Study On The Interface Characteristics And Properties Of Aluminum/Steel Welding Joints Regulated By Surface Texturing And Pre-set Powder

The aluminum-steel composite welded structure has a wide range of application requirements in automobile manufacturing,aerospace and shipbuilding because it can fully utilize the inherent advantages of the two materials.However,due to the large difference in physical and chemical properties of the two materials,it is not easy to obtain well-formed and excellent-performance aluminum-steel dissimilar metal welded joints by the traditional fusion welding process,which seriously affects the aluminum/steel dissimilar metal structural parts in the above industrial fields safely use.In article,DP590 dual-phase steel and 6061 aluminum alloy commonly used in automobile manufacturing are used as the research object,selects ER4043 aluminum-silicon welding wire as the filler material,and aluminum/steel dissimilar metals are welded by TIG fusion brazing method.Through auxiliary process of laser texturing of steel plate surface and pre-set Al₂O₃ powder to adjust the thickness,distribution state and interface micro-morphology of intermetallic compounds in the interface reaction layer to achieve the purpose of improving the mechanical properties of the joint.To this end,mainly carried out the following theoretical process research and obtained important results.Firstly,use a laser marking machine to texturize the surface of the steel plate to obtain the groove shape of the steel surface.Through a large number of welding experiments in the early stage,obtained a range of adjustable parameters of the welding process that can ensure the pre-groove shape on the surface of the steel plate can be retained after welding.Based on this adjustment interval,focus on the study of the effect of laser texturing line spacing on the interface structure and properties of aluminum/steel dissimilar metal TIG arc welding brazing joints.As a result,it was found that the intermetallic compounds generated by the reaction at the interface of the aluminum/steel welded joint showed a non-uniform distribution along the texturing groove.The textured groove not only increases the reaction contact area of liquid aluminum and steel,but also enables the mechanical interface of the brazed interface,which is beneficial to improve the mechanical strength of the joint.At the same time,the presence of texturing grooves has a negative impact on the wet spreading of molten metal on the steel surface to a certain extent,reducing the weld forming ability.Secondly,the method of pre-set Al₂O₃ powder before welding was used to study the influence rule of Al₂O₃ powder on the interface structure and properties of aluminum/steel dissimilar metal TIG arc welding brazed joints.After adding high melting point and high hardness Al₂O₃ powder,On the one hand,Al₂O₃ powder absorbs arc heat leads to reduces the input of arc heat to the base material,slows the interdiffusion of Fe atoms and Al atoms,and leads to a reduction in the thickness of the intermetallic compound layer at the joint interface;On the other hand,the addition of powder particles leads to an increase in the roughness of the steel surface,which hinders the wet spreading of liquid aluminum on the surface of the steel plate.The tensile test results of the joint show that the preset alumina powder process can improve the mechanical properties of the joint to a small extent.Finally,the interfacial characteristics,performance change rules and mechanism of the aluminum/steel dissimilar metal TIG brazing joint under the combined action of surface texturing pretreatment and pre-prepared alumina powder were studied.Observing the micro-morphology of the interface,it was found that some of the alumina powder particles were agglomerated and existed in the texturing groove,forming slag inclusion defects.However,compared with direct aluminum/steel fusion brazing,the presence of Al₂O₃ powder changes the original continuous structure of the intermetallic compound layer,and the mechanical properties of the joint are still slightly improved.The above research results show that whether the laser texturized surface pretreatment or the method of presetting alumina powder can significantly change the joint interface morphology and intermetallic compound distribution,and can effectively improve the mechanical properties of the aluminum/steel dissimilar metal arc fusion welding joint.This study laid a theoretical foundation and method support for changing the microstructure characteristics of aluminum/steel welded joints through physical control methods to improve the mechanical properties of the joints.