Damage evolution of titanium alloy laser-welded joint during hot deformation: Experiment and modeling

The damage evolution of TA15 titanium alloy laser-welded joint during hot deformation was studied by tensile tests and the GTN model. Tensile tests of the welded joint at 900°C with different strain rates were carried out, and the evolution of cracks and voids in the welded joint during the tensile deformation was characterized. The response surface method combined with genetic algorithm was used to calibrate the GTN model at high temperature. The GTN parameters of titanium alloy welded joint under different strain rates at 900°C were obtained. Results show that the voids first germinate at the grain boundary and gradually expand along the grain boundary during the tensile deformation. The inner wall of the welding porosity is easy to become the source of crack damage during the deformation, and the shape of porosity changes from round to oval gradually with the increase of strain. The true stress-strain curves obtained by simulation agree well with the experimental results, and the error between the predicted fracture strain and the experimental result is less than 5%. The developed GTN damage model was used in the simulation of hot gas free bulging, which demonstrates that it can predict the damage evolution and fracture behavior of the weld seam accurately under different conditions.