Study On Microstructures And Properties Of Aluminum And Aluminum Alloy Stainless Steel Friction Welding

Today,with the increasingly serious environmental problems,energy saving and emission reduction has become one of the important research topics in the automobile manufacturing industry.Aluminum/stainless steel composite structure has the characteristics of low density and high thermal conductivity of aluminum alloy,as well as the characteristics of high strength and corrosion resistance of steel.Using aluminum/stainless steel composite structure to replace the all steel structure can not only reduce the weight but also reduce the cost,which is to achieve Lightweight structure is one of the effective methods to meet different performance requirements.However,due to the great difference in physical properties between aluminum alloy and stainless steel,and easy to produce intermetallic compounds,resulting in the poor weldability of the two materials,so the research on friction welding between aluminum alloy and stainless steel dissimilar metals has important theoretical significance and practical application value.The microstructure and mechanical properties of 1060 Aluminum Alloy/304stainless steel and 6082 aluminum alloy/304 stainless steel dissimilar metal friction welding joints were systematically studied by using friction welding technology.The temperature of the joint center can reach 475?during the friction welding of 1060Aluminum Alloy and 304 stainless steel There are two intermetallic compounds,Fe₂Al₅and feal3,at the interface.After tensile test,the fracture mode of the joint is brittle ductile mixed fracture.The peak hardness of the joint appears on the side of the interface near the stainless steel,up to 473HV.The interface temperature of 6082 aluminum alloy and 304stainless steel in the welding process can reach 493?,and the main bonding mode of the joint is metallurgical bonding It was found that the silicon element in the intermetallic compound Fe₂Al₅ 6082 aluminum alloy inhibited Fe₂Al₅ and changed the morphology of Fe₂Al₅ in the steel/aluminum dissimilar metal friction welded joint.After tensile test,the fracture mode of the joint is also brittle ductile mixed fracture,and the peak hardness of the joint appears on the side of the interface near the stainless steel,with the maximum value of 220HV.The selection of welding process parameters has a significant impact on the forming,microstructure and mechanical properties of aluminum alloy/stainless steel friction welding joint.Choosing the appropriate welding time,rotation speed,friction pressure and upset pressure is conducive to improving the forming and welding quality of friction welding joint.The welding time mainly changes the heat input during the welding process,thus affecting the diffusion rate between atoms and indirectly changing the metallurgical bonding strength of the interface;the friction pressure mainly changes the strain gradient of the joint metal,indirectly changes the diffusion coefficient between atoms,and affects the mutual diffusion rate of the iron and aluminum atoms,and then the friction pressure changes the heat input during the welding process,making the temperature of the joint metal The degree gradient changes,which affects the mutual diffusion rate between atoms.The rotation speed mainly affects the metallurgical reaction of the joint from the following two aspects:the increase of rotation speed will increase the heat input in the welding process,thus changing the diffusion rate between elements,directly promoting the metallurgical reaction;secondly,the increase of welding heat input will extend the cooling time of the joint,making the original The increase of upset pressure makes the metal gap smaller,the contact between atoms closer,the density of vacancy and atom in lattice larger,and the interface atoms are fully activated,which accelerates the diffusion rate between atoms,and directly leads to the increase of element diffusion distance.The process parameters mainly affect the heat input,holding time and strain gradient during friction welding,and then affect the metallurgical bonding degree.The influence of post weld annealing treatment on 6082 aluminum alloy/304stainless steel joint was studied.Annealing treatment promoted the diffusion of joint elements,the thickness of intermetallic compound increased with the increase of annealing temperature,and the tensile strength increased first and then decreased with the increase of annealing temperature.The tensile strength of the joint annealed at 280?increased significantly,reaching 246mpa.The corrosion resistance of the joint was improved obviously With the increase of annealing temperature,the corrosion products of joints are mainly alumina.