Grain growth and texture evolution of weld seam during solidification in laser beam deep penetration welding of 2219 aluminum alloy

Abstract

Laser beam deep penetration welding (LBDPW) was performed to connect the 2219 aluminum alloy butt joint with different parameters. Then, the LBDPW process of 2219 aluminum alloy was modeled using a coupled FE-CA model, i.e., finite element couple with cellular automaton, which contained FE model that simulates temperature field and CA model that calculates microstructure evolution. Furthermore, the microstructure evolution in LBDPW of 2219 aluminum alloy was characterized under optical microscopy and a scanning electron microscopy (SEM). At the same time, the association between LBDPW processing thermal cycles and macrostructure/microstructure evolution is studied. The results show that the final microstructure of the welded joint included fine equiaxed grains in the equiaxed grains zone (EQZ), columnar in the fusion zone (FZ) and coarse equiaxed grains in the weld seam center zone. Moreover, it was indicated that the size of grains is associated with the temperature gradient of the welding process. Besides, the size of EQZ became narrow and uniform because of the undercooling increase, leading to the rise in the heat input.