Effect of Laser Power on Residual Stress in Bottom-Locking Welded Joints Between TC4 and TA18 Titanium Alloys: Numerical Modeling and Experiments

In aerospace manufacturing, laser welding of TC4/TA18 dissimilar titanium alloys in bottom-locking configurations is essential for lightweight design, yet the residual stress behavior of such joints remains insufficiently understood. This study systematically examines the influence of laser power on residual stress distribution in laser-welded TC4/TA18 bottom-locking tubular joints. Welded specimens were fabricated at three distinct laser power levels (600 W, 800 W, and 1000 W). Experimental characterization included macroscopic morphology analysis and residual stress measurement using the blind-hole drilling method, among other techniques. Concurrently, a three-dimensional thermo-elastic-plastic finite element model was established based on ABAQUS 2022 to simulate the transient temperature field and stress–strain field during the welding process. The results indicate that due to the differences in thermophysical properties between the two titanium alloys and the wall thickness effect, both the temperature field and residual stress distribution of the TC4/TA18 dissimilar titanium alloy bottom-locking joints exhibit significant asymmetry. Laser power exerts a selective influence on the residual stress field: within the parameter range of this study, increasing laser power can significantly reduce the peak hoop stress of TA18 thin-walled tubes and TC4 thick-walled tubes, as well as the peak axial stress of TC4 thick-walled tubes, while remarkably increasing the peak axial stress of TA18 thin-walled tubes. The numerical simulation results are in good agreement with the experimental data, verifying that the established finite element model is an effective tool for predicting welding outcomes.