Study On Adhesive Process And Joint Properties Of5083Aluminum Alloy

With the development of high-speed railway at home and abroad, using aluminum alloy to instead steel materials is one of the most effective way of lightening weight of bodywork in the rolling stock manufacturing process. But the weldability of aluminum alloy is relatively poor, besides riveting and screw connection can produce stress concentration, so the excellent bonding of aluminum alloy has become an important research topic. Adhesive bonding is widely used in vehicle manufacturing, with a lot of advantages, such as simplifying manufacturing process, reducing manufacturing cost, lightening structure weight, decreasing stress concentration factor of component, etc. So the technology of aluminum alloy adhesive bonding has also become a subject of great significance.In this paper, using a-cyanoacrylate as adhesive,5083aluminum alloy treated by cleaning, sandblasting, anodic oxidation, coupling agent were bonded. The effect of surface treatment on adhesive process, joint strength and durability were studied through scanning electron microscopy (SEM) observation, analysis of surface morphology of substrate, shear test of joint, energy dispersion spectrum (EDS) analysis of fracture surface and IR spectra examination of adhesive, etc.The results indicated that the surface oil and grease are removed through acetone cleaning, the surface of original parent metal is flat and has low surface energy, adhesive force and mechanical meshing force are both lesser, so the shear strength of the joint is the lowest, and the fracture model is interface fracture. Impurities and oxide of the parent metal are removed by sandblasting process, the activity and the adsorption capacityof the parent metal surface are improved, the wettability of the adhesive to the substrate is increased, what’s more, the area of bonding surface and mechanical meshing strength are also improved with the increasing of surface roughness, so the shear strength of the joint is elevated by43.6%comparing to the sample that treated merely by acetone cleaning. After anodic oxidation, the Al2O3nano-hole is formed on the surface of parent metal, the specific surface area and mechanical meshing force are improved significantly, besides dispersion forceand van der Waals force in the adhesive interface increases with the generation of polarity oxideγ-Al2O3on the surface of parent metal, so the shear strength of the joint is elevated by223.1%comparing to the sample treated merely by acetone cleaning, the fracture model is mixture fracture based on cohesive fracture. Adding of5%KH-550coupling agent results in the production of Al-O-Si chemical bonding between the adhesive and parent metal, the strength of joint that treated by simple cleaning and sandblasting increases by52.8%and89.05%respectively, but for the sample treated by anodic oxidation, Coupling agent forms a layer of polysiloxane film which blocks the infiltration of adhesive into the nanopore, mechanical meshing force is therefore reduced, the strength of the joint is lower than the sample without coupling agent.In different environments, because of the influence of acidic medium, corrosive ions, oxygen molecules and water molecules, the hydrolyzation, swelling, desorption and thermal oxidation occured in adhesive molecules and the corrosion and hydrous oxidation took place on the surface of aluminum alloy, the shear strength of joint decreases with the increasing of holding time. As the exposure environmental temperature goes up, the degradation rate of the bonding strength increases. In the same exposure conditions, the durability of aluminum alloy joint after different surface treatment is different, i.e., anodic oxidation> sandblasting+5%coupling agent>sandblasting processing>acetone cleaning. The effect of exposure environment on the durability of joint with same surface treatment is different, namely, H2SO4solution>NaCl solution>water>temperature.