Comparison of performance of laser powder bed fusion thin-walled TC11 alloy samples welded via laser welding and electron beam welding

Studying the laser welding (LW) of three-dimensional printed materials is of important significance for developing the composite manufacturing of large structures that combines additive manufacturing and welding. Taking a laser powder bed fusion (LPBF) TC11 thin-walled cylinder as the base metal (BM), joints obtained by LW and existing electron beam welding (EBW) procedure were compared in terms of microstructures and mechanical properties. In addition, the joints were annealed at 950℃ for 0.5 h, followed by air cooling to room temperature, and then heated to 580℃ for 2 h, followed by air cooling. The microhardness of the as-welded LW joint is slightly higher than that of EBM joints on the whole. The heat affected zone (HAZ) of as-welded LW joint shows the lowest microhardness, which is 413.7 ± 15.4HV on average. While α′ phases are decomposed, dislocation density reduces, and α′/α phases are coarsened in FZ of EBW joint, so FZ of EBW joints exhibits the lowest microhardness, being 398.4 ± 11.7HV on average. After annealing, the distribution trends for microhardness of the two types of joints both remain unchanged. Before annealing, the strength and plasticity of laser welded joints are higher, at 1395.7 ± 64.6 MPa and 6.94 ± 0.08%, respectively. After annealing, the width of α phases in the joints increases obviously, and globular α phases with a small length-to-width ratio appear in FZ of EBW joint, which to some extent improves the ability to coordinate deformation. Therefore, the EBW joints achieve a better balance between strength and plasticity, with average values of 1103.1 ± 34.9 MPa and 9.37 ± 0.20%, respectively. These joints all fracture at FZ, showing mixed fracture and ductile fracture before and after annealing. The above results indicate that the composite manufacturing combining AM and welding based on LW is feasible.