Research On Dissimilar Material Laser Welding Between Cu And Al

Copper and aluminum have been widely used in electronics and electrical fields.There is a promising use of the joints between Cu and Al, which can effectively savecosts and reduce the weight of equipments. However, there are great differencesbetween these two metals in physical and chemical properties, resulting in poorweldability. Nowadays, laser welding between dissimilar metals is a cutting-edgetopic. We carried out the research of laser welding between Cu and Al, which hasgreat theoretical and practical significance in study of welding between dissimilarmetals.First of all, a simulation model of Cu-Al lap joint has been optimized based onComputational Fluid Dynamics (CFD) method. Air was added into the computationaldomain. Surface between air and copper was set as free surface. According to theresults, the optimization and correction of the model have greatly increased theprecision of simulation. Due to the great differences of physical properties,solidification speed of Cu and Al were different. Thus, during the process ofsolidification, certain phenomenon appeared in the welding pool, which is theseparation of Cu welding pool and Al welding pool.Second, we carried out several laser welding experiments between Cu and Al.Results showed that the weld appearances in the Cu side and Al side are different. Nouniform and continuous fusion line was found, the fusion width of Cu side was muchnarrower than Al side. Besides,‘convex of Al’existed between the interface of Cuand Al.Third, SEM and EDS were applied to observe and analyze the transition zonebetween Cu and Al. Component analysis and observation of the microstructure of thejoints showed that four distinct zones with various intermetallic compounds (IMCs)and structures formed in the intermediate layer, which determined the correspondingjoint strength.Last but not least, shear-tensile and hardness tests were carried to evaluate themechanical properties of the joints. Fracture morphology and composition wereanalyzed to explain the relationship between the microstructure and mechanicalproperties of joints. Fracture occurred in the zone with20.08-54.65%Cu. Eutectic and hypoeutectic structures containing a significant amount of θ-CuAl2led to a weak joint.The relationship between mechanical properties and thickness of the differentintermediate zones was thoroughly illustrated.