasticity of the alloy,but excessive Cu content will reduce the plasticity of laminates.When the Cu content was 3%,properties of the laminate are the best among all contents,which reached 315 MPa and 1.31%,respectively.The elastic modulus of the laminates prepared by solder with 4%,5% Cu content significantly increased,which is beneficial to achieve the purpose of carbon fiber reinforcement.（2）Si element in the solder is in the form of monatomic silicon,there are only η（Zn）,α（Al）and Si phase in the Zn-8Al-XSi solder.The Si phase directly affects the mechanical properties of laminates,as Si content increased from 0.5% to 2.5%,the elongation of laminates decreased gradually,while the tensile strength increased at first and then decreased.The tensile strength and elongation of the laminate with 1% Si were the best,which reached 365 MPa and 0.78% respectively.To improve the mechanical properties of laminates,the Si content in Zn-8Al-XSi solder should be controlled below 1%.（3）With the increase of annealing time,intergranular segregation in Zn-8Al-1Si solder slows down,the grain composition and the grain size becoming more uniform,the tensile strength of laminate becomes smaller,and the elongation becomes larger.Grain composition homogenization is the decisive factor in plastic toughness enhancement. |
