Improved Joint Strength During Electron Beam Welding of Al 6082-T6 Plates by Means of a DC Magnetron Sputtered Nb Filler

In the present work, the incorporation of Nb in the volume of weld seams during electron beam welding of Al6082-T6 plates was investigated. The Nb was introduced into the weld seam in the form of a direct current (DC) magnetron-sputtered filler. The experiments were conducted with different technical parameters where the power of the heat source was constant, but the geometry of the oscillation of the electron beam was varied. In the first case, circular oscillation was used with a radius rosc = 0.2 mm, and in the second case, elliptical beam oscillation was used with a length l = 2 mm and a width d = 0.2 mm. The structure of the samples and some mechanical properties were investigated. A mathematical model was prepared, and the obtained results were comparable to the experimentally obtained ones. Using circular oscillation, poor miscibility of the aluminum and niobium, poor melting of the Nb filler, and a high concentration of defects were observed. No intermetallic compounds (IMCs) were detected in this case. In the case of applying elliptical beam oscillation, excellent miscibility between aluminum and niobium was achieved, and a homogeneous spread of Al3Nb intermetallics along the entire volume of the weld seam was achieved. This increased the density of the joint by minimizing the formation of defects, such as solidification pores, and by decreasing the size of the secondary phase particles within the weld seam from 33.11–61.41 µm to 3.63–7.75 µm. This resulted in an increase in the mechanical properties, with the average hardness of the fusion zone going from 72.6 ± 3.3 HV to 83.4 ± 3.5 HV and the average tensile strength going from 225 ± 8 MPa to 275 ± 8 MPa.