Investigation On Laser Welding Of Aluminum Alloy With Different Thickness And Microstructure And Mechanical Properties

Tailor-welded Blanks is a way of fabrication in car designing and manufacturing in which metal plates of different specification were chosen.Through laser cutting and welding technology,some parts of the car body were made according to the specification and properties of different parts of the car body.In this paper,aluminum alloy 5052 and 5056 were used to make the finished qualified plates through laser welding with the self-made aluminum alloy special clamps.SEM,EPMA,AAS,XRD,EDS,micro-hardness tester and tensile experiments were taken into use to study the metallographic structure,composition and the welding line.The model profile of burning evaporation of Mg in the welding line after its burnt solidification was also found.The properties of two kinds of aluminum alloy welding plate were also investigated.The results showed,the structure of the center of the welding line was fine and even cellular equiaxed grain. The composition in the center of the welding line wereα(Al)+β(Mg₂Al₃)with little FeAl₃ and SiMg₂.The loss of Mg was growing with the increase of Mg content in the aluminum alloy.It exited the softening phenomena in the heat affected zone in the parent metal of welding aluminum alloy 5052.The vertical elongation of the welding aluminum alloy specimen was decreased apparently.Meanwhile,the fracture of the specimen with horizontal tensile appeared in the heat-affected zone.That was because the half-hard state of the heat-affected plate was softened during laser welding.The fracture of the welding aluminum alloy 5056 lied in thin parent plate with horizontal tensile and its fracture was ductile.After the study on the reason of the fracture of aluminum alloy 5052, recrystallization annealing was conducted on the laser welding plate.The observation of the structure and evaluation of its properties were conducted through metalloscope, tensile testing machine and micro-hardness tester.The results showed that even structures in both the parent metal and the welding line happened after recrystallization of aluminum alloy 5052 and 5056 respectively.The equivalent tensile strength and yield strength decreased a little,but the ductility increased greatly.The elongation was 3 times compared with before,that's the half of the parent plate's elongation.The hardness of the annealing parent metal plate 5052 decreased apparently,close to the hardness of thick parent metal and fusion zone. The properties of aluminum alloy 5056 didn't change very much.