Mechanical Property And Solderability Study On SiCp/7075Al Composites

In order to fill the gap in research on7XXX Al alloys matrix composites,SiCp/7075Al composites was made by squeeze casting in this paper with particle meandiameter of5μm and volume fraction.Aging behavior, mechanical property,microstructure, electroless nickel-phosphorus plating and solderability of this compositeshave been researched for widespread use.7075Al and SiCp/7075A composites were aged under120℃,150℃and180℃respectively up to96hours. Both of the two materals reached their peak aging at120℃/24h,150℃/9h and180℃/0.4h. The aging-hardness diageam was been analysed. Thecomposites had the same aging behivor: the higher of the aging temperature the earlier ofthe peak ageing would be, and the hardness at the peak ageing would be lower. Thecomposites got its highest tensile strength of616.6MPa at120℃/24h. Microstructure andDSC diagram of both of the materials have been analysed, it showed that the introducinreinforcing particles could improve the dislocation density in the matrix, howere, didn’tmake the precipitated phase show up early. Dislocation’ movement and precipitatedphase’s nucleation and growth were the two main factors that influence the strength of thecomposites during aging process. Aging under120℃a mass of dislocation remained andthe small precipitated phase distributed uniformly in matrix when came the aging peak sothe higher strength was got. Aging under150℃and180℃the dislocation densitydecreased and precipitated phase got bigger and less so the lower strength was got.After prtreatment of acid ethching with1:1HNO3and secondary zinc coating, XPSwas used to analys the zinc coatint surface. It showed that using secondary zinc coatingcould move the oxidation film successfully and got a thin and compact zinc layer. A doublecomplexing agent platng solution with citric-lactic acid was used in this paper. The effectof the plating solution composition and technological parameter to on the coating growthrate and phosphorus content was investigated. SEM, XRD, Micro Scratch Test separatelyanalysed the film’s morphology, phases, and bonding strength with the composites. Itshowed that this composite can be successfully eletroless plated with prtreatment ofsecondary zinc coating and a double complexing agent platng solution with citric-lacticacid.The wetting angle of Sn-Cu filler was studied under270℃for different holding time.Then Sn-Cu filler was used to solder the composites with the Ni-P film. MetallurgicalMicroscope, SEM, XRD and Element Line Scanning separately analysed soldering seamfor IMC micro morphology, fracture, phases and distribution of the elements. It showed that (Cu_y,Ni_1-y)₆Sn₅first appeared on the interface, as the holding time went by it coveredby (Ni_x,Cu_1-x)₃Sn₄. With the increase of the holding time the strength of the joint firstincrease then decrease. Under270℃for3min the joint got its highest shear streangth23.7MPa.