Research On Welding And Riveting Hybrid Joining Of Aluminum Alloy And Resin-based Composites

In the wave of low-carbon economy,high-end equipment lightweight manufacturing technology has been rapid development.Aluminum due to its eminent processability,excellent mechanical properties and good corrosion resistance and resin composites due to its high strength,high fatigue resistance and good corrosion resistance are widely used in the aerospace,rail transportation and automotive manufacturing industries.However,the joining technology of dissimilar materials with great distinct physical and chemical properties has become a major problem,which is paid for more and more attentions.Since some existing methods for joining aluminum alloy and resin-based composite materials still have great limitations,this thesis proposes a new method for joining aluminum alloy and resin-based composite materials named laser-Arc heat source welding and riveting hybrid joining technology.The experiment uses 6061-T6 aluminum alloy and carbon fiber reinforced polyetheretherketone as the base material.The aluminum alloy rivets are used to rivet the two plates in advance,and the aluminum alloy plate is on the upper and the composite material plate is under.Then,the laser-arc hybrid heat source is used to weld the rivet and the aluminum alloy plate by girth welding.The energy regulation of the hybrid heat source is used to control the heat distribution of the joint,and the aluminum alloy and the resin-based composite material are reliably and effectively joined.At the same time,the paper also discusses the influence of experimental parameters and rivet structure changes on joint forming and mechanical properties.The microstructure observation,element composition and valence state analysis of the well-formed stepped rivet joints were carried out,and the joining mechanism of the welded and riveted hybrid joints was obtained.The research results show that the laser-arc heat source welding and riveting hybrid joining technology can realize the effective joining of aluminum alloy and resin-based composite materials.The parameters affecting the formation and performance of the final hybrid joint are mainly laser power,TIG arc current and welding speed.For this innovative method,the butt stepped rivet assembly method can obtain better molding and excellent mechanical properties,its tensile shear fracture load reaches 2150 N,which is about 85% of the strength of the base metal,and the failure form is composite base metal fracture.However,the butt straight rivet assembly method is well formed but the mechanicalproperties are poor,its tensile shear fracture load is only 1205 N,and the failure form is the aluminum rivet coming out along the weld.The hybrid joint obtained by the well-formed stepped rivet was analyzed in more depth.It was found that the laser peak current has a wider process parameter window than the TIG arc current.Therefore,the temperature distribution of the joint is mainly controlled by laser power,and the TIG arc current is supplemented.The macroscopic and microscopic features of the typical joint section were analyzed.The contact interface between the aluminum alloy and the resin-based composite was microscopically analyzed.It can be concluded that the interface formed a sawtooth shape due to the heat source,and the heterogeneous material produced a strong mechanical anchoring effect.Moreover,the presence of carbon can be detected in the region of the 10-20 μm width of the side of the aluminum alloy near the interface of the welded and riveted hybrid joint.Further,the detection and analysis of the element valence at the interface revealed that there is a metal carbonate of aluminum at the interface,which proves the chemical bonding between the heterogeneous materials,which proves that there is a strong interface interaction at the interface.Therefore,the three kinds of joining mechanism of welding and riveting joints is proposed: aluminum alloy plate-rivet welded joint,aluminum alloy rivet head self-locking phenomenon and aluminum alloy-composite interface chemical mechanical interaction.Although the three joining mechanisms act on different regions of the joint,they coordinate and cooperate with each other,which positively promotes the forming and mechanical properties of the welded and riveted hybrid joint.