RESUMO
In this study, Al-Mg and Al-Mg-Sc ER5356 welding wires were adopted, and the effects of the Sc element on the wetting behavior of the molten metal and the porosity of the deposited metal were investigated. Al-Mg-Sc and Al-Mg welding wires exhibit wetting angles of 17.2 and 12.4°, respectively, and their porosities of deposited metal were 0.885 and 0.454%, respectively. Adding the Sc element to ER5356 welding wires reduced the surface tension and then increased the pore difference pressure, wettability, and spreadability of the molten pool, which is beneficial for pore overflow. Besides, adding Sc elements could increase the molten droplet size and the metallic vapor recoil for the ER5356 wire and then stabilize droplet transfer.
RESUMO
The dissimilar metal welding joint is connected by the metallurgical bond of intermetallic compounds at the interface, which easily causes stress concentration at the interface and cracks continuously along the interface, resulting in low reliability in impact environments. A novel multi-layer plug and bolt connection for TC4/7A52 dissimilar metal butt joints is proposed in this manuscript and analyzes the influence mechanism of the structural design on impact toughness. The impact toughness of the Ti/Al composite butt joint is 30.3 J/cm2, which is 2.6 times that of the 7A52 BM. The layered toughening design significantly reduces stress concentrations for the butt joint at impact for the Ti/Al composite butt joint. Upon impact, the Ti/Al composite butt joint does not fracture continuously at the V-notch and exhibits significant macroscopic plastic deformation. For the microstructure of each TC4 and 7A52 layer in the impact fracture, more intragranular slip systems are activated and show a higher dislocation density. Therefore, this structural design can enable dissimilar metals to absorb more impact energy during the impact process.