Study On TLP Diffusion Bonding Of S355Steel/6005A Aluminum Alloy Dissimilar Metal

Energy conservation and emission reduction become the theme of industrialproduction in current century. It also gives rise to higher request is needed for lighterstructural parts in industrial production, so composite construction of dissimilar metalwelding attracts more and more attention. Now steel/aluminum composite structure iswidely applied in different areas. Transient Liquid Phase-Diffusion Bonding (TLP-DB) isvery applicable to dissimilar metal welding, due to the character of low bondingtemperature and small residual stress.Pure Cu foil and Al-Cu/Al-Si-Cu eutectic alloy foils were used as interlayersrespectively to realize S355steel/6005A aluminum alloy (steel/aluminum) TLP-DB and thebonding process was under the protection of flowing argon. The effect of bondingparameters, including bonding time and bonding temperatures on microstructure andmechanical properties of the Fe/Al TLP-DB joints have been studied. The microstructure ofFe/Al TLP-DB joints and morphology of fracture surfaces were characterized by SEM andEDS. The Fe/Al TLP-DB joints microhardness distribution and shear strength were used toevaluate the mechanical properties. The phase of fracture surfaces was analyzed by XRD.Fe/Al TLP-DB was successfully realized when used pure Cu foil as interlayer and thejoints were consecutive. Pure Cu foil prevented mass Fe-Al brittle intermetallic compoundsformation and improved joints quality. The diffusion layer width increased and atomicdiffused more adequately with the rising bonding temperature and bonding time. Under thepressure of0.5MPa, the maximum strength77.4MPa of the joint was obtained at580℃for30min. The joint was first fractured along microcrack at diffusion layer near steel and thecharacteristic of brittle fracture is presented. The phases of fracture surface were FeAl、FeAl3and Al solid solution.Fe/Al TLP-DB was successfully realized when used Al-Cu eutectic alloy foil asinterlayer and the joints were consecutive. Compared with the joints used pure Cu foil asinterlayer at the same process parameter, the joints quality were better, which is mainly because that the foil was eutectic composition and sped up eutectic liquid generation. Underthe pressure of0.5MPa, the maximum strength79.2MPa of the joint was obtained at580℃for30min. The phases of fracture surface in steel side were FeAl3、FeAl2and AlCu3, and inAl side were FeAl3and Al solid solution.Fe/Al TLP-DB was successfully realized at lower bonding temperature of540℃whenused Al-Si-Cu eutectic alloy foil as interlayer and the joints were consecutive. Comparedwith the joints used pure Cu foil and Al-Cu eutectic foil as interlayers at the same bondingtime, diffusion layer width is more narrow, which is mainly because that Si restrained Fespreading from steel to aluminum. The microhardness increased with the bondingtemperature increasing, while the shear strength decreased. The maximum strength60.2MPa of the joint was obtained at540℃for30min. The phases of fracture surface wereFeAl2、AlCu3、FeAl3and Al solid solution.